Avastin Ups Blood Clot Risk

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A study found that people who got Avastin (chemical name: bevacizumab) as part of a cancer treatment plan were about 30% more likely to develop a serious blood clot in a vein compared to people being treated for the same type of cancer who didn't get Avastin. Doctors call a blood clot in a vein a venous thromboembolism.

Avastin is a targeted therapy approved by the U.S. Food and Drug Administration to be used in combination with Taxol (chemical name: paclitaxel) to treat people with advanced (metastatic) HER2-negative breast cancer who haven't yet received chemotherapy. Avastin also is used to treat other advanced cancers, including lung, colon, and kidney cancer. Avastin is given intravenously.

Avastin works by blocking the growth of new blood vessels in a cancer tumor. (Growing new blood vessels is called angiogenesis). With no new blood vessels, the cancer doesn't get the nutrients it needs to grow. Cancer cells can make a protein, called vascular endothelial growth factor (VEGF), to make angiogenesis happen. Avastin blocks the VEGF protein. Researchers think that blocking the VEGF protein may make blood clots in veins more likely to form, which is why the risk of venous thromboembolism is higher in people treated with Avastin.

Common side effects of Avastin include high blood pressure, nosebleeds, and extra protein in the urine. People treated with Avastin also may have weakness, pain, and diarrhea. Other possible side effects are more serious, including a higher risk of stroke or heart problems, kidney malfunction, and reduced white blood cell count.

Doctors thought Avastin might increase the risk of developing a serious blood clot in a vein, but the research results were mixed. The results from the study reviewed here strongly suggest that Avastin DOES increase the risk of a blood clot in a vein.

The researchers looked at information from 15 studies involving almost 8,000 people being treated with Avastin for cancer (including breast cancer). Overall, the risk of getting a blood clot in a vein was about 30% higher in people treated with Avastin compared to people who didn't get Avastin. But the increase in blood clot risk was different depending on the type of cancer being treated. The highest risk of a blood clot was seen when Avastin was used to treat colon cancer and certain lung cancers. The risk of a blood clot wasn't as high when Avastin was used to treat breast cancer.

Symptoms of blood clots in the leg or the arm include:

  • pain
  • swelling
  • warmth, redness, and tenderness over the vein (called phlebitis)

A blood clot that breaks free and travels to the lungs can be serious and even life threatening. A blood clot in the lungs can cause chest pain, shortness of breath, and a decrease in blood oxygen levels. These symptoms can develop suddenly or gradually over time.

People being treated for breast and other cancers have a higher than average risk of developing venous thromboembolism. Many factors add to this higher risk:

  • the cancer itself
  • surgery, particularly when lymph nodes are removed
  • a decrease in physical activity during recovery from surgery and during other treatments
  • cancer treatments, including chemotherapy, targeted therapy, and hormonal therapy

The best way to deal with a blood clot in a vein is to stop it from happening. Talk to your doctor about your venous thromboembolism risk and ask how you can manage that risk.

Visit the blood clots page in the Breastcancer.org Side Effects section to read some general tips on how to prevent blood clots.

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