Doctors sometimes find that the outcomes of women diagnosed with breast cancer that are treated in a "real world" setting are different than the outcomes reported in clinical trials. A study found that the real world survival statistics of women diagnosed with metastatic breast cancer and treated with chemotherapy and Avastin (chemical name: bevacizumab) were similar to the survival statistics of women in clinical trials looking at the same treatment combination. Metastatic breast cancer is cancer that has spread to parts of the body away from the breast.
These results were presented at the 2010 San Antonio Breast Cancer Symposium (SABCS).
Avastin is a targeted therapy medicine that is given intravenously. Avastin works by blocking the growth of new blood vessels that cancer cells need to grow and function. A protein called vascular endothelial growth factor (VEGF) makes new blood vessels grow in cancer cells. Avastin blocks the VEGF protein.
Avastin is currently approved by the U.S. Food and Drug Administration (FDA) to be used in combination with Taxol (chemical name: paclitaxel) to treat metastatic, HER2-negative breast cancer that hasn't been treated with chemotherapy. Avastin also is used to treat advanced-stage lung, colon, and kidney cancer.
In December 2010, the FDA decided to recommend removing the breast cancer indication for Avastin because newer results suggested that the benefits of Avastin don't outweigh the risks. This recommendation is being appealed by the company that makes Avastin.
In this study, called ATHENA, 2,264 women diagnosed with metastatic breast cancer between September 2006 and March 2009 were treated with Avastin and one or more chemotherapy medicines. More than 580 women (26%) were diagnosed with triple-negative breast cancer. Triple-negative breast cancer is:
Overall, about 15% to 20% of breast cancers are triple-negative. Triple-negative cancers are usually more aggressive and harder to treat than cancers that are hormone-receptor-positive and/or HER2-positive. Hormonal therapy and the targeted therapies Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib) usually don't work on triple-negative breast cancer.
The ATHENA study was NOT designed to show that using Avastin was better than not using Avastin. Instead, the researchers compared the outcomes of women in the ATHENA study to the outcomes of women in earlier studies that compared the benefits of using Avastin to treat breast cancer to the benefits of not using it.
Most of the women in the ATHENA study received one of two taxane chemotherapy medicines with Avastin:
- 34% got paclitaxel (brand names: Taxol)
- 33% got docetaxel (brand name: Taxotere)
Other women got different chemotherapy medicines.
- 11% got a combination of taxanes
- 5% got Xeloda (chemical name: capecitabine)
Like the earlier Avastin trials, the regimens with Avastin given to all the women in ATHENA were the first treatment they got for metastatic cancer. Doctors call this first-line treatment.
Overall, the average survival time of the women in ATHENA (25.2 months) was similar to the survival time in earlier studies on Avastin (25.2 to 30.2 months). Average survival time for women with triple-negative cancer was 18.3 months and average survival for women age 70 or older was 20.5 months.
The percentages of women diagnosed with different types of breast cancers or specific groups of women who survived for at least 1 year were:
- 59.8% of women diagnosed with triple-negative cancer
- 77.3% of women diagnosed with cancer that wasn't triple-negative
- 68.2% of women age 70 or older
- 73.0% of women younger than 70
Side effects in the ATHENA study were similar to those in the earlier Avastin studies. Avastin side effects include high blood pressure, bleeding (nosebleeds, for example), and extra protein in the urine. People treated with Avastin also may have weakness, pain, and diarrhea. Avastin also may cause other serious side effects, including a higher risk of stroke or heart problems, kidney malfunction, and reduced white blood cell count (neutropenia), which can increase the risk of serious infection.
Although the ATHENA study results showed overall survival statistics similar to survival statistics in earlier Avastin studies, no study has ever shown that adding Avastin to a standard chemotherapy regimen increases overall survival. This means that women live for about the same amount of time whether or not they get Avastin.
Research has shown that combining Avastin with one of several chemotherapy medicines lengthens the time before the cancer grows or spreads (progression-free survival). Still, many experts believe that the small improvement in progression-free survival with no improvement in overall survival isn't meaningful, especially when considering the risk of serious side effects. Also, using Avastin to treat metastatic breast cancer has not been shown to ease metastatic breast cancer symptoms. These reasons are why the FDA decided to recommend removing the breast cancer indication for Avastin.
But many doctors believe that the benefits of Avastin for certain women diagnosed with metastatic breast cancer are worth the risks of treatment. Doctors can choose to use Avastin to treat metastatic breast cancer whether or not that particular use is officially approved by the FDA. Still, loss of approval can make it less likely that insurers will pay for Avastin to treat breast cancer.
If you've been diagnosed with metastatic breast cancer, you and your doctor will develop a treatment plan that will likely include chemotherapy and possibly hormonal therapy and/or targeted 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 the FDA recommendation. It's likely that your doctor will recommend that you stick with your treatment plan unless it stops being effective or you have severe side effects.
Stay tuned to Breastcancer.org Research News for updates on the FDA recommendation regarding Avastin.