Baseline tumor size as an independent prognostic factor for overall survival in patients with metastatic melanoma treated with the anti-PD-1 monoclonal antibody MK-3475.

3015 Background: We explored baseline tumor size (BTS) as a prognostic factor in addition to standard prognostic variables for overall survival (OS) in pts with metastatic melanoma treated with MK-3475. Methods: In a phase I clinical trial, 411 pts received MK-3475 2 mg/kg Q3W, 10 mg/kg Q3W, or 10 mg/kg Q2W. Response was assessed every 12 wk by RECIST 1.1 by independent central review. BTS was quantified as the sum of the longest dimensions of all RECIST target lesions. Log-rank, Kaplan-Meier (KM), and Cox proportional hazards regressions were used to identify independent prognostic factors for OS. Cutpoints and combinations of prognostic factors were determined by binary tree analysis. Results: Of the 411 melanoma pts studied, 365 had measurable tumors at baseline and a median follow-up duration of 10 mo as of the 10/18/2013 cutoff date. Median OS was not reached, and 1-y OS was 71% in all 411 pts and 69% in the 365 pts included in this analysis. By univariate analysis, the following traditional factors ...