The use of baseline tumor size to prognosticate overall survival in stage IV melanoma patients treated with the PD-1 inhibitor pembrolizumab

Historically patients who developed stage IV melanoma were expected to live less than one year. Clinical outcome was heterogeneous as evidenced by a tail end to the overall survival (OS) curve which identifies a small subset of patients, encompassing less than 10% of the total population, who are long term survivors (1).