Effectiveness of PD1-inhibitors in advanced Merkel cell carcinoma: Real life data in a Swedish cohort.

Abstract

e22063 Background: Merkel Cell Carcinoma (MCC) is a highly aggressive neuroendocrine skin cancer that affects the elderly. Most cases are associated with the Merkel cell polyomavirus. It has previously been shown in clinical trials that MCC respond to immunotherapy with PD1 and PDL1-inhibition. PD1-inhibitiors have been used to treat MCC at Karolinska University Hospital in Sweden since 2016. The aim of this study is to describe the PD1-MCC-cohort at Karolinska. Methods: Patients with inoperable MCC that were treated with PD1-inhibitor at the oncology dept between August 2016 and February 2020 at Karolinska were included in the study, and response data was assessed retrospectively. Response was assessed clinically and through CT-scans. Results: Among 12 treated pts, median age was 75 yrs, 8 male and 4 female, 10 were treatment naive, 2 with prior chemotherapy. 10 pts received pembrolizumab and 2 pts nivolumab. No pts discontinued treatment due to side-effects. Comorbidities seen in the cohort were amongst others Atrial fibrillation (4 pts), Systemic Lupus Erythematosus (1), Hypertension (6), COPD (1), Aortic stenosis (2) and congestive heart failure (1). Follow-up time was median 10 months (range 2-43). First evaluation varied between 2-4 months with the majority at ~3 months. At first evaluation ORR was 75% and PFS and OS was 75% and 100% respectively. At 10 months, PFS and OS rates were 58% and 67% respectively. At study end mean PFS was 15,4 months and mean OS 17,8 months. 6 pts (50%) were still in response. Conclusions: PD1-inhibitors in clinical use in this cohort induced rapid and durable tumor responses in patients with advanced MCC, and the treatment was well tolerated. Our conclusion is that a PD1-inhibitor is a feasible and effective treatment for advanced Merkel Cell Carcinoma in the clinical setting.