Priya Rastogi, MD, Associate Professor of Medicine at the University of Pittsburgh Medical Center, discussed the findings at the session. She noted that previous studies have also shown higher pathologic complete response rates among HER2-enriched patients who were hormone receptor–negative, and higher rates in more aggressive subtypes. “CALGB 40601 is consistent with research from similar studies demonstrating increased pathologic complete responses with dual blockade plus chemotherapy, vs single agents,” at least in a subset of patients, she said.

She noted that the study was most similar to NSABP B-41, as in both studies the trastuzumab/chemotherapy arm performed better than anticipated. In NSABP B-41, pathologic complete response rates were 52.5% with trastuzumab and 62% with dual blockade (P = .095), while in the current study these rates were 46% and 56%, respectively (P = .12).

In general, dual blockade consistently increases pathologic complete response rates, reaching 61% to 77% in the hormone receptor–negative subtype, she noted. But dual blockade also adds toxicity and expense, and since it does not benefit all patients, researchers must identify a means of predicting which patients benefit from it, she added. ■

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