Marcus Butler, MD, from the Princess Margaret Cancer Centre, Toronto, Canada, discusses data on the efficacy of pembrolizumab treatment in advanced mucosal melanoma, which he presented at the European Cancer Congress of the European Cancer Organisation (ECCO) 2017 in Amsterdam, Netherlands. This type of melanoma develops for unknown reasons unrelated to UV light exposure, and historically has a lower response rate and overall survival (OS) following various treatments. The development of new melanoma treatments, particularly immunotherapy, led Dr Butler to investigate the efficacy of these in mucosal melanoma by combining the results from the KEYNOTE-001 (NCT01295827), KEYNOTE-002 (NCT01704287), and KEYNOTE-006 (NCT01866319) studies for patients with advanced mucosal melanoma. He discusses the results, which indicate that mucosal melanoma patients benefit from pembrolizumab treatment. While the response rate is lower than for melanoma patients, Dr Butler argues that the effect is still clinically meaningful, and may be a good choice particularly as anti-PD-1 therapy has very few side effects and is well tolerated by the majority of patients.