Monitoring Treatment Response With On-board DWI During Neo-adjuvant Chemo-radiation for Rectal Cancer Using Magnetic Resonance-guided-radiotherapy Systems

This study is testing an advanced MRI imaging technique to monitor how rectal cancer responds to chemoradiation therapy in real time. Patients receive standard chemo-radiation treatment on an MRI-guided radiotherapy machine, and special scans (DWI — diffusion-weighted imaging) are done during treatment to track how the tumor is shrinking or changing. **You may be eligible if...** - You are over 18 years old - You have rectal cancer confirmed by biopsy - Your cancer has been recommended for combined chemotherapy and radiation (chemoradiation) before surgery - You are in adequate physical condition (Karnofsky index ≥70 or ECOG 0–1) - Women of childbearing age must use effective contraception **You may NOT be eligible if...** - You have metal implants or other contraindications to MRI - Your cancer has spread to distant organs (metastatic disease) - You have serious health conditions making chemoradiation unsafe - You are pregnant Talk to your doctor to see if this trial is right for you.