Pembrolizumab vs. Observation in People With Triple-negative Breast Cancer Who Had a Pathologic Complete Response After Chemotherapy Plus Pembrolizumab

Adverse events will be determined using the latest version of the Common Terminology Criteria for Adverse Events (CTCAE). The proportions of patients with a grade 3 or higher AE will be compared between the arms using a chi-square test. A similar analysis will be done to compare the grade 3 or higher irAE rates

Defined as the time from randomization to death due to any cause. OS will be compared between treatment arms using the hazard ratio (and stratified log-rank test) from a stratified Cox model

Defined as the time from randomization to first invasive local or regional recurrence. The cumulative incidence of LRR will be compared between treatment arms using a log-rank test (and estimated using Kaplan-Meier curves).

Radiation adverse events include pneumonitis, hypothyroidism and dermatitis. Radiation AE event rates will be determined for patients who received radiation. The numerator is the number of patients with the radiation AE and the denominator is the number of patients who received radiation. The analysis of the radiation related adverse event rates will only include patients who received radiation treatment. The radiation AE rates will be compared between the two arms using a chi-square test.