These results are promising. The fact that there were two patients with a complete response caught my eye. This is very exciting in metastatic triple-negative breast cancer. These were heavily pretreated patients; 85% had more than four lines of prior therapy,” said Aditya Bardia, MD, a breast medical oncologist at Massachusetts General Hospital, Harvard Medical School, Boston.

Dr. Bardia added, we need to be mindful of three things. First, while there is no doubt immunotherapy is promising, one should note the study is small (less than 100 patients), single-arm, and MPDL3280A cannot be considered the standard of care yet. Also, while PD-L1 is a potential biomarker, we need other biomarkers that can help predict the likelihood of response and help more breast cancer patients get the “home-run.” Second, up to 55% of patients had adverse events, including some patients with grade 3 and 4 toxicity, and risk of autoimmune conditions is real. We need more data to characterize the efficacy and safety of this drug. Third, there are other anti–PD-L1 and anti–PD-1 immunotherapy agents under development, and it is not clear whether MPDL3280A will be better than these agents and what the best combination and sequence strategy should be. Some of these issues are being investigated in clinical trials and the results are eagerly awaited. ■

Disclosure: Dr. Bardia reported no potential conflicts of interest.