The Radiation Oncology-Biology Integration Network (ROBIN) Molecular Characterization Trial (MCT) of Standard Short Course Radiotherapy for Rectal Cancer

This study is collecting tumor samples and blood from patients with rectal cancer who are receiving a short course of radiation therapy before surgery. Researchers want to understand the biology of how tumors respond to radiation at a molecular level, which could help improve future treatments. **You may be eligible if...** - You are 18 or older and have been diagnosed with rectal cancer (adenocarcinoma) confirmed by biopsy - Your cancer has not spread to distant parts of the body - You have not had prior pelvic radiation, chemotherapy, or surgery for rectal cancer - You are in good physical condition (ECOG performance status 0–1) - Your blood counts and organ function meet the study's requirements **You may NOT be eligible if...** - Your rectal cancer has come back after previous treatment - Your cancer cannot be surgically removed - You have previously had a stem cell or organ transplant - You are currently taking immune-suppressing medications above a certain dose - You are receiving other cancer treatments or experimental therapies Talk to your doctor to see if this trial is right for you.