Abstract
Background and Study Aims: In rectal tumors invasion of the rectal fat and perirectal lymph nodes are generally
regarded as independent prognostic factors in most prospective series. There are no
studies in the literature concerning interobserver agreement on the staging of rectal
cancer by endorectal ultrasonography (EUS). The aim of the present study was to assess
interobserver agreement using EUS in the TN staging of rectal cancer.
Patients and Methods: Thirty-seven patients with rectal cancer were investigated at two centers using EUS
as part of the pretherapeutic staging (Olympus EUM-3 or EUM-20). All examinations
were videotaped and reviewed six months later by four independent observers who assessed
the stage of the tumor (from uT1 to uT4) and lymphatic invasion on a blinded basis.
When the tumor was assessed as uT3, the observers specified the degree of involvement
of the rectal fat (in millimeters). Interobserver agreement was estimated using the
kappa coefficient (k) and the intraclass correlation coefficient (ICC). Agreement
was classed as poor (k < 0.40), fair to good (0.40 ≤ k < 0.75) or excellent (k ≤ 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 tumors; there was a significant
interobserver correlation for the exact measure of the extent of rectal fat (ICC = 0.65).
The agreement was also good (k = 0.54, CI 0.47 to 0.61) for metastatic lymph nodes.
Conclusion: As in the case of esophageal cancer, interobserver agreement on the staging of uT2
tumors is poor with EUS. The evaluation of rectal tumors with a poor prognosis shows
good interobserver agreement.
