Real world treatment practices and outcomes of metastatic Merkel cell carcinoma: A retrospective study.

Abstract

e21546 Background: Merkel cell carcinoma is an aggressive neuroendocrine skin cancer with frequent metastasis and a high mortality rate. Immunotherapy has been associated with improved outcomes in patients with mMCC [1]. This study aims to evaluate the current treatment practices for mMCC at our cancer center and comparing outcomes between patients receiving immunotherapy (IT) and those receiving chemotherapy (CT). Methods: We conducted a retrospective analysis of patients diagnosed with mMCC treated with systemic therapy between 2021 and 2024 through the electronic medical record system at Hartford Healthcare. Patients with active malignancy other than mMCC were excluded. Patient demographics, treatment regimens, overall survival (OS) and progression free survival (PFS) in months (mo) was compared between groups that received IT vs CT as first line. Kaplan Meyer analysis and Log Rank tests were used to assess differences in OS and PFS. The study was approved by the IRB. Being a rare diagnosis (annual incidence rate of 0.7 per 100,000 person-years in the United States [2]), the sample size of this study was limited. Results: 19 patients with mMCC were included in the study. 10 received IT (pembrolizumab) and 9 received CT (etoposide and carboplatin). Average age at diagnosis was 72.5 years in the IT group and 65.5 years in the CT group. The mean OS was 23.5 mo vs 13.17 mo and median OS was 23.5 mo vs 9.46 mo (p = 0.042) in the IT and CT group respectively. The mean PFS was 15.67 vs 5.21 months and median PFS was 14.52 mo vs 3.02 mo (p = 0.019) in the IT group and CT group respectively. Conclusions: This study reflects current treatment practices at our center demonstrating IT offering a superior OS and PFS compared to CT in patients with mMCC. Despite the established efficacy of IT, it is noteworthy that CT was still utilized in approximately half of the patients in this study despite its inferior clinical and safety profile. This highlights the importance of further research into the factors driving treatment choices, including clinician preferences and individual patient factors. References: Bhanegaonkar A, Liu FX, Boyd M, Fulcher N, Kim R, Krulewicz S, Smith J, Cowey CL. Real-World clinical outcomes in patients with locally advanced or metastatic Merkel cell carcinoma treated in US oncology clinical practices: results from SPEAR-Merkel. The oncologist. 2021 Sep 1;26(9):e1633-43. Paulson KG, Park SY, Vandeven NA, Lachance K, Thomas H, Chapuis AG, Harms KL, Thompson JA, Bhatia S, Stang A, Nghiem P. Merkel cell carcinoma: current US incidence and projected increases based on changing demographics. Journal of the American Academy of Dermatology. 2018 Mar 1;78(3):457-63. Results. Survival Immunotherapy Chemotherapy Log Rank (Mantel-Cox) P value Median Overall survival in months 23.589 (19.262-27.917) 9.462 (0.055-18.869) 0.042 Median Progression free survival in months 14.522 (0.624-28.419) 3.023 (2.351-3.695) 0.019