Accuracy of endoscopic ultrasound for restaging rectal cancer following neoadjuvant chemoradiation therapy

Endoscopic ultrasound (EUS) provides important information in the initial staging of patients with rectal cancer. Preoperative combined modality chemotherapy and radiation (neoadjuvant therapy) for patients with locally advanced rectal cancer may reduce local recurrence and improve survival. The accuracy of EUS restaging of rectal cancer after chemoradiation has not been extensively studied and its usefulness is unclear. The aim of this study was to verify the accuracy of EUS in staging rectal cancer after neoadjuvant chemoradiation in a large cohort of patients.

EUS staging was performed before and after concurrent 5-fluorouracil and hyperfractionated radiotherapy in 82 patients with recently diagnosed locally advanced rectal cancer. All patients underwent subsequent surgical resection and complete pathologic staging.

After chemoradiation, 16 patients (20%) had no residual disease at pathologic staging. (T0N0). However, EUS correctly predicted complete response to chemoradiation in only 10 of 16 patients (63%). Overall accuracy of EUS post chemoradiation for pathologic T-stage was only 48%. Fourteen percent were understaged and 38% overstaged. EUS accuracy for N-stage was 77%. The T-category was correctly staged before surgery in 23 of the 56 responders (41%) and in 16 of 24 nonresponders (67%). EUS was unable to accurately distinguish postradiation changes from residual tumor.

EUS staging of rectal cancer after chemoradiation is inaccurate, especially in the group of patients with visual and EUS evidence of response. Its routine use for staging purposes after neoadjuvant chemoradiation for rectal cancer should be discouraged.