Treatment Intensification Arms

CAPOX was limited to three cycles based on evidence that reduced-cycle TNT preserved high response rates with more favourable toxicity outcomes. CXB delivers a high-dose intraluminal radiation boost directly to the tumour with limited exposure to surrounding structures. MR-guided radiotherapy enables precise, response-adaptive dose escalation. Local excision is available only in Arm 3 for small remnants after chemotherapy and is excluded from boost arms because additional local radiation increases morbidity risk from later endoluminal surgery. After SCRT, patients receive one of three intensification strategies depending on centre capability: CXB boost, MR-guided EBRT boost, or CAPOX chemotherapy.