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Transit endoscopic ultrasound of colorectal cancer using a 12 MHz catheter probe Featured

The objective of this study was to examine the accuracy of a 12 MHz ultrasound catheter probe in the pre-operative staging of colorectal cancer by assessing the depth of tumour infiltration and involvement of pericolonic lymph nodes.

159 patients with colorectal cancer who underwent ultrasound examination with a 12 MHz catheter probe were studied prospectively. The results of this imaging procedure were compared with the histological findings of the resected specimens. The accuracy of the 12 MHz ultrasound catheter probe for depth of invasion (T category) was 85% (131/154) for all tumours, 87% (46/53) for pT1 tumours, 60% (9/15) for pT2 tumours, 89% (74/83) for pT3 tumours and 67% (2/3) for pT4 tumours. The accuracy for tumours of the rectum and colon was 81% and 89%, respectively. The accuracy of the probe for nodal staging (N category) was 67% (76/114) overall. The sensitivity was 70% (33/47), the specificity 64% (43/67), the positive predictive value 58% (33/57) and the negative predictive value 75% (43/57). Endoscopic ultrasound using a 12 MHz catheter probe accurately assessed tumour stage, although nodal staging remained suboptimal. This method may aid in the selection of treatment for patients with colorectal cancer.

(AKAHOSHI. K. ; The British Journal of Radiology, 74 (2001), 1017–1022)

Different treatment concepts, including local excision, radical resection and multimodality therapy, are available for colorectal cancer depending on the tumour stage [1, 2]. Consequently, access to an accurate and reliable method for staging these tumours pre-operatively is essential if patients are to receive appropriate treatment. However, it is difficult to assess the depth of tumour invasion by the routine methods of barium enema, colonoscopy and CT. Endoscopic ultrasound (EUS) examination has added a new dimension to the evaluation of tumour invasion and lymph node involvement in gastrointestinal cancer [2–21]. A number of studies have reported the usefulness of conventional EUS for staging colorectal cancer [4–15, 21]. However, conventional EUS has several disadvantages, including the high cost of equipment, the use of two instruments (one for endoscopy and one for EUS), limited manoeuverability of the echoendoscope and the failure of the endoscope to traverse tight stenoses and reach the caecum. The ultrasound catheter probe (UCP) has been developed to solve these problems. This system is half as expensive as the standard EUS system. The major advantage of the 12 MHz UCP system is that it can be used with a wide variety of endoscopes. It can be inserted through the working channel of a conventional colonoscope and used under direct endoscopic visualization. However, experience in the pre-operative staging of colorectal cancer with the relatively low frequency 12 MHz UCP has not been reported. We therefore performed a prospective study to examine the accuracy of the 12 MHz UCP in the pre-operative staging of colorectal cancer.

Materials and method

Patients

159 consecutive patients with a diagnosis of colorectal cancer, confirmed by preliminary endoscopy and endoscopic biopsies, were evaluated between November 1997 and March 2000. The patients consisted of 90 men and 69 women, with a mean age of 68 years (range 40–89 years). The tumour was located in the caecum in 8 patients, in the ascending colon in 16 patients, in the transverse colon in 9 patients, in the descending colon in 10 patients, in the sigmoid colon in 40 patients, and in the rectum in 76 patients. Surgical resection was performed in 141 patients and endoscopic resection in 18 patients. The resected tumours were assessed histopathologically according to the TNM staging system [22]. Findings from the pre-operative 12 MHz UCP were compared with the pathological findings in the resected specimens. The pathologist (KN) was blinded to the results of the EUS examination. There were 54 pT1 tumours, 17 pT2 tumours, 85 pT3 tumours and 3 pT4 tumours. EUS was performed prior to surgery after obtaining informed consent from the patients.

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