This is a single-center, bidirectional (retrospective and prospective) registry study aimed at evaluating the safety and efficacy of Non-Operative Management (NOM) and Organ-Preserving Functional Surgery (OPFS) in patients with mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) or POLE-mutated gastrointestinal (GI) cancers who received neoadjuvant immunotherapy.Patients achieving a clinical complete response (cCR) or near-cCR may undergo a "Watch \& Wait" (W\&W) strategy, while those with near-cCR or non-cCR ($\\le ymrT2N0$) may undergo local excision (LE) or endoscopic resection (ESD/EMR). Patients undergoing radical operation (RO) will serve as the control cohort to compare oncological outcomes and safety data.