Marabelle A, Le DT, Ascierto PA, et al. - Given the identified antitumor activity of pembrolizumab, an anti–programmed death-1 monoclonal antibody, against high microsatellite instability (MSI-H)/DNA mismatch repair (dMMR) cancer, researchers here sought to report data from the phase II KEYNOTE-158 study of pembrolizumab in patients with previously treated, advanced noncolorectal MSI-H/dMMR cancer. Pembrolizumab 200 mg was provided once every 3 weeks to eligible patients with histologically/cytologically confirmed MSI-H/dMMR advanced noncolorectal cancer who experienced failure with prior therapy. Enrollment of 233 patients was done; these patients represented 27 tumor types, with endometrial, gastric, cholangiocarcinoma, and pancreatic cancers being the most common. During the median follow up of 13.4 months, objective response rate of 34.3% was observed (95% CI, 28.3% to 40.8%). Outcomes support the use of pembrolizumab for treating previously treated MSI-H/dMMR advanced noncolorectal cancer, regardless of anatomic site or origin or tumor histology. A complete response was observed in nearly one-third of patients with an objective response. Most importantly, durable tumor responses were noted: the median duration of response has not yet been reached and it was determined that more than three-quarters of responders have had durable responses of 24 months or longer in a Kaplan-Meier analysis. Encouraging results regarding progression-free survival and overall survival were observed. They estimated 24-month overall survival rate of 48.9%.