Leisha A. Emens, MD, PhD

Leisha A. Emens, MD, PhD, of the Bloomberg~Kimmel Institute for Cancer Immunotherapy at Johns Hopkins University, commented on the promise of anti–programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) agents in triple-negative breast cancer. She noted that “an emerging theme across multiple small data sets” is that response rates may be higher in previously untreated patients. It also seems that PD-L1 expression is associated with a higher likelihood of response, although responses in PD-L1–negative patients may still occur. 

“PD-L1 is an imperfect biomarker. It appears to enrich for response, but the context is quite important,” she said. In addition, for patients with advanced breast cancer, first-line treatment checkpoint inhibition may be more beneficial. 

These data in metastatic disease presented at the ASCO Meeting reflect the data for another checkpoint inhibitor, atezolizumab (Tecentriq), reported at the 2017 American Association of Cancer Research Meeting. Of 112 patients, the response rate was 10%, rising to 13% among patients who had PD-L1–positive disease and dropping to 5% among the PD-L1–negative cohort. Previously untreated patients responded better, with a 26% rate. Both 1- and 2-year overall survival rates were 100% for responders. In contrast, the 1-year survival rate was 69% for patients with stable disease and 33% for those with disease progression. 

“Early data suggest the best survival benefit is seen with complete and partial responders, and there is also some survival benefit with stable disease, relative to progressive disease,” Dr. Emens said. 

More Thoughts on Pembrolizumab 

In an interview, Harold Burstein, MD, Associate Professor of Medicine at Harvard Medical School and a breast cancer specialist at Dana-Farber Cancer Institute, Boston, also shared his thoughts on pembrolizumab. “The low response rate as a single agent suggests there may be a role for pembrolizumab, but we will have to figure out how to give it with other drugs,” he said. 

Referring to the I-SPY 2 data, he noted the high rates of pathologic complete response when given with chemotherapy. “It’s a clue that giving chemotherapy and the checkpoint inhibitors may be the way to go in triple-negative breast cancer,” added Dr. Burstein. ■

DISCLOSURE: Dr. Emens is a consultant and on the advisory board for Celgene, Vaccinex, Amgen, AstraZeneca, Syndax, Peregrine, Bayer, ETHeRNA, Molecuvax, and Gritstone; has received research funding from Genentech, Roche, EMD Serono, MaxCyte, Merck, AstraZeneca, Aduro Biotech, and Corvus; and has received royalties from Aduro INC Licensing/vaccine. Dr. Burstein reported no conflicts of interest.