Multimodal Assessments Are Needed for Restaging after Neoadjunvant Chemoradiation Therapy in Rectal Cancer Patients

PURPOSE: Restaging after neoadjuvant treatment is done for planning the surgical approach and, increasingly, to determine whether additional therapy or resection can be avoided for selected patients. MATERIALS AND METHODS: Local restaging after neoadjuvant chemoradiation therapy (nCRT) was performed in 270 patients with locally advanced (cT3or4 or N+) rectal cancer. Abdomen and pelvic computed tomography (APCT) was used in all 270 patients, transrectal ultrasound (TRUS) in 121 patients, and rectal magnetic resonance imaging (MRI) in 65 patients. Findings according to imaging modalities were correlated with pathologic stage using Cohen’s kappa (κ) to test agreement and intra-class correlation coefficient α to test reliability. RESULTS: Accuracy for prediction of ypT stage according to three imaging modalities was 45.2% (κ=0.136, α=0.380) in APCT, 49.2% (κ=0.259, α=0.514) in rectal MRI, and 57.9% (κ=0.266, α=0.520) in TRUS. Accuracy for prediction of ypN stage was 66.0% (κ=0.274, α=0.441) in APCT, 71.8% (κ=0.401, α=0.549) in rectal MRI, and 66.1% (κ=0.147, α=0.272) in TRUS. Of 270 patients, 37 (13.7%) were diagnosed as pathologic complete responder after nCRT. Rectal MRI for restaging did not predict complete response. On the other hand, TRUS did predict three complete responders (κ=0.238, α=0.401). CONCLUSION: APCT, rectal MRI, and TRUS are unreliable in restaging rectal cancer after nCRT. We think that multimodal assessment with rectal MRI and TRUS may be the best option for local restaging of locally advanced rectal cancer after nCRT.