Radiation sensitivity and efficacy in aggressive and non-aggressive basal cell carcinoma (BCC) of the skin: Image Guided Superficial Radiation Therapy achieves high rate of local control in sclerosing, infiltrative, morpheaform and micronodular BCC subtypes as well as in non high risk BCCs, an analysis of 7994 BCC lesions.

Abstract

Background High risk (HR) basal cell carcinoma (BCC) subtypes have been associated with high recurrence rates that is felt to be better managed surgically. Specifically, Mohs Micrographic Surgery (MMS) is considered most effective for aggressive HR BCCs and superior to traditional nonsurgical techniques, including radiation. Recently, superficial radiation therapy with high resolution ultrasound image guidance called Image Guided Superficial Radiation Therapy (IGSRT) displayed high local control (LC) rates and is an emerging non-surgical alternative to MMS for non-melanoma skin cancer (NMSC). Objectives We present the largest experience in the USA on treatment of BCCs using IGSRT and specifically evaluate if there are differences in LC between HR BCC versus non-HR subtypes using this technology. Methods A retrospective analysis was conducted on 7,994 BCC lesions treated with IGSRT in the continental United States. We compared the results of BCCs treated with IGSRT separated by HR vs non HR groups including 339 HR BCC lesions and 7655 non HR BCC lesions. High risk was defined as infiltrative, micronodular, morpheaform, and sclerosing subtypes. Non-HR BCC included superficial, nodular, and not otherwise specified (NOS) subtypes. Local control (LC) rates at two and five years were calculated with actuarial life-table and Kaplan-Meier methods and statistically compared using log rank tests. Results IGSRT treatment of the HR BCC group showed no recurrences with two and five-year actuarial and KM LC rates all at 100%. In comparison, the non-HR BCC cohort achieved similar two and five-year actuarial LC rates of 99.71% and 99.24% (KM LC at 99.5% and 99.23%), respectively. No statistical differences in LC rates between the two cohorts (p=0.278 each) resulted. Patients tolerated treatment well with little or rare high grade RTOG toxicity reported in both cohorts. Conclusion HR BCC may be treated just as effectively as low risk BCC using IGSRT and presents a viable alternative to MMS. The targeted approach using IGSRT, incorporating high resolution dermal ultrasound (HRDUS), appear to enhance treatment accuracy and effectiveness demonstrating high LC rates in all subtypes of BCC comparable to MMS and is a viable non-surgical option.