A CRM-Inclusive ypT Staging System Enhances Survival Prediction in Rectal Cancer Post-Neoadjuvant Therapy

This study proposes a novel staging system that integrates circumferential resection margin (CRM) status with the ypT category to enhance prognostic accuracy following neoadjuvant chemoradiotherapy (nCRT) for rectal cancer, addressing limitations of the current ypT classification. We analyzed data from 4,308 rectal adenocarcinoma patients treated with nCRT followed by surgery, using the Taiwan Cancer Registry and National Health Insurance Research Database (2011–2021). CRM involvement was defined as a margin ≤ 1 mm. Positive CRM was significantly associated with worse 5-year survival (adjusted odds ratio [aOR] 0.44; 95% CI 0.31–0.61). Due to low rates of CRM positivity in ypT0–2, a modified ypT classification was developed, stratifying patients into new ypT3 (ypT3 and CRM−), new ypT4A (ypT4A and CRM−), new ypT4B (ypT3 and CRM + or ypT4B and CRM−), and new ypT4C (ypT4A and CRM + or ypT4B and CRM+). This refined system demonstrated improved prognostic performance compared to the current AJCC TNM classification (Harrell’s c-statistic: 0.756 vs. 0.752, P = 0.034). Incorporating CRM into ypT staging offers better survival stratification and may inform more personalized postoperative treatment strategies for rectal cancer patients.