A CRM-Integrated ypT Staging System Improves Prognostic Stratification Following Neoadjuvant Therapy in Rectal Cancer
Wan-Hsuan Chow1, Chung-Han Ho2,3, Yi-Chen Chen2
1Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan.
Introduction:
The ypT staging system has limited prognostic value after neoadjuvant therapy, as it primarily reflects only tumor characteristics alone. 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.
Methods:
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. Overall survival was assessed using multivariable Cox regression, and prognostic performance of the proposed CRM-integrated ypT staging system was compared with the American Joint Committee on Cancer (AJCC) TNM system using Harrell's c-statistic.
Results:
CRM involvement (≤1 mm) was significantly associated with worse 5-year survival (adjusted odds ratio, 0.44; 95% CI, 0.31-0.61). Due to the low rate of CRM positivity in ypT0-2 patients, a modified ypT classification was established: 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 system demonstrated better prognostic discrimination than the current AJCC classification (Harrell's c-statistic: 0.756 vs. 0.752, P = 0.034).
Conclusions:
Incorporating CRM into the ypT stage offers survival stratification and may guide more individualized postoperative treatment strategies for rectal cancer patients after nCRT.
