Lung cancer, which is most frequently caused by cigarette smoking, is the leading cause of cancer-related death in the United States, claiming almost 162,460 lives in 2006. Spiral computed tomography (CT or CAT) scans are being tested as a new way to find early lung cancer in smokers and former smokers. At present, however, questions remain about the technology's risks and benefits as a screening tool.

Promising evidence from several studies shows that the scans can detect small lung cancers. But detecting these early tumors has not been proven to reduce the likelihood of dying from lung cancer, the gold standard for any cancer screening test. The National Cancer Institute (NCI) has designed a large study that should conclusively answer if either spiral CT or chest X-ray can reduce lung cancer deaths. Other recent studies have looked at survival rather than mortality, which can be misleading because screening generally does increase survival rates (the proportion of patients alive at some point after the diagnosis of their cancer) but may not decrease mortality rates.

While spiral CT scans may eventually prove to be an effective lung cancer screening tool, they can trigger unnecessary invasive testing or even chest surgery that may potentially lead to decreased pulmonary function or death. Scarring from smoking and other non-cancerous changes in the lungs can mimic tumors on CT scans, challenging the radiologists who read them. Interpretations of the scans can vary, leading to confusion about recommendations for follow-up care.

About 25 percent to 60 percent of CT scans of smokers and former smokers will show abnormalities that are not cancer. When these suspicious areas, or nodules, are found, the physician may recommend waiting several months to a year before a repeat scan to see if the nodule has grown.

The physician may also advise an immediate lung biopsy, a potentially risky procedure that involves the removal of a small amount of tissue, either through a scope fed down the windpipe (bronchoscopy) or with a needle through the rib cage (CT-directed needle biopsy). Possible complications from biopsies include partial collapse of the lung, bleeding, infection, and pain and discomfort.

Depending on the size and location of the nodule, chest surgery (thoracotomy) to obtain a larger biopsy may be recommended. Thoracotomy is a major surgery that removes substantial amounts of lung tissue; the procedure can damage nerves in the chest and may lead to chronic pain, as well as result in decreased pulmonary function or death.

Sixty percent of the hospitals in the United States own a spiral CT machine. These machines are routinely used for staging lung and other cancers to determine how advanced the cancer is after diagnosis. But recently, some hospitals have begun promoting spiral CT scans to smokers for early detection of lung cancer, despite the lack of evidence that such scans can decrease mortality. Each scan costs $300 to $1,000.

Some experts worry that this marketing may lead smokers to falsely believe that they can continue smoking without increasing their risk of dying from lung cancer. Eighty-five percent of all lung cancers are caused by smoking, and the only proven way to reduce the risk of lung cancer is not to smoke. For people who do smoke, quitting reduces the risk of lung cancer considerably over the course of several years.

Research has shown that high-risk individuals say they would participate in a study comparing spiral CT to chest X-rays, even if the individuals were selected to receive another intervention instead of spiral CT. This research served as a preliminary study in which about 3,000 smokers were recruited over several months to receive either a CT scan or a chest X-ray. The study provided important information on how much follow-up (additional scans, biopsies, surgery, etc.) is needed after each type of lung cancer screening. In addition, this short-term, feasibility study determined that the willingness of high-risk people to participate in such a trial translated into actual participation. Medical centers that are part of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial began this feasibility study in September 2000 and the results were published in 2004.

This feasibility study led the way to the NCI-sponsored National Lung Screening Trial (NLST), which is now tracking over 53,000 smokers and former smokers to see if those who are screened with spiral CT scans have a lower mortality rate than those who receive a chest X-ray.

The PLCO also is separately examining whether annual chest X-rays, which are easier to perform than spiral CT scans, can reduce mortality from lung cancer. The PLCO trial began in 1994 and is following nearly 155,000 men and women. People participating in the PLCO Cancer Screening Trial cannot participate in the National Lung Screening Trial.

How spiral CT works: Spiral CT uses X-rays to scan the entire chest quickly, in 12 to 20 seconds, during a single breath-hold. Throughout the procedure, the patient lies very still on a table. The patient passes through the X-ray machine, which is shaped like a doughnut with a large hole. The machine rotates around the patient and a computer creates images from the scan, which can be reconstructed into a three-dimensional model of the lungs.

For more information on the National Lung Screening Trial, please visit http://www.cancer.gov/nlst on the Internet.

For more information on the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, please visit http://dcp.cancer.gov/programs-resources/groups/ed/programs/plco on the Internet.

