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

Objectives: Factors limiting the accuracy of endorectal ultrasound in stagi ng, locally advanced primary rectal cancer after preoperative neoadjuvant r adiochemotherapy (RCT) were evaluated. Methods: Patients (n = 84) with initial locally advanced rectal cancer (uT3 /uT4) undergoing RO resection were investigated after preoperative treatmen t 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 pe rformed. Results: The accuracy to predict the depth of tumor infiltration (T-categor y) was found to correlate with downstaging. The T-category was correctly st aged before surgery in 15 of the 51 responders (29%) and in 27 of 33 nonres ponders (82%), whereas misinterpretation occurred in 36 of the responders ( 71%) and in 6 of the nonresponders (18%) (p < 0.001). Neither tumor distanc e from anal verge nor tumor location correlated with the staging accuracy. Lymph node involvement was correctly assessed in 48 patients (57%). Wall in vasion was correctly ascertained in 42 patients (50%), with under estimatio n in 11 patients (13%) and overestimation in 31 patients (37%). Conclusions: After radiochemotherapy, endosonography does not provide a sat isfactory accuracy for preoperative staging of rectal cancer. New interpret ation and diagnostic criteria are needed for the prediction of treatment re sponse.