P57 Retrospective review of patients with lentigo maligna treated with topical 5% imiquimod (Aldara®) at a single tertiary UK centre: need for more practical standardized treatment guidelines in the UK

Abstract Lentigo maligna (LM) is an in situ melanoma arising on chronically sun-damaged skin predominantly on the head and neck. While surgery is the gold standard treatment for LM, imiquimod 5%, which is an immune-response modifier, is a well-reported off-licence treatment in both primary and adjuvant settings. Various treatment regimens have been published. We present our retrospective experience of using imiquimod to treat LM over 10 years at a UK tertiary melanoma centre. We report on indications, treatment regimes, side-effects and treatment efficacy. We identified 71 patients with LM treated with imiquimod with a mean age at diagnosis of 73.3 years. Ninety-three per cent were located on the head and neck. Forty-three per cent (n = 29/67) of patients were treated primarily (following punch biopsy diagnosis or incomplete excision with visible pigmentation remaining) and 57% (n = 38/67) with adjuvant treatment (excision with narrow or close margins, < 3 mm with no visible pigmentation). Invasive disease was seen in 17% of those treated primarily and 45% treated with adjuvant therapy. There were various treatment regimens, but the majority (55%) had treatment prescribed five times weekly for 11–12 weeks, with no significant difference in treatment regimens between the two treatment groups. Inflammation was recorded as none (20%), mild (21%), moderate (21%) and severe (20%). Side-effects were redness (40%), pain (17%), ulceration (7%) and systemic symptoms (6%). Fifty-nine per cent of the primary group had visible clearance; a previous study reported a 71% clinical response in this cohort. Three of the responders relapsed, with two progressing to LM melanoma within 8 years. Forty-eight per cent remained disease free, with a mean follow-up of 27 months. Of those treated with adjuvant therapy, 89% remained clinically disease free at mean follow-up of 19 months. Recurrence in the adjuvant group was reported as 5.6% (Lallas A, Moscarella E, Kittler H et al. Real-world experience of off-label use of imiquimod 5% as an adjuvant therapy after surgery or as a monotherapy for lentigo maligna. Br J Dermatol 2021; 185:675–7). Our limitations include a lack of post treatment biopsies. In 2021, an Australian study reported a practical guide on the use of imiquimod for LM (Guitera P, Waddell A, Paton E et al. A practical guide on the use of imiquimod cream to treat lentigo maligna. Australas J Dermatol 2021; 62:478–85). We propose the need for clearer UK guidelines describing the escalation and de-escalation of treatment in the event of no response and toxicity, respectively. We suggest using a patient application diary to ensure compliance and document changes in treatment and inflammation.