Exploring the Treatment Duration of PD-1 Neoadjuvant Therapy in Stage II-III dMMR Rectal Cancer: a Prospective，Multicentre, Single-arm Study
This study aims to explore the optimal number of cycles of PD-1 monotherapy required at minimum, under the premise of ensuring pathological complete response (pCR) among patients with dMMR/MSI-H rectal cancer. Participants will receive preoperative monotherapy with PD-1 antibodies, with regular reassessments every 2 cycles. Surgical intervention will be performed if clinical complete response (cCR) is achieved. Researchers will compare the pathological complete response rates, adverse reactions, and three-year event-free survival rates across different treatment cycles.
• 1.Age: 18 to 80 years old, male or female;
• 2.Patients with histologically or cytologically confirmed dMMR/MSI-H rectal adenocarcinoma, clinical stage II-III;
• 3.No prior systemic therapy, including chemotherapy, radiotherapy, immunotherapy, or targeted therapy;
• 4.ECOG Performance Status (PS) score of 0-1;
• 5.Estimated life expectancy of ≥ 3 months;
• 6.Normal function of major organs, with no severe abnormalities in blood, heart, lung, liver, kidney, bone marrow, or immunodeficiency. Laboratory tests must meet the following criteria: Hemoglobin (Hb) ≥ 90 g/L; White blood cell count (WBC) ≥ 3.0 × 10\^9/L; Neutrophil count (NEUT) ≥ 1.5 × 10\^9/L; Platelet count (PLT) ≥ 90 × 10\^9/L; Liver function (Aspartate Aminotransferase AST or Alanine Aminotransferase ALT) ≤ 2.5 times the upper limit of normal (ULN); Renal function (serum creatinine sCr) ≤ 1.5 times ULN; Total bilirubin (TBIL) ≤ 1.5 times ULN; Urine protein and occult blood \< 2+; Fecal occult blood \< 2+;
• 7.Subjects must voluntarily participate in this study, sign the informed consent form, demonstrate good compliance, and cooperate with follow-up visits;
• 8.The investigator believes that the patient can benefit from the treatment. Physical status score PS ≤ 2;
• 9.Patients and their families must understand and be willing to participate in this study, providing written informed consent.