Abstract
Local recurrence after breast cancer surgery presents a critical challenge, demanding novel local immunotherapies capable of eliminating residual disease while avoiding systemic toxicity. In situ-forming hydrogels, functionalized with bioactive cargoes, represent a promising platform for precise spatiotemporal drug delivery directly into the post-resection tumor microenvironment. This review comprehensively examines the core design principles governing these advanced materials, highlighting their biocompatibility, stimuli-responsive behavior, tunable mechanics for conforming to surgical cavity, and capacity for multifunctional integration. A key mechanism discussed is how this controlled release profile orchestrates a temporal progression from innate immune activation to robust adaptive immunity. Despite significant promise, translational success faces substantial hurdles, including efficacy validation, scalable manufacturing, regulatory pathway definition, and the lack of predictive biomarkers. Future research priorities include optimizing drug/antigen release kinetics, establishing standardized characterization methods for complex biohybrid systems, and designing adaptive clinical trials incorporating detailed immunomonitoring. By integrating functional biomaterials with immuno-oncology, in situ-forming hydrogels offer a paradigm-shifting approach for postoperative cancer treatment. This review provides a strategic roadmap to accelerate their translation from bench to bedside.