Topical Imiquimod For Lentigo Maligna: Survival Analysis Of 103 Cases With 17 Years Follow-Up

Topical imiquimod 5% cream has been investigated as off-label primary or adjuvant treatment for melanoma in situ, lentigo maligna type (LM). Herein, we present the largest known case series of lentigo maligna treated with topical imiquimod, with up to 17 years of follow-up, and include a recurrence-free survival analysis. In this case series, 103 lesions were retrospectively evaluated for treatment response and recurrence following a course of topical imiquimod with or without tazarotene gel 0.1% pretreatment between January 1, 2002 and March 31, 2019, and prospectively followed through November 15, 2019. Over median follow-up of 5.1 years (mean = 6.2 years, S = 5.2 years, range, 0.08-17.1 years), including 29.1% LM with >10 years follow-up, we observed a response rate of 97.1% (100/103), with 8 local recurrences (8/100, 8.0%) developing at mean 2.9 years (SD: 2.7 years). Local recurrence was significantly associated with a history of failed excision (P= 0.001), <60 applications of imiquimod (P= 0.04) and partial clinical clearance (P= 0.0003). Recurrence-free survival analysis demonstrated significant risk-stratification for low and high-risk groups (P= 0.0001). Long term risk for recurrence showed significant differences among low-and high-risk cases, with low-risk cases demonstrating favorable long-term outcomes, comparable to conventional and staged surgery. Our observed low recurrence in a large case series with long-term followup suggests the efficacy of topical 5% imiquimod for LM and emphasizes the need for randomized control trials comparing imiquimod with, or as an adjunct to, surgical treatment.