Breast Cancer Coverage from Every Angle

Pathologic Complete Response With Pembrolizumab for Triple-Negative Breast Cancer

By: Cordi Craig
Posted: Tuesday, April 7, 2020

According to the phase III, double-blind KEYNOTE-522 trial, published in The New England Journal of Medicine, patients with early triple-negative breast cancer who were treated with pembrolizumab plus neoadjuvant chemotherapy achieved significantly higher pathologic complete responses than those patients who received placebo plus neoadjuvant chemotherapy. Peter Schmid, MD, of Queen Mary University of London, and colleagues observed the benefits of pembrolizumab across most risk categories, including those with low PD-L1 expression.

In a 2:1 ratio, the research team randomly assigned a total of 1,174 patients with previously untreated stage II or III triple-negative breast cancer from 181 sites across 21 countries. Patients were assigned to receive neoadjuvant pembrolizumab plus chemotherapy (n = 784) or placebo plus chemotherapy (n = 390).

Among the first 602 patients who were randomly assigned, significantly more patients treated with pembrolizumab achieved a pathologic complete response compared with those who received the placebo (64.8% vs. 51.2%, respectively; P < .001). After a median follow-up of 15.5 months, 7.4% of 58 patients in the pembrolizumab arm versus 11.8% of 46 patients in the placebo arm experienced disease progression that precluded surgery, had local or distant recurrence or a secondary primary tumor, or died of any causes.

The incidence of treatment-related adverse events was similar between the two groups. Grade 3 or higher treatment-related adverse events were reported in 78% of patients in the pembrolizumab group and 73% of those in the placebo group. Overall, three patients (0.4%) in the pembrolizumab arm died, and a single patient (0.3%) in the placebo arm died.

“The short duration of follow-up at this early time point precludes the assessment of mature survival data and the long-term safety profile, both of which are important considerations in patients receiving potentially curative treatment,” the investigators noted.

Disclosure: For full disclosures of the study authors, visit

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