Node-sparing Short-Course Radiation Combined With CAPOX and Tislelizumab for MSS Rectal Cancer

Inclusion criteria

• Patients who have a strong willingness to preserve the anus and are willing to receive neoadjuvant therapy.
• Male or Female aged 18-75.
• Patients diagnosed with low rectal cancer within 10 cm from the lower edge of the tumor to the anal verge by pelvic MRI and anorectoscopy, the clinical stage is cT3-4bN0/+M0, and the lymph nodes are limited to the mesorectum.
• Histologically confirmed rectal adenocarcinoma; Genetic testing suggests MSI-L or MSS, or tumor biopsy immunohistochemistry reveals pMMR, that is, MSH1, MSH2, MSH6, and PMS2 are all positive.
• Eastern Cooperative Oncology Group (ECOG) score 0-1.
• No previous treatment (including anti-tumor therapy, immunotherapy or pelvic radiation).
• Laboratory tests indicating no contraindications to radiotherapy, chemotherapy and immunotherapy.
• Informed consent form signed.

Exclusion criteria

• Patients with a previous history of malignant tumors besides rectal cancer.
• Patients with distant metastases before enrollment.
• Patients with positive internal or external iliac lymph nodes are assessed by MRI or CT.
• Patients with obstruction, perforation, or bleeding that require emergency surgery.
• Patients with severe concomitant diseases and estimated survival time ≤ 5 years.
• Allergic to any component of the therapy.
• Patients who received immunosuppressive or systemic hormone therapy for immunosuppressive purposes within 1 month prior to the initiation of therapy.
• Patients who have received any other experimental drug (including immunotherapy) or participated in another interventional clinical trial within 30 days before screening.
• Factors leading to study termination, such as alcoholism, drug abuse, other serious illnesses (including psychiatric disorders) requiring combination therapy, and patients with severe laboratory abnormalities.
• Patients with congenital or acquired immune deficiency (such as HIV infection).
• Vulnerable groups, including mentally ill, cognitively impaired, critically ill patients, minors, pregnant or lactating women, illiterate, etc.
• Other conditions that investigators consider not suitable for this study.