Accuracy of transrectal ultrasound after preoperative radiochemotherapy compared to computed tomography and magnetic resonance in locally advanced rectal cancer

The aim of the present study was to compare the restaging results obtained by transrectal ultrasound (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) performed after preoperative chemoradiation with pathologic staging of the operative specimen. From January 2008 to December 2009, all the consecutive patients with locally advanced rectal cancer that underwent neoadjuvant therapy at our department were evaluated. The results of diagnostic examinations and the definitive pathological examination were considered and compared. Thirty-seven patients were included in the study (27 males, 73%), mean age was 65.5 years (range 45-82 years). In all the patients TRUS and CT and in 20 patients MRI were performed before and after the treatment. Concerning the depth of invasion after treatment TRUS agreed with histopathology in 25/37 patients (67.5%), CT agreed in 22/37 cases (59.5%), and MRI in 12/20 cases (60%). Considering only neoplasia with stage T3, TRUS agreed in 23/24 cases (96%), CT in 19 cases (79%), and MRI in 10/12 cases (83.5%). Considering the tumors that did not exceed the rectal wall (T0, T1, and T2), TRUS agreed with histology in 2/13 cases (15.5%), CT in 3/13 cases (23%), and MRI 2/8 cases (25%). Concerning the presence of positive lymph nodes TRUS agreed with histology in 28/37 cases (75.5%), while CT agreed in 21/37 cases (56.5%) and MRI in 11/20 cases (55%). The concordance between the techniques was found to be low. Transrectal ultrasonography resulted as the most accurate method to determine neoplastic wall infiltration and lymph node involvement even after radiochemotherapy. In most cases, considering the poor correlation between the diagnostic procedures and the disagreement of the results, a restaging performed only with TRUS could be proposed, limiting the use of the other imaging methods to selected cases.