Definitive radiotherapy for Merkel cell carcinoma confers clinically meaningful in-field locoregional control: A review and analysis of the literature.

Abstract

Merkel cell carcinoma (MCC) is an uncommon radiosensitive, neuroendocrine malignancy. Treatment often involves surgery; however, older, sicker patients may not be candidates for an operation. Institutions have published data favoring the role of definitive radiotherapy for macroscopic locoregional disease. Our objective was to report the outcome of patients treated with definitive radiotherapy. We performed a systematic review of Medline, PubMed, and Embase databases for reported cases or series of definitive radiotherapy for macroscopic locoregional MCC. The mean radiation dose did not significantly differ between primary and regional sites (48.7 ± 13.2 vs 49.4 ± 10.1 Gy, P = .74). The rate of recurrence was calculated on the basis of the site of disease (11.7%) and per patient (14.3%). Recurrence was significantly more likely to occur at regional than at primary irradiated sites (16.3% vs 7.6%, P = .02). There was no association between radiotherapy dose and incidence of recurrence or nonrecurrence; primary (42.7 ± 23 vs 49.3 ± 11.8 Gy, P = .197) and regional (48.6 ± 10 vs 49.5 ± 10.3 Gy, P = .77). A limitation of this report is that most publications were retrospective; heterogeneity was present in the size of MCC and in radiotherapy details. Definitive radiotherapy for locoregional macroscopic MCC was found to confer clinically meaningful local and regional in-field control.