Avastin Doesn’t Help Treat HER2-Positive Breast Cancer

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Doctors hoped Avastin (chemical name: bevacizumab) would be an effective breast cancer treatment when the U.S. Food and Drug Administration conditionally approved it for this use in 2008. The targeted therapy, which is also used to treat advanced-stage lung, colon, and rectum cancers, stops the growth of blood vessels that help tumors grow.

In late 2011, the FDA removed the breast cancer indication from Avastin, saying that follow-up studies hadn’t proven the drug was effective and safe for breast cancer treatment.

Still, many doctors continue to use it off-label, prescribing it to women diagnosed with breast cancer if they think the medicine will offer benefits. Most commonly, Avastin is used in combination with chemotherapy to treat metastatic breast cancer. Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.

But new research has continued to be disappointing. A study found that adding Avastin to a regimen of Herceptin (chemical name: trastuzumab) and standard chemotherapy didn’t improve the outcomes of women diagnosed with early-stage HER2-positive breast cancer.

HER2-positive breast cancers have too many copies of the HER2/neu gene, which make too much of the HER2 protein. Herceptin fights HER2-positive breast cancers by blocking the cancer cells’ ability to receive growth signals.

The study, “Primary results from BETH, a phase 3 controlled study of adjuvant chemotherapy and trastuzumab ± bevacizumab in patients with HER2-positive, node-positive or high risk node-negative breast cancer,” was presented on Dec. 11, 2013 at the 2013 San Antonio Breast Cancer Symposium by Dr. Dennis Slamon, M.D., Ph.D., of the University of California-Los Angeles. Dr. Slamon led the research team that discovered the HER2/neu gene and then developed Herceptin to treat HER2-positive breast cancers.

The BETH (Bevacizumab and Trastuzumab in HER2-Positive Breast Cancer) study looked at 3,500 women with early-stage, HER2-positive, node-positive or high-risk node-negative breast cancer. Node-positive means breast cancer was found in the lymph node(s) closest to the tumor. Node-negative means no cancer was in the lymph nodes.

After surgery to remove the cancer, the women were treated with one of two chemotherapy regimens. One regimen contained an anthracycline chemotherapy medicine and Herceptin. The other contained a non-anthracycline chemotherapy medicine and Herceptin. Anthracycline chemotherapy medicines are:

  • Adriamycin (chemical name: doxorubicin)
  • Ellence (chemical name: epirubicin)
  • Doxil (chemical name: liposomal doxorubicin)
  • daunorubicin (brand names: Cerubidine, DaunoXome)
  • mitoxantrone (brand name: Novantrone)

Anthracyclines work by damaging cancer cells’ genes and interfering with their reproduction.

Half the women were randomly assigned to also receive Avastin.

After about 3 years of follow-up, there were no differences in outcomes between women who received Avastin and women who didn’t:

  • overall survival (the time the women lived, with or without the cancer coming back) was about 96% in both groups
  • disease-free survival (the time the women lived without the cancer coming back) was about 92% in both groups

Avastin also caused more severe side effects:

  • 27% of the women who got Avastin had severe side effects
  • 8% of the women who didn’t get Avastin had severe side effects

Women who got Avastin had higher rates of high blood pressure, bleeding, heart failure, and excess protein in the urine.

The results of this study and others have convinced many doctors that Avastin adds no benefits while causing more side effects when used to treat breast cancer.

Still, not all doctors are ready to give up on using Avastin to treat breast cancer. More research is needed to figure out for exactly which types of breast cancer Avastin is a good treatment.

If you've been diagnosed with HER2-positive breast cancer, you and your doctor will develop a treatment plan that will likely include chemotherapy and targeted therapies, and possibly hormonal therapy medicines. No matter which treatments are recommended for you, you may want to talk to your doctor about:

  • why each treatment is recommended (including any combinations)
  • treatment timing and sequence
  • the expected benefits, risks, and side effects of each treatment

If you're already getting Avastin and are responding to treatment, you may want to ask your doctor about this study. It's likely that your doctor will recommend that you stick with your treatment plan unless it stops being effective or unacceptable side effects develop. If your insurance company will not cover the cost of your Avastin treatment, talk to someone on your medical team about your options for getting help to afford continuing treatment.

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