Merkel cell carcinoma: improved outcome with adjuvant radiotherapy.

BACKGROUND: Merkel cell carcinoma is an aggressive primary cutaneous neuroendocrine carcinoma. Patients remain at high risk of locoregional and distant relapse despite treatment. Most studies support the incorporation of locoregional adjuvant radiotherapy in reducing the risk of relapse.
METHODS: Between 1980 and 2002, 86 patients diagnosed with Merkel cell carcinoma were treated with curative intent at Westmead Hospital, Sydney. Multivariate analysis was performed using Cox regression analysis. Disease-free survival and overall survival was calculated using Kaplan-Meier survival curves.
RESULTS: Median age at diagnosis was 75 years (range 46-89 years) in 49 men and 37 women. Median duration of follow up was 31 months (range 6-153 months). Fifty-one (59%) patients presented with a primary lesion, 19 (22%) with a primary lesion and clinical nodal disease and 16 (19%) with lymph node metastases from an unknown primary. A total of 47 of 86 (55%) relapsed with regional nodal relapse, the commonest site of first relapse. Local relapse was similar for patients undergoing surgery (5/37; 14%) compared with surgery and adjuvant radiotherapy (3/25; 12%). Nodal relapse occurred in 14 of 36 (37%) treated with surgery compared with 7 of 38 (18%) patients treated with surgery and adjuvant radiotherapy. Patients treated with surgery and adjuvant radiotherapy experienced a better median disease free survival compared to those undergoing surgery alone (10.5 months vs 4 months; P < 0.01). The 5-year overall and disease-free survival rate for the entire study population was 47% and 25%, respectively. Twenty-six patients (30%) died as a result of Merkel cell carcinoma.
CONCLUSION: Merkel cell carcinoma is an aggressive skin cancer. The addition of adjuvant radiotherapy markedly improves regional control rates and should be considered best practice.