"If patients have detection of an adenoma, we remove the adenoma then follow up the patient every three to five years with colonoscopy," Dr. Emanuele Neri said in a presentation today at the European Congress of Radiology (ECR). Neri is from the University of Pisa in Pisa, Italy.
"In some high-risk cases, we can use an individualized follow-up in patients with (resected) villous adenomas, malignant adenomas, and large adenomas," Neri said. "But despite the recommendations of the gastroenterologists to follow up every one to two years, many patients refuse colonoscopy -- we know this. So we aimed to evaluate the role of CT colonography (CTC or VC) as an alternative to colonoscopy in the follow-up of asymptomatic patients who underwent polypectomy."
The study examined 49 patients with a history of polypectomy, who underwent VC one to four years (mean one year) postpolypectomy, followed by conventional colonoscopy, except for 15 patients who refused it.
Following standard cathartic preparation, MDCT was performed for all patients using 5-mm collimation and a 1.25-mm reconstruction interval, at 120 kVp and 50 mAs. A primary 2D reading technique with 3D problem-solving was employed.
VC was positive in 21of the 49 patients who underwent colonoscopy, Neri said. Only 13 of 28 patients who were negative were willing to undergo further examination with colonoscopy; VC results were compared to colonoscopy for these 13 cases.
At virtual colonoscopy, 35 polyps were found in 25 of the 49 patients. Of these, 21 were considered clinically insignificant at less than 6 mm in diameter. Fourteen were 6 mm or larger. For polyps 6 mm and smaller, VC had sensitivity and specificity of 71% and 65%, respectively. For lesions 6 mm and larger, VC had sensitivity and specificity of 92% and 88%, respectively. There were two advanced adenomas and one carcinoma at histology, all detected at VC.
In response to a question from the audience, Neri said the gastroenterologists at his institution were "not happy" with the idea of VC follow-up of these patients. However, he said, patients who have undergone colonoscopy "don't want to do it again."
He suggested a protocol of follow-up every three years for most of these patients, perhaps alternating VC with optical colonoscopy.
A recently published study from Taiwan followed up 434 patients after polypectomy (two to 55 months). Eighty subjects showed strong clinical evidence for recurrent cancer. All underwent VC (5-mm collimation, 2.5-mm slice thickness) and same-day colonoscopy (Yah-Tong You et al, World Journal of Gastroenterology, January 2006, Vol. 12:1, pp. 123-126).
"Local recurrence was found in 51 patients," You and colleagues wrote. "Seventy-five of the 80 patients had adequate colonic inflation throughout the entire colon. Two of the five remaining patients had inadequate transverse colon distension, and three had inadequate sigmoid colon distension, though additional air was insufflated and the positions of the patient were changed. In contrast-enhanced (VC), all the five patients showing thickened segmental colon wall and external luminal tumor mass compression were classified as present local recurrence."
Compared to colonoscopy, VC had sensitivity of 100%, specificity of 83%, and an overall accuracy of 94% for detecting recurrent local cancer, they concluded.
By Eric Barnes
AuntMinnie.com staff writer
March 4, 2006
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Colonoscopy performed too often after polypectomy, August 17, 2004
VC screening trials find good sensitivity, high patient acceptance, October 30, 2002
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