Short-course RT Followed by NALIRIFOX Plus Pucotenlimab as Neoadjuvant Therapy for High-risk Locally Advanced Rectal Cancer With MSS/pMMR

Inclusion criteria

• . Age: 18-70 years;
• . ECOG PS score: 0-1;
• . Pathologically confirmed rectal adenocarcinoma with immunohistochemistry and/or genetic testing showing MSS/pMMR status;
• . Lesion located ≤10 cm from the anal verge, confirmed by colonoscopy or digital rectal examination;
• . According to the 8th edition of the 2018 AJCC Cancer Staging Manual and the 2008 ESMO staging criteria for lower rectal cancer: patients with stage II/III rectal cancer staged by MRI or endorectal ultrasound, who have at least one of the following high-risk factors: cT4a with more than half the circumference of the bowel invaded (measured by MRI), cT4b (resectable), cT3 with tumor penetration ≥5 mm beyond the muscularis propria (T3c/d) and positive extramural venous invasion (EMVI+) (for mid-upper rectal tumors), cN2, MRF+ (≤2 mm); for lower rectal tumors located on the anterior wall, additional criteria include T3 stage and tumor occupying \>50% of the bowel circumference; for tumors primarily located on the lateral-posterior wall in the lower rectum, tumor penetration through the bowel wall (internal anal sphincter) ≥5 mm; for tumors invading the external anal sphincter or levator ani muscle (staged as stage IV). Preoperative T staging is based on endorectal ultrasound and rectal MRI; N staging on abdominal CT; M staging on abdominal and chest CT. If symptoms are present, appropriate imaging studies (brain MRI or whole-body bone scan) should be performed. Patients with MRI contraindications may be cautiously included based on CT and endorectal ultrasound staging. All patient staging must be reviewed and confirmed by a multidisciplinary team (MDT).