Evaluation of immune-related response criteria (irRC) in patients (pts) with advanced melanoma (MEL) treated with the anti-PD-1 monoclonal antibody MK-3475.

3006^ Background: Unique response patterns have been observed with immunotherapies, and both objective response and prolonged disease stabilization can occur after an initial increase in tumor size. irRC were developed to better characterize response to immunotherapy, but it is unclear how irRC perform in pts treated with PD-1 blockade. Here, we describe unique patterns of response to MK-3475 in MEL pts and evaluate irRC as an alternative criterion for comprehensive response assessment. Methods: Source population was pts from 3 MEL cohorts treated with MK-3475 2 mg/kg every 3 wk (Q3W), 10 mg/kg Q3W, or 10 mg/kg Q2W in a phase I trial. Tumor imaging was performed every 12 wk. Response was assessed by irRC and RECIST 1.1 by central review; irRC was used for pt management. Tumor flare and atypical delayed response were identified by using centrally assessed irRC data among pts on MK-3475 for ≥28 wk. Tumor flare was defined as unconfirmed PD at assessment 1 (ie, wk 12) and non-PD at assessment 2. Atypical del...