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

Abstract

Background Though NCCN recommends consideration of localized adjuvant radiation following clear-margin surgery for cutaneous squamous cell carcinoma (CSCC) with large caliber (≥0.1mm) nerve invasion (LCNI) and other high-risk features, only a single small study has compared surgery plus adjuvant radiation (S+ART) to surgical monotherapy (SM) for CSCC. Objectives Compare surgery plus adjuvant radiation (S+ART) to surgical monotherapy (SM) for primary CSCCs with LCNI and other risk factors. Methods Matched retrospective cohort study of primary CSCCs (matched on gender, age, immune status, type of surgery, diameter, differentiation, depth and LCNI) treated with S+ART versus SM. Subgroup analysis of CSCCs with LCNI was performed. Results 62 CSCCs were included in matched analysis (S + ART: 31, SM: 31) and 33 in LCNI analysis (S+ART: 16, SM: 17). There was no significant difference in local recurrence (LR), metastasis, or death from disease in either analysis. Risk of LR was low (7, 8%) with 3 of the LRs being effectively treated upon recurrence. Limitations Single academic center, non-randomized design. Conclusion Adjuvant radiation did not improve outcomes compared to SM due to a low baseline risk of recurrence; although ART for named nerve invasion and LCNI of 3 or more 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.