Surgical Monotherapy Versus Surgery Plus Adjuvant Radiotherapy in High‐Risk Cutaneous Squamous Cell Carcinoma: A Systematic Review of Outcomes

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.