Organ preservation in rectal cancer: an endoscopist's perspective on current evidence and future directions.

Rectal cancer management has increasingly shifted toward organ-preserving strategies that aim to maintain oncologic control while preserving bowel, urinary, and sexual functions. Although radical surgery remains highly effective, its substantial long-term functional morbidity underscores the need for less invasive, risk-adapted approaches. This review summarizes current evidence and emerging directions in organ-preserving treatment for rectal cancer, with a particular focus on the evolving role of endoscopists in patient selection, treatment decision making, endoscopic treatment, and post-treatment surveillance. Recent advances in risk stratification have improved the potential for more accurate patient selection. Refined histopathological risk criteria, predictive nomograms, artificial intelligence-based models, and emerging liquid biopsy biomarkers, such as circulating tumour DNA, are being explored to better estimate the risk of lymph node metastasis after endoscopic resection. In parallel, novel endoscopic techniques, such as peranal endoscopic myectomy and endoscopic intermuscular dissection, have expanded the technical feasibility of en bloc resection for challenging rectal lesions. Local excision followed by adjuvant chemoradiotherapy represents a promising investigational strategy, with ongoing trials, such as TESAR and JCOG1612 (RESCUE), that are expected to clarify its safety and efficacy. Total neoadjuvant therapy has become a central treatment paradigm for locally advanced rectal cancer, achieving higher pathological complete response rates and improved disease-related outcomes compared with conventional neoadjuvant chemoradiotherapy. Additionally, non-operative management (watch-and-wait) after total neoadjuvant therapy, supported by prospective trials and international registries, has established a strong evidence base for organ preservation in carefully selected patients. In molecularly selected patients with mismatch repair-deficient or microsatellite instability-high tumours, immune checkpoint inhibitor-based therapy has emerged as a promising organ-preserving strategy, although current evidence remains limited to early-phase prospective studies. Despite these advances, optimal patient selection and long-term oncologic safety remain under investigation. Further prospective studies and international collaboration are needed to establish robust evidence and optimize the implementation of organ-preserving strategies in rectal cancer.