The 37th annual San Antonio Breast Cancer Symposium (SABCS) took place on December 9-13. The annual five-day program provides a forum for communication and education in breast cancer research.
Read on for part two of our four-part series of the most compelling research presented at the conference. Did you miss part one? Read it here.
Cancer immunotherapy was a hot topic at SABCS. The recent success of new PDL-1 inhibitors — drugs that prevent tumors from shutting down the body’s anti-tumor immune response — in other cancers have spurred similar studies in breast cancer.
Clinical trials to test PDL-1 inhibitors in combination with other immune-therapy approaches and standard chemotherapies are ongoing. While it’s too early to tell whether these therapies will be as successful in breast as they have been for some other cancers, particularly advanced melanoma, early results from one study in advanced breast cancer suggest a durable response.
Many in the field including Dr. Nora Disis of Seattle’s University of Washington, caution that, in some patients receiving immunotherapy, tumors will continue to grow before responding to the therapy. These observations, which have been reported in other immunotherapy trials, suggest that early study time points may not accurately predict a clinical benefit of the treatment.
Anti-PDl-1 therapies are just one immunotherapy approach. Other strategies to boost anti-tumor immunity may emerge, as scientists better understand the tumor immune microenvironment and how immune programs are activated through therapy.
Tumor infiltrating lymphocytes (TILs) are white blood cells dispersed among tumor cells and are an active area of research. Studies discussed at SABCS suggest TILs’ presence influences how well tumors respond to some therapies.
While the effect of TILs on cancer outcomes has not been confirmed, several studies have reported that triple negative breast cancers respond better to chemotherapy when high concentrations of TILs are present. Dr. Edith Perez presented data in HER2+ patients, in which the presence of TILs improved response to chemotherapy, but not to the anti-HER2 drug Herceptin™.
These studies, while preliminary, are laying the groundwork for the development of immune biomarkers that may help predict or inform an individual’s response to treatment, as well as possible strategies to boost anti-tumor immunity and the body’s natural ability to fight cancer.
Combination therapies will be key to the success of immunotherapy. Response rates in melanoma patients increased by 50-60 percent with combination immunotherapies and Dr. Disis believes the same will be true for breast cancer patients. The Breast International Group announced at SABCS it will be launching a trial to test the combination of an anti-PD-1 therapy and Herceptin in patients with HER2+ breast cancer whose cancer has spread while on treatment with Herceptin™.
Another class of drugs that has yielded considerable excitement in the research community is the CDK4/6 inhibitors. These drugs act to block tumor proliferation by interfering with the signals that allow tumor cells to divide. One of these drugs, palbociclib, more than doubled progression-free survival in ER+ breast cancers that had progressed on anti-hormone therapies. Palbociclib is currently on fast track by the FDA and is expected to be approved in 2015.
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