CT Colonography vs Colonoscopy for the Detection of Advanced

Neoplasia

David H. Kim, M.D., Perry J. Pickhardt, M.D., Andrew J. Taylor, M.D., Winifred K. Leung, M.D., Thomas C. Winter, M.D., J. Louis Hinshaw, M.D., Deepak V. Gopal, M.D., Mark Reichelderfer, M.D., Richard H. Hsu, M.D., and Patrick R. Pfau, M.D.

NEJM Oct 4, 2007 Volume 357:1403-1412

Background

Ct Colonography

http://www.radiologyinfo.org/en/photocat/photos_pc.cfm?image=vcoloMovie.jpg&pg=ct_colo

Colorectal cancer:– A major cause of cancer-related

mortality in the US (55,000 deaths/yr)

– Preventable by detection and removal of its precursor:

advanced colonic adenoma

Colonic adenoma progression

Small adenomas < 5mm dysplasia

Advance colonic adenomas

>10mm Cancer

10 yrs

Most likely Hyperplastic

Usually do not progress to cancer

Study Objective

–Optical colonoscopy (OC) is currently the preferred screening and preventive strategy of CRC by AGS

–CT colonography (CTC) is a non-invasive promising alternative screening method

–Most trials examining CTC had failed to show comparative sensitivity/specificity to OC.

Methods

Study design: Single center, non randomize clinical trial comparing CTC vs OC screening in a 25 month period

Study population: 6283 pt referred by primary care providers.

• 3120 CTC screening • 3163 OC screening

Inclusion/Exclusion criteria• Inclusion

– Asymptomatic and average risk for colorectal CA

• Exclusion– Prior polyp surveillance– History of bowel disorder (IBD,

polyposis syndromes, hereditary non polyposis colorectal cancer syndrome)

Screening Methods

• Pt identified with advanced neoplasm (mass/polyps > 6mm) by CTC were given the option of surveillance with CTC or removal of the polyp by OC.

• In the OC group, All polyps/masses found were removed, regardless of size or significance.

• All removed masses were evaluated for location relative to the splenic flexure, morphologic characteristics, and histology.

Screening Methods

• Lesions were divided into two categories:– Polyps

• Large: > 10mm• Small: 6-9 mm• Diminutive: 5mm or less

– Invasive mass

Statistics

• A positive test was defined as detection of polyps of any size in the OC group and polyps of >6mm in the CTC group.

• The two tests were compared using student’s T-test and Chi square analyses

Results

Optical colonoscopy

http://www.murrasaca.com/colonoscopy.htm

A sessile polyp

An adenomatous polyp

3120 Patients were enrolled in CTC screening

Routine follow-up in 5 yrs

2716 (87.1%) had negative findings

404 (12.9%) had positive findings

With 394 polyps (>6mm)

158 (5.1%) chose ongoing imaging surveillance

227 adenomas

246 (7.9%) underwent OC with polypectomy

With 193 polyps

123 Advanced neoplastic lesions

14 Cancers 153 non-neoplastic tumors

More Information

Summary of Results• Both CTC and OC had comparative

diagnostic yield for both types of advance neoplasia (p= 0.81)

• CTC had an advantage of safety, no requirement for sedation, and detecting extra-colonic abnormalities

• There were larger number of polypectomies in the OC (2434) vs. in the CTC (561) while total advance neoplasias were similar in both (121/2434 vs 123/561)

PPV for advance neoplasia

• TP / TP+FP

– CTC 123 / 561

– OC 121 / 2434

Discussion

Study Strength• Large sample size, similar baseline

characteristics• Relevant exclusion criteria• Detailed pathological characterization of

tissues in addition to imaging to establish comparative detection

• Could have significant clinical and economical impact on current practice of colon CA screening

Weakness• Non blinded/non-randomized (selection

bias)• single Center• Technical advancement may vary between

centers for effective CTC screening• True negatives in pts with lesions < 5mm in

the CTC group is not determined

Clinical Practice Relevance

• Offers CTC as a non-invasive alternative to OC for comparative detection of colonic neoplasias

• Eliminates the need for a large number of unnecessary colonoscopies and polypectomies

• Due to variability in technical resources CTC may not yet be a potential replacement for OC in many practice settings

Thank you