Hypofractionated Radiotherapy for Merkel Cell Carcinoma

Abstract Purpose/Objective(s): Merkel cell carcinoma (MCC) radiation treatment has historically involved standard 1.8-2 Gy fractions treated daily over 4-6 weeks. Hypofractionated treatment regimens have demonstrated tumor control and toxicity equivalence to standard fractionation regimens for common cutaneous malignancies such as basal cell and squamous cell carcinomas. Herein we report the outcomes of hypofractionated versus standard fractionation radiotherapy for MCC at our institution. Materials/Methods: The study involved a retrospective review of 29 treatment courses for MCC. Treatment characteristics and patient outcomes were analyzed. Subsequent patient outcomes, including acute toxicities, as well as recurrence and survival results, were collected. The cumulative incidence of local and distant failures was estimated, with death as a competing risk. Results: A total of 24 patients were included, of which 13 received standard fractionation with curative intent, 10 received hypofractionated radiotherapy with curative intent, and 6 received single fraction (8 Gy) palliative radiation. Half the patients were treated to a head/neck site. A subset of patients treated adjuvantly with curative intent included 8 standard fractionation and 8 hypofractionated radiotherapy patients. No statistically significant differences in local and/or distant failure or overall survival was observed between the patient groups. Conclusion: Hypofractionated radiotherapy for MCC was associated with similar treatment outcomes relative to standard fractionation. In our limited patient sample, hypofractionated radiation treatment achieved similar results with similar toxicity and fewer treatments. Further analysis of a larger patient population with longer follow up is needed to confirm treatment tolerability and efficacy.