Background and study aims: This paper describes experience in the staging of rectal cancer using a new software program for three-dimensional endoscopic ultrasonography (EUS) that works without electromagnetic sensors and can be used even with electronic radial or linear rectal probes.
Materials and methods: From May 2003 to March 2004, 35 three-dimensional endorectal ultrasound (ERUS) examinations were carried out using this program. The indication for ERUS was local staging of rectal cancer in all cases. The three-dimensional software imaging program forms part of a new ultrasound scanning system (Hitachi 6500 or 8000) and allows reconstruction of the two-dimensional EUS images in six different scans.
Results: Thirty-five rectal cancers were assessed using two-dimensional and three-dimensional EUS. Using two-dimensional imaging, it was not possible to assess precisely the degree of involvement of the mesorectum (more or less than 50%). No differences were evident with three-dimensional EUS for superficial tumors (T1 and T2N0), but in six of 15 patients classified as having T3N0 lesions, three-dimensional EUS revealed malignant lymph nodes, a finding that was confirmed surgically in five of the six cases. Three-dimensional EUS also made it possible to assess the degree of infiltration of the mesorectum precisely in all cases, demonstrating complete invasion of the mesorectum in eight cases. These findings were confirmed in all cases by the surgical data. Two-dimensional EUS correctly assessed 25 of the 35 rectal tumors (71.4%) in relation to the T and N classifications, and three-dimensional EUS increased this figure to 31 correct evaluations out of 35 (88.6%).
Conclusion: Three-dimensional ERUS is easy to carry out using this new software program. There is no need for an external sensor mounted at the tip of the probe, and manipulation of the rectal probe is facilitated. Three-dimensional ERUS can be carried out using linear and radial electronic probes with the same ultrasound equipment. Three-dimensional ERUS allows more precise staging of lesions and better definition of the mesorectal margins, and this has a direct impact on therapeutic decision-making in patients with rectal cancer.