Value of endorectal ultrasonography in measuring the extent of mesorectal invasion and substaging of T3 stage rectal cancer.

The present study aimed to determine the value of endorectal ultrasound (ERUS) and magnetic resonance imaging (MRI) for T3 rectal cancer, and substaging of T3 rectal cancer by measuring the extent of mesorectal invasion (EMI). The clinical data of patients with rectal cancer who were admitted to the general surgical department of Peking Union Medical College Hospital (Beijing, China) were reviewed and analyzed. Two ultrasound practitioners independently measured the EMI on ERUS, and a radiologist measured the EMI on MRI. The consistency of ERUS measurements between the two doctors was assessed using intraclass consistency (ICC) analysis. T3 stages were subdivided into T3a (EMI ≤5 mm) and uT3b (EMI >5 mm). The accuracy of MRI and ERUS in T3 rectal cancer, and T3 substaging of rectal cancer was assessed and compared according to the pathological results. The Bland-Altman scatter plot demonstrated good consistency between the ERUS measurement and pathology measurement. Furthermore, the consistency of the ERUS measurement between the two doctors was good (ICC, 0.9344; 95% confidence interval, 0.8789-0.9645). The diagnostic accuracies for T3 rectal cancer, for the two ultrasound doctors and for MRI were 86.9% (53/61), 85.2% (52/61), and 90.2% (55/61), respectively. The accuracy, sensitivity and specificity for the two individual ultrasound doctors in the substaging of T3 tumors were 79.1% (34/43), 66.7% (10/15), and 85.7% (24/28), compared with 67.4% (31/43), 60% (9/15), and 82.1% (23/28), respectively. The accuracy of MRI in the substaging of T3 tumors was 86.0% (37/43), which was not statistically higher compared with those of ERUS (P>0.05). In conclusion, ERUS is a valuable tool for measuring the EMI and substaging T3 rectal cancer, and thus, can be complementary to MRI in selecting the appropriate treatment for rectal cancer.