ABSTRACT
BACKGROUND: Radiotherapy (RT) is a risk factor for nonmelanoma skin cancer (NMSC), specifically basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), but whether features, histology, or recurrence of NMSC after RT resemble those observed in the general population is unknown. METHODS: A retrospective review (1994-2017) was performed within the Adult Long-Term Follow-Up Program and Dermatology Service at Memorial Sloan Kettering Cancer Center. Demographics, clinical features, histology, treatment, and recurrence were collected for this patient cohort that was under close medical surveillance. Pathology images were reviewed when available. RESULTS: A total of 946 survivors (mean age, 40 years [SD, 13]) were assessed for NMSC. The mean age at first cancer diagnosis was 16 years (range, 0-40 years [11]), and the most common diagnosis was Hodgkin lymphoma (34%; n=318). In 63 survivors, 281 primary in-field lesions occurred, of which 273 (97%) were BCC and 8 (3%) were SCC. Mean intervals from time of RT to BCC and SCC diagnosis were 24 years (range, 2-44 years) and 32 years (range, 14-46 years), respectively. The most common clinical presentation of BCC was macule (47%; n=67), and the most common histologic subtypes were superficial for BCC (48%; n=131) and in situ for SCC (55%; n=5). Mohs surgery predominated therapeutically (42%; n=117), the mean duration of follow-up after treatment was 6 years (range, 12 days-23 years), and the 5-year recurrence rate was 1% (n=1). CONCLUSIONS: Most NMSCs arising in sites of prior RT were of low-risk subtypes. Recurrence was similar to that observed in the general population. Current guidelines recommend surgical intervention for tumors arising in sites of prior RT because they are considered to be at high risk for recurrence. These findings suggest that an expanded role for less aggressive therapy may be appropriate, but further research is needed.