Schäfer Laura¹, Weber Mia², Koch Ben³, Wagner Julia⁴, Fischer Sophie⁵, Klein Julia⁶, Hoffmann Tom⁷, Wolf Lea⁸
ABSTRACT:
Immune checkpoint inhibitors (ICIs) have revolutionized the treatment landscape of various malignancies, yet response rates remain limited, necessitating robust predictive biomarkers. This review provides a comprehensive overview of current and emerging biomarkers associated with ICI response, spanning both tumor-intrinsic and host-related factors. We highlight key components of the tumor microenvironment (TME), including PD-L1 expression, tumor mutational burden (TMB), and immune cell infiltration profiles, as critical predictors of therapeutic efficacy. Additionally, we explore peripheral blood-based biomarkers such as circulating immune cell subsets, cytokine levels, and cell-free DNA (cfDNA) as minimally invasive tools for patient stratification and real-time monitoring. Integration of multi-omic data and machine learning approaches offers promise in refining biomarker-driven precision immunotherapy. Understanding and validating these diverse biomarkers across cancer types will be essential for optimizing clinical outcomes and guiding individualized treatment strategies.