Merkel Cell Carcinoma: 27-year Experience at the Peter MacCallum Cancer Center

Abstract

Merkel Cell Carcinoma (MCC) is an uncommon but aggressive skin cancer and the optimal management remains controversial. For MCC confined to the local and/or regional areas, our center has adopted a combined modality approach whenever possible in the past three decades, namely surgery followed by radiotherapy (RT). More recently, concurrent chemotherapy has been added to RT for selected patients. The purpose of this retrospective study is to review the treatment outcome of these patients. Patients presenting to our center between January 1980 and July 2006 with the diagnosis of MCC and without distant metastases were included. The primary endpoint was locoregional control. The Kaplan-Meier method of survival analysis was used for all time-to-event analyses. Subgroups were compared using the log-rank test. Cox proportional hazard regression was used to investigate factors predictive for locoregional control. We identified 176 patients (89 males and 87 females) in our medical records database. The median age was 79 years (range, 19-97). The median follow-up was 2.2 years for all patients and 3.9 years for those alive at last follow-up. The primary tumor locations were: head and neck (56%), upper limb (14%), lower limb (19%), trunk (5.7%), and unknown primary (4.5%). 132 (75%) patients presented at initial diagnosis and 44 (25%) presented with local and/or regional recurrence following previous surgery. 62 (35%) patients had regional disease at presentation. Initial surgery to the primary tumor involved local excision or wide local excision in 140 patients and biopsy only in 28 patients. Nodal surgery was performed in 33 patients. 165 (94%) patients received RT and 29 of them had concurrent chemotherapy. The RT field encompassed the primary site only (19%), the primary and regional nodes (64%), or regional nodes only (11%). The median RT dose was 50 Gy (range, 18-60) and the median number of fractions was 24 (range, 3-31). Grade 3 acute skin toxicity was seen in 20 patients. Locoregional recurrence developed in 33 (19%) patients: 6 local, 8 in-transit, 15 regional, 4 local and regional. The median time to locoregional recurrence was 8 months. Distant metastases developed in 43 (24%) patients. Age, primary tumor size, and RT (no RT vs <45 Gy vs ≥45 Gy) were predictive for locoregional control on univariate analysis, but only RT remained significant on multivariate analysis. The estimated 5-year actuarial rates for locoregional control, progression free survival, and overall survival were 76%, 60%, and 45%, respectively. The locoregional control rate for MCC in our study is comparable to other reported series using combined modality treatment, and appears superior to series using surgery alone. Radiotherapy should be an integral part of treatment for this tumor.