Albumin-to-Alkaline Phosphatase Ratio as a Novel Prognostic Marker of Nivolumab Monotherapy for Previously Treated Metastatic Renal Cell Carcinoma

Background/Aim: The relationship between albumin-to-alkaline phosphatase ratio (AAPR) and the outcome of patients with metastatic renal cell carcinoma (mRCC) treated with immune checkpoint inhibitors remains unresolved. We aimed to clarify the prognostic role of AAPR in nivolumab monotherapy for previously treated mRCC. Patients and Methods: We retrospectively evaluated 60 patients with mRCC treated with nivolumab after failure of at least one molecular targeted therapy. The patients were stratified into two groups based on the baseline AAPR. The threshold of AAPR was determined using receiver-operating characteristics and Youden index analyses. Overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) of nivolumab therapy were compared between the high and low AAPR groups. Results: The threshold of AAPR was set at 0.3, and 20 patients (33%) were assigned to the low AAPR group. The median OS and PFS were significantly lower in the low AAPR group than those in the high group (OS: 8.3 months vs. not reached, p<0.0001; PFS: 2.9 vs. 10.4 months, p=0.0006). Moreover, ORR was significantly lower in the low AAPR group than in the high group (16% vs. 45%, p=0.0397). Multivariate analyses further showed that AAPR was an independent factor for OS [HR=0.27 (95% CI=0.090.77), p=0.0151] but not for PFS (p=0.174). Conclusion: Baseline AAPR was significantly associated with outcome in patients with mRCC receiving nivolumab monotherapy and may, therefore, constitute an effective prognostic factor for nivolumab treatment.