Adjuvant radiation following clear margin resection of high T-stage cutaneous squamous cell carcinoma halves the risk of local and locoregional recurrence: A dual-center retrospective study.

Background: Although adjuvant radiation (ART) following clear margin surgery is recommended for select high-risk cutaneous squamous cell carcinomas, efficacy data are limited.

Objective: To evaluate the impact of ART on outcomes following clear margin surgery for high T-stage cutaneous squamous cell carcinomas.

Methods: A 20-year retrospective cohort study at 2 academic centers of high T-stage cutaneous squamous cell carcinomas (Brigham and Women's Hospital T2b or T3) with negative histologic margins post resection. Local recurrence (LR) and locoregional recurrence (LRR) were compared by whether tumors received ART or observation.

Results: A total of 508 tumors were included, of which 96 underwent ART (ART). ART had a lower 5-year cumulative incidence of LR (ART, 3.6% [95% CI, 1.6%-7.7%] vs ART, 8.7% [95% CI, 6.3%-12.0%]) and LRR (ART, 7.5% [95% CI, 4.4%-11.9%] vs ART, 15.3% [95% CI, 11.9%-22.1%]). Recurrent tumors ≥6 cm or Brigham and Women's Hospital T3 tumors were classified as high-risk due to a higher 5-year cumulative incidence of LRR (High-risk, 26.3% [95% CI, 19.0%-35.7%]). High-risk tumors treated with ART had a lower 5-year cumulative incidence of LRR (ART, 17.2% [95% CI, 11.9%-26.4%] vs ART, 31.0% [95% CI, 26.1%-40.8%]).

Limitations: Retrospective design, heterogeneous population, variations in radiation protocols.

Conclusion: ART following clear margin surgery for high T-stage cutaneous squamous cell carcinomas resulted in half the risk of LR and LRR.