Modified Wong's classification improves the accuracy of rectal cancer staging by endorectal ultrasound and MRI.

BACKGROUND: Douglas Wong proposed a new classification of tumor penetration in the rectal wall (T stage) in an attempt to incorporate the prognostic heterogeneity of T3 rectal cancers into the preoperative staging. OBJECTIVE: This study aimed to evaluate if the accuracy of endorectal ultrasound and MRI in predicting rectal cancer T staging improves when using a modified Wong's classification. DESIGN: This prospective series compares local standard TN staging and a modified Wong's classification. SETTINGS: This study was conducted by a specialized Colorectal Multidisciplinary Team at a tertiary teaching hospital. PATIENTS: Seventy patients underwent surgery for middle or low rectal cancer between 2002 and 2008 without neoadjuvant radiochemotherapy. We compared the preoperative staging with the pathological staging to determine the preoperative accuracy of endorectal ultrasound and MRI when using a modified Wong’s classification vs the standard TN classification. INTERVENTIONS: A modified version of Wong’s classification was used for preoperative and pathological staging. MAIN OUTCOME MEASURES: The primary outcome measured was the accuracy in the preoperative T staging. RESULTS: The overall accuracy of endorectal ultrasound and MRI in assessing T staging was 68.6% and 72.9% (uT1/2, 90%; uT3, 58.3%; and uT4, 100% and rT1/2, 88%; rT3, 63.4%; and rT4, 75%). By using the proposed modified Wong's classification, the overall accuracy of endorectal ultrasound and MRI improved to 82.9% and 90%. LIMITATIONS: The interobserver variability in radiological assessment was not evaluated. CONCLUSION: With use of the modified Wong's classification proposed in this study, the overall accuracy of preoperative imaging in assessing T staging of rectal cancer is substantially improved, especially when endorectal ultrasound and MRI stage match, enhancing the selection of patients for neoadjuvant radiochemotherapy.