Study on the Safety and Efficacy of MR-Linac Technique in Patients With Unresectable Locally Advanced Colon Cancer

Pre-specified run-in/feasibility phase. As outlined in the registered protocol, this record includes an initial feasibility (run-in) phase conducted under the same eligibility criteria and intervention as the definitive efficacy/safety phase. The run-in is designed solely to evaluate operational and workflow feasibility. The run-in is not powered for efficacy and will not test efficacy or survival hypotheses.

Pre-specified feasibility thresholds for proceeding include, for example: protocol adherence ≥85-90%, adaptive-plan success ≥80-90%, and accrual feasibility ≥80% of the target. The run-in sample size is capped (≈24 patients), and its endpoints/time frames are listed under Outcome Measures. Meeting these thresholds triggers continuation to the definitive phase without changing the intervention or eligibility.

Inclusion criteria

• Patients over 18 years old
• Patients can remain in a stationary position on the treatment bed for 1-1.5 hours
• ECOG score 0-1
• Pathological diagnosis of colon adenocarcinoma, clinical stage cT4N0-2M0
• Organ function is normal, and the following conditions are required: white blood cell count ≥3.5×10^9/L; platelet count ≥100×10^9/L; hemoglobin ≥90g/L. Total bilirubin level ≤1.5× upper limit of normal (ULN); AST and ALT levels ≤2.5 × ULN; endogenous creatinine clearance rate: 56-122ml/min; serum creatinine <1.0× ULN; serum albumin ≥30g/L.
• Able to adhere to the study protocol during the research period
• Signed written informed consent

Exclusion criteria

• Patients with dMMR or MSI-H
• Presence of other types of tumors in addition to colon adenocarcinoma
• Claustrophobia or inability to undergo MRI or treatment due to the presence of metal implants or other reasons
• Distant metastasis (M1)
• Pregnant or lactating women
• Previous anti-tumor treatment
• Concurrent use of prohibited drugs for treatment
• Known history of positive human immunodeficiency virus testing or known acquired immunodeficiency syndrome.
• Clinically significant (i.e., active) cardiovascular disease: cerebrovascular accident/stroke (<6 months prior to enrollment), myocardial infarction (<6 months prior to enrollment), unstable angina pectoris, congestive heart failure (≥New York Heart Association class II) or severe arrhythmia requiring medication treatment
• Individuals with uncontrolled epilepsy, central nervous system disorders or a history of mental illness, whose clinical severity may hinder signing informed consent or affect patient compliance with oral medication according to the investigator's judgement
• Organ transplant surgery requiring immunosuppressive therapy
• Severe, uncontrolled recurrent infections or other severe, uncontrolled comorbidities