Accuracy of endorectal ultrasound after preoperative radiochemotherapy in locally advanced rectal cancer.

Objectives: Factors limiting the accuracy of endorectal ultrasound in staging, locally advanced primary rectal cancer after preoperative neoadjuvant radiochemotherapy (RCT) were evaluated.

Methods: Patients (n = 84) with initial locally advanced rectal cancer (uT3/uT4) undergoing R0 resection were investigated after preoperative treatment that combined radiotherapy up to 45 Gy with two cycles of chemotherapy (5-FU and leucovorin on d 1-5 and 22-28). At 4 to 6 weeks after completion of RCT and before tumor resection, preoperative endoluminal ultrasound was performed.

Results: The accuracy to predict the depth of tumor infiltration (T-category) was found to correlate with downstaging. The T-category was correctly staged before surgery in 15 of the 51 responders (29%) and in 27 of 33 nonresponders (82%), whereas misinterpretation occurred in 36 of the responders (71%) and in 6 of the nonresponders (18%) (p < 0.001). Neither tumor distance from anal verge nor tumor location correlated with the staging accuracy. Lymph node involvement was correctly assessed in 48 patients (57%). Wall invasion was correctly ascertained in 42 patients (50%), with under estimation in 11 patients (13%) and overestimation in 31 patients (37%).

Conclusions: After radiochemotherapy, endosonography does not provide a satisfactory accuracy for preoperative staging of rectal cancer. New interpretation and diagnostic criteria are needed for the prediction of treatment response.