Pre-treatment C-reactive protein level is a prognostic marker of patients treated with immune checkpoint inhibitors for renal cell carcinoma: a systematic review and meta-analysis.

[BACKGROUND] C-reactive protein (CRP) is one of the most important markers reflecting systemic inflammatory response. The objective of this study was to evaluate the prognostic value of CRP in patients undergoing treatment with immune checkpoint inhibitor (ICI) for renal cell carcinoma.

[METHODS] We performed a systematic search of PubMed, Cochrane Library, and Web of Science databases in July 2024, following the PRISMA statement. A pooled meta-analysis was conducted to assess the prognostic value of CRP. We also evaluated the prognostic values of CRP kinetics.

[RESULTS] The search identified 12 non-randomized controlled trials (NRCTs), of which 7 assessed the prognostic value of CRP and 5 evaluated CRP kinetics. Higher CRP level before treatment with ICI was a predictor of overall survival (OS) [hazard ratio (HR): 3.97, 95% confidence interval (CI): 2.27-6.94]. In a subgroup of patients treated with nivolumab alone, the pooled HR of OS and progression-free survival (PFS) was HR: 5.67, 95% CI: 2.12-15.12 and HR: 1.62, 95% CI: 1.01-2.61, respectively. "CRP flare-responders" defined as having CRP elevation of at least double the baseline during the first month after ICI-initiation followed by a decrease below the baseline within 2 months and "CRP-responders" defined as having a decrease in CRP levels of at least 30% from baseline within 3 months, did not show significantly better prognosis regarding PFS.

[CONCLUSIONS] Pre-treatment CRP level may stand as a good prognostic indicator in patients receiving ICI for renal cell carcinoma.