Oncologists have a variety of medicines they can use to treat cancer. Each drug works in a different way, so doctors often give patients different types of drug at the same time to deliver a one-two blow to tumors. One type of drug used in metastatic cancer helps prevent the development of new blood vessels that feed tumors, a process called angiogenesis.
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What Is Angiogenesis?
Angiogenesis is a normally balanced, biological process whereby our body develops new blood vessels as needed to deliver nutrients and oxygen and to eliminate metabolic waste and carbon dioxide. In cancer, however, tumors hijack this process for their own benefit.
“Angiogenesis happens during cancer formation, growth and — most importantly — spread,” says Dr. Davendra Sohal, an oncologist at the Cleveland Clinic. “Tumors need a blood supply to grow so they require new blood vessels. The native blood supply is insufficient, so angiogenesis is stimulated by the cancer itself for its own growth.”
Angiogenesis in cancer is controlled by proteins released by the tumor cells. The most common of these is vascular endothelial growth factor, or VEGF. According to the National Cancer Institute, when VEGF binds to receptors on the surface of endothelial cells (cells that line the inside of cavities in the body), it initiates signals within the cells that promote the growth and survival of new blood vessels. Tumors can also stimulate cells close to the tumor to produce new blood vessels. This allows the tumor to invade nearby tissue and plays an important role in the spread of cancer.
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Anti-Angiogenesis Drugs
“We have drugs that [target] angiogenesis,” says Dr. Daniel Landau, an oncologist at UF Health Cancer Center — Orlando Health. The most common of these is Avastin, which has been in clinical use for about 10 years. “Avastin is a direct anti-VEGF [therapy,]” he says. Oncologists use Avastin in lung, colorectal, kidney and brain tumors. It’s even used in macular degeneration (a degenerative eye disease) to effect change in blood vessel growth in the eyes.
Anti-angiogenesis medicines help control the process of new blood vessel development, Sohal says. They choke the blood supply to the cancer, preventing it from getting blood and nutrients.
Avastin is administered intravenously every 14 days to colon cancer patients for as long as it’s working and the patient can tolerate it, Landau says. It’s used in conjunction with chemotherapy in patients whose cancer has already spread. The chemotherapy kills cancer cells, while the anti-angiogenesis drugs prevent tumors from healing via new blood vessels (the one-two punch). “[This combination of drugs] is 20 to 30 percent better than a treatment regimen that doesn’t have an anti-angiogenesis [drug],” Landau says.
“Avastin has been shown to be effective in metastatic disease, not early stage cancer,” Sohal says. In colon cancer, for example, if the cancer spreads to the liver, it builds a new home for itself there and creates its own blood supply. Anti-angiogenesis drugs help prevent spreading tumors from taking root in the new location.
In addition to Avastin, there are other, newer anti-angiogenesis drugs as well. They all do the same thing (prevent the growth of new blood vessels) and they are almost always given in conjunction with chemotherapy. For example, Landau says, there are a few pill forms of anti-angiogenesis drugs for kidney cancer, which targets the EGFR pathway (EGFR is a different protein).
“[These drugs] don’t work for everyone,” Landau says. They work well in certain cancers, but not in others (for example, breast cancer). They can also wear off as time goes on. In the case of kidney cancers, Landau says, once you block one pathway for developing blood vessels, the tumor learns to develop others. Cancer can use these new pathways to escape the effects of Avastin or other anti-angiogenesis drugs. “We’re now developing drugs that target multiple pathways,” Landau says.
Side Effects from Anti-Angiogenesis Drugs
Most side effects of anti-angiogenesis drugs are related to blood supply, Sohal says. For example, they can interfere in healing. Wounds from injury or surgery require a rich blood supply, so healing can be impaired in someone taking anti-angiogenesis medications. “We’ll stop [these drugs] before surgery [and hold off] until after the patient heals,” Sohal says.
Other side effects include blood clots and high blood pressure. Patients can develop high blood pressure or, if they already have high blood pressure, it can worsen, so doctors monitor these patients closely. In rare cases, anti-angiogenesis treatments can cause gastrointestinal perforations (tears) or fistulas (permanent, abnormal openings in the gastrointestinal tract).
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Chemotherapy and anti-angiogenesis drugs can’t cure metastatic cancer or prevent recurrence; they can only help prolong survival. “Cancer is a smart animal,” Sohal says. “It can find ways to fight back.” When patients develop resistance to chemotherapy, it’s time to change to a different chemotherapy drug, he says. “We’ll continue to use angiogenesis drugs as long as we have another chemotherapy option. However, by themselves, anti-angiogenesis drugs don’t do a whole lot.”
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What Are Anti-Angiogenesis Drugs to Treat Cancer? originally appeared on usnews.com
