Highlights from the San Antonio Breast Cancer Symposium 2009: An Update

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A recap of the 2008 San Antonio Breast Cancer Symposium.

Many women develop breast tumors that are sensitive to estrogen—a female hormone that can feed a tumor’s growth and development. So for the past 15 years, researchers have experimented with hormonal drugs to figure out which drugs work best, how they should be sequenced (if giving more than one hormonal agent), and how long they should be taken.

In February 2008, Avastin (bevacizumab) received approval for metastatic breast cancer, despite the fact that an advisory panel for the FDA said the drug did not offer enough benefit (specifically in survival) to justify its use. Hoping to more clearly define the potential and the limits of the drug, researchers have continued testing Avastin in breast cancer, including as second-line therapy.

New data from the RIBBON-2 trial involved 684 women with HER2-negative metastatic breast cancer who had already received one course of chemotherapy. The women received another session of chemotherapy with or without Avastin.

The results: Adding Avastin to chemotherapy as a second-line treatment increased progression-free survival—the length of time the disease did not worsen—by approximately two months (from 5.1 months to 7.2 months). Furthermore, the RIBBON-2 study has not found an improvement in overall survival with the addition of Avastin, but 43 percent of women in the study were still alive.

In July, an FDA advisory panel met and recommended revoking the approval due to the disappointing results from RIBBON-2 and other more recent Avastin trials. A previous study had shown progression-free survival increase of about five months—data on which the FDA had originally based its accelerated approval decision. The FDA is expected to make a decision on Avastin by Dec. 17.

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Scientists at the 2009 San Antonio Breast Cancer Symposium reported on women who initially started on the aromatase inhibitor Aromasin (exemestane) did no better than the women who switched to Aromasin later from tamoxifen. Regarding the likelihood of cancer recurring or a difference in survival, researcher Daniel Rea, MD, of the University of Birmingham said, "There is no difference whatsoever."

Another study examined whether being premenopausal at diagnosis made a difference in outcomes. All women were menopausal during the study, either naturally, because of surgical removal of the ovaries or because of chemotherapy treatment. Premenopausal women who took tamoxifen for five years, followed by another aromatase inhibitor called Femara (letrozole), were less likely to have a recurrence than women who took only tamoxifen for the initial five years.

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Taking Herceptin (trastuzumab) with, as opposed to after, chemotherapy helped more women live longer without a recurrence, new research found.

Investigators randomly assigned roughly 3,000 patients with stage 1 to stage 3 HER2-positive breast cancer who had already undergone surgery to receive either chemotherapy alone (Adriamycin [doxorubicin] and cyclophosphamide followed by Taxol [paclitaxel]), chemotherapy followed by Herceptin or chemotherapy given with Herceptin (paired with Taxol).

Herceptin after chemotherapy outperformed chemotherapy alone, but simultaneous use proved superior to both. For the 954 women who received Herceptin after chemotherapy, 79.8 percent were alive and free of recurrence after five years. In the 949 women given Herceptin at the same time as chemotherapy, 84.2 percent were recurrence-free at five years, a difference that is statistically significant. Only approximately 3 percent of patients in each Herceptin arm experienced heart toxicity.

Because the Food and Drug Administration-approved use of Herceptin allows for either approach, these data suggest Herceptin should be given at the same time as chemotherapy, said lead investigator Edith Perez, MD, of the Mayo Clinic in Florida, at a press briefing.

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Advanced breast cancer patients taking Xgeva (denosumab) not only had fewer bone complications, but these complications also took longer to develop compared with Zometa (zoledronic acid).

For the 2,046 patients given either Xgeva or Zometa, Xgeva reduced the risk of developing a single skeletal-related event (SREs), such as a fracture, the need for radiation or surgery to the bone or spinal cord compression, by 18 percent compared with Zometa. Xgeva also reduced the risk of developing multiple SREs by 23 percent. In total, there were 474 SREs in 30.7 percent of patients in the Xgeva group versus 608 events in 36.5 percent of patients on Zometa. Plus, Xgeva better controlled bone pain, with a median of 88 days until patients experienced moderate or severe pain, compared with 64 days with Zometa.

A small percentage of patients in both arms experienced jawbone damage, known as osteonecrosis of the jaw (2 percent with Xgeva and 1.4 percent with Zometa) or kidney problems (4.9 percent and 8.5 percent, respectively).

Based on the data from this and other studies, the FDA approved Xgeva in November to help prevent SREs in patients with cancer that has spread to the bone.

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