Pembrolizumab (Keytruda, Merck) plus chemotherapy demonstrated a statistically significant improvement in pathological complete response rate (pCR) as a neoadjuvant therapy in patients with triple-negative breast cancer (TNBC), according to new data from a phase 3 study.
 
Approximately 15% to 20% of patients with breast cancer are diagnosed with TNBC, which can be more difficult to treat than other breast cancer subtypes, according to Merck.
 
The KEYNOTE-522 clinical trial is investigating pembrolizumab in combination with chemotherapy compared with chemotherapy alone as a neoadjuvant therapy, followed by pembrolizumab compared with placebo as adjuvant therapy in patients with TNBC. A total of 1174 patients participated in the study.
 
Patients received either:
  • Pembrolizumab (every 3 weeks) plus paclitaxel (weekly) and carboplatin (weekly or every 3 weeks) for 4 cycles as neoadjuvant therapy prior to surgery, followed by 9 cycles of pembrolizumab (every 3 weeks) as adjuvant therapy post-surgery.
  • Placebo (every 3 weeks) plus paclitaxel (weekly) and carboplatin (weekly or every 3 weeks) for 4 cycles, followed by placebo plus cyclophosphamide and either doxorubicin or epirubicin (every 3 weeks) for 4 cycles, followed by 9 cycles of placebo (every 3 weeks) as adjuvant therapy post-surgery. 
Based on an interim analysis, pembrolizumab in combination with chemotherapy demonstrated a statistically significant improvement in pCR rates compared with chemotherapy alone, regardless of PD-L1 status, according to the data.
 
“These findings from this innovatively designed trial with Keytruda mark the first time an anti-PD-1 therapy plus chemotherapy has demonstrated a statistically significant improvement in pathological complete response rate as a neoadjuvant, or pre-surgical, segment of treatment for triple-negative breast cancer,” Roger M. Perlmutter, MD, PhD, president of Merck Research Laboratories, said in a statement. “TNBC is an aggressive malignancy with a high rate of recurrence within the first 5 years of diagnosis. We are encouraged by these results and plan to discuss these data with health authorities and to present these findings at an upcoming medical congress.”
 
According to Merck, the trial will continue without changes to evaluate the other dual-primary endpoint of event-free survival, per the trial design.
 
Reference
Merck’s Keytruda (pembrolizumab) in Combination with Chemotherapy Met Primary Endpoint of Pathological Complete Response (pCR) in Pivotal Phase 3 KEYNOTE-522 Trial in Patients with Triple-Negative Breast Cancer [news release]. Merck. https://www.mrknewsroom.com/news-release/oncology/mercks-keytruda-pembrolizumab-combination-chemotherapy-met-primary-endpoint-pa. Accessed July 29, 2019.