Lentigo maligna (LM) is a melanoma subtype that occurs on sun-damaged skin in the elderly. Dermal invasive melanoma developing from LM is called LM melanoma (LMM) and has the same prognosis as other melanoma subtypes. The standard treatment for LM is surgery, which offers the lowest risk of recurrence. Alternatives exist, however, including radiotherapy (RT).

Describe a real-life cohort of patients with LM/LMM treated with RT and assess prognostic factors for recurrence.

This is a retrospective monocentric real-life study conducted in Bordeaux University Hospital. All LM or LMM patients treated with RT between 2009 and 2020 were included. RT was administered using a superficial or orthovoltage X-ray (kV) with a dose of 40 Gy in 10 fractions over 5 weeks.

Ninety-one patients were included: 67 LM and 24 LMM. Sixty-four patients were female, the mean age was 77 (range: 50‑96) in LM group, and 80 (range: 56–98) in LMM group. The mean duration of post-RT follow-up was 25.1 months (range: 0–100). Fourteen recurrences were observed (15.4%): 10 in LM group (14.9%) and 4 in LMM group (16.7%). Most recurrences occurred in the irradiation field: 8/10 in LM group, and 2/4 in LMM group. Recurrences were more frequent in men (6/27 vs 8/64) and on the eyelid area (4/14) compared to others locations. The risk of recurrence was also higher in patients with at least one prior treatment failure (8/36 (22.2%) vs 6/55 (10.9%)). There were significantly fewer recurrences for patients who had achieved a complete response at 3 months compared to those with a partial response (7.1% vs 28.6%, p = 0.0159).

Radiotherapy is a therapeutic alternative to surgery to be considered for selected patients with LM.