In English | En español
Questions About Cancer? 1-800-4-CANCER

NCI Dictionary of Cancer Terms

Page Options

  • Print This Page

Widget

NCI Dictionary of Cancer Terms


193 results found for:       O



O(6)-benzylguanine    listen   (… BEN-zul-GWAH-neen)
A drug that may improve the response of cancer cells to chemotherapy.

ob/gyn      
A branch of medicine that specializes in the care of women during pregnancy and childbirth and in the diagnosis and treatment of diseases of the female reproductive organs. It also specializes in other women’s health issues, such as menopause, hormone problems, contraception (birth control), and infertility. Also called obstetrics and gynecology.

obatoclax    listen   (oh-BA-toh-klax)
A substance being studied in the treatment of several types of cancer. Obatoclax blocks the actions of certain proteins that cells need to live and it may kill cancer cells. It is a type of apoptosis inducer, a BCL2 protein antagonist, and a BH3 mimetic.

obatoclax mesylate    listen   (oh-BA-toh-klax MEH-zih-layt)
A substance being studied in the treatment of several types of cancer. It is a form of obatoclax, which blocks the activity of certain proteins needed for cells to live and may cause tumor cells to die. It is a type of apoptosis inducer.

obese    listen   (oh-BEES)
Having an abnormally high, unhealthy amount of body fat.

obesity    listen   (oh-BEE-sih-tee)
A condition marked by an abnormally high, unhealthy amount of body fat.

obinutuzumab    listen   (OH-bin-yoo-TOO-zoo-mab)
A drug used with another drug to treat chronic lymphocytic leukemia (CLL) that has not already been treated. It is also being studied in the treatment of other types of cancer. Obinutuzumab binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of leukemia cells. This may help the immune system kill cancer cells. Obinutuzumab is a type of monoclonal antibody. Also called Gazyva.

objective improvement    listen   (ub-JEK-tiv im-PROOV-ment)
An improvement that can be measured by the health care provider (for example, when a tumor shrinks or there are fewer cancer cells in the blood).

objective response    listen   (ub-JEK-tiv reh-SPONTS)
A measurable response.

oblimersen sodium    listen   (oh-blih-MER-sen SOH-dee-um)
A substance being studied in the treatment of cancer. It may kill cancer cells by blocking the production of a protein that makes cancer cells live longer and by making them more sensitive to anticancer drugs. It is a type of antisense oligodeoxyribonucleotide. Also called augmerosen, bcl-2 antisense oligodeoxynucleotide G3139, and Genasense.

observation    listen   (OB-ser-VAY-shun)
In medicine, watching a patient’s condition but not giving treatment unless symptoms appear or change.

observational study    listen   (OB-ser-VAY-shuh-nul STUH-dee)
A type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the outcome (for example, no treatment is given).

obsessive-compulsive disorder    listen   (ob-SEH-siv-kum-PUL-siv dis-OR-der)
An anxiety disorder in which a person has intrusive ideas, thoughts, or images that occur repeatedly, and in which he or she feels driven to perform certain behaviors over and over again. For example, a person may worry all the time about germs and so will wash his or her hands over and over again. Having an obsessive-compulsive disorder may cause a person to have trouble carrying out daily activities.

obstetrician    listen   (OB-steh-TRIH-shun)
A doctor who specializes in caring for women during pregnancy and childbirth. Obstetricians also care for the fetus (unborn baby), treat problems with pregnancy, and deliver babies.

obstetrics and gynecology    listen   (ob-STEH-trix ... GY-neh-KAH-loh-jee)
A branch of medicine that specializes in the care of women during pregnancy and childbirth and in the diagnosis and treatment of diseases of the female reproductive organs. It also specializes in other women’s health issues, such as menopause, hormone problems, contraception (birth control), and infertility. Also called ob/gyn.

obstruction    listen   (ub-STRUK-shun)
Blockage of a passageway.

obtundation    listen   (ob-tun-DAY-shun)
A dulled or reduced level of alertness or consciousness.

occult primary tumor    listen   (uh-KULT PRY-mayr-ee TOO-mer)
Cancer in which the site of the primary (original) tumor cannot be found. Most metastases from occult primary tumors are found in the head and neck.

occult stage non-small cell lung cancer    listen   (uh-KULT ... sel lung KAN-ser)
Cancer cells are found in sputum (mucus coughed up from the lungs), but no tumor can be found in the lung by imaging tests or bronchoscopy, or the tumor is too small to be checked.

occupational therapist    listen   (AH-kyoo-PAY-shuh-nul THAYR-uh-pist)
A health professional trained to help people who are ill or disabled learn to manage their daily activities.

OCT      
A procedure that uses infrared light waves to give three-dimensional (3-D) pictures of structures inside tissues and organs. The pictures are made by a computer linked to the light source. Also called optical coherence tomography.

octreotide    listen   (ok-TREE-oh-tide)
A drug similar to the naturally occurring growth hormone inhibitor somatostatin. Octreotide is used to treat diarrhea and flushing associated with certain types of tumors.

octreotide scan    listen   (ok-TREE-oh-tide skan)
A type of radionuclide scan used to find carcinoid and other types of tumors. Radioactive octreotide, a drug similar to somatostatin, is injected into a vein and travels through the bloodstream. The radioactive octreotide attaches to tumor cells that have receptors for somatostatin. A radiation-measuring device detects the radioactive octreotide, and makes pictures showing where the tumor cells are in the body. Also called somatostatin receptor scintigraphy and SRS.

ocular melanoma    listen   (AH-kyoo-ler MEH-luh-NOH-muh)
A rare cancer of melanocytes (cells that produce the pigment melanin) found in the eye. Also called intraocular melanoma.

odds ratio    listen   (… RAY-shee-oh)
A measure of the odds of an event happening in one group compared to the odds of the same event happening in another group. In cancer research, odds ratios are most often used in case-control (backward looking) studies to find out if being exposed to a certain substance or other factor increases the risk of cancer. For example, researchers may study a group of individuals with cancer (cases) and another group without cancer (controls) to see how many people in each group were exposed to a certain substance or factor. They calculate the odds of exposure in both groups and then compare the odds. An odds ratio of one means that both groups had the same odds of exposure and, therefore, the exposure probably does not increase the risk of cancer. An odds ratio of greater than one means that the exposure may increase the risk of cancer, and an odds ratio of less than one means that the exposure may reduce the risk of cancer. Also called relative odds.

odor    listen   (OH-der)
A smell.

odorant    listen   (OH-deh-runt)
A substance that gives off a smell.

