Comparison of EUS, CT and MRI in staging of rectal cancer

Background: Endoscopic ultrasound (EUS) is the potential imaging modality to accurately evaluate local invasion and perirectal lymph nodes in rectal cancer. However, overstaging of early lesions and limitations such as operator and experience dependency, tolerance of patient, and limited range of depth of the transducer may affect the accuracy of EUS. The aim of this study was to assess the correlations of staging between EUS, CT and MRI before and after neoadjuvant chemoradiation (CCRT) and the accuracy of these images in staging rectal cancer.

Methods: Between August, 2006 and August, 2007, 48 consecutive patients with rectal cancer received staging workup before CCRT with EUS and CT or EUS and MRI were enrolled. Ultrasonic miniature probes (Olympus: UM2R) or Slim Probe (Olympus: MH908) for EUS staging was used. AJCC 6th edition was applied for staging. Restaging with EUS and CT or EUS and MRI was performed after CCRT followed by surgical excision.

Results: A total of forty-eight cases (29 men and 19 women) were enrolled in the study. The age of these patients ranged from 37 to 86 years old (mean age: 59.4 ± 12.3 years old). In pre-CCRT T-staging, the Pearson Correlation coefficient of EUS versus CT and EUS versus MRI were 0.526 and 0.644, respectively. (p=0.005, p=0.001); in nodal staging, the Pearson Correlation coefficient of EUS versus CT and EUS versus MRI were 0.269and 0.218 (p=0.174, p=0.330). Moreover, the Pearson Correlation coefficient of AJCC staging of EUS versus CT and EUS versus MRI were 0.388 and 0.250. (p=0.046, p=0.262) After CCRT, histological examination of surgical specimens was obtained in 37 patients. The accuracy of T-staging in EUS, CT and MRI was 68.8% (11/16), 52.3% (11/21) and 46.2% (6/13) respectively by using pathology as gold standard. In nodal staging, the accuracy of EUS, CT and MRI was 64.2% (9/14), 72.7% (16/22) and 64.2% (9/14) respectively.

Conclusions:

In pre-CCRT workup, T-staging of EUS is correlated well with CT and MRI. However, in nodal staging, there was no significance between EUS, CT and MRI. After CCRT, EUS has the best accuracy in T staging and CT has the highest accuracy in nodal staging. EUS, CT and MRI all have tendency of overstaging, especially in T0-T2 disease after CCRT. Combined use of these modalities in staging of rectal cancer is recommended for better accuracy in the future.