Background Adjuvant radiotherapy (ART) has been recommended for squamous cell carcinoma (SCC) with a high risk of recurrence, particularly perineurally invasive disease. The utility of ART is unknown. This study compares reported outcomes of high-risk SCC treated with surgical monotherapy (SM) with those of surgery plus ART (S+ART). METHODS The Medline database was searched for reports of high-risk SCC treated with SM or S+ART that reported outcomes of interest: local recurrence, regional or distant metastasis, or disease-specific death. Results There were no controlled trials. Of the 2,449 cases of high-risk SCC included, 91 were treated with S+ART. Tumor stage and surgical margin status before ART were generally unreported. In 74 cases of perineural invasion (PNI), outcomes were statistically similar between SM and S+ART. In 943 high-risk SCC cases in which clear surgical margins were explicitly documented, risks of local recurrence, regional metastasis, distant metastasis, and disease-specific death were 5%, 5%, 1%, and 1%, respectively. ConclusionS High cure rates are achieved in high-risk cutaneous SCC when clear surgical margins are obtained. Current data are insufficient to identify high-risk features in which ART may be beneficial. In cases of PNI, the extent of nerve involvement appears to affect outcomes, with involvement of larger nerves imparting a worse prognosis. The authors have indicated no significant interest with commercial supporters.
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