People with advanced melanoma treated with pembrolizumab had different reported responses depending on the tool used to measure that response, according to a study involving 655 individuals.

Participants took pembrolizumab 2 or 10 mg/kg every 2 or every 3 weeks. Investigators measured atypical response patterns and survival using immune-related response criteria (irRC) and Response Evaluation Criteria in Solid Tumors (RECIST).

Among the results:

• 24 (7%) of the 327 patients who had sufficient imaging had atypical responses (15 early and 9 delayed).

• Of 592 patients who survived ≥12 weeks, 84 (14%) had progressive disease according to RECIST but nonprogressive disease per irRC.

• More than three-fourths of patients with nonprogressive disease per both criteria survived 2 or more years.

• Survival rates were ~38% in those with progressive disease according to RECIST but nonprogressive disease per irRC, and ~17% in those with progressive disease per both criteria.

Citation: Hodi F, Hwu W, Kefford R, et al. Evaluation of immune-related response criteria and RECIST v1.1 in patients with advanced melanoma treated with pembrolizumab. [Published online ahead of print March 7, 2016]. Am J Clin Oncol. doi:10.1200/JCO.2015.64.0391.