Abstract Background Immunotherapy for colorectal cancer (CRC) has long been constrained by limited clinical efficacy. While traditional perspectives attribute this to the immunosuppressive nature of the tumor microenvironment, this study proposes a novel paradigm: the primary tumor resides in an environment saturated with complex gut microbiota. The staggering volume of microbial antigens creates overwhelming "environmental noise," which severely compromises the immune system’s ability to recognize tumor-specific antigens. Hypothesis We propose the "Pure Antigen Reservoir" (PAR) hypothesis. When cancer cells metastasize to lymph nodes or other distant organs, they escape the microbial interference of the primary site. In these relatively "sterile" tissue environments, metastatic cancer cells present more distinct and high-fidelity antigenic fingerprints, forming a natural, high-quality antigen reservoir. Consequently, the early stage of metastasis should not be viewed merely as disease progression, but as a critical "Strategic Window" for initiating potent immunotherapy. Mechanism and Strategy Utilizing physical intervention techniques—such as Lymphatic Pressure Balance Extraction (LPBE) or PPDAP methods—we can precisely retrieve "pure tumor fragments" (Nano-Antigen Fragments, NAFs) free from microbial noise at the metastatic site. These fragments can more effectively prime dendritic cells (DCs) to elicit high-precision T-cell responses. This targeted priming is designed to trigger a systemic Abscopal Effect, enabling the immune system to successfully identify and eradicate cancer cells at the primary site, thereby overcoming immune evasion. Conclusion This hypothesis provides a robust theoretical framework for low-cost, high-efficiency autologous immunotherapy. By shifting the therapeutic focus from the "antigenically noisy" primary site to the "antigenically pure" metastatic window, this approach offers a potential breakthrough for the current stalemate in CRC immunotherapy, paving the way for more accessible and democratized medical options for patients globally. (Key Terms for Reference) Environmental Noise; Pure Antigen Reservoir (PAR); Strategic Window; Sterile environment; High-fidelity; Autologous Immunotherapy; Democratized medical options;
Li Chung Lee (Sun,) studied this question.