Dr McArthur on the Efficacy of Pembrolizumab Plus Neoadjuvant Chemo in TNBC

“In KEYNOTE-522, where pembrolizumab was added to neoadjuvant chemotherapy, it improved pathologic complete response rates, but more importantly, there were improvements in 3-year event-free survival [in patients with early triple-negative breast cancer].”

Heather McArthur, MD, MPH, FASCO, the clinical director of Breast Cancer and the Komen distinguished chair in Clinical Breast Cancer Research at the University of Texas Southwestern Medical Center, discussed the efficacy of pembrolizumab (Keytruda) plus neoadjuvant paclitaxel/carboplatin for the treatment of patients with early triple-negative breast cancer (TNBC).

The phase 3 KEYNOTE-522 trial (NCT03036488), which evaluated the efficacy and safety of pembrolizumab (Keytruda) plus paclitaxel/carboplatin vs placebo plus paclitaxel/carboplatin, demonstrated improvements in pathologic complete response rates (pCRs), McArthur began. Additionally, she noted that patients in the pembrolizumab arm (n = 784) achieved a 3-year event-free survival (EFS) rate of 84.5% (95% CI, 81.7%- 86.9%) compared with 76.8% (95% CI, 72.2%-80.7%) in the placebo arm (n = 390). Of note, data from KEYNOTE-522 supported the July 2021 FDA approval of pembrolizumab plus neoadjuvant paclitaxel/carboplatin for the treatment of patients with high-risk early TNBC, and as a single agent following surgery. Following the approval, the regimen has become standard of care for patients with TNBC, McArthur emphasized. In the trial, the overall survival (OS) data were revealed to be immature, and 10.2% and 14.1% of patients died from the pembrolizumab and placebo arms, respectively. Notably, the estimated 36-month OS rate was 89.7% (95% CI, 87.3%-91.7%) in the pembrolizumab arm compared with 86.9% (95% CI, 83.0%-89.9%) in the placebo arm.

Furthermore, in her clinical practice, chemotherapy and immunotherapy are sequenced in a similar manner to KEYNOTE-522, McArthur explained. Specifically, paclitaxel and carboplatin are given weekly, with pembrolizumab given once every 3 weeks for the first 3 months. For the subsequent 3 months, doxorubicin (Adriamycin) and cyclophosphamide are given together with pembrolizumab before patients undergo surgery, McArthur concluded.