Screening: Colonoscopy vs. CT Colonography
Screening: Colonoscopy vs. CT Colonography
Objectives: Visualizing the entire colorectum in screening is an advantage of colonoscopy, and also computed tomographic (CT) colonography, another potentially suitable screening test. Our objective was to compare screening CT colonography and colonoscopy in an asymptomatic average-risk population, and to determine whether providing a choice of tests increased participation.
Methods: One thousand and four hundred subjects from the general community, randomly selected from the parliamentary electoral roll, were allocated one of three screening groups: colonoscopy, CT colonography, or a choice of these tests, and were sent an institutional letter of invitation. Those with symptoms, colorectal cancer in first-degree relatives, or colonoscopy within 5 yr were ineligible. Outcome measures were participation, acceptability of screening, and yield for advanced colorectal neoplasia in participants.
Results: Of the subjects, 24.9% were ineligible; the overall participation rate was 18.2% (184/1,009). Participation in each screening group was not different. Both tests were accompanied by the same high levels of acceptability; most participants found colonoscopy (87%) and CT colonography (67%, p < 0.001) less unpleasant than expected. About 29% (26/89) CT colonography subjects had a positive screening test. The yield of advanced colorectal neoplasia was 8.7% (95% CI 5-14%), with no difference in yield between tests.
Conclusion: Colorectal neoplasia screening by colonoscopy or CT colonography was associated with modest participation, high levels of acceptability, and similar yield for advanced colorectal neoplasia. Providing a choice of test did not increase participation.
Population-based screening for colorectal neoplasia (CRN) provides the opportunity to detect early stage cancer and remove premalignant polyps, yet screening recommendations of North American, European and Australian authorities widely differ. In Australia, for asymptomatic subjects without a strong family history of colon cancer, the National Health and Medical Research Council suggest annual fecal occult blood testing (FOBT) and consideration of additional 5-yearly flexible sigmoidoscopy from age 50. In Great Britain, limited resources largely preclude population-based screening. By contrast, North American groups recommend screening from age 50, and most suggest there are insufficient data to choose among annual FOBT, 5-yearly flexible sigmoidoscopy, a combination of annual FOBT and 5-yearly flexible sigmoidoscopy, 5-yearly barium enema, or 10-yearly colonoscopy.
Supporters of colonoscopy-based screening justifiably point out the superior accuracy of this test for CRN, though data are lacking on important issues such as participation and acceptability in the setting of screening, and concerns have been expressed over availability and safety. Participation is a critical factor in determining cost-effectiveness of any screening strategy. Providing a choice of screening tests may improve participation in screening but, although this intuitively makes sense, is a concept that has not been widely tested.
The recent development of computed tomographic colonography (CTC) has added yet another possible CRN screening tool. Like colonoscopy, it allows examination of the entire bowel after bowel preparation, yet it is relatively noninvasive and does not require sedation. For patients with symptoms or risk factors for bowel cancer, accuracy for detecting medium (6-9 mm diameter) and large (≥ 10 mm) polyps by some centers of excellence closely approaches that for colonoscopy undertaken by skilled endoscopists. In a recent population-based screening pilot program using CTC, we found a good level of participation and high degree of acceptability for this technique.
In this study, we wished to provide a comparison of CTC and colonoscopy as population-based primary screening tests, and to evaluate whether a choice of tests influenced participation. Specifically, the study was designed to determine whether providing a choice of screening by CTC or colonoscopy increased participation. The other objectives were to compare CTC and colonoscopy in relation to participation, acceptability, and yield of advanced CRN and, in doing so, to also provide novel data on colonoscopy-based population screening.
Objectives: Visualizing the entire colorectum in screening is an advantage of colonoscopy, and also computed tomographic (CT) colonography, another potentially suitable screening test. Our objective was to compare screening CT colonography and colonoscopy in an asymptomatic average-risk population, and to determine whether providing a choice of tests increased participation.
Methods: One thousand and four hundred subjects from the general community, randomly selected from the parliamentary electoral roll, were allocated one of three screening groups: colonoscopy, CT colonography, or a choice of these tests, and were sent an institutional letter of invitation. Those with symptoms, colorectal cancer in first-degree relatives, or colonoscopy within 5 yr were ineligible. Outcome measures were participation, acceptability of screening, and yield for advanced colorectal neoplasia in participants.
Results: Of the subjects, 24.9% were ineligible; the overall participation rate was 18.2% (184/1,009). Participation in each screening group was not different. Both tests were accompanied by the same high levels of acceptability; most participants found colonoscopy (87%) and CT colonography (67%, p < 0.001) less unpleasant than expected. About 29% (26/89) CT colonography subjects had a positive screening test. The yield of advanced colorectal neoplasia was 8.7% (95% CI 5-14%), with no difference in yield between tests.
Conclusion: Colorectal neoplasia screening by colonoscopy or CT colonography was associated with modest participation, high levels of acceptability, and similar yield for advanced colorectal neoplasia. Providing a choice of test did not increase participation.
Population-based screening for colorectal neoplasia (CRN) provides the opportunity to detect early stage cancer and remove premalignant polyps, yet screening recommendations of North American, European and Australian authorities widely differ. In Australia, for asymptomatic subjects without a strong family history of colon cancer, the National Health and Medical Research Council suggest annual fecal occult blood testing (FOBT) and consideration of additional 5-yearly flexible sigmoidoscopy from age 50. In Great Britain, limited resources largely preclude population-based screening. By contrast, North American groups recommend screening from age 50, and most suggest there are insufficient data to choose among annual FOBT, 5-yearly flexible sigmoidoscopy, a combination of annual FOBT and 5-yearly flexible sigmoidoscopy, 5-yearly barium enema, or 10-yearly colonoscopy.
Supporters of colonoscopy-based screening justifiably point out the superior accuracy of this test for CRN, though data are lacking on important issues such as participation and acceptability in the setting of screening, and concerns have been expressed over availability and safety. Participation is a critical factor in determining cost-effectiveness of any screening strategy. Providing a choice of screening tests may improve participation in screening but, although this intuitively makes sense, is a concept that has not been widely tested.
The recent development of computed tomographic colonography (CTC) has added yet another possible CRN screening tool. Like colonoscopy, it allows examination of the entire bowel after bowel preparation, yet it is relatively noninvasive and does not require sedation. For patients with symptoms or risk factors for bowel cancer, accuracy for detecting medium (6-9 mm diameter) and large (≥ 10 mm) polyps by some centers of excellence closely approaches that for colonoscopