A new rectal ultrasonographic method for the staging of rectal cancer

Radial transrectal ultrasound is the most frequently used method for preoperative staging of rectal cancer. Accuracy rates of transrectal ultrasound have fallen significantly to 64% and 70% for tumor and node staging, respectively. The use of a frontal probe may overcome the drawbacks of radial transrectal ultrasound. This study was designed to compare the accuracy of frontal transrectal ultrasound performed with a frontal probe with the classic procedure, which uses a radial probe, in the preoperative T and N staging of rectal cancer.

Seventy-four patients with rectal adenocarcinoma underwent both techniques. Thirty patients had a neoadjuvant treatment. The staging accuracy of both methods was determined by comparing the results of each with the findings of surgical histopathologic evaluation.

Forty-six men and 28 women were recruited. Frontal transrectal ultrasound was performed in all patients. Staging was amenable in only 58 patients with the radial transrectal ultrasound because the tumors were either stenotic or too proximal. Frontal transrectal ultrasound was accurate in the T staging of 89% of the tumors, whereas radial transrectal ultrasound was accurate in only 69% (P = 0.004). The difference was even more significant when we compared accuracy among the 58 patients in whom both examinations were completed (P = 0.002). Both methods had similar accuracy for lymph node staging. Neoadjuvant treatment had no influence on accuracy. No overstaging of the tumor occurred with the frontal transrectal ultrasound. Understaging was more frequently encountered with radial transrectal ultrasound than with frontal transrectal ultrasound (26% vs. 11%, respectively; P = 0.036).

Compared with radial transrectal ultrasound, frontal transrectal ultrasound has a better accuracy for T staging of rectal cancer. Its advantage in overcoming the drawbacks of radial transrectal ultrasound may make this procedure the method of choice for rectal cancer staging.