The role of radiotherapy alone in patients with merkel cell carcinoma: reporting the Australian experience of 43 patients.

Abstract

To review the role of radiotherapy (RTx) alone in patients with Merkel cell carcinoma (MCC). 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. 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. 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.