Pembrolizumab was evaluated in a phase 2 trial with 20 patients with LM, of whom 17 out of 20 from BC (6 patients with HER2-positive BC), with a 3 month-OS of 60%, and a median OS of 3.6 months (90% CI 2.2–5.2 months) [30]. The gene discussed is ERBB2; the disease is breast cancer.