- A female patient who is a woman of child-bearing potential (WCBP) and a male patient with a partner who is a WCBP must agree to use a medically accepted method for preventing pregnancy for the duration of immunotherapy and neoadjuvant chemotherapy and until after completion of breast surgery or, for patients who do not receive neoadjuvant chemotherapy, for a minimum of 4 months following the last dose of pembrolizumab