The Role of Radiotherapy Alone in Patients With Merkel Cell Carcinoma: Reporting the Australian Experience of 43 Patients

Purpose: To review the role of radiotherapy (RTx) alone in patients with Merkel cell carcinoma (MCC). Methods and Materials: The records of 43 patients with MCC treated with RTx alone between 1993 and 2007 at the Westmead and Royal Brisbane/Mater Hospitals, Australia, were reviewed. Multivariate analysis was performed by use of Cox regression analysis. Results: The median age was 79 years (range, 48-91 years) in 19 women (44%) and 24 men (56%). All patients were white, and 5 (12%) had immunosuppression. A majority (56%) underwent irradiation at initial diagnosis, with the remainder (44%) treated in the relapse setting. The median duration of follow-up was 39 months. The head and neck comprised the most frequently treated site (47%). The median maximum lesion size was 30 mm (range, 5-130 mm). Relapse developed in 60% of patients, with most being out-of-field relapses. The in-field control rate was 75%. Most out-of-field relapses were to visceral organs. Relapse developed outside the irradiated field in 53% of patients. On multivariate analysis, only nodal status (negative nodes vs. nodes present) was significantly associated with relapse-free survival, with p = 0.005 (hazard ratio, 0.25; 95% confidence interval, 0.96-0.663). Overall survival at 2 and 5 years was 58% and 37%, respectively. Conclusions: Patients with MCC treated with RTx have a high likelihood of obtaining in-field control. Doses of 50 to 55 Gy in 20 to 25 fractions are recommended. A minority of patients are cured, with many dying of systemic relapse. Lower dose fractionation schedules (e.g., 25 Gy in 5 fractions) may be considered in patients with a very poor performance status.