Evaluation of the Efficiency and Safety of Stereotactic Body Radiation Therapy Combined With PD-1 Antibody in the Treatment of Unresectable Locally Recurrent Rectal Cancer: A Prospective, Multicenter, Single-Arm, Open Label, Phase II Study
This is a prospective study to delve into the therapeutic benefits of combining stereotactic body radiation therapy (SBRT) with PD-1 monoclonal antibody treatment for patients with unresectable locally recurrent rectal cancer (ULRRC). Our aim is to ascertain the safety of this approach and to offer robust, evidence-based medical guidance for the management of ULRRC using this innovative combination therapy. Researchers will combine SBRT with PD-1 for ULRRC to see if this treatment can provide a benefit of survival. Participants will: 1. Receive chemotherapy combined with PD-1 therapy for 1 cycle → SBRT treatment → Chemotherapy combined with PD-1 therapy for 3-6 cycles (assessment 6 weeks after SBRT treatment) → Surgery/Maintenance therapy. 2. Visit the clinic once every 3 months for checkups and tests
• Before implementing procedures related to the research protocol rather than routine care, informed consent forms with the subject's voluntary signature and dated must be obtained in accordance with regulations and institutional guidelines;
• Patients with pMMR/MSS colorectal cancer;
• Age between 18 and 75 years;
• Tumor recurrence confirmed by histology, cytology, or imaging, and the multidisciplinary team (MDT) including surgeons assesses that the recurrent lesion cannot achieve a one-stage R0 resection (unresectable is defined as: 1. Pelvic MRI showing sacral infiltration at or above S2, 2. And/or lateral pelvic wall invasion, 3. And/or obturator vascular nerve infiltration, 4. After MDT discussion, there are no indications for a one-stage R0 resection, 5. The patient refuses total pelvic exenteration or debulking surgery);
• Locally recurrent rectal adenocarcinoma without clear distant metastasis at diagnosis/MDT team assesses oligometastases as resectable/controllable (UICC 8th edition);
• No prior radiotherapy, or a gap of more than 6 months between the completion of initial radiotherapy and the start of retreatment, with a previous radiotherapy dose of less than 50.4Gy, and no late toxicity in the small bowel or bladder;
• ECOG performance status 0-1;
• Peripheral blood counts and liver and kidney functions within the following allowed ranges (tested within 15 days before treatment start):
‣ White blood cells (WBC) ≥ 3.0×10\^9/L or Absolute Neutrophil Count (ANC) ≥ 1.5×10\^9/L;
∙ Hemoglobin (HGB) ≥ 80 g/L;
• Platelets (PLT) ≥ 100×10\^9/L;
⁃ Liver transaminases (AST/ALT) \< 3.0 times the upper limit of the normal range;
‣ Total bilirubin (TBIL) \< 1.5 times the upper limit of the normal range;
∙ Creatinine (CREAT) \< 1.5 times the upper limit of the normal range;
• No history of other malignancies, not pregnant or breastfeeding, and should use effective contraception during the study period and for 6 months after the last administration;
⁃ Expected survival ≥ 12 months.