A Phase II Exploratory Multicenter Randomized Controlled Clinical Trial to Evaluate the Effectiveness of Neoadjuvant Short-Course Radiotherapy (SCRT) Followed by CAPEOX Chemotherapy and Serplulimab in Microsatellite Stable (MSS) or Proficient Mismatch Repair (pMMR) Rectal Cancer With Synchronous Oligometastases
Objective: This project aims to evaluate the effectiveness of iTNT combined with SCRT in MSS/pMMR rectal cancer patients with synchronous oligometastases. The novel approach integrates SCRT with CAPEOX chemotherapy and Serplulimab, potentially improving complete response rates, organ preservation opportunities, and overall treatment efficacy while reducing recurrence risks. This pioneering study represents the first investigation of iTNT in synchronous rectal cancer oligometastases, offering a potentially transformative treatment strategy for this challenging patient population. Research Innovation: The study uniquely combines SCRT, CAPEOX chemotherapy, and Serplulimab in a neoadjuvant setting for MSS/pMMR synchronous rectal cancer oligometastases, addressing an unmet clinical need and potentially establishing a new treatment paradigm in this field.
• \- Has signed the written Informed Consent Form (ICF) and is able to comply with protocol-specified visits and procedures.
• Age between 18-75 years.
• Histologically confirmed primary rectal adenocarcinoma, with MRI showing tumor location within 10cm from the anal verge.
• Synchronous oligometastatic rectal cancer confirmed by comprehensive imaging evaluation (contrast-enhanced CT, contrast-enhanced MRI, PET-CT, etc.), with ≤2 metastatic sites and ≤5 total metastatic lesions.
• Microsatellite stability status confirmed as MSS (using the NCI-recommended 5 microsatellite markers: BAT25, BAT26, D5S346, D2S123, D17S250) or proficient mismatch repair (pMMR) status confirmed by immunohistochemistry showing positive nuclear expression of all 4 MMR proteins (MLH1, MSH2, MSH6, PMS2).
• At least one measurable lesion according to RECIST v1.1 criteria.
• Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-1.
• Adequate organ function and bone marrow reserve, defined as follows:
• Complete blood count:
• Absolute Neutrophil Count (ANC) ≥1.5×109/L Platelet count (PLT) ≥100×109/L Hemoglobin (HGB) ≥10.0g/dL
• Liver function:
• Total Bilirubin (TBIL) ≤1.5×Upper Limit of Normal (ULN) Alanine transaminase (ALT) and Aspartate aminotransferase (AST) ≤3×ULN Serum albumin (ALB) ≥35 g/L
• Renal function:
• Serum creatinine ≤1.5×ULN or creatinine clearance ≥50 mL/min (calculated using Cockcroft-Gault formula \[see Appendix 3\] or standard 24-hour urine collection method) Urine protein by dipstick \<2+ For subjects with baseline urine protein ≥2+ by dipstick, 24-hour urine protein must be \<1g
• Coagulation:
• International Normalized Ratio (INR) ≤1.5 Activated partial thromboplastin time (APTT) ≤1.5×ULN Certain anticoagulant medications (such as antiplatelet agents, vitamin K antagonists) must be discontinued 7-14 days before surgery and replaced with alternative medications (such as low molecular weight heparin) No concurrent serious diseases that would threaten subject survival (leading to expected survival \<5 years).
• Women of childbearing potential and men whose partners are of childbearing potential must use effective contraception during the entire treatment period and for 6 months after treatment completion. Female subjects must either have evidence of post-menopausal status, or if pre-menopausal, have a negative urine or serum pregnancy test.