Virtual colonoscopy vs conventional colonoscopy in patients at high risk of colorectal cancer – a prospective trial of 150 patients

Abstract

Objective Virtual colonoscopy (VC) ⁄ CT colonography has advantages over the well-documented limitations of colonoscopy ⁄ barium enema. This prospective blinded investigative comparison trial aimed to evaluate the ability of VC to assess the large bowel, compared to conventional colonoscopy (CC), in patients at high risk of colorectal cancer (CRC).Method We studied 150 patients (73 males, mean age 60.9 years) at high risk of CRC. Following bowel preparation, VC was undertaken using colonic insufflation and 2D-spiral CT acquisition. Two radiologists reported the images and a consensual agreement reached. Direct comparison was made with CC (performed later the same day). Interobserver agreement was calculated using the Kappa method. Postal questionnaires sought patient preference.Results Virtual colonoscopy visualized the caecum in all cases. Five (3.33%) VCs were classified as inadequate owing to poor distension ⁄ faecal residue. CC completion rate was 86%. Ultimately, 44 patients had normal findings, 44 had diverticular disease, 11 had inflammatory bowel disease, 18 had cancers, and 33 patients had 42 polyps. VC identified 19 cancers -a sensitivity and specificity of 100% and 99.2% respectively. For detecting polyps > 10 mm, VC had a sensitivity and specificity (per patient) of 91% and 99.2% respectively. VC identified four polyps proximal to stenosing carcinomas and extracolonic malignancies in nine patients (6%). No procedural complications occurred with either investigation. A Kappa score achieved for interobserver agreement was 0.777.Conclusion Virtual colonoscopy is an effective and safe method for evaluating the bowel and was the investigation of choice amongst patients surveyed. VC provided information additional to CC on both proximal and extracolonic pathology. VC may become the diagnostic procedure of choice for symptomatic patients at high risk of CRC, with CC being reserved for therapeutic intervention, or where a tissue diagnosis is required.

CT Colonography to exclude colorectal cancer in symptomatic patients

“…However, the evidence on the accuracy of CTC in excluding CRC in the setting of symptomatic, older patients is less conclusive [19,20].…”

Non-Invasive Endoscopy Technique - Virtual Colonoscopy

“…(Kim et al, 2007;Macari et al, 2011;Pedersen et al, 2003;Pescatore et al, 2000;Pickhardt et al, 2011;Pilch-Kowalczyk et al, 2004;Roberts-Thomson et al, 2008;Sutherland et al, 2011;White et al, 2009) (Fig 3,4). Virtual examinations carry the advantages including being relatively noninvasive, safe, and acceptable by clinicians (Ekci & Yildirim, 2009;Johnson & Dackman., 2000;Leksowski el al., 2011;McHugh et al, 2011;Vining, 1996).…”

“…Following that, virtual colonoscopy was used in patients who cannot tolerate the conventional colonoscopy procedure. (Bakir et al, 2004;Ferrucci, 2001;Labianca & Merelli, 2010;White et al, 2009). The positive results regarding patient tolerance with this minimally invasive technique confirmed this idea.…”

“…It has taken the place of double contrast barium enema because of its superior efficiency. Despite its efficacy in the evaluation and treatment of colonic pathology, colonoscopy also has disadvantages such as being invasive, risk of perforation and hemorrhage, low patient tolerance, sedation requirement, perforation risk, and conditions in which the evaluation can not be properly finished (Anderson et al, 1992;Consolo et al, 2008;Detsky, 2001;Kim et al, 2007;White et al, 2009). Patient intolerance is among the most important problems with the existing screening methods.…”

Editor`s Comments

“…In this context, certain pathological features, most notably, nuclear polymorphism and crowding rather than mitotic activity show prognostic value for the prediction of metachronous colorectal cancer in screened populations who already have a rectosigmoid adenoma defining those patients best served by postpolypectomy surveillance [10] where the utilization of new endoscopic-guided imaging modalities define at-risk polyps in patients where these are detected by limited endoscopy [11]. These newer approaches even when endoscopic screening is limited will have implications for polypectomy and full colonic evaluation [12] as too will first-up less invasive screening modalities which will direct either flexible sigmoidoscopy or colonoscopy [13,14].…”