Outcomes of Merkel Cell Carcinoma Treated with Radiotherapy without Radical Surgical Excision

Achieving clear surgical margins in Merkel cell carcinoma (MCC) can be difficult due to tumor location or patient comorbidity. Clinical impression suggests that radiation treatment achieves good control of macroscopic disease. A retrospective chart review was undertaken of all patients with pathological evidence of MCC and treated with curative intent at the BC Cancer Agency between 1979 and 2007. This is a report on the outcomes of those with gross disease treated with radiotherapy, without radical surgery. Fifty-seven patients received definitive radiotherapy to the primary and/or nodal disease. Median age was 75 years and median follow-up was 34 months (84.5 months for those alive at last follow-up). American Joint Committee on Cancer (AJCC) stage distribution was 23, 19, and 58 % for stages I, II, and III, respectively. Tumor control at sites treated for macroscopic disease was 88 % at 12 months and 82 % at 2 years, and 5-year local relapse-free survival (RFS) was 90 %. Five-year RFS, cancer-specific survival (CSS), and overall survival were 57, 68, and 39 %, respectively. On univariate and multivariate analyses, only male sex was associated with a worse RFS, and a radiotherapy dose > 50 Gy was associated with a better CSS. The retrospective nature of the study and small sample size limit the strength of the conclusions. Radical radiotherapy is effective in the curative treatment of MCC, especially in patients who would tolerate wide surgical excision poorly, or where it would cause significant cosmetic or functional deficits.