WEDNESDAY, Jan. 25 (HealthDay News) -- The addition of the cancer-fighting medication Avastin to chemotherapy prior to breast cancer surgery increases the chance that all of the cancer will be removed, according to new research.

However, when looking at which patients might benefit the most from this therapy, two recent studies found conflicting results, and neither study was yet able to address whether or not the addition of Avastin (bevacizumab) early in the treatment process would improve survival rates.

Information on survival will be especially important for defining Avastin's role in early breast cancer treatment. That's because in November 2011, the U.S. Food and Drug Administration (FDA) revoked Avastin's approval for the treatment of breast cancer that has spread to other parts of the body. With metastatic breast cancers, the agency felt the survival benefits were lacking, and the drug carries significant risks. Avastin is, however, still FDA-approved as a treatment for some metastatic colon, brain, kidney and lung cancers.

"The bevacizumab story is not done. The addition of Avastin to neoadjuvant chemotherapy in women with operable breast cancer increased the rate of women having the disappearance of their breast cancer at the time of surgery," said Dr. Harry Bear, lead author of one of the new studies.

"With more follow-up of these trials and several others, we may find that bevacizumab actually does increase the cure rate. But, it may not be for all breast cancers; it may just be for some," said Bear, a professor and chairman of the division of surgical oncology at Virginia Commonwealth University's Massey Cancer Center in Richmond.

Results of the studies are published in the Jan. 26 edition of the New England Journal of Medicine.

Bear's study included more than 1,200 women who had been diagnosed with breast cancer. None of the women had yet had surgery to remove their tumors. All of the women had tumors that were at least 2 centimeters (about 0.8 inches) in diameter, and none had metastatic cancer.

The women received chemotherapy before surgery (neoadjuvant therapy). They were randomly assigned to treatment groups that included the chemotherapy drugs docetaxel, capecitabine and gemcitabine in various doses and combinations. They were also randomly assigned to receive Avastin or not during their first six cycles of chemotherapy.

The study found that adding capecitabine or gemcitabine to docetaxel therapy didn't improve response rates. But the addition of Avastin increased the rate of "pathological complete response" -- meaning the tumor disappeared before surgery -- from 28.2 percent to 34.5 percent, according to the study.

However, the addition of Avastin also increased the risk of serious side effects, such as high blood pressure and heart problems.

The second study, conducted in Germany, included almost 2,000 women with an average tumor size of 4 centimeters (about 1.6 inches). As in Bear's study, the women were randomly assigned to several neoadjuvant chemotherapy groups. In this study, however, treatment was with docetaxel, epirubicin and cyclophosphamide. They were also randomly assigned to receive Avastin or not.

Overall, the odds of pathological complete response were increased by 29 percent with the addition of Avastin. However, when the researchers looked at tumors by hormone receptor status, they found that it was primarily women with triple-negative cancers who showed a significant response to Avastin. Having a triple-negative breast cancer means that a cancer's growth isn't influenced by hormones such as estrogen or progesterone. If a tumor is called hormone receptor-positive, it means that hormones, such as estrogen, can help fuel that cancer's growth.

In Bear's study, the investigators found Avastin had an effect on both hormone receptor-positive and hormone receptor-negative cancers, but there appeared to be slightly more benefit for the hormone receptor-positive women.

Bear said a number of factors could explain these seemingly conflicting findings. The differences may have something to do with the women involved in each study, he said. Some of the women in the German study had more advanced cancers. And, the chemotherapy regimens weren't the same, he explained.

Commenting on the findings, Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, said that "these studies suggest that for certain patients, there may be a benefit to using Avastin prior to surgery for breast cancer."

However, Lichtenfeld added, "what we don't know from these studies is which women would benefit the most, and we don't have the long-term follow-up on these women to see if the survival or the course of the disease is improved."

Both Lichtenfeld and Bear acknowledged that because Avastin isn't FDA-approved for the treatment of breast cancers, insurance companies may be reluctant to pay for these treatments outside of a clinical trial setting.

"There still remain significant questions about the benefits of using Avastin in breast cancer," Lichtenfeld pointed out. "There is an increased risk of side effects, and there's a cost to adding this treatment. Based on these two studies, it's difficult to say whether any particular women should consider this treatment. As with many similar research findings, it's important to talk to your own doctor to get a better understanding of your potential risks and benefits," he added.

More information

To learn more about Avastin, visit the U.S. National Library of Medicine.