THE ROLE OF POSTOPERATIVE RADIATION AND CHEMORADIATION IN MERKEL CELL CARCINOMA: A SYSTEMATIC REVIEW OF THE LITERATURE

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Objective. A systematic review of the literature was undertaken to investigate whether adjuvant radiotherapy and/or chemotherapeutics offered any additional benefit than surgery alone. Background. Merkel cell carcinoma (MCC) is a relatively rare cutaneous malignancy with a high recurrence and mortality rate. Few recommendations exist for the treatment of MCC, but the general consensus is the surgical excision as the initial treatment. However, postoperative use of adjuvant radiotherapy and/or chemotherapeutics remains unclear. Methods. A PubMed, MEDLINE search was conducted between 1995-2013, to identify reported cases of surgically treated MCC. Patient characteristics that were extracted include age, gender, size and location of primary tumor, clinical stage and nodal involvement. Assessment of outcomes were reviewed and reported as overall survival (OS), OS after one year, three years, local control (LC) after one year, three years, crude recurrence, time to recurrence and toxicity. Inclusion criteria included a primary tumor of MCC in any stage, positive or negative metastases to lymph nodes, lesions of any size, and primary treatment that included curative surgery followed by observation, radiation within 3 months, or chemoradiation within 3 months. A subset analysis was performed contrasting observation and RT treatments based on the mean tumor size for the study. Results. 34 studies (n = 4475) were included. The median age was 73 years, median follow-up was 36 months and there was a 1.5:1 ratio of men to women. All 4475 patients had surgery, 1975 had no further treatment, 1689 received postoperative RT, and 301 received postoperative chemoRT. The most common primary site was face/head/neck, 47.8%. Stage 1 was the most common clinical stage at diagnosis (57%), though it was not equally represented in each cohort. 3-year LC was found to be 20% [median 10%] in the observation cohort, compared to 65% [62%] with postoperative RT and 67% [75%] with postoperative chemoRT; these findings were statistically significant (P < 0.001). Recurrence was found to be 38% [60%] in the observation cohort, compared to 23% [20%] with postoperative RT; this was statistically significant (P < 0.001). 3-year OS was found to be 56% [57%] in the observation cohort, compared to 70% [78%] with postoperative RT and 73% [76%] with postoperative chemoRT; these findings were statistically significant (P < 0.001). The observation cohort had a median OS of 44 months compared with 64 months (P < 0.001) in the postoperative RT cohort. There was no