INTEROBSERVER AGREEMENT IN THE STAGING OF RECTAL-CANCER USING ENDOSCOPIC ULTRASONOGRAPHY

Background and Study Aims: In rectal tumors invasion of the rectal fat and perirectal lymph nodes are generally regarded as independent prog nostic factors in most prospective series, There are no studies in the literature concerning interobserver agreement on the staging of recta l cancer by endorectal ultrasonography (EUS). The aim of the present s tudy vests to assess interobserver agreement using EUS in the TN stagi ng of rectal cancer. Patients and Methods: Thirty-seven patients with rectal cancer were investigated at two centers using EUS as part of th e pretherapeutic staging (Olympus EUM-3 or EUM-20). All examinations w ere videotaped and reviewed six months later by four independent obser vers who assessed the stage of the tumor (from uT1 to uT4) and lymphat ic invasion on a blinded basis. When the tumor was assessed as uT3, th e observers specified the degree of involvement of the rectal fat (in millimeters). Interobserver agreement was estimated using the kappa co efficient (k) and the intraclass correlation coefficient (ICC). Agreem ent was classed as poor (k < 0.40), fair to good (0.40 less than or eq ual to k < 0.75) or excellent (k less than or equal to 0.75). Results: Agreement was fair for uT1 tumors (k = 0.40) and poor for uT2 tumors (k = 0.20). Agreement was good (k = 0.58; CI 0.51 to 0.65) for uT3 tum ors; there was a significant interobserver correlation for the exact m easure of the extent of rectal fat (ICC = 0.65). The agreement was als o good (k = 0.54, CI 0.47 to 0.61) for metastatic lymph nodes, Conclus ion: As in the case of esophageal cancer, interobserver agreement an t he staging of uT2 tumors is poor with EUS. The evaluation of rectal tu mors with a poor prognosis shows good interobserver agreement.