Topical immunotherapy with diphencyprone (DPCP) for in-transit and unresectable cutaneous melanoma lesions: an inaugural Canadian series

Background: Diphencycprone (DPCP) is an immune contact sensitizer applied to melanoma lesions. Early studies show favorable efficacy. We present the first North-American series of patients treated with DPCP.Methods: A single center retrospective study of patients with in-transit or unresectable melanoma lesions treated with DPCP from December 1,2014 to December 31,2015 was completed. Primary objectives were response rate and toxicity. Secondary objective was health-related quality of life assessment with the Functional Assessment of Cancer Therapy-Melanoma (FACT-M) questionnaire.Results: Fifteen consecutive patients were identified with median age of 78 (range 43-92). 73% of patients had prior treatment. Two patients (13%) had a complete response after 25 and 32weeks, respectively. Four patients (27%) had a partial response with a mean treatment time of 30weeks (range 6-51weeks). Six (40%) had stable disease. Six patients stopped DPCP - three from systemic progression and three from toxicity. The most common toxicity was blisters; one patient had significant skin ulceration that resolved on stopping DPCP. Median FACT-M score was 142.95 (possible total 172). Mean overall follow-up time was 22.7weeks.Conclusion: DPCP is a feasible option for in-transit and other melanoma cutaneous lesions ineligible/refractory to surgery and may delay need for systemic therapy.