Clinical utility of combining the C-reactive protein-to-albumin ratio and systemic immune-inflammation index for prognostic assessment in metastatic renal cell carcinoma

Background Inflammation-based biomarkers may refine prognostic stratification in patients with metastatic renal cell carcinoma (mRCC). This study evaluated the prognostic value of the pretreatment C-reactive protein-to-albumin ratio (CAR) and systemic immune-inflammation index (SII) in patients with mRCC receiving first-line systemic therapy. Methods We retrospectively analyzed 117 patients who received first-line systemic therapy between January 2001 and April 2022. Pretreatment CAR and SII were evaluated as readily available blood-based inflammatory biomarkers. Overall survival (OS) was defined as the primary outcome, and progression-free survival (PFS) was defined as the secondary outcome. Exploratory cutoffs were CAR 0.0731 and SII 533.81. Results High CAR and high SII were independently associated with shorter OS after adjustment for IMDC risk classification and nephrectomy status. The adjusted HRs were 2.36 for high CAR (95% CI, 1.30–4.27; p = 0.005) and 2.58 for high SII (95% CI, 1.42–4.69; p = 0.002). Patients with concurrent elevation of both CAR and SII had the shortest OS compared with those with neither marker elevated (HR, 6.39; 95% CI, 2.76–14.77; p < 0.001). Adding CAR and SII to International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) improved the optimism-corrected C-index for OS from 0.641 to 0.733. Conclusions Pretreatment CAR and SII were associated with OS in patients with mRCC receiving first-line systemic therapy. These readily available biomarkers may help refine OS risk assessment when used alongside established clinical factors, but external validation is required before clinical implementation.