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TIL Levels and Response to Pembrolizumab in Metastatic Triple-Negative Breast Cancer

By: Meg Barbor, MPH
Posted: Tuesday, October 3, 2017

Increased tumor-infiltrating lymphocyte (TIL) levels may be associated with a greater response to pembrolizumab monotherapy in patients with metastatic triple-negative breast cancer, particularly in the first-line setting. These findings are based on the phase II KEYNOTE-086 trial, which was presented by Sherene Loi, MD, of Peter MacCallum Cancer Center, Melbourne, at the 2017 European Society for Medical Oncology (ESMO) Congress (Abstract LBA13).

Researchers analyzed data on pembrolizumab monotherapy in approximately 200 patients with previously treated metastatic triple-negative breast cancer. These patients had any programmed cell death ligand 1 (PD-L1) expression (cohort A) or had previously untreated PD-L1–positive disease (cohort B). A total of 147 samples and 46 samples were obtained from cohorts A and B, respectively.

Higher median TIL levels were observed in cohort B compared with cohort A (17.5% vs. 5%) and in lymph node vs. non–lymph node samples (10% vs. 5%).

Response to pembrolizumab treatment showed a significant relationship to TIL levels. For instance, in cohort A, the overall response rate in patients with at least median TIL levels was 6%, compared with 2% in patients who had less than median TIL levels; in cohort B, the overall response rate was 39% in those with at least median TIL levels versus 9% in those who had less than median TIL levels. The median TIL level in responders compared with nonresponders was 10% versus 5% in cohort A and 50% versus 15% in cohort B.