Fibrinogen Levels in Patients with Metastatic Renal Cell Carcinoma Treated with Nivolumab: Results of a Multicenter Prospective Trial

Background: Introduction of immune checkpoint inhibitors in the standard of care for metastatic renal cell carcinoma (mRCC) requires robust but yet simple biomarkers to predict efficacy of immunotherapy. Objective: The aim of this study was to evaluate the association between fibrinogen levels and efficacy of second-line therapy with nivolumab in mRCC. Methods: This is a prospective multicenter biomarker study. Fibrinogen levels were measured one week prior to second-line nivolumab therapy and six times monthly. A high fibrinogen level was defined as ≥5 g/L. Patients were divided into two cohorts: high (H) and normal (N) fibrinogen levels. The primary endpoint was overall survival (OS). Results: The median OS was 31.5 months (95% confidence interval [CI], 27.9 to 35.1) in cohort N vs. 20.9 months (95% CI, 18.1 to 23.7) in cohort H (hazard ratio [HR], 0.39; 98.5% CI, 0.21 to 0.7; P = 0.002). The median progression-free survival was 9.4 months (95% CI, 5.5 to 14.1) in cohort N and 4.0 months (95% CI, 2.9 to 5.1) in cohort H (HR, 0.65; 95% CI, 0.51 to 0.72; P < 0.001). The objective response rate was higher in N cohort (33% vs. 17% ; P = 0.012). No statistically significant changes of fibrinogen concentration during nivolumab therapy were found. Conclusion: The study demonstrated an association of hyperfibrinogenemia with worse clinical outcomes of second-line nivolumab monotherapy in patients with mRCC. Further validation of fibrinogen as a predictive biomarker for immunotherapy efficacy in patients with mRCC is warranted.