OEPA      
An abbreviation for a chemotherapy combination that is often used with radiation therapy to treat a certain type of childhood Hodgkin lymphoma in males. It includes the drugs vincristine sulfate (Oncovin), etoposide, prednisone, and doxorubicin hydrochloride (Adriamycin). Also called OEPA regimen.

OEPA regimen    listen   (… REH-jih-men)
An abbreviation for a chemotherapy combination that is often used with radiation therapy to treat a certain type of childhood Hodgkin lymphoma in males. It includes the drugs vincristine sulfate (Oncovin), etoposide, prednisone, and doxorubicin hydrochloride (Adriamycin). Also called OEPA.

ofatumumab    listen   (OH-fa-TOO-moo-mab)
A drug used to treat chronic lymphocytic leukemia (CLL) that has not gotten better with other anticancer drugs. It is also used with chlorambucil in patients who have not already been treated and cannot receive certain anticancer drugs. It is also being studied in the treatment of other types of cancer. Ofatumumab binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of leukemia and lymphoma cells. This may help the immune system kill cancer cells. Ofatumumab is a type of monoclonal antibody. Also called Arzerra and HuMax-CD20.

OFF      
An abbreviation for a chemotherapy combination used to treat pancreatic cancer. It includes the drugs oxaliplatin, fluorouracil, and leucovorin (folinic acid). Also called OFF regimen.

OFF regimen    listen   (… REH-jih-men)
An abbreviation for a chemotherapy combination used to treat pancreatic cancer. It includes the drugs oxaliplatin, fluorouracil, and leucovorin (folinic acid). Also called OFF.

off-label    listen   (... LAY-bel)
Describes the legal use of a prescription drug to treat a disease or condition for which the drug has not been approved by the U.S. Food and Drug Administration.

Office for Human Research Protections    listen   (AH-fis … HYOO-mun reh-SERCH proh-TEK-shuns)
The office within the U.S. Department of Health and Human Services (DHHS) that protects the rights, welfare, and well-being of people involved in clinical trials. It also makes sure that the research follows the law 45 CFR 46 (Protection of Human Subjects). Also called OHRP.

ofloxacin    listen   (oh-FLOK-suh-sin)
An antibiotic drug used to treat infection. It belongs to the family of drugs called quinolone antibiotics.

OGF      
A substance that relieves pain and is being studied in the treatment of some types of cancer. OGFs bind to cells in the body, including tumor cells, which have OGF receptors on the surface. This may help stop the growth of the tumor cells. It may also prevent the growth of blood vessels that tumors need to grow. An OGF is a type of biological response modifier and a type of antiangiogenesis agent. Also called opioid growth factor.

OGX-011      
A substance being studied in the treatment of cancer. It blocks the production of a protein called clusterin, which helps cells live longer. This may kill cancer cells that need clusterin to grow. It may also make cells more sensitive to anticancer drugs. It is a type of antisense oligonucleotide, and a type of chemosensitizing agent. Also called custirsen sodium.

OHRP      
The office within the U.S. Department of Health and Human Services (DHHS) that protects the rights, welfare, and well-being of people involved in clinical trials. It also makes sure that the research follows the law 45 CFR 46 (Protection of Human Subjects). Also called Office for Human Research Protections.

ointment    listen   (OYNT-ment)
A substance used on the skin to soothe or heal wounds, burns, rashes, scrapes, or other skin problems. Also called unguent.

olanzapine    listen   (oh-LAN-zuh-peen)
A drug used to treat certain mental disorders. It is also being studied in the treatment of nausea and vomiting caused by some cancer treatments. It is a type of antipsychotic and a type of monoamine antagonist. Also called Zyprexa and Zyprexa Zydis.

olaparib    listen   (oh-luh-PAYR-ib)
A substance being studied in the treatment of breast, ovarian, and prostate cancers caused by mutations (changes) in the BRCA1 and BRCA2 genes. It is also being studied in the treatment of other types of cancer. It blocks an enzyme involved in many functions of the cell, including the repair of DNA damage. DNA damage may be caused by normal cell actions, UV light, some anticancer drugs, and radiation used to treat cancer. Olaparib may cause cancer cells to die. It is a type of targeted therapy agent and a type of poly (ADP-ribose) polymerase inhibitor. Also called AZD2281 and PARP inhibitor AZD2281.

Oleptro    listen   (oh-LEP-troh)
A drug used to treat depression. It may also be used to help relieve anxiety and insomnia (trouble sleeping) and to treat certain other disorders. Oleptro increases the level of the chemical serotonin in the brain, which helps improve mood. It is a type of antidepressant. Also called trazodone.

olfaction    listen   (ol-FAK-shun)
The sense of smell.

olfactory    listen   (ol-FAK-tuh-ree)
Having to do with the sense of smell.

olfactory bulb    listen   (ol-FAK-tuh-ree bulb)
A rounded mass of tissue that contains several types of nerve cells that are involved in the sense of smell. There are two olfactory bulbs on the bottom side of the brain, one above each nasal cavity. The olfactory bulbs receive information about smells from the nose and send it to the brain by way of the olfactory tracts.

olfactory system    listen   (ol-FAK-tuh-ree SIS-tem)
The parts of the body involved in sensing smell, including the nose and many parts of the brain. Smell may affect emotion, behavior, memory, and thought.

olfactory transduction    listen   (ol-FAK-tuh-ree tranz-DUK-shun)
A series of events in which cells in the nose bind to scent-bearing molecules and send electrical signals to the brain where they are perceived as smells.

oligoastrocytoma    listen   (AH-lih-goh-AS-troh-sy-TOH-muh)
A brain tumor that forms from both oligodendrocytes and astrocytes, which are types of glial cells (cells that cover and protect nerve cells in the brain and spinal cord and help them work the way they should). An oligoastrocytoma is a type of mixed glioma.

