This is a single-center, exploratory clinical study for patients with newly diagnosed, high-risk, locally advanced rectal cancer. The study aims to evaluate the effectiveness and safety of a comprehensive pre-surgery (neoadjuvant) treatment strategy.
All participants will receive a short course of radiation therapy (25 Gy in 5 fractions) over one week. This will be followed by a combination of chemotherapy (Liposomal Irinotecan, Oxaliplatin, and Capecitabine) and immunotherapy (Sintilimab). This combined treatment is administered for six cycles.
For patients who achieve a complete response, the option to avoid immediate surgery and enter a close monitoring program ("Watch and Wait") will be considered.
Voluntary Participation: Subjects voluntarily participate in the study, sign the informed consent form, and have good compliance.
Age and Gender: Age between 18 and 75 years, any gender.
Pathological Diagnosis: Histologically or cytologically confirmed rectal adenocarcinoma; confirmed mismatch repair proficient (pMMR) or microsatellite stable (MSS) by genetic testing or immunohistochemistry.
Disease Stage: Assessed as high-risk, mid-low (distance from the anal verge ≤10 cm) locally advanced rectal cancer by colonoscopy, digital rectal exam, or MRI. High-risk definition: Meeting at least one of the following: cT4, extramural vascular invasion (EMVI), tumor deposits, involvement of the mesorectal fascia or intersphincteric plane.
Other Malignancies: Diagnosis of another malignancy within 5 years prior to the first dose, except for adequately treated basal cell carcinoma, squamous cell carcinoma of the skin, carcinoma in situ, localized prostate cancer, or papillary thyroid cancer, etc.
Allergy: Known or suspected allergy to the study drugs or any of their excipients.
Pregnancy and Lactation: Pregnant or lactating women, or women planning to become pregnant during the study or within 6 months after the last dose.
Central Nervous System Disease: Known active epilepsy, active central nervous system (CNS) metastases, spinal cord compression, carcinomatous meningitis, or leptomeningeal disease.