Balloon sheath miniprobe compared to conventional EUS in the staging of colorectal cancer

Conventional endoscopic ultrasonography was a valuable modality in staging the invasion depth of colon cancer. However, it is not widely used because of its difficulty in detecting small or flat lesions and obtaining a cross-sectional image due to tight stricture of tumor lesions and in those lesions located at or over a bend of the colon. Due to this, mistaging or understaging is often seen. We conducted a prospective study using a new technique and instrument (balloon sheath with miniprobe) in colon cancer staging and compared it with the conventionally used endosonography.

One hundred and thirty-four patients underwent preoperative staging using two different instruments. Seventy-three patients were evaluated with conventional endoscopic ultrasonography while the other 61 patients were evaluated with the balloon sheath miniprobe.

The balloon sheath miniprobe had an overall accuracy rate of 85%; 100% in T1; 78% in T2; 90% in T3 and 40% in T4. Lymph node metastasis was correctly determined in 67% with a sensitivity and specificity rate of 56% and 75%, respectively. The overall accuracy rate of endoscopic ultrasonography in staging colon carcinoma was 89%; 83% in T1; 83% in T2; 93% in T3 and 71% in T4. Overall accuracy rate in lymph node metastasis evaluation was 77%. Sensitivity was 77% and specificity was 76%. Inability to obtain a clear cross-sectional image using the miniprobe was 3.3%, while that of the endoscopic ultrasonography was 11%.

The balloon sheath miniprobe is a good alternative for evaluating lesions over the proximal colon and is superior to other modalities in obtaining a cross-sectional image even in tight, stenotic lesions. One limitation is its difficulty in assessing deeper structures such as lymph node groups and contiguous organ involvement.