oligodendrocyte    listen   (AH-lih-goh-DEN-droh-site)
A cell that forms the myelin sheath (a layer that covers and protects nerve cells) in the brain and spinal cord. An oligodendrocyte is a type of glial cell.

oligodendroglial tumor    listen   (AH-lih-goh-den-DROH-glee-ul TOO-mer)
A rare, slow-growing tumor that begins in oligodendrocytes (cells that cover and protect nerve cells in the brain and spinal cord). Also called oligodendroglioma.

oligodendroglioma    listen   (AH-lih-goh-DEN-droh-glee-OH-muh)
A rare, slow-growing tumor that begins in oligodendrocytes (cells that cover and protect nerve cells in the brain and spinal cord). Also called oligodendroglial tumor.

oligofructose-enriched inulin    listen   (AH-lih-goh-FROOK-tose-en-RICHT IN-yoo-lin)
A substance that is used to improve the health of the digestive system and bones and is being studied in the prevention of colon cancer. Oligofructose-enriched inulin is made by combining two substances that occur naturally in many plants, including chicory root, wheat, bananas, onion, and garlic. Oligofructose-enriched inulin helps healthy bacteria grow in the intestines and helps the body absorb calcium and magnesium. Also called Raftilose Synergy 1.

oltipraz    listen   (OL-tih-praz)
A drug used in cancer prevention.

omacetaxine mepesuccinate    listen   (OH-mah-seh-TAK-seen MEH-peh-SUK-sih-nayt)
A drug used to treat certain types of chronic myelogenous leukemia (CML) that have not gotten better after treatment with other anticancer drugs. It is also being studied in the treatment of other types of cancer. Omacetaxine mepesuccinate blocks certain proteins involved in cancer cell growth and may kill cancer cells. It is a type of plant alkaloid. Also called homoharringtonine and Synribo.

omega-3 fatty acid    listen   (oh-MAY-guh-3 ...)
A type of fat obtained in the diet and involved in immunity.

omentectomy    listen   (OH-men-TEK-toh-mee)
Surgery to remove part or all of the omentum.

omentum    listen   (oh-MEN-tum)
A fold of the peritoneum (the thin tissue that lines the abdomen) that surrounds the stomach and other organs in the abdomen.

omeprazole    listen   (oh-MEH-pruh-zole)
A drug that inhibits gastric acid secretion.

Ommaya reservoir    listen   (oh-MY-uh REH-zer-vwahr)
A device surgically placed under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.

ON 01910.Na      
A substance being studied in the treatment of cancer. It blocks certain proteins that are needed for cell growth and may kill cancer cells. ON 01910.Na is a type of protein kinase inhibitor and a type of benzyl styryl sulfone analog.

onabotulinumtoxinA    listen   (ON-uh-BAH-choo-LY-num-TOK-sin-A)
A drug used to treat certain medical conditions. These include severe underarm sweating and severe muscle spasms in the neck and shoulders. OnabotulinumtoxinA is also used to smooth wrinkles on the face. It is being studied in the treatment of pain in patients with skin leiomyomas (benign smooth muscle tumors) and other conditions. It is a form of a toxin made by the bacterium Clostridium botulinum.

Oncaspar    listen   (ON-kah-spar)
A drug used to treat acute lymphoblastic leukemia (ALL). It is a form of the drug asparaginase that is linked to a substance called PEG, which makes the drug stay in the body longer. Asparaginase is an enzyme that breaks down the amino acid asparagine and may block the growth of tumor cells that need asparagine to grow. It is a type of protein synthesis inhibitor. Also called PEG-asparaginase and pegaspargase.

Oncaspar-IV    listen   (ON-kah-spar …)
A drug used to treat acute lymphoblastic leukemia (ALL). It is a form of the anticancer drug PEG-asparaginase that stays in the body longer. Oncaspar-IV is an enzyme that breaks down the amino acid asparagine and may block the growth of tumor cells that need asparagine to grow. It is a type of protein synthesis inhibitor. Also called EZN-2285 and SC-PEG E. coli L-asparaginase.

oncogene    listen   (ON-koh-jeen)
A gene that is a mutated (changed) form of a gene involved in normal cell growth. Oncogenes may cause the growth of cancer cells. Mutations in genes that become oncogenes can be inherited or caused by being exposed to substances in the environment that cause cancer.

oncologist    listen   (on-KAH-loh-jist)
A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation.

oncology    listen   (on-KAH-loh-jee)
A branch of medicine that specializes in the diagnosis and treatment of cancer. It includes medical oncology (the use of chemotherapy, hormone therapy, and other drugs to treat cancer), radiation oncology (the use of radiation therapy to treat cancer), and surgical oncology (the use of surgery and other procedures to treat cancer).

oncology nurse    listen   (on-KAH-loh-jee...)
A nurse who specializes in treating and caring for people who have cancer.

oncology pharmacy specialist    listen   (on-KAH-loh-jee FAR-muh-see SPEH-shuh-list)
A licensed pharmacist with special training in how to design, give, monitor, and change chemotherapy for cancer patients. Also called BCOP and board certified oncology pharmacy specialist.

oncolysate    listen   (on-KAH-lih-sayt)
An extract made from cancer cells.

oncolysis    listen   (on-KAH-lih-sis)
The lysis (breakdown) of cancer cells. This can be caused by chemical or physical means (for example, strong detergents or high-energy sound waves) or by infection with a strain of virus that can lyse cells.

oncolytic virotherapy    listen   (ON-koh-LIH-tik VY-roh-THAYR-uh-pee)
Treatment using an oncolytic virus (a virus that infects and breaks down cancer cells but not normal cells ). Oncolytic virotherapy may make it easier to kill tumor cells with chemotherapy and radiation therapy. It is a type of targeted therapy. Also called oncolytic virus therapy, viral therapy, and virotherapy.

oncolytic virus    listen   (ON-koh-LIH-tik VY-rus)
A type of virus that infects and lyses (breaks down) cancer cells but not normal cells. Oncolytic viruses can occur naturally or can be made in the laboratory by changing other viruses. Certain oncolytic viruses are being studied in the treatment of cancer. They may make it easier to kill tumor cells with chemotherapy and radiation therapy.

oncolytic virus therapy    listen   (ON-koh-LIH-tik VY-rus THAYR-uh-pee)
Treatment using an oncolytic virus (a virus that infects and breaks down cancer cells but not normal cells ). Oncolytic virus therapy may make it easier to kill tumor cells with chemotherapy and radiation therapy. It is a type of targeted therapy. Also called oncolytic virotherapy, viral therapy, and virotherapy.

