Recurrence and mortality rates with different treatment approaches of Merkel cell carcinoma: a systematic review and meta-analysis

Background: Comprehensive treatment recommendations for Merkel cell carcinoma are complex. We aimed to systematically review the published data on recurrence and mortality rates associated with various treatment approaches for Merkel cell carcinoma. Methods: Search of MEDLINE, Embase, Web of Science, and Scopus from inception to August 2015. Studies were included that reported comparative survival and recurrence data for two or more treatment modalities. Two reviewers independently reviewed and abstracted recurrence and mortality rates. Event rates for individual treatment arms in each study were pooled and meta-analyzed across studies using a random-effects model. Results: Fifty-two retrospective studies met inclusion criteria, revealing a total of 1,804 patients with primary Merkel cell carcinoma with data available for analyses. The recurrence rate was higher for surgery alone (55.0%) versus a combination of surgery and radiotherapy (39.0%) (odds ratio, 2.089; 95% CI, 1.374–3.177; P < 0.001). Combination therapy including surgery, radiotherapy, and chemotherapy had a higher mortality rate (44.6%) than did combined surgery and radiotherapy (23.2%) (odds ratio, 2.688; 95% CI, 1.196–6.037; P = 0.02). Conclusions: The treatment of Merkel cell carcinoma with surgery plus adjuvant radiotherapy may produce lower recurrence rates.