Induction Systemic Therapy Followed by Response-Adapted Consolidative Radiation in Locally Advanced Non-Melanoma Skin Cancer: A Retrospective Case Series

Background: There exists an unmet clinical need to define definitive management strategies for patients with locally advanced non-melanoma skin cancers (NMSC), particularly if not amenable to surgical resection. Methods: We retrospectively reviewed a case series of locally advanced unresectable NMSC treated with induction systemic treatment followed by response-adapted consolidative radiation. Results: We identified 15 patients who met study criteria, including seven with basal cell carcinoma (BCC), six with cutaneous squamous cell carcinoma (CSCC), and two with Merkel cell carcinoma (MCC). Clinical complete response (CR) by physical examination was observed in all 15 patients. No locoregional or distant recurrences were observed in any histologic subtype after completion of radiation (median follow-up from completion of radiation: 18.1 months BCC, 22.5 months CSCC, 22.7 months MCC). The median duration of observed response (DOOR), measured from first clinical response was 26.9 months (26.2 BCC, 29.4 CSCC, 27.1 MCC). Radiation treatment volumes were response-adapted with median gross tumor volume reduction of 55.3% (15.3%–100%). Median treatment-free response was 20.5 months. No unexpected systemic therapy related toxicities were identified. Conclusions: In this single-institution retrospective case series, induction systemic therapy followed by response-adapted consolidative radiation was feasible and associated with durable disease control in selected patients with locally advanced unresectable NMSC.