# # #

• National Cancer Institute Fact Sheet 5.2, Computed Tomography (CT): Questions and Answers ¹
  (http://www.cancer.gov/cancertopics/factsheet/Detection/CT)
• What You Need To Know About™ Lung Cancer ²
  (http://www.cancer.gov/cancertopics/wyntk/lung)
• Lung Cancer Home Page ³
  (http://www.cancer.gov/cancertopics/types/lung)
• National Lung Screening Trial Home Page ⁴
  (http://www.cancer.gov/nlst)
• Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial Web Page ⁵
  (http://dcp.cancer.gov/programs-resources/groups/ed/programs/plco)

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• Call NCI’s Cancer Information Service at 1–800–4–CANCER (1–800–422–6237)
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Glossary Terms

Not normal. An abnormal lesion or growth may be cancer, premalignant (likely to become cancer), or benign (not cancer).

The removal of cells or tissues for examination by a pathologist. The pathologist may study the tissue under a microscope or perform other tests on the cells or tissue. There are many different types of biopsy procedures. The most common types include: (1) incisional biopsy, in which only a sample of tissue is removed; (2) excisional biopsy, in which an entire lump or suspicious area is removed; and (3) needle biopsy, in which a sample of tissue or fluid is removed with a needle. When a wide needle is used, the procedure is called a core biopsy. When a thin needle is used, the procedure is called a fine-needle aspiration biopsy.

A procedure that uses a bronchoscope to examine the inside of the trachea, bronchi (air passages that lead to the lungs), and lungs. A bronchoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue to be checked under a microscope for signs of disease. The bronchoscope is inserted through the nose or mouth. Bronchoscopy may be used to detect cancer or to perform some treatment procedures.

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.

An x-ray of the structures inside the chest. An x-ray is a type of high-energy radiation that can go through the body and onto film, making pictures of areas inside the chest, which can be used to diagnose disease.

Pain that can range from mild to severe, and persists or progresses over a long period of time.

Having to do with the colon or the rectum.

In medicine, a medical problem that occurs during a disease, or after a procedure or treatment. The complication may be caused by the disease, procedure, or treatment or may be unrelated to them.

The process of identifying a disease, such as cancer, from its signs and symptoms.

Monitoring a person's health over time after treatment. This includes keeping track of the health of people who participate in a clinical study or clinical trial for a period of time, both during the study and after the study ends.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body and can spread throughout the body. The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on where the infection occurs. When the body’s natural defense system is strong, it can often fight the germs and prevent infection. Some cancer treatments can weaken the natural defense system.

In medicine, a treatment or action taken to prevent or treat disease, or improve health in other ways.

The removal of a small piece of lung tissue to be checked by a pathologist for cancer or other diseases. The tissue may be removed using a bronchoscope (a thin, lighted, tube-like instrument that is inserted through the trachea and into the lung). It may also be removed using a fine needle inserted through the chest wall, by surgery guided by a video camera inserted through the chest wall, or by an open biopsy. In an open biopsy, a doctor makes an incision between the ribs, removes a sample of lung tissue, and closes the wound with stitches.

Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.

The state of being mortal (destined to die). Mortality also refers to the death rate, or the number of deaths in a certain group of people in a certain period of time. Mortality may be reported for people who have a certain disease, live in one area of the country, or who are of a certain gender, age, or ethnic group.

The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. The National Cancer Institute conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the National Cancer Institute Web site at http://www.cancer.gov. Also called NCI.

The removal of tissue or fluid with a needle for examination under a microscope. When a wide needle is used, the procedure is called a core biopsy. When a thin needle is used, the procedure is called a fine-needle aspiration biopsy.

A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.

A growth or lump that may be malignant (cancer) or benign (not cancer).

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.

Medical doctor.

A gland in the male reproductive system. The prostate surrounds the part of the urethra (the tube that empties the bladder) just below the bladder, and produces a fluid that forms part of the semen.

Having to do with the lungs.

Checking for disease when there are no symptoms. Since screening may find diseases at an early stage, there may be a better chance of curing the disease. Examples of cancer screening tests are the mammogram (breast), colonoscopy (colon), Pap smear (cervix), and PSA blood level and digital rectal exam (prostate). Screening can also include checking for a person’s risk of developing an inherited disease by doing a genetic test.

Performing exams and tests to learn the extent of the cancer within the body, especially whether the disease has spread from the original site to other parts of the body. It is important to know the stage of the disease in order to plan the best treatment.

A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.

The percentage of people in a study or treatment group who are alive for a certain period of time after they were diagnosed with or treated for a disease, such as cancer. The 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 diagnosis or treatment. Also called overall survival rate.

An operation to open the chest.

A group or layer of cells that work together to perform a specific function.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm.

The airway that leads from the larynx (voice box) to the bronchi (large airways that lead to the lungs). Also called trachea.

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.