3D echoendoscopy and miniprobes for rectal cancer staging

Background: rectal cancer staging using rigid probes or echoendoscopes has some limitations. The aim of the study was to compare rectal cancer preoperative staging using conventional endoluminal ultrasonography with three-dimensional endoscopic ultrasonography and miniprobes. Materials and methods: sixty patients were included and evaluated with: a) a conventional echoendoscope (7.5 and 12 MHz); b) miniprobes (12 MHz); and c) the Easy 3D Freescan software for three-dimensional endoscopic ultrasonography. The reference or gold standard was conventional endoluminal ultrasonography in all cases and pathological assessment for those without preoperative therapy. The differences in T and N staging accuracy in both longitudinal and circumferential extension were evaluated. Results: with regard to T staging, conventional endoluminal ultrasonography had an accuracy of 85% (compared to pathological analysis), and the agreement between miniprobes vs conventional endoluminal ultrasonography (kappa = 0.81) and three-dimensional endoscopic ultrasonography vs conventional endoluminal ultrasonography (k = 0.87) was significant. In addition, miniprobes had an accuracy of 82% and three-dimensional endoscopic ultrasonography had a higher accuracy (96%). With regard to N staging, conventional endoluminal ultrasonography had an accuracy of 91% with a sensitivity of 78%. However, the agreement between miniprobes and conventional endoluminal ultrasonography and three-dimensional endoscopic ultrasonography and conventional endoluminal ultrasonography (k = 0.70) was lower. Interestingly, miniprobes had a lower accuracy of 81% whereas three-dimensional endoscopic ultrasonography had an accuracy of 100% without any false negative. No false positives were observed in any of the techniques. Accuracy for T and N staging was not influenced by longitudinal or circumferential extensions of the tumor in all types of endoscopic ultrasonography analyzed. Conclusions: miniprobes and especially three-dimensional endoscopic ultrasonography may be relevant during rectal cancer staging.