Radiotherapy for inoperable Merkel cell carcinoma: a systematic review and pooled analysis

Cumulative data on radiation monotherapy for Merkel cell carcinoma (MCC) is lacking. We sought to synthesize all available data on treatment outcomes for radiation monotherapy for inoperable stage I-III MCC. We performed a systematic review of the current literature. Articles published in English in the PubMed database up to July 29, 2016, were evaluated. Eight case reports, 4 case series, and 6 retrospective studies, yielding 68 patients, were included in our analysis. Of the 24 stage I/II patients treated with local irradiation, 6 (25%) relapsed and 1 (4%) died from MCC. Of the 24 stage I/II patients treated with local and regional nodal irradiation, 5 (21%) relapsed and 2 (8%) died from MCC. Of the 20 stage III patients treated with local and regional nodal irradiation, 12 (60%) relapsed and 7 (35%) died from MCC. Radiation monotherapy appears to be a reasonable treatment modality for patients with inoperable stage I-III MCC. Further investigation with prospective studies is needed to draw definitive conclusions.