SIB-RT Combined With CAPOX and PD-1 for High-Risk Rectal Cancer

A Prospective Single-Arm Phase II Clinical Study of Neoadjuvant Short-Course Radiotherapy With Simultaneous Integrated Boost Combined With Capecitabine-Oxaliplatin and PD-1 Inhibitor Therapy in High-Risk Locally Advanced Rectal Cancer

The biological effective dose of short-course radiotherapy is relatively lower compared to long-course radiotherapy, which may lead to an increased local recurrence rate in patients with mid to low rectal cancer who are at high risk of locally advanced disease due to insufficient radiation dose. Combining short-course radiotherapy with simultaneous integrated boost (SIB) and immunotherapy-chemo regimens could potentially further enhance tumor regression and improve local control, providing a promising treatment option for high-risk locally advanced rectal cancer patients. Therefore, this clinical trial aims to explore the safety and effectiveness of a short-course SIB radiotherapy regimen combined with immunotherapy and chemotherapy as neoadjuvant treatment for locally advanced rectal cancer, based on short-course radiotherapy combined with chemotherapy and immunotherapy.

Inclusion Criteria:

• Participants must voluntarily agree to join this study and sign an informed consent form.
• Age at the time of signing the informed consent form must be between 18 and 75 years.
• Histologically confirmed diagnosis of rectal adenocarcinoma.
• High-risk locally advanced pMMR/MSS rectal cancer, categorized according to the AJCC/UICC 8th edition clinical staging and in reference to the inclusion criteria of the RAPIDO study, must meet at least one of the following conditions: cT4 stage, cN2 stage, involvement of the mesorectal fascia (MRF), or presence of laterally enlarged lymph nodes, with M0 status.
• The inferior margin of the tumor must be ≤10 cm from the anal verge.
• No prior anti-cancer treatment for rectal cancer (including local-regional and systemic therapy).
• Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) score of 0-1.
• At least one measurable lesion according to RECIST v1.1 criteria.
• Normal function of major organs without severe abnormalities in hematological, cardiovascular, pulmonary, hepatic, renal, or bone marrow function; laboratory tests must meet the following requirements:

Hemoglobin (Hb) ≥ 70 g/L; White blood cell count (WBC) ≥ 3.0 × 10^9/L; Neutrophil count (NEUT) ≥ 1.5 × 10^9/L; Platelet count (PLT) ≥ 100 × 10^9/L; Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels ≤ 2.5 times the upper limit of normal (ULN); Total bilirubin (TBIL) ≤ 1.5 times the upper limit of normal (ULN); Renal function (serum creatinine, sCr) level ≤ 1.5 times the upper limit of normal (ULN).

Exclusion Criteria:

• Evidence of distant metastasis.
• Recurrent rectal cancer.
• Documented allergy to the investigational drug and/or its excipients.
• Contraindications to radiotherapy and/or chemotherapy.
• Women who are pregnant or breastfeeding.
• A history of other malignancies.
• Patients who have participated in other clinical trials involving investigational drugs within the last 6 months.
• Patients deemed inappropriate for inclusion in this study as determined by the investigator.