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

BACKGROUND:Cumulative data on radiation monotherapy for Merkel cell carcinoma (MCC) is lacking. OBJECTIVE:We sought to synthesize all available data on treatment outcomes for radiation monotherapy for inoperable stage I-III MCC. METHODS:We performed a systematic review of the current literature. Articles published in English in the PubMed database up to July 29, 2016, were evaluated. RESULTS: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. CONCLUSIONS: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.