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Avastin Helps Reduce Cancer Growth but Increases Side Effects and Doesn’t Improve Survival

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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 advanced-stage breast cancer.

But continuing research has continued to be somewhat disappointing. A study found that combining Avastin with the hormonal therapy Femara (chemical name: letrozole) improved disease-free survival in women diagnosed with advanced-stage, hormone-receptor-positive breast cancer. Still, adding Avastin didn’t improve overall survival and caused more side effects.

The study was presented on June 1, 2015 at the American Society of Clinical Oncology Annual Meeting. Read the abstract of “Phase III trial evaluating the addition of bevacizumab to letrozole as first-line endocrine therapy for treatment of hormone-receptor-positive advanced breast cancer: CALGB 40503 (Alliance).”

Disease-free survival is how long a woman lives without the cancer growing. Overall survival is how long a woman lives with or without the cancer growing.

This study involved 343 postmenopausal women diagnosed with advanced-stage, hormone-receptor-positive breast cancer that hadn’t been treated with hormonal therapy. The cancers were either locally advanced, meaning they had spread beyond the breast to nearby tissue such as the skin or the chest wall, or they were metastatic, meaning they had spread to parts of the body away from the breast, such as the bones or liver.

The women were randomly assigned to get either:

  • Femara alone (2.5 mg per day)
  • Femara plus Avastin (15 mg/kg every 3 weeks)

Femara is a pill, usually taken once per day. Avastin is given intravenously, which means it is dripped into your body through a needle inserted into a vein.

After slightly more than 3 years of follow-up, the researchers found that women who got Femara plus Avastin had better progression-free survival than women who got only Femara:

  • progression-free survival was 20 months for women who got Femara plus Avastin
  • progression-free survival was 16 months for women who got Femara alone

This difference was statistically significant, which means that it was likely due to the difference in treatment rather than just because of chance.

The researchers also found that more of the women who got Femara plus Avastin -- 69% -- responded to the treatment compared to 49% of the women who got Femara alone. This difference also was statistically significant.

Still, the women who got Avastin didn’t live any longer than the women who didn’t get Avastin.

Women who were treated with Femara and Avastin also experienced more side effects:

  • 24% of the women who got Femara and Avastin developed high blood pressure compared to 2% of the women who got only Femara
  • 11% of the women who got Femara and Avastin had proteinuria (excess protein in the urine) compared to none of the women who got only Femara

The side effects were also more severe for women getting Femara and Avastin:

  • about 50% of women getting Femara and Avastin reported a grade 3, 4, or 5 side effect
  • less than 14% of women getting Femara alone reported a grade 3, 4, or 5 side effect

More women getting the Femara-Avastin combination also stopped treatment because of side effects:

  • 21 women getting Femara and Avastin stopped treatment
  • 2 women getting Femara alone stopped treatment

The results of this and other studies have persuaded 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 advanced-stage, hormone-receptor-positive breast cancer, you and your doctor will develop a treatment plan that will likely include hormonal therapy, and possibly targeted therapy and chemotherapy 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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