This study aims to evaluate the safety and effectiveness of a combination treatment including a PD-1 inhibitor (serplulimab), oncolytic virus H101, short-course radiotherapy, and XELOX chemotherapy as total neoadjuvant therapy in patients with locally advanced low rectal cancer (cT1-3N0M0).
In this prospective, multicenter, single-arm phase II study, eligible patients will receive a standardized treatment regimen consisting of intratumoral injection of oncolytic virus H101, short-course radiotherapy, chemotherapy, and immunotherapy over multiple cycles. Tumor response will be assessed using imaging, endoscopy, and clinical evaluation after completion of treatment.
The primary objective is to determine the 1-year clinical complete response rate. Secondary outcomes include tumor response rate, organ preservation rate, survival outcomes, and treatment safety.
The results of this study may help improve treatment strategies for rectal cancer, increase the rate of complete response, and provide more opportunities for organ preservation while maintaining safety.
Age 18 to 80 years, male or female.
Histologically confirmed low rectal adenocarcinoma, with tumor located ≤5 cm from the anal verge.
Clinical stage T1-3N0M0 according to AJCC staging criteria.
Mismatch repair-proficient (pMMR) or microsatellite stable (MSS) tumor confirmed by immunohistochemistry or genetic testing.
Histology other than rectal adenocarcinoma (e.g., gastrointestinal stromal tumor, lymphoma).
Prior pelvic radiotherapy.
Prior treatment with PD-1, PD-L1, or CTLA-4 inhibitors.
Known allergy to study drugs or their components.
Single group
Serplulimab
DrugSerplulimab is a humanized monoclonal antibody targeting programmed cell death protein-1 (PD-1). It will be administered intravenously at a fixed dose of 300 mg on Day 1 of each 3-week cycle for a total of 6 cycles. Serplulimab is given in combination with chemotherapy, radiotherapy, and oncolytic virus therapy as part of total neoadjuvant treatment. The aim is to enhance anti-tumor immune response and improve treatment efficacy.
Oncolytic Virus H101
Biological/VaccineH101 is a recombinant human adenovirus type 5 oncolytic virus that selectively replicates in and lyses tumor cells while stimulating anti-tumor immune responses. It will be administered by intratumoral injection on Day 1 of Cycle 1 and Day 1 of Cycle 4. The dose will be determined based on tumor size. H101 is used in combination with immunotherapy, chemotherapy, and radiotherapy to enhance tumor cell killing and improve immune activation.
XELOX Chemotherapy
DrugXELOX chemotherapy consists of oxaliplatin and capecitabine. Oxaliplatin will be administered intravenously at a dose of 130 mg/m² on Day 1, and capecitabine will be given orally at a dose of 1000 mg/m² twice daily from Day 1 to Day 14 of each 3-week cycle. A total of 6 cycles will be administered. Chemotherapy is combined with immunotherapy, radiotherapy, and oncolytic virus therapy to improve tumor response.
Short-course Radiotherapy
RadiationShort-course radiotherapy will be delivered to the rectal tumor using intensity-modulated radiation therapy (IMRT). The total dose is 25 Gy administered in 5 fractions over one week. Radiotherapy is given during the treatment course in combination with immunotherapy, chemotherapy, and oncolytic virus therapy. It aims to enhance local tumor control and stimulate anti-tumor immune response.
1-year Clinical Complete Response Rate
Clinical complete response (cCR) is defined as no evidence of residual tumor based on digital rectal examination, endoscopy showing mucosal healing or scar, and imaging (MRI or CT) without tumor signal or metabolic activity, and no distant metastasis. The proportion of patients achieving cCR and maintaining it for at least 1 year will be evaluated.
Objective Response Rate
The proportion of participants who achieve complete response (CR) or partial response (PR) based on imaging assessments according to RECIST criteria.
Organ Preservation Rate
The proportion of patients who achieve clinical complete response and avoid radical surgery, thereby preserving the rectum.
Disease-Free Survival
Time from treatment initiation to the occurrence of disease recurrence, metastasis, or death from any cause.
Overall Survival
Time from treatment initiation to death from any cause.
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