High magnification chromoscopic colonoscopy or high frequency 20 MHz mini probe endoscopic ultrasound staging for early colorectal neoplasia: a comparative prospective analysis.

BACKGROUND

Successful endoscopic management of early colorectal cancer using endoscopic mucosal resection requires the mandatory prediction of invasive depth and lymph node metastasis. Previous data using the Nagata crypt types Vn(B)/(C) as clinical indicators of T2/N+ disease have shown low specificity (50%) with a tendency to over stage lesions. New mini probe ultrasound "through the scope" imaging permits staging of lesions proximal to the rectum using direct endoscopic visualisation.

AIM

To compare the staging accuracy of the Nagata crypt type V with mini probe high frequency 20 MHz endoscopic ultrasound.

METHODS

Sixty two patients with a Paris type II flat cancer were imaged using magnification colonoscopy followed by 20/12.5 MHz ultrasound in a "back to back" design. Crystal violet staining (0.05%) at 100x magnification permitted Nagata crypt criteria to be defined. Submucosal deep invasion (sm3+) was defined at ultrasound by the presence or absence of a disrupted third sonographic layer. Predicted T0/1:N0 lesions were resected using endoscopic mucosal resection with the remaining referred for surgery. Ultrasound and magnification staging were then compared with the resected histopathological specimens.

RESULTS

One patient was excluded from the study due to poor bowel preparation. Fifty two lesions from 52 patients therefore met inclusion criteria (12 sm1/13 sm2/27 sm3+). Ultrasound (20 MHz) was significantly more accurate for invasive depth staging compared with Nagata stage (p<0.0001) (overall accuracy 93% and 59%, respectively). The sensitivity for lymph node metastasis detection using ultrasound and magnification was 80% and 31%, respectively (p<0.001). The negative predictive value of ultrasound for invasive depth was better than that observed using magnification (88%/47%, respectively). The prevalence of nodal disease overall was 19% (10/52), with 80% (8/10) node positive lesions occurring in the sm3+ lesion group.

CONCLUSIONS

High frequency 20 MHz ultrasound is superior to magnification alone when differentiating T1/2 disease with a high positive predictive value for sm3 differentiation. Sm3+ invasion was associated with nodal metastasis.