Real-world safety and effectiveness of avelumab in immune-compromised (IC) and non-IC patients with Merkel cell carcinoma (MCC): Results from a prospective German registry (MCC-TRIM).

9543 Background: MCC is a rare and aggressive form of skin cancer. Avelumab was the first immunotherapy approved for patients with metastatic MCC in Europe. Immunosuppression is an established risk factor for developing MCC, but IC patients have typically been excluded from clinical trials of immunotherapies. We report an analysis of clinical characteristics, survival outcomes, and safety in IC and non-IC patients with MCC treated with avelumab in routine clinical practice in Germany. Methods: This prospective, noninterventional, multicenter, dynamic cohort study (MCC-TRIM; EUPAS25338) enrolled patients with MCC in Germany between April 2019 and September 2023. Primary data from a study-specific electronic case report form and secondary data from the German national skin cancer registry were combined. For this analysis, avelumab-treated patients were grouped as IC or non-IC based on prespecified comorbid conditions and concomitant medications. Survival outcomes with first-line avelumab treatment were assessed using the Kaplan-Meier method. Results: Among 875 patients with MCC (various disease stages) enrolled in the study, 243 were treated with avelumab, of whom 189 (77.8%) were considered non-IC and 54 (22.2%) were considered IC. Patient characteristics are summarized in the Table. At data cutoff (March 2024), median follow-up (IQR) was 14.3 months (6.4-29.4) in the non-IC subgroup and 8.9 (4.2-22.8) in the IC subgroup. In non-IC and IC subgroups, median (95% CI) overall survival from start of first-line avelumab was 38.2 (15.7-not estimable) and 9.9 (4.8-29.8) months, and median progression-free survival was 7.9 (4.0-11.6) and 4.3 (1.0-7.8) months, respectively. The incidence rate of ADRs related to avelumab was 1.01 (95% CI, 0.75-1.34) events per person-year in the non-IC subgroup and 0.71 (95% CI, 0.32-1.45) events per person-year in the IC subgroup. Conclusions: Results from this German nationwide registry showed the safe and effective use of avelumab in routine clinical practice for IC and non-IC patients with MCC. Non-IC (n=189) IC (n=54) Mean age at diagnosis (SD), years 74.8 (10.2) 76.4 (8.1) Male, n (%) 122 (64.6) 35 (64.8) Stage at diagnosis, n (%) Early stage (I, II, or unknown) III IV 38 (20.1)80 (42.3)71 (37.6) 13 (24.1)19 (35.2)22 (40.7) ECOG performance status ≤1, n (%) 153 (81.0) 40 (74.0) Comorbidities, n (%) Diabetes Chronic obstructive pulmonary disease Cerebrovascular disease/stroke Moderate or severe renal disease Ischemic heart disease/myocardial infarction Moderate or severe liver disease Thyroid disorder Inflammatory bowel disease Rheumatoid arthritis 36 (19.0)5 (2.6)2 (1.1)11 (5.8)21 (11.1)3 (1.6)17 (9.0)4 (2.1)5 (2.6) 14 (25.9)4 (7.4)3 (5.6)5 (9.3)8 (14.8)04 (7.4)2 (3.7)5 (9.3)