Radiotherapy for lentigo maligna and lentigo maligna melanoma - a systematic review

Lentigo maligna (LM) is the most common subtype of in situ melanoma und occurs frequently in the sun-exposed head and neck region in elderly patients. The therapeutic "gold standard" is surgical excision, as there is the risk of progression to invasive (lentigo maligna) melanoma (LMM). However, surgery is not feasible in certain patients due to age, comorbidities or patient preference. Radiotherapy using Grenz rays or superficial X-rays has been established as non-invasive alternative for the treatment of LM and LMM. We performed a systematic literature search of MEDLINE and Embase databases in September 2019 and identified 14 patient series using radiotherapy for LM or LMM. No prospective trials were found. The 14 studies reported a total of 1243 lesions (1075 LM and 168 LMM) treated with radiotherapy. Local recurrence rates ranged from 0 to 31% and were comparable to surgical series in most of the reports on radiotherapy. Superficial radiotherapy was prescribed in 5-23 fractions with a total dose of 35-57 Gy. Grenz ray therapy was prescribed in 42-160 Gy in 3-13 fractions with single doses up to 20 Gy. Cosmetic results were reported as "good" to "excellent" for the majority of patients.In conclusion, the available low-level evidence suggests that radiotherapy may be a safe and effective treatment for LM and LMM. Data from prospective trials such as the phase 3 RADICAL trial are needed to confirm these promising findings and to compare radiotherapy to other non-surgical therapies and to surgery.