FAN score comprising fibrosis-4 index, albumin-bilirubin score and neutrophil-lymphocyte ratio is a prognostic marker of urothelial carcinoma patients treated with pembrolizumab.

It is important to identify prognostic and predictive markers of metastatic urothelial carcinoma (mUC) treated with immunocheckpoint inhibitors. We sought to establish a prognostic marker for patients with mUC treated with pembrolizumab based on only blood test results. We included 165 patients with mUC in the discovery cohort and 103 with mUC who were treated with pembrolizumab in the validation cohort. Multivariate and Cox regression analyses were used to analyse the data. In the discovery cohort, the fibrosis-4 index (hazard ratio [HR]: 2.13, 95% confidence interval [CI] 1.20-3.76, p = 0.010), albumin-bilirubin score (HR 1.91, 95% CI 1.27-2.88, p = 0.002), and neutrophil-lymphocyte ratio (HR: 1.84, 95% CI 1.22-2.79, p = 0.004) were independent significant prognostic factors. We established a 'FAN score' that included these three aforementioned items, which were assigned one point each. We divided patients into the 0-1 point (n = 116) and 2-3 points (n = 49) groups. The FAN score was a significant prognostic marker for cancer-specific survival (CSS) (HR 1.48, 95% CI 1.19-1.83, p < 0.001) along with the Eastern Cooperative Oncology Group Performance Status. The FAN score was also a prognostic factor of progression-free survival (PFS) (HR: 1.25, 95% CI 1.01-1.54, p = 0.036) along with the presence of liver metastasis. In the validation cohort, the FAN score was a significant prognostic factor for CSS (HR: 1.48, 95% CI 1.19-1.85, p = 0.001) and PFS (HR: 1.29, 95% CI 1.02-1.62, p = 0.034). We established the FAN score as a prognostic marker for patients with mUC treated with pembrolizumab.