Onconase    listen   (ON-koh-nays)
A substance being studied in the treatment of cancer. It is a type of ribonuclease enzyme. Also called ranpirnase.

Oncophage    listen   (ON-koh-fayj)
A vaccine made from a patient’s tumor cells that may help the body’s immune system kill cancer cells. This vaccine is used to treat kidney cancer, a type of brain cancer called glioma, and metastatic melanoma (a type of skin cancer that has spread). It is also being studied in the treatment of other types of cancer. Also called gp96 heat shock protein-peptide complex vaccine, gp96 HSP-peptide complex, and vitespen.

Oncotype DX breast cancer assay    listen   (ON-koh-tipe … brest KAN-ser A-say)
A test that is used to help predict whether breast cancer will spread to other parts of the body or come back. The test looks at the activity of 21 different genes in breast cancer tissue of women who have early-stage breast cancer that is estrogen receptor positive and has not spread to the lymph nodes. If there is a high risk that the cancer will spread or come back, it may be used to help plan treatment with anticancer drugs. Also called 21-gene signature.

Oncovin    listen   (ON-koh-vin)
A drug used to treat acute leukemia. It is used in combination with other drugs to treat Hodgkin disease, non-Hodgkin lymphoma, rhabdomyosarcoma, neuroblastoma, and Wilms tumor. Oncovin is also being studied in the treatment of other types of cancer. It blocks cell growth by stopping cell division. It is a type of vinca alkaloid and a type of antimitotic agent. Also called vincristine sulfate.

ondansetron hydrochloride    listen   (on-DAN-seh-tron HY-droh-KLOR-ide)
A drug used to prevent nausea and vomiting caused by chemotherapy and radiation therapy. It is also used to prevent nausea and vomiting after surgery. Ondansetron hydrochloride blocks the action of the chemical serotonin, which binds to certain nerves and may trigger nausea and vomiting. Blocking serotonin may help lessen nausea and vomiting. It is a type of serotonin receptor antagonist and a type of antiemetic. Also called Zofran.

Onrigin    listen   (ON-rih-jin)
A drug used to treat acute myelogenous leukemia (AML). It is also being studied in the treatment of several other types of cancer. It blocks cell growth by damaging the cell’s DNA and may kill cancer cells. It is a type of alkylating agent. Also called Cloretazine and laromustine.

onset of action    listen   (... AK-shun)
The length of time it takes for a medicine to start to work.

Ontak    listen   (ON-tak)
A drug used to treat cutaneous T-cell lymphoma that can bind the cytokine IL-2 and that has not responded to other treatment. It is also being studied in the treatment of other types of cancer. Ontak is made by combining a part of IL-2 with a bacterial toxin. The IL-2 part of the drug attaches to the cancer cells and then the toxin kills the cells. Ontak is a type of immunotoxin and a type of fusion toxin. Also called denileukin diftitox.

ONYX-015      
A modified cold virus that selectively grows in and destroys certain types of cancer cells and leaves normal cells undamaged.

oophorectomy    listen   (oh-oh-foh-REK-toh-mee)
Surgery to remove one or both ovaries.

Opana    listen   (oh-PA-nuh)
A drug used to treat moderate to severe pain. It is also used as a sedative before surgery, to help with anesthesia during surgery, during labor, and to treat anxiety caused by some medical conditions. It is made from morphine and binds to opioid receptors in the central nervous system. Opana is a type of opioid and a type of analgesic agent. Also called Numorphan and oxymorphone hydrochloride.

open biopsy    listen   (OH-pen BY-op-see)
A procedure in which a surgical incision (cut) is made through the skin to expose and remove tissues. The biopsy tissue is examined under a microscope by a pathologist. An open biopsy may be done in the doctor’s office or in the hospital, and may use local anesthesia or general anesthesia. A lumpectomy to remove a breast tumor is a type of open biopsy.

open colectomy    listen   (... koh-LEK-toh-mee)
An operation to remove all or part of the colon through a long incision made in the wall of the abdomen. When only part of the colon is removed, it is called a partial colectomy.

open label study    listen   (OH-pen LAY-bel STUH-dee)
A type of study in which both the health providers and the patients are aware of the drug or treatment being given.

open prostatectomy    listen   (… PROS-tuh-TEK-toh-mee)
Surgery to remove part or all of the prostate gland through an incision in the lower abdomen or perineum (the area between the anus and scrotum). An open prostatectomy may be done to remove an enlarged prostate gland in benign prostatic hyperplasia (BPH) or as a treatment for prostate cancer.

open resection    listen   (… ree-SEK-shun)
Surgery to remove part or all of an organ or a tumor and nearby lymph nodes. The incision is large enough to let the surgeon see into the body.

operable    listen   (AH-peh-ruh-bul)
Describes a condition that can be treated by surgery.

ophthalmic    listen   (of-THAL-mik)
Having to do with the eye.

ophthalmologist    listen   (OF-thul-MAH-loh-jist)
A doctor who specializes in diagnosing and treating eye problems, including injury and disease.

ophthalmoscope    listen   (of-THAL-moh-skope)
A lighted instrument used to examine the inside of the eye, including the retina and the optic nerve.

ophthalmoscopy    listen   (OF-thul-MOS-koh-pee)
An exam that uses a magnifying lens and a light to check the fundus of the eye (back of the inside of the eye, including the retina and optic nerve). The pupils may be dilated (enlarged) with medicated eye drops so the doctor can see through the pupil to the back of the eye. Ophthalmoscopy may be used to check for eye problems, such as glaucoma, macular degeneration, eye cancer, optic nerve problems, or eye injury. Also called fundoscopy and funduscopy.

