3408 - A CRM-Integrated ypT Staging System Improves Prognostic Stratification Following Neoadjuvant Therapy in Rectal Cancer
Presenter(s)
W. H. Chow1, C. C. Yang1, C. H. Ho2, Y. C. Chen2, and H. Y. Huang3; 1Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan, 2Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan, 3Division of Colorectal Surgery, Department of Surgery, Chi Mei Medical Center, Tainan, Taiwan
Purpose/Objective(s): The current ypT staging system for rectal cancer, which assesses only tumor invasion depth, lacks accuracy in predicting survival outcomes after neoadjuvant chemoradiotherapy (nCRT) and surgery. Circumferential resection margin (CRM) involvement is an established independent prognostic factor for local recurrence and survival but plays a limited role in clinical decision-making. This study evaluates a novel T staging system that integrates CRM with the pathological T stage to improve prognostic accuracy.
Materials/Methods: Data from the Taiwan Cancer Registry and National Health Insurance Research Database (2008–2017) were analyzed, including rectal adenocarcinoma patients treated with nCRT followed by surgery. CRM =1 mm was defined as positive. A new ypT staging system incorporating CRM was compared with current AJCC TNM system for 5-year survival prediction using Harrell’s c-statistic.
Results: Among 4308 patients, 64.1% were under 65 years old, and 70.7% were male. Positive CRM was associated with significantly worse 5-year survival (adjusted hazard ratio [aHR] 0.44; 95% CI 0.31–0.61). Due to less patients had CRM positive in ypT0-2, we defined the new prognostic staging system by stratifying the risk of the 5-year survival into new ypT3 (ypT3 and CRM-); new ypT4A (ypT4A and CRM-); new ypT4B (ypT3 and CRM+; ypT4B and CRM-); new ypT4C (ypT4A and CRM+; ypT4B and CRM+). This new ypT staging system improved predictive accuracy over the AJCC TNM classification (Harrell’s c-statistic: 0.756 vs. 0.752, P = 0.034).
Conclusion: Incorporating CRM into ypT staging enhances prognostic discrimination beyond conventional TNM staging. This novel system may better identify high-risk patients, guiding more intensive adjuvant treatment strategies.