On July 26, 2021, the FDA accelerated the approval of a new indication for the PD-1 inhibitor pembrolizumab (Keytruda; Merck), for the treatment of patients with high-risk, early-stage triple-negative breast cancer (TNBC) in combination with chemotherapy as a neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery.
“Even when TNBC is diagnosed early, 30% to 40% of patients will suffer cancer recurrence after standard neoadjuvant chemotherapy and surgery,” said Joyce O’Shaughnessy, MD, Chair, Breast Cancer Prevention Research, Baylor University Medical Center Texas Oncology/US Oncology Network, Dallas, in a press release. “Therefore, there is a high unmet need for new treatment options. [This] approval is very welcome news and has the potential to change the treatment paradigm by now including an immunotherapy as part of the regimen for patients with high-risk early-stage TNBC.”
This new indication is based on results of the randomized, multicenter, phase 3 KEYNOTE-522 trial, which included 1174 patients with newly diagnosed, previously untreated, high-risk, early-stage TNBC. Patients were randomized in a 2:1 ratio to pembrolizumab plus chemotherapy (N = 784) or placebo plus chemotherapy (N = 390).
The primary end points were pathologic complete response rate and event-free survival. Secondary end points included overall survival, efficacy in the subset of patients with PD-L1–positive disease, and safety. The pathologic complete response rate was 63% (95% CI, 59.5%-66.4%) for patients in the pembrolizumab plus chemotherapy arm versus 56% (95% CI, 50.6%-60.6%) for those in the chemotherapy-alone arm. The number of patients who experienced an event-free survival was 123 (16%) and 93 (24%), respectively.
The most common (≥20%) adverse reactions were fatigue (70%), nausea (67%), alopecia (61%), rash (52%), constipation (42%), diarrhea and peripheral neuropathy (41% each), stomatitis (34%), vomiting (31%), headache (30%), arthralgia (29%), pyrexia (28%), cough (26%), abdominal pain (24%), decreased appetite (23%), insomnia (21%), and myalgia (20%).