We retrospectively reviewed all patients with metastatic melanoma treated with pembrolizumab in our institution in a 12 month period between 1st June 2015 and 1st June 2016. We aimed to identify the overall response rate (CR & PR), ongoing response rate and clinical benefit rate (CR, PR & SD) after 4 cycles of pembrolizumab for comparison with prospective published clinical trials.
We identified patients using ICD codes for melanoma and cross-linked this with our pharmacy record of pembrolizumab administration. All patients with metastatic melanoma given at least 1 cycle of pembrolizumab 2mg/kg every 3 weeks between 1/6/15 and 1/6/16 were included. Clinical data was sourced from the patients’ electronic medical record and response was determined by immune-related response criteria.
77 patients were identified. Baseline characteristics: 52M:25F; median age 72y (range 39-90); 54 cutaneous primary site (70%), 12 unknown primary site, 3 ocular primary site ,2 mucosal primary site; 56 mutation wild type (73%), BRAF mutations in 15 patients, NRAS mutations 5 patients; 24 patients had brain metastasis (31%); pembrolizumab was first line treatment in 59 patients (77%); 4 patients had Grade 3/4 toxicity (5.2%).
Overall response (CR & PR) in 33 patients (43%); Responses were ongoing in 27 of 33 patients (82%) after a median follow-up of 5.3 months (3-426 days)
Clinical benefit (CR, PR & SD) in 43 patients (55.8%) after 4 cycles of pembrolizumab; Median 6 month progression free survival and estimated 1 year survival benefit expected by November 2016
Unlike ’real world’ audits of chemotherapy benefit, our single institution experience of pembrolizumab in metastatic melanoma revealed comparative efficacy in overall response rate and clinical benefit rate after 4 cycles of pembrolizumab compared with published clinical trials. This is despite an older cohort of patients with a higher rate of brain metastasis using a lower dose of pembrolizumab. We hypothesize this result may be due to the high percentage of patients treated with pembrolizumab in the first line, though prospective clinical trials are needed to confirm this.