Advances in Combination Cancer Therapies: Integrated Nanotechnology and Tumor Microenvironment Modulation

Cancer therapy has advanced considerably, yet durable disease control remains constrained by drug resistance, systemic toxicity, and the immunosuppressive and heterogeneous tumor microenvironment (TME). Conventional surgery, chemotherapy, and radiotherapy are still essential, but often fail to eradicate resistant tumor niches, prompting multimodal therapies. Nanotechnology offers a versatile enabling platform that can improve pharmacokinetics, promote tumor-selective accumulation, co-deliver complementary agents, and actively modulate the TME. This review critically synthesizes recent advances in nano-enabled combination therapies that integrate chemotherapy, radiotherapy, immunotherapy, targeted therapy, gene therapy, and stem cell-based approaches to overcome biological barriers in cancer treatment. We examine the design principles of nanocarriers and the mechanisms by which multifunctional platforms improve precision delivery, reduce off-target toxicity, coordinate spatial and temporal drug release, and reprogram immunologically "cold" tumors to a more immune-permissive state. Instead of cataloging individual systems, we identify cross-cutting design criteria such as payload compatibility, stimuli-responsive release, immune activation, and TME remodeling that govern therapeutic synergy and translational feasibility. Here, we discuss key challenges such as biocompatibility, scalable manufacturing, patient selection, biomarker development, and clinical validation and propose a framework for prioritizing the most promising multifunctional nanoplatforms for clinical translation. This review provides a critical roadmap for integrating nanotechnology and TME modulation into the next generation of combination cancer therapies.