Dr. Tolaney on the Need to Develop Additional Biomarkers in mTNBC

Sara M. Tolaney, MD, MPH, associate director, Susan F. Smith Center for Women’s Cancers, director of Clinical Trials, Breast Oncology, and senior physician, Dana-Farber Cancer Institute, and an assistant professor of medicine, Harvard Medical School, discusses the need to develop additional biomarkers of response in metastatic triple-negative breast cancer (mTNBC).

The introduction of immunotherapy, such as atezolizumab (Tecentriq) and pembrolizumab (Keytruda), has been a welcome addition to the mTNBC armamentarium, says Tolaney. However, additional biomarkers of response to immunotherapy beyond PD-L1 expression are needed, Tolaney explains. Moreover, not all PD-L1–positive patients will benefit from immunotherapy and many patients who do respond initially will eventually develop resistance to therapy.

Early research efforts with targeted sequencing panels suggested that high tumor mutational burden (TMB) and loss of PTEN could be predictive biomarkers of benefit and resistance for patients with mTNBC, Tolaney explains. Specifically, high TMB appeared to be associated with improved progression-free survival and overall survival, whereas PTEN loss appeared to confer lack of benefit to immunotherapy, concludes Tolaney.