Efficacy and prognostic factors of adjuvant radiotherapy for cutaneous squamous cell carcinoma: A systematic review and meta‐analysis

Abstract Although adjuvant radiotherapy has been used for cutaneous squamous cell carcinoma, its outcome benefits, especially for patients with clear surgical margins, have not been statistically estimated, and the characteristics that can indicate patients who require adjuvant therapy need to be validated with more evidence. We conducted a systematic review and meta‐analysis of literature on the survival outcomes and prognostic factors in patients with cSCC treated by surgery with or without adjuvant radiotherapy. Twenty related studies involving 2605 patients met our inclusion criteria. The significant survival outcomes of adjuvant radiotherapy included lower recurrence (OR, 0.56; 95% CI, 0.36–0.85), longer disease‐free survival (OR, 2.17; 95% CI, 1.23–3.83) and longer overall survival (OR, 2.94; 95% CI, 1.75–4.91). Significant prognostic factors for poor outcomes were perineural invasion (HR, 1.61; 95% CI, 1.24–2.09), involved surgical margins (HR, 2.34; 95% CI, 1.42–3.83) and immunosuppression (HR, 3.02; 95% CI, 2.14–4.25) while adjuvant radiotherapy significantly contributed to better overall survival (HR, 0.47; 95% CI, 0.34–0.65). In conclusion, this systematic review suggests that in cutaneous squamous cell carcinoma patients with risk factors, including metastasis to the parotid gland, perineural invasion and immunosuppression, the use of adjuvant radiotherapy may be beneficial irrespective of surgical margin status.