opiate    listen   (OH-pee-ut)
A substance used to treat pain or cause sleep. Opiates are made from opium or have opium in them. Opiates bind to opioid receptors in the central nervous system. Examples of opiates are codeine, heroin, and morphine. An opiate is a type of analgesic agent.

opioid    listen   (OH-pee-OYD)
A substance used to treat moderate to severe pain. Opioids are like opiates, such as morphine and codeine, but are not made from opium. Opioids bind to opioid receptors in the central nervous system. Opioids used to be called narcotics. An opioid is a type of alkaloid.

opioid growth factor    listen   (OH-pee-OYD grothe FAK-ter)
A substance that relieves pain and is being studied in the treatment of some types of cancer. Opioid growth factors bind to cells in the body, including tumor cells, which have opioid growth factor receptors on the surface. This may help stop the growth of the tumor cells. It may also prevent the growth of blood vessels that tumors need to grow. An opioid growth factor is a type of biological response modifier and a type of antiangiogenesis agent. Also called OGF.

OPPA      
An abbreviation for a chemotherapy combination that is often used with radiation therapy to treat a certain type of childhood Hodgkin lymphoma in females. It includes the drugs vincristine sulfate (Oncovin), prednisone, procarbazine hydrochloride, and doxorubicin hydrochloride (Adriamycin). Also called OPPA regimen.

OPPA regimen    listen   (... REH-jih-men)
An abbreviation for a chemotherapy combination that is often used with radiation therapy to treat a certain type of childhood Hodgkin lymphoma in females. It includes the drugs vincristine sulfate (Oncovin), prednisone, procarbazine hydrochloride, and doxorubicin hydrochloride (Adriamycin). Also called OPPA.

opportunistic infection    listen   (AH-per-too-NIS-tik in-FEK-shun)
An infection caused by an organism that does not normally cause disease. Opportunistic infections occur in people with weakened immune systems.

oprelvekin    listen   (oh-PREL-veh-KIN)
A drug used to increase the number of blood cells, especially platelets, in some cancer patients receiving chemotherapy. Oprelvekin is a form of interleukin-11 (a cytokine normally made by support cells in the bone marrow) that is made in the laboratory. It is a type of biological response modifier. Also called Neumega, recombinant human interleukin-11, and rhIL-11.

OPT-80      
A substance being studied in the treatment of diarrhea caused by infection with Clostridium difficile (a type of bacteria that can grow without oxygen) in cancer patients. OPT-80 is a type of antibiotic. Also called PAR-101 and tiacumicin B.

optic chiasm    listen   (OP-tik ky-A-zum)
The place in the brain where some of the optic nerve fibers coming from one eye cross optic nerve fibers from the other eye. Also called optic chiasma.

optic chiasma    listen   (OP-tik ky-AZ-muh)
The place in the brain where some of the optic nerve fibers coming from one eye cross optic nerve fibers from the other eye. Also called optic chiasm.

optic nerve    listen   (OP-tik nerv)
The nerve that carries messages from the retina to the brain.

optic neuritis    listen   (OP-tik noo-RY-tis)
Inflammation of the optic nerve (the nerve that carries messages from the back of the eye to the brain). It may be caused by infection, drugs, toxins, and diseases of the immune system, such as multiple sclerosis. Symptoms include sudden changes in vision in one eye, including loss of vision and pain with eye movement. The symptoms often disappear within a few weeks.

optic pathway glioma    listen   (OP-tik ... glee-OH-muh)
A rare, slow-growing tumor that usually forms in the optic nerve, optic chiasm, or optic tract. These are parts of the nervous system that carry messages from the eye to the brain. Also called visual pathway glioma.

optic tract    listen   (OP-tik trakt)
The nerves that travel from the optic chiasm (place in the brain where some of the optic nerve fibers cross) into certain parts of the brain involved in vision.

optical coherence tomography    listen   (OP-tih-kul koh-HEER-ents toh-MAH-gruh-fee)
A procedure that uses infrared light waves to give three-dimensional (3-D) pictures of structures inside tissues and organs. The pictures are made by a computer linked to the light source. Also called OCT.

optical spectroscopy    listen   (OP-tih-kul spek-TROS-koh-pee)
In medicine, a technique that uses low power light, fiberoptic instruments, and detectors to examine tissue. It is being studied as a way to identify differences between normal cells and cells that may become cancer, and as a way to identify cancer cells that remain in the edges of tumor tissue removed from a patient.

optimism    listen   (OP-tih-MIH-zum)
The tendency to believe that there is good in everything and to have positive thoughts about most things that happen.

oral    listen   (OR-ul)
By or having to do with the mouth.

oral and maxillofacial surgeon    listen   (OR-ul ... MAK-sih-loh-FAY-shul SER-jun)
A dentist who specializes in surgery of the mouth, face, and jaw.

oral cancer    listen   (OR-ul KAN-ser)
Cancer that forms in tissues of the oral cavity (the mouth) or the oropharynx (the part of the throat at the back of the mouth).

oral cavity    listen   (OR-ul KA-vih-tee)
Refers to the mouth. It includes the lips, the lining inside the cheeks and lips, the front two thirds of the tongue, the upper and lower gums, the floor of the mouth under the tongue, the bony roof of the mouth, and the small area behind the wisdom teeth.

oral cavity cancer    listen   (OR-ul KA-vih-tee KAN-ser)
Cancer that forms in tissues of the oral cavity (the mouth). The tissues of the oral cavity include the lips, the lining inside the cheeks and lips, the front two thirds of the tongue, the upper and lower gums, the floor of the mouth under the tongue, the bony roof of the mouth, and the small area behind the wisdom teeth.

oral chemotherapy    listen   (OR-ul KEE-moh-THAYR-uh-pee)
Treatment with drugs given by mouth to kill cancer cells or stop them from dividing.

oral contraceptive pill    listen   (OR-ul KON-truh-SEP-tiv ...)
A pill used to prevent pregnancy. It contains hormones that block the release of eggs from the ovaries. Most oral contraceptives include estrogen and progestin. Also called birth control pill.

oral surgeon    listen   (OR-ul SER-jun)
A dentist with special training in surgery of the mouth and jaw.

orantinib    listen   (oh-RAN-tih-nib)
A substance being studied in the treatment of cancer. Orantinib blocks proteins involved in the growth and spread of cancer cells. It may also prevent the growth of new blood vessels that tumors need to grow. It is a type of tyrosine kinase inhibitor and a type of antiangiogenesis agent. Also called SU006668 and SU6668.

orchidectomy    listen   (or-kih-DEK-toh-mee)
Surgery to remove one or both testicles. Also called orchiectomy.

orchiectomy    listen   (or-kee-EK-toh-mee)
Surgery to remove one or both testicles. Also called orchidectomy.

oregovomab    listen   (oh-reh-GOH-voh-mab)
A monoclonal antibody that is being studied in the treatment of ovarian cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to substances in the body, including cancer cells. Oregovomab binds to the CA-125 antigen, which is found on most ovarian cancer cells. Also called OvaRex.

organ    listen   (OR-gun)
A part of the body that performs a specific function. For example, the heart is an organ.

organelle    listen   (OR-guh-NEL)
A small structure in a cell that is surrounded by a membrane and has a specific function. Examples of organelles are the nucleus (a structure that contains the cell’s chromosomes and is where RNA is made), mitochondria (structures that make energy for the cell), and lysosomes (sac-like containers filled with enzymes that digest and help recycle molecules in the cell).

organic food    listen   (or-GA-nik …)
Food produced without the use of man-made fertilizer, drugs that increase growth, or drugs that kill insects, bacteria, or other living things. In the United States, the Department of Agriculture sets standards for growing, harvesting, processing, and labeling organic foods.

organism    listen   (OR-guh-NIH-zum)
A living thing, such as an animal, a plant, a bacterium, or a fungus.

orgasm    listen   (OR-ga-zum)
The final part of the sex act, which involves contraction of sexual organs and a sudden release of endorphins, leading to a feeling of pleasure. In males, orgasm usually occurs with release of semen.

Oriental medicine    listen   (OR-ee-EN-tul MEH-dih-sin)
A medical system that has been used for thousands of years to prevent, diagnose, and treat disease. It is based on the belief that qi (the body's vital energy) flows along meridians (channels) in the body and keeps a person’s spiritual, emotional, mental, and physical health in balance. Oriental medicine aims to restore the body’s balance and harmony between the natural opposing forces of yin and yang, which can block qi and cause disease. Oriental medicine includes acupuncture, diet, herbal therapy, meditation, physical exercise, and massage. Also called TCM and Traditional Chinese Medicine.

oropharyngeal cancer    listen   (OR-oh-fuh-RIN-jee-ul KAN-ser)
Cancer that forms in tissues of the oropharynx (the part of the throat at the back of the mouth, including the soft palate, the base of the tongue, and the tonsils). Most oropharyngeal cancers are squamous cell carcinomas (cancer that begins in flat cells lining the oropharynx).

oropharynx    listen   (OR-oh-FAYR-inx)
The part of the throat at the back of the mouth behind the oral cavity. It includes the back third of the tongue, the soft palate, the side and back walls of the throat, and the tonsils.

orthodox medicine    listen   (OR-thuh-DOX MEH-dih-sin)
A system in which medical doctors and other healthcare professionals (such as nurses, pharmacists, and therapists) treat symptoms and diseases using drugs, radiation, or surgery. Also called allopathic medicine, biomedicine, conventional medicine, mainstream medicine, and Western medicine.

orthopedic surgeon    listen   (OR-thuh-PEE-dik SER-jun)
A surgeon who specializes in diagnosing and treating injuries and diseases of the musculoskeletal system. This includes the bones, joints, tendons, ligaments, and muscles.

orthotopic    listen   (OR-thoh-TAH-pik)
In medicine, refers to something that occurs in the normal or usual place in the body. It is often used to describe tissue or an organ that is transplanted into its normal place in the body.

OS      
The length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that patients diagnosed with the disease are still alive. In a clinical trial, measuring the OS is one way to see how well a new treatment works. Also called overall survival.

oseltamivir phosphate    listen   (oh-sel-TA-mih-veer FOS-fayt)
A drug used to prevent and to treat influenza virus infections. It blocks the release of the virus from infected cells. It is a type of antiviral agent. Also called Tamiflu.

OSI-774      
A drug used to treat certain types of non-small cell lung cancer. It is also used with gemcitabine hydrochloride to treat pancreatic cancer that cannot be removed by surgery or has spread to other parts of the body. It is being studied in the treatment of other types of cancer. OSI-774 blocks a protein called epidermal growth factor receptor (EGFR), which may help keep cancer cells from growing. It is a type of EGFR tyrosine kinase inhibitor. Also called CP-358,774, erlotinib hydrochloride, and Tarceva.

OSI-7904L      
A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called thymidylate synthase inhibitors.

OSI-906      
A substance being studied in the treatment of cancer. It blocks a protein called IGF-1R, which is found at high levels in some types of tumors. IGF-1R is needed for cell growth and blocking it may cause tumor cells to die. OSI-906 is a type of IGF-1R inhibitor. Also called IGF-1R inhibitor OSI-906.

osmolality    listen   (OZ-moh-LA-lih-tee)
The concentration of particles dissolved in a fluid. The osmolality of serum can help diagnose several medical conditions such as dehydration, diabetes, and shock.

osmotic    listen   (oz-MAH-tik)
Having to do with osmosis (the passage of a liquid through a membrane from a less concentrated solution to a more concentrated one). This causes the more concentrated solution to become diluted, and makes the concentrations in both solutions more equal. Osmotic also refers to a type of laxative that increases the amount of water in the large intestine, which softens the stool to help it pass more easily.

osteitis deformans    listen   (OS-tee-I-tis dih-FOR-manz)
A chronic condition in which both the breakdown and regrowth of bone are increased. Osteitis deformans occurs most frequently in the pelvic and leg bones, skull, and lower spine. It is most common in older individuals, and may lead to bone pain, deformities, and fractures. Also called Paget disease of bone.

osteochondroma    listen   (OS-tee-oh-kon-DROH-muh)
A benign (not cancer) tumor that has both bone and cartilage in it. This type of tumor usually occurs at the ends of the long bones of the arms and legs or in the pelvis or shoulder. It may cause abnormal growth of the arms, hands, and legs; problems moving the joints; and pain, numbness, and tingling. There may be one or more tumors, and having multiple tumors runs in families. Osteochondromas may also occur at some point in time after cancer treatment, such as stem cell transplant.

osteogenic sarcoma    listen   (OS-tee-oh-JEH-nik sar-KOH-muh)
A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteosarcoma.

osteolytic    listen   (OS-tee-oh-LIH-tik)
Causing the breakdown of bone.

osteomalacia    listen   (OS-tee-oh-muh-LAY-shuh)
A condition in adults in which bones become soft and deformed because they don’t have enough calcium and phosphorus. It is usually caused by not having enough vitamin D in the diet, not getting enough sunlight, or a problem with the way the body uses vitamin D. Symptoms include bone pain and muscle weakness. When the condition occurs in children, it is called rickets. Also called adult rickets.

osteomyelitis    listen   (OS-tee-oh-MY-eh-LY-tis)
Inflammation of the bone caused by an infection, which may spread to the bone marrow and tissues near the bone. Osteomyelitis can cause severe pain in the infected bone. If it is not treated, it can kill bone tissue.

osteonecrosis    listen   (OS-tee-oh-neh-KROH-sis)
A condition in which there is a loss of blood flow to bone tissue, which causes the bone to die. It is most common in the hips, knees, shoulders, and ankles. It may be caused by long-term use of steroid medicines, alcohol abuse, joint injuries, and certain diseases, such as cancer and arthritis. It may also occur at some point in time after cancer treatment that included methotrexate, bisphosphonates, or corticosteroids. Also called aseptic necrosis, avascular necrosis, and ischemic necrosis.

osteopenia    listen   (OS-tee-oh-PEE-nee-uh)
A condition in which there is a lower-than-normal bone mass or bone mineral density (the amount of bone mineral contained in a certain amount of bone). Osteopenia is a less severe form of bone loss than osteoporosis.

osteoporosis    listen   (OS-tee-oh-puh-ROH-sis)
A condition that is marked by a decrease in bone mass and density, causing bones to become fragile.

osteosarcoma    listen   (OS-tee-oh-sar-KOH-muh)
A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteogenic sarcoma.

ostomy    listen   (OS-toh-mee)
An operation to create an opening (a stoma) from an area inside the body to the outside. Colostomy and urostomy are types of ostomies.

OTC      
Refers to a medicine that can be bought without a prescription (doctor's order). Examples include analgesics (pain relievers), such as aspirin and acetaminophen. Also called nonprescription and over-the-counter.

otolaryngologist    listen   (OH-toh-LAYR-in-GAH-loh-jist)
A doctor who specializes in treating diseases of the ear, nose, and throat. Also called ENT doctor.

ounce    listen   (ownts)
A measure of weight (one-sixteenth pound) and volume (one-eighth cup).

outcome    listen   (OWT-kum)
A specific result or effect that can be measured. Examples of outcomes include decreased pain, reduced tumor size, and improvement of disease.

outpatient    listen   (OWT-pay-shunt)
A patient who visits a health care facility for diagnosis or treatment without spending the night. Sometimes called a day patient.

OvaRex    listen   (OH-vuh-REX)
A monoclonal antibody that is being studied in the treatment of ovarian cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to substances in the body, including cancer cells. OvaRex binds to the CA-125 antigen, which is found on most ovarian cancer cells. Also called oregovomab.

ovarian    listen   (oh-VAYR-ee-un)
Having to do with the ovaries, the female reproductive glands in which the ova (eggs) are formed. The ovaries are located in the pelvis, one on each side of the uterus.

ovarian ablation    listen   (oh-VAYR-ee-un a-BLAY-shun)
Surgery, radiation therapy, or a drug treatment to stop the functioning of the ovaries. Also called ovarian suppression.

ovarian borderline malignant tumor    listen   (oh-VAYR-ee-un BOR-der-line muh-LIG-nunt TOO-mer)
A condition in which cells that may become cancer form in the thin layer of tissue that covers an ovary (female reproductive gland in which eggs are made). In this condition, tumor cells rarely spread outside of the ovary. Also called ovarian low malignant potential tumor.

ovarian cancer    listen   (oh-VAYR-ee-un KAN-ser)
Cancer that forms in tissues of the ovary (one of a pair of female reproductive glands in which the ova, or eggs, are formed). Most ovarian cancers are either ovarian epithelial carcinomas (cancer that begins in the cells on the surface of the ovary) or malignant germ cell tumors (cancer that begins in egg cells).

ovarian epithelial cancer    listen   (oh-VAYR-ee-un eh-pih-THEE-lee-ul KAN-ser)
Cancer that occurs in the cells on the surface of the ovary. Also called epithelial ovarian cancer.

ovarian germ cell tumor    listen   (oh-VAYR-ee-un jerm sel TOO-mer)
An abnormal mass of tissue that forms in germ (egg) cells in the ovary (female reproductive gland in which the eggs are formed). These tumors usually occur in teenage girls or young women, usually affect just one ovary, and can be benign (not cancer) or malignant (cancer). The most common ovarian germ cell tumor is called dysgerminoma.

ovarian low malignant potential tumor    listen   (oh-VAYR-ee-un...muh-LIG-nunt poh-TEN-shul TOO-mer)
A condition in which cells that may become cancer form in the thin layer of tissue that covers an ovary (female reproductive gland in which eggs are made). In this condition, tumor cells rarely spread outside of the ovary. Also called ovarian borderline malignant tumor.

ovarian shielding    listen   (oh-VAYR-ee-un SHEEL-ding)
A procedure done during radiation therapy in which a protective cover is placed on the outside of the body, over the area of the ovaries and other parts of the female reproductive system (ovaries, fallopian tubes, uterus, cervix, and vagina). This may prevent damage from radiation therapy. Ovarian shielding is a type of fertility preservation.

ovarian suppression    listen   (oh-VAYR-ee-un suh-PREH-shun)
Surgery, radiation therapy, or a drug treatment to stop the functioning of the ovaries. Also called ovarian ablation.

ovary    listen   (OH-vuh-ree)
One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.

over-the-counter    listen   (OH-ver-the-KOWN-ter)
Refers to a medicine that can be bought without a prescription (doctor's order). Examples include analgesics (pain relievers), such as aspirin and acetaminophen. Also called nonprescription and OTC.

overactive thyroid    listen   (... THY-royd)
Too much thyroid hormone. Symptoms include weight loss, chest pain, cramps, diarrhea, and nervousness. Also called hyperthyroidism.

overall survival    listen   (oh-ver-AWL ser-VY-vul)
The length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that patients diagnosed with the disease are still alive. In a clinical trial, measuring the overall survival is one way to see how well a new treatment works. Also called OS.

overall survival rate    listen   (oh-ver-AWL ser-VY-vul rayt)
The percentage of people in a study or treatment group who are still alive for a certain period of time after they were diagnosed with or started treatment for a disease, such as cancer. The overall survival rate is often stated as a five-year survival rate, which is the percentage of people in a study or treatment group who are alive five years after their diagnosis or the start of treatment. Also called survival rate.

overdiagnosis       (OH-ver-DY-ug-NOH-sis)
Finding cases of cancer with a screening test (such as a mammogram or PSA test) that will never cause any symptoms. These cancers may just stop growing or go away on their own. Some of the harms caused by overdiagnosis are anxiety and having treatments that are not needed.

overdose    listen   (OH-ver-dose)
An amount of drug that is more than what should be taken at one time.

overexpress    listen   (OH-ver-ek-SPRES)
In biology, to make too many copies of a protein or other substance. Overexpression of certain proteins or other substances may play a role in cancer development.

overgrowth syndrome    listen   (OH-ver-grothe SIN-drome)
A group of genetic disorders in which there is an abnormal increase in the size of the body or a body part that is often noted at birth. Examples of overgrowth syndromes include neurofibromatosis, Sotos syndrome, Beckwith-Wiedemann syndrome, Simpson-Golabi-Behmel syndrome, Weaver syndrome, Proteus syndrome, Sturge-Weber syndrome, and fragile X syndrome. Many of these syndromes increase the risk of cancer.

overtreatment       (OH-ver-TREET-ment)
Treatment of a cancer that would have gone away on its own or never caused any symptoms. These cancers are usually found on a screening test. Overtreatment may lead to problems and harmful side effects from cancer therapies that are not needed.

overweight    listen   (OH-ver-WAYT)
Being too heavy for one’s height. Excess body weight can come from fat, muscle, bone, and/or water retention. Being overweight does not always mean being obese.

ovulation    listen   (ov-yoo-LAY-shun)
The release of an egg from an ovary during the menstrual cycle.

OX-40      
A protein being studied in the treatment of cancer. Substances that attach to OX-40 on the surface of T cells (a type of white blood cell) may help the T cells grow and kill more cancer cells. OX-40 is a type of tumor necrosis factor (TNF) receptor. Also called CD134.

oxaliplatin    listen   (ok-SA-lih-pla-tin)
A drug used with other drugs to treat colorectal cancer that is advanced or has come back. It is also being studied in the treatment of other types of cancer. Oxaliplatin attaches to DNA in cells and may kill cancer cells. It is a type of platinum compound. Also called Eloxatin.

oxandrolone    listen   (ok-SAN-droh-lone)
A drug used to help patients gain weight after injury, chronic infection, or severe illness. It belongs to the family of drugs called anabolic steroids.

oxidation    listen   (OK-sih-DAY-shun)
A chemical reaction that takes place when a substance comes into contact with oxygen or another oxidizing substance. Examples of oxidation are rust and the brown color on a cut apple.

oxidative metabolism    listen   (OK-sih-DAY-tiv meh-TA-buh-lih-zum)
A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also called aerobic metabolism, aerobic respiration, and cell respiration.

oxidative stress    listen   (OK-sih-DAY-tiv ...)
A condition in which antioxidant levels are lower than normal. Antioxidant levels are usually measured in blood plasma.

oxide    listen   (OK-side)
A type of chemical substance that is a combination of oxygen and another substance. Oxides are found in essential oils.

oxidize    listen   (OK-sih-dize)
To cause oxidation (a chemical reaction that takes place when a substance comes into contact with oxygen or another oxidizing substance).

oxycodone hydrochloride    listen   (OK-see-KOH-done HY-droh-KLOR-ide)
A drug used to treat moderate to severe pain. It is made from morphine and binds to opioid receptors in the central nervous system. Oxycodone hydrochloride is a type of analgesic agent and a type of opiate.

oxygen    listen   (OK-sih-jen)
A colorless, odorless gas. It is needed for animal and plant life. Oxygen that is breathed in enters the blood from the lungs and travels to the tissues.

oxygen radical    listen   (OK-sih-jen RA-dih-kul)
A type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell. A build up of oxygen radicals in cells may cause damage to DNA, RNA, and proteins, and may cause cell death. An oxygen radical is a free radical. Also called reactive oxygen species.

oxygen saturation test    listen   (OK-sih-jen SA-chuh-RAY-shun…)
A test that measures the amount of oxygen being carried by red blood cells. One method uses a device that shines light through a finger. The device measures the amount of oxygen in the blood based on the way red blood cells carrying oxygen absorb and reflect light. In another method blood is taken from an artery and the amount of oxygen is measured directly. An oxygen level that is lower than normal may be a sign of lung disease or other medical conditions.

oxygen therapy    listen   (OK-sih-jen THAYR-uh-pee)
Treatment in which a storage tank of oxygen or a machine called a compressor is used to give oxygen to people with breathing problems. It may be given through a nose tube, a mask, or a tent. The extra oxygen is breathed in along with normal air. Also called supplemental oxygen therapy.

oxymorphone hydrochloride    listen   (OK-see-MOR-fone HY-droh-KLOR-ide)
A drug used to treat moderate to severe pain. It is also used as a sedative before surgery, to help with anesthesia during surgery, during labor, and to treat anxiety caused by some medical conditions. It is made from morphine and binds to opioid receptors in the central nervous system. Oxymorphone hydrochloride is a type of opioid and a type of analgesic agent. Also called Numorphan and Opana.

Back to TopBack to Top