Differential Outcomes Among Immunosuppressed Patients With Merkel Cell Carcinoma: Impact of Immunosuppression Type on Cancer-specific and Overall Survival

Objectives: Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin cancer with higher incidence among whites, elderly, and immunosuppressed patients. Although immunosuppressed MCC patients are at higher risk of recurrence and MCC-related death, it is unknown whether immunosuppression type is associated with differential outcomes. Materials and Methods: We retrospectively evaluated 89 nonmetastatic MCC patients with a diagnosis of chronic immunosuppression. Immunosuppression was categorized as chronic lymphocytic leukemia (31% of cohort), other hematologic malignancies (18%), solid organ transplant (21%), autoimmune disease (21%), and human immunodeficiency virus acquired deficiency syndrome (8%). Progression-free survival (PFS) and MCC-specific survival (MSS) were estimated with the cumulative incidence function. Overall survival (OS) was estimated by the Kaplan-Meier method. Results: With a median follow-up of 52 months, 53 deaths occurred (42 from MCC, 7 unknown, and 4 non-MCC). Two-year PFS, MSS, and OS were 30%, 55%, and 52%, respectively. Human immunodeficiency virus/acquired deficiency syndrome and solid organ transplant patients were diagnosed with MCC at a younger age (median 55 and 59 y, respectively) and with more advanced stage disease compared with other immunosuppressed subgroups. PFS did not significantly differ among the 5 immunosuppression subgroups (P=0.30), but significant differences were observed in MSS and OS (both P=0.01). Controlling for potential confounders for OS, including age and stage, immunosuppression type was still significantly associated with risk of death (P=0.01). Conclusions: Among immunosuppressed MCC patients, recurrent MCC is the major cause of mortality. The risk of death from MCC differs among immunosuppression types, suggesting important biological differences in host-tumor immune interactions. Portions of this work were funded from the Cancer Center Support Grant (NCI 5 P30 CA015704-43). The authors declare no conflicts of interest. Reprints: Yolanda D. Tseng, MD, Department of Radiation Oncology, University of Washington, 1959 NE Pacific Street, P.O. Box 356043, Seattle, WA 98195. E-mail: ydt2@uw.edu. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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