The impact of immune status on clinical outcomes in patients with Merkel cell carcinoma.

Abstract

8590 Background: Merkel Cell Carcinoma (MCC) is an aggressive cutaneous malignancy of neuroendocrine origin associated with immunosuppression presumably through infection with Merkel Cell Polyomavirus present in >80% of patients (pts). The impact of immune status on clinical outcomes in pts with MCC is unknown. The primary objective of this study was to compare clinical characteristics and outcomes of pts with MCC who are immunosuppressed (ISP) versus non-immunosuppressed (non-ISP). Methods: We performed a retrospective chart review on pts with MCC diagnosed at the Mayo Clinic between 1981 and 2009. A dermatopathologist confirmed all cases. ISP was defined as pts diagnosed with chronic lymphocytic leukemia, HIV, solid organ transplant recipients, or chronic immunosuppressive medication. The association between ISP status and overall survival was summarized using the hazard ratio (HR) and 95% confidence interval (CI) estimated from a Cox regression model. Results: Of the 268 pts identified and included in the study, 38 (14%) were ISP. We found no differences in age, tumor size, tumor location, stage of disease, or recurrence rate in ISP vs Non-ISP. Among pts who had Stage 3-4 disease, there was no difference in the size of the primary between groups. Among pts with Stage 1-2 disease, ISP status was not significantly associated with poorer survival (HR 1.5, 95% CI 0.7-3.3). However, among pts with Stage 3-4 disease, ISP pts had significantly poorer survival compared to non-ISP pts (HR 2.7, 95% CI 1.2 - 6.2). Conclusions: Baseline clinical characteristics of pts with MCC do not differ based on immunosuppression, and outcomes do not differ in pts in regards to immunosuppression in early stage MCC (Stage 1-2). However, in pts with Stage III-IV MCC, ISP pts have a worse clinical outcome suggesting that metastatic MCC either behaves more aggressively in ISP pts either through intrinsic differences in the biology of the tumor or improved immune evasion in ISP pts. These results should be cautiously interpreted given the small number (n=12) of immunosuppressed pts with advanced stage MCC. The authors will update their data with an additional 58 patients by the date of presentation.