Next Generation STAR-TREC (NG-ST) - Organ Preservation in Early Rectal Cancer

Inclusion Criteria: * Age ≥ 18 years * Written informed consent * Biopsy-proven rectal adenocarcinoma * Tumor located \<12 cm from the anal verge * MRI-staged T1-T3b tumor * N0 or NX (no radiologic evidence of nodal metastases) * M0 or MX (no radiological evidence of distant metastases) * ECOG performance status 0-1 * Multidisciplinary team (MDT) assessment confirming that both total mesorectal excision (TME) and chemoradiotherapy are feasible treatment options Exclusion Criteria: * MRI-defined N1 or higher nodal disease * Distant metastases (M1) * MRI extramural vascular invasion (mriEMVI) * Threatened mesorectal fascia (≤1 mm on MRI) * Maximum tumor diameter \> 40 mm * MRI defined mucinous tumor * No residual luminal tumor following prior endoscopic resection * Recurrent rectal cancer * Prior pelvic radiotherapy * Uncontrolled significant cardiorespiratory comorbidity * Known complete dihydropyrimidine dehydrogenase (DPYD) deficiency * Known Gilbert's syndrome * Pregnancy or breastfeeding * Concomitant medication contraindicated with capecitabine that cannot be safely discontinued * Age \<18 years