Evaluation of the utility of localized adjuvant radiation for node-negative primary cutaneous squamous cell carcinoma with clear histologic margins

Though the National Comprehensive Cancer Network recommends consideration of localized adjuvant radiation after clear-margin surgery for cutaneous squamous cell carcinoma (cSCC) with large-caliber (≥0.1-mm) nerve invasion (LCNI) and other high-risk features, only a single small study has compared surgery plus adjuvant radiation therapy (S+ART) to surgical monotherapy (SM) for cSCC.Compare S+ART to SM for primary cSCCs with LCNI and other risk factors.Matched retrospective cohort study of primary cSCCs (matched on sex, age, immune status, type of surgery, diameter, differentiation, depth, and LCNI) treated with S+ART versus SM. A subgroup analysis of cSCCs with LCNI was performed.In total, 62 cSCCs were included in matched analysis (31 S+ART and 31 SM) and 33 cSCCs in the LCNI analysis (16 S+ART and 17 SM). There were no significant differences in local recurrence, metastasis, or death from disease in either analysis. Risk of local recurrence was low (8%, 7/89), with 3 of the local recurrences being effectively treated upon recurrence.Single academic center and nonrandomized design.Adjuvant radiation did not improve outcomes compared with SM due to a low baseline risk of recurrence, although adjuvant radiation for named nerve invasion and LCNI of ≥3 nerves has been shown to improve outcomes in a prior study. Randomized studies are needed to define the subset of cSCC for whom adjuvant radiation has utility.