Role of definitive radiotherapy in treating patients with inoperable Merkel cell carcinoma: the Westmead Hospital experience and a review of the literature.

Merkel cell carcinoma (MCC) is an uncommon aggressive primary cutaneous neuroendocrine carcinoma with a propensity to spread to regional lymph nodes and distant sites. The head and neck is the commonest site for presentation (50-60%) and recent evidence suggests patients treated with excision (to achieve a negative microscopic margin) and adjuvant wide-field radiotherapy (RTx) have an improved survival compared with surgery alone. Surgery is often not possible in elderly patients with multiple co-morbidities and in patients with advanced lesions. Definitive RTx therefore remains an option in these inoperable patients, with data to report its benefit. We report the results of eight patients with inoperable MCC treated with RTx alone between 1993 and 2007 at Westmead Hospital, Sydney, Australia, and also review the relevant literature on definitive RTx in the treatment of MCC. The median age at diagnosis was 82.5 years in five women and three men. All patients were Caucasian and none were immunosuppressed. Seven of eight patients were clinically node-positive. The mean duration of follow up was 12 months. A median dose of 50 Gy was prescribed. Seven of eight patients with inoperable MCC achieved in-field control, with most eventually relapsing distantly. Treatment-related toxicity was acceptable. In keeping with our results, other studies also report high rates of in-field locoregional control following RTx alone. These findings highlight the radioresponsiveness of advanced MCC and support a recommendation of moderate-dose RTx alone in select cases. Lower-dose palliative dose fractionation schedules (e.g. 25 Gy in five fractions) may be considered in patients of very poor performance status.