Supplementary Material for: X-Ray therapy of Skin Cancer at Critical Facial Sites: Results of a tertiary referral centre

Background: Therapeutic management of skin cancer (SC) in the “H-area” of the face is challenging due to the demands of function, cosmesis, and efficacy.
Objective: To evaluate the efficacy and safety of superficial radiotherapy (RT) for skin cancer in the “H-area” of the face and to identify predictors of recurrence.
Methods: Retrospective analysis of patients with SC in the "H-area" of the face treated with superficial RT at the University Hospital of Zurich, Switzerland, between 2010 and 2021. The study included cases of basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and in situ SCC (isSCC), lentigo maligna melanoma (LMM), lentigo maligna (LM), and primary cutaneous T/B-cell lymphoma (pcTCL and pcBCL).
Results: We identified 550 lesions in 382 patients. Estimated relapse rates at 5 years were lowest for SCC (3.2%), isSCC (1.9%), and BCC (9.7%), while LMM and LM showed estimated relapse rates of 28.9% and 35.0%, respectively. Significant predictive factors for overall recurrence were increased Common Terminology Criteria for Adverse Events (CTCAE) grades with a Hazard Ratio (HR) of 1.9 (1.1-3.4), and the treatment of secondary lesions with a HR of 2.6 (1.4-5.1).
Conclusion: RT is a valuable treatment option for malignant skin tumors, especially NMSC, in high-risk areas, including the facial 'H-area', providing favorable results with minimal side effects