Lack of Clinically Significant Relationships of Age or Body Mass Index with Merkel Cell Carcinoma Immunotherapy Outcomes.

Simple Summary: Merkel cell carcinoma is a rare, aggressive skin cancer prone to spreading. While anti-PD-1/PD-L1 immunotherapy has improved outcomes for advanced MCC, about half of such patients do not see long-lasting benefits. This study examined how age and body mass index (BMI) affect the response to immunotherapy in 183 advanced MCC patients from a single-center-based, longitudinal database. The analysis showed that age impacts treatment response, with patients significantly older than 70 years responding less effectively. However, age did not influence other outcomes, including progression-free survival, MCC-specific survival, and overall survival. Similarly, BMI did not significantly affect any immunotherapy outcomes. These results suggest that age and BMI should not be used to determine immunotherapy eligibility in MCC, highlighting the need for unbiased patient selection for this treatment. Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with a high risk of metastasis. The development of anti-PD-1/PD-L1 immunotherapy has improved outcomes for advanced MCC, yet about 50% of such patients do not achieve durable responses. This study analyzed the effects of age and body mass index (BMI) on immunotherapy response in 183 advanced MCC patients from a single-center longitudinal database. Using Fine–Gray or Cox regression models, treatment response, progression-free survival (PFS), MCC-specific survival, and overall survival (OS) were evaluated. Age showed a significant non-linear relationship with treatment response (p = 0.04), with patients much older or younger than 70 years less likely to respond. However, age was not significantly associated with PFS (p = 0.21), MCC-specific survival (p = 0.72), or OS (p = 0.36). Similarly, BMI was not significantly correlated with treatment response (p = 0.41), PFS (p = 0.52), MCC-specific survival (p = 0.78), or OS (p = 0.71). Unlike previous studies suggesting that obesity and advanced age improve outcomes in other cancers, these associations were not observed in MCC. These findings suggest that age and BMI should not influence eligibility for immunotherapy in MCC patients, emphasizing the importance of unbiased patient selection for this treatment. [ABSTRACT FROM AUTHOR]