Neoadjuvant Bevacizumab + Chemotherapy Combined With Short-course Radiotherapy

This study is testing bevacizumab (a drug that blocks tumor blood vessel growth) plus chemotherapy, followed by a short course of radiation, as a pre-surgery treatment for people with locally advanced rectal cancer that has specific gene mutations (KRAS or NRAS positive). **You may be eligible if...** - You are between 18 and 75 years old - You have biopsy-confirmed rectal cancer (adenocarcinoma) - Your tumor has KRAS or NRAS mutations, without BRAF mutations or high microsatellite instability - MRI confirms locally advanced disease (spread into surrounding tissue or nearby lymph nodes) - You have no intestinal obstruction and no distant spread detected on scans - You are in good general health (ECOG 0–1) with adequate organ function **You may NOT be eligible if...** - Your tumor has BRAF mutations or high microsatellite instability - Your cancer has spread to distant organs - You have intestinal obstruction - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.