Clinical aspect of combined immunotherapy and radiotherapy effect on tumor immune microenvironment in hepatobiliary and pancreatic cancers.

Hepatobiliary and pancreatic cancers (HBPCs) remain among the most aggressive nature and lethal malignancies, presenting formidable challenges in their treatment. Surgical resection remains the cornerstone of curative treatment for early-stage HBPCs; however, advanced cases often necessitate a multidisciplinary systematic approach incorporating radiotherapy and immunotherapy. In recent years, innovations in radiotherapy technology have facilitated the precise and targeted delivery of tumoricidal doses, minimizing damage to surrounding normal tissue and expanding the application of radiotherapy in treating HBPCs. Moreover, the intricate impact of radiotherapy on the tumor immune microenvironment (TIME) is being increasingly understood. Synergizing radiotherapy with immunotherapy to induce a robust and sustained antitumor immune response, both locally at the irradiated site and systemically throughout the body, represents a promising and increasingly critical avenue of current research. This review begins by delineating the heterogeneity of the TIME in HBPCs and discusses how radiotherapy can either stimulate or suppress the TIME under various conditions. It also highlights recent preclinical and clinical advances in combining radiotherapy with immunotherapy, which have shown potential in improving local control rates and inducing systemic antitumor responses. This emerging paradigm warrants sustained research to fully realize its therapeutic potential in HBPC management.