Angiogenesis is the process by which the body makes new blood vessels, according to the National Cancer Institute. Additional blood supply is necessary for tumors to grow to the point where they can spread to other tissues in a process which is known as metastasis. Antiangiogenic cancer therapies work to block the blood supply of tumors, which can prevent them from growing.
Function
Tumors need to be able to create new blood vessels because they rapidly outgrow the already existing blood supply. If tumors do not create new blood vessels, they cannot grow. Tumors typically need to grow to a certain size before they can spread to other tissues throughout the body. Angiogenesis inhibitors work by blocking the development of these new blood vessels, which limits their blood supply and impairs their growth.
Types
There are three main kinds of antiangiogenic cancer therapies, the Angiogenesis Foundation explains. True angiogenesis inhibitors work by preventing the tumor from creating new blood vessels. The second type, known as vascular targeting agents, work by blocking the blood supply that the tumor already has. Finally, some kinds of antiangiogenesis therapies attack cells in blood vessels along with cancer cells. Regardless of the mechanism, all antiangiogenesis drugs work by attempting to limit blood flow to the tumor.
Side Effects
Antiangiogenic cancer therapy typically has fewer side effects than conventional chemotherapy, the American Cancer Society explains. Conventional chemotherapy damages cells that are rapidly dividing, including healthy cells in the body. Antiangiogenic cancer therapies, on the other hand, typically only affect cancer cells since they target cells making new blood vessels and the body normally does not need to make new blood vessels on a regular basis. Antioangiogenesis drugs do raise the risk of gastrointestinal bleeding because they cause holes to develop in the stomach and intestines. Antiangiogenesis drugs can also increase blood pressure. These drugs should not be used in the first few weeks after surgery because they can impair healing.
Effects
There are eight different angiogenesis inhibitors that have been approved by the Food and Drug administration for the treatment of cancer, the Angiogenesis Foundation explains. These drugs are the first ones to be effective at treating advanced liver and kidney cancer. The exact effects of these drugs varies, however, depending on the type of cancer. These treatments are more effective against certain kinds of tumors, such as liver and kidney tumors, which need a rich blood supply. In addition, there appears to be a certain amount of variability between patients as to the effectiveness of these drugs. In some patients, tumors will stop growing or shrink in response to angiogenesis inhibitors whereas in other patients the drugs will have a much reduced effect. Researchers are trying to determine the cause for this variability, the Angiogenesis Foundation notes.
Combination
A recent movement in cancer therapy is to combine angiogenesis inhibitors with conventional chemotherapy treatments, radiation and other treatments, the American Cancer Society explains. In some cases, combining the two treatment approaches works better than either treatment used on its own. For example, some early studies found that one angiogenesis inhibitor, known as bevacizumab, did not improve survival in cancer patients. However, when combined with chemotherapy, it improved survival more than chemotherapy alone.
