- What is angiogenesis?
Angiogenesis is the formation of new blood vessels. Angiogenesis is a process
controlled by certain chemicals produced in the body. Some of these chemicals
stimulate cells to repair damaged blood vessels or form new ones. Other chemicals,
called angiogenesis inhibitors, signal the process to stop.
- Why is angiogenesis important in cancer?
Angiogenesis plays an important role in the growth and spread of cancer.
New blood vessels “feed” the cancer cells with oxygen and nutrients,
allowing these cells to grow, invade nearby tissue, spread to other parts
of the body, and form new colonies of cancer cells.
- How can angiogenesis be stopped in tumors?
Because tumors cannot grow or spread without the formation of new blood
vessels, scientists are trying to find ways to stop angiogenesis. They are
studying natural and synthetic angiogenesis inhibitors, also called antiangiogenic
agents, in the hope that these chemicals will prevent or slow down the growth
of cancer by blocking the formation of new blood vessels.
- Are any angiogenesis inhibitors currently being
used to treat cancer in humans?
Yes. In 2004, the U.S. Food and Drug Administration (FDA) approved bevacizumab
(Avastin®) for use with other drugs to treat colorectal cancer that has spread
to other parts of the body and some non-small cell lung cancers. Bevacizumab
was the first angiogenesis inhibitor proven to delay tumor growth and, more
importantly, extend the lives of patients.
The FDA has also approved other drugs with antiangiogenic activity as cancer
therapies for multiple myeloma, mantle cell lymphoma, gastrointestinal stromal
tumors (GIST), and kidney cancer. Researchers are exploring the use of these
drugs to treat other cancers too.
- What are the advantages of angiogenesis inhibitors?
Angiogenesis inhibitors usually have only mild side effects and are not
toxic to most healthy cells. Tumors do not seem to develop a resistance to
angiogenesis inhibitors, even when given over a long period of time, unlike
the resistance seen when chemotherapy drugs are used.
Angiogenesis inhibitors seem to help some chemotherapy drugs and radiation
therapy work more effectively when given in combination.
- What are the limitations of angiogenesis inhibitors?
Angiogenesis inhibitor therapy may not necessarily kill tumors, but instead
may keep tumors stable. Therefore, this type of therapy may need to be administered
over a long period. Because angiogenesis is important in wound healing and
in reproduction, long-term treatment with antiangiogenic agents could cause
problems with bleeding, blood clotting, heart function, the immune system,
and the reproductive system (1).
- Does angiogenesis inhibitor therapy have any complications
or side effects?
A patient’s immune system may be compromised, making the patient more
susceptible to infection and causing wounds to heal poorly, if at all. Patients
may experience reproductive problems, and damage to the fetus is likely if
a patient becomes pregnant while taking the antiangiogenic drug. Heart problems
and high blood pressure could be made worse, and bleeding or blood clots could
increase (1).
Since angiogenesis inhibitor therapy is still under investigation, all of
the possible complications and side effects are still unknown.
- What does the future hold for angiogenesis inhibitor
therapy?
Other angiogenesis inhibitors are currently being evaluated in clinical trials
(research studies) but have not yet been proven to be effective against cancer
in humans. These studies include patients with cancers of the breast, prostate,
brain, thyroid, pancreas, lung, stomach, ovary, and cervix; some leukemias
and lymphomas; Kaposi sarcoma; and several other cancer types. If the results
of clinical trials show that other angiogenesis inhibitors are both safe and
effective in treating cancer in humans, these agents may be approved by the
FDA and made available for widespread use. To learn more about clinical trials,
call the National Cancer Institute’s (NCI) Cancer Information Service
at the telephone number listed below or visit the clinical trials page of
the NCI’s Web site at http://www.cancer.gov/clinicaltrials on the Internet.
The NCI is a part of the National Institutes of Health.
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