Towards Precision Medicine in Metastatic Renal Cell Carcinoma: The Role of Emerging Biomarkers

RCC remains a therapeutically challenging malignancy, particularly in its metastatic stage, in which treatment resistance and limited response durability persist despite recent advances in immunotherapy and targeted therapies. Although immune checkpoint inhibitors (ICIs) have significantly improved outcomes for a subset of patients, reliable prognostic and predictive biomarkers to guide therapy selection are still lacking. Current clinical models, such as the International Metastatic RCC Database Consortium (IMDC) risk score, offer only limited insight into the molecular and immunologic complexity of RCC. Emerging molecular biomarkers implicated in resistance mechanisms reflect the underlying heterogeneity of RCC and may inform future therapeutic strategies. Kidney Injury Molecule-1 (KIM-1), a transmembrane protein that is up-regulated in RCC and detectable in circulation, has demonstrated potential as a non-invasive biomarker for diagnosis, prognosis, and treatment monitoring. Liquid-biopsy approaches, including the analysis of circulating tumour DNA (ctDNA), microRNAs (miRNAs), and long non-coding RNAs (lncRNAs), are also gaining traction due to their minimally invasive nature and potential for real-time disease monitoring. This review aims to provide a structured overview of emerging biomarkers in metastatic RCC, critically evaluate their current clinical applicability, and propose a biologically informed framework for their integration into clinical decision-making. In addition, we propose a conceptual IMDC-Plus framework that integrates clinical, biological, and early dynamic markers to improve risk stratification in the era of immunotherapy (IO).