The Usefulness of Serum Interleukin-6 as a Predictor of Response to Atezolizumab plus Bevacizumab Combination Treatment in Hepatocellular Carcinoma

Introduction: In atezolizumab plus bevacizumab (Atezo/Bev) combination treatment, both drugs act on the immune system. Previously, we reported that immunological changes after Atezo/Bev administration for unresectable hepatocellular carcinoma (uHCC) revealed significant alterations in interleukin (IL)-6, soluble IL-2 receptor, tumor necrosis factor-alpha, and programmed cell death-1 levels. Among these variable factors, serum levels of IL-6 can be easily measured on a commercial basis. Therefore, this study aimed to investigate the utility of serum IL-6 as a predictor of tumor response to Atezo/Bev treatment for uHCC. Method: The study included 44 patients with HCC treated with Atezo/Bev. Blood samples were collected before and 3 weeks after treatment, and tumor response was assessed using contrast-enhanced computed tomography 6 weeks after treatment. Results: Significant changes in serum IL-6 levels were observed in patients treated with Atezo/Bev as first-line therapy but not in those treated with it as second-line or later-line therapy. In patients treated with Atezo/Bev as first-line therapy, serum IL-6 levels increased significantly after treatment in patients with a complete or partial response but not in patients with stable or progressive disease. Furthermore, compared to other tumor markers such as alpha-fetoprotein, Lens culinaris agglutinin-reactive fraction of alpha-fetoprotein, and des-gamma-carboxyprothrombin, serum IL-6 levels exhibited the highest sensitivity in predicting tumor response during the treatment period. Conclusion: In patients with uHCC treated with Atezo/Bev, serum IL-6 levels could serve as a potential predictor of tumor response. Elevated levels after treatment may indicate a favorable tumor response and prognosis.