Circulating KIM-1 and survival outcomes in renal cell carcinoma: A systematic review and meta-analysis

Renal cell carcinoma (RCC) exhibits substantial clinical heterogeneity, and conventional clinicopathological models have limited ability to provide precise individualized risk stratification. Circulating kidney injury molecule-1 (KIM-1) is an emerging, minimally invasive biomarker with potential prognostic relevance in RCC. However, existing studies have reported inconsistent findings. This meta-analysis aimed to systematically synthesize current evidence and clarify the prognostic significance of circulating KIM-1 in RCC.

A systematic review and meta-analysis was conducted in accordance with PRISMA 2020 guidelines. Studies evaluating the association between circulating KIM-1 levels and survival outcomes in RCC were included. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using random-effects models. Predefined subgroup analyses stratified by disease setting and KIM‑1 quantification method were conducted to explore potential sources of heterogeneity. Leave-one-out sensitivity analysis and publication bias assessment were also implemented.

A total of 7 studies encompassing 8 independent cohorts with 2,415 RCC patients were included. Elevated circulating KIM‑1 was significantly associated with worse overall survival (OS; HR = 1.70, 95% CI: 1.22-2.35), progression‑free survival (PFS; HR = 1.34, 95% CI: 1.05-1.72), and disease‑free survival (DFS; HR = 1.72, 95% CI: 1.45-2.04). Subgroup analyses demonstrated consistent prognostic effects across localized/adjuvant and advanced/metastatic disease settings, as well as categorical and continuous KIM‑1 detection strategies. Sensitivity analyses generally supported the direction of the associations, although variability was observed across individual studies.

Elevated circulating KIM-1 is associated with adverse survival outcomes in RCC; however, given the heterogeneity of included cohorts and limited certainty of evidence, these findings should be considered exploratory and require further prospective validation.