Staging of rectal cancer by EUS: depth of infiltration in T3 cancers is important

Background EUS is an established method for staging of rectal cancer. Nevertheless, there are few data about the significance of infiltration depth measured by EUS. Objective Assessment of accuracy of T and N staging by EUS with attention to infiltration depth as provided by EUS. Design Part retrospective, part prospective study. Setting Community and tertiary referral hospital, covering the period before neoadjuvant therapy for advanced rectal cancer was established. Patients Eighty-three patients (60% men) with untreated rectal cancer. Intervention EUS examination. Main Outcome Measurements We examined the correlation between EUS findings and postoperative histology. T3 cancers as diagnosed by EUS were classified into minimally invasive (1-2 mm) or advanced (>2 mm) tumors depending on the depth of infiltration beyond the muscularis propria. Results Accuracy of T staging and N status was 76% and 63%, respectively. Overstaging by EUS was more common in minimally invasive T3 by EUS (uT3) (8 of 16 [50%]) compared with advanced uT3 tumors (1 of 24 [4%]) ( P = .01). Accuracy of EUS discrimination between T1/2 and T3/4 in rectal cancer for all but minimally invasive uT3 rectal tumors was 88%. Limitations Partly retrospective analysis. Conclusions EUS examination of rectal carcinoma determines T stage with high accuracy. Additionally, it provides information beyond T and N staging. The 50% probability of overstaging patients with minimally invasive uT3N0 by EUS may argue for managing these cancers as stage I disease, ie, to refer the patient for surgery without neoadjuvant therapy.