SCRT Followed by Camrelizumab Combined With Fluzoparib and Chemotherapy as Neoadjuvant Therapy for LARC

This study is testing a combination of treatments before surgery for people with locally advanced rectal cancer (cancer in the lower part of the large bowel that has not yet spread to distant organs). The approach includes short-course radiation, an immunotherapy drug (camrelizumab), a PARP inhibitor (fluzoparib), and chemotherapy — all given together to try to shrink the tumor before an operation. **You may be eligible if...** - You are 18–75 years old - You have a confirmed rectal adenocarcinoma (the most common type of rectal cancer) that is locally advanced - Your tumor is "proficient mismatch repair" or "microsatellite stable" (pMMR/MSS) — a specific genetic type your doctor can test for - The bottom of your tumor is within 10 cm of the anal opening - You have not received prior radiation or chemotherapy for this cancer **You may NOT be eligible if...** - Your cancer has spread to distant organs (metastatic) - Your tumor has a different genetic type (microsatellite instability-high) - You have previously had pelvic radiation - You have serious heart, liver, or kidney problems Talk to your doctor to see if this trial is right for you.