This retrospective study aims to develop an AI-assisted 3D modeling system to improve staging accuracy for stage II-III locally advanced rectal cancer (LARC). High-quality CT images from Taichung Veterans General Hospital will be used to reconstruct tumor boundaries and spatial relationships. The AI model will be trained and validated against MRI and pathology results to predict circumferential resection margin (CRM) status. Outcomes include sensitivity, specificity, accuracy, and agreement with standard imaging. This system seeks to support precise tumor staging and inform future clinical decision-making.

Inclusion Criteria:

• Diagnosed with rectal cancer, clinical stage II-III, with no distant metastasis (M0)
• Age over 18 years, with adequate physical status classified as American Society of Anesthesiologists (ASA) I-III, capable of receiving treatment and surgery
• No history of other malignancies or major diseases affecting study assessment within the past three years.
• Complete medical records, including available CT and MRI imaging.

Exclusion Criteria:

• Patients with clinical stage I or IV rectal cancer.
• Age under 18 years, or physical status not meeting American Society of Anesthesiologists (ASA) I-III criteria, unable to undergo surgery or related treatment.
• Presence of other major diseases or malignancies affecting tumor assessment (e.g., diagnosis of another malignancy within the past three years, uncontrolled cardiovascular disease).
• Incomplete medical records or imaging data, including missing required CT or MRI images.

The study population consists of adult patients (≥18 years) diagnosed with stage II-III locally advanced rectal cancer (LARC) without distant metastasis (M0), who received care at Taichung Veterans General Hospital (TVGH), Taiwan. Eligible participants have adequate physical status (ASA I-III) to undergo standard treatment and surgery, no history of other malignancies or major diseases affecting tumor assessment within the past three years, and complete medical records including CT and MRI imaging. Patients with stage I or IV disease, insufficient physical status, major comorbidities, or incomplete imaging/medical records are excluded.