Application and Exploration of Personalized ctDNA-MRD Detection Technology in Predicting the Efficacy of Neoadjuvant Therapy for Rectal Cancer

Inclusion Criteria: * 1: Signed a written informed consent form and voluntarily participated in this study * 2: Aged 18-75 years, regardless of sex * 3: Histopathologically confirmed rectal adenocarcinoma * 4: Clinical stage II-III as assessed by MRI (according to the AJCC 8th edition) * 5: Distance from the lower tumor margin to the anal verge ≤10 cm * 6: Surgically resectable * 7: Able to swallow tablets normally * 8: ECOG PS 0-1 * 9: No prior antitumor therapy for rectal cancer, including radiotherapy, chemotherapy, or surgery * 10: Scheduled to undergo surgical treatment after completion of neoadjuvant therapy * 11: No surgical contraindications * 12: Normal function of major organs, including: complete blood count, blood biochemistry, and coagulation function Exclusion Criteria: * 1: History of allergy to monoclonal antibodies, any component of tislelizumab, or capecitabine * 2: Prior or ongoing receipt of any tumor-directed surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapy, etc * 3: Presence of any active autoimmune disease or history of autoimmune disease * 4: History of immunodeficiency, including a positive HIV test result, other acquired or congenital immunodeficiency disorders, or history of organ transplantation or allogeneic bone marrow transplantation * 5: Poorly controlled cardiac clinical symptoms or diseases, including but not limited to: heart failure of NYHA class II or above, unstable angina, myocardial infarction within the past year, or clinically significant supraventricular or ventricular arrhythmia that remains poorly controlled without or despite clinical intervention * 6: Diagnosis of another malignancy within 5 years prior to the first use of the study drug, except for malignancies with low risk of metastasis or death (5-year survival rate \>90%), such as adequately treated basal cell carcinoma or squamous cell carcinoma of the skin, or carcinoma in situ of the cervix, which may be considered for inclusion * 7: Pregnant or lactating women * 8: Other factors, as judged by the investigator, that may lead to premature termination of the study, such as other severe diseases (including psychiatric disorders) requiring concomitant treatment, alcohol abuse, drug abuse, family or social factors, or any condition that may affect the safety or compliance of the participant