Noninvasive Early Diagnosis of Colorectal Cancer Using Odor-Targeted Capture, Point-of-Care Testing, and Intelligent Analysis

Inclusion Criteria: * Age 18 to 85 years, male or female * Histopathologically or cytologically confirmed colon or rectal cancer (TNM stage I-IV) for colorectal cancer group * Histopathologically confirmed adenomatous polyps, sessile serrated lesions, traditional serrated adenomas, or other precancerous lesions for precancerous lesion group * No abnormality on colonoscopy within the past year; no personal history of colorectal cancer or other malignancies; no chronic diseases requiring long-term treatment for healthy control group * Willing and able to provide signed informed consent Exclusion Criteria: * Hereditary colorectal cancer syndromes (e.g., familial adenomatous polyposis, hereditary non-polyposis colorectal cancer) * Autoimmune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis) * Severe cardiovascular, respiratory, or urinary system diseases * Other primary malignant tumors * Hematological diseases * Unable to comply with study procedures (e.g., sample collection or questionnaires) * Planning to become pregnant, pregnant, or breastfeeding * Suspected or confirmed alcohol or drug abuse * Known allergy to any drug used for colorectal cancer treatment * Participation in another interventional drug clinical trial within the past month * Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study