Leucine Plus Radiochemotherapy for Neoadjuvant Treatment of Locally Advanced Rectal Cancer

This study tests whether adding leucine (an amino acid found in protein-rich foods) to standard chemoradiation treatment before surgery improves outcomes for people with locally advanced rectal cancer, potentially helping the body better respond to therapy. **You may be eligible if...** - You are between 18 and 80 years old - You have been diagnosed with locally advanced rectal adenocarcinoma (cancer in the lower bowel) confirmed by MRI — specifically cT3 or higher, or cancer that has spread to nearby lymph nodes - The bottom edge of your tumor is within 10 cm of the anal opening - You have not had any prior treatment for rectal cancer - You are in good enough health to receive chemoradiation (ECOG 0–1) **You may NOT be eligible if...** - You have already received treatment for rectal cancer (other than traditional Chinese medicine) - You have had a heart attack, stroke, or uncontrolled heart failure in the past 6 months - You have severe kidney or liver problems - You are pregnant or breastfeeding - Your blood counts or organ function do not meet minimum safety thresholds Talk to your doctor to see if this trial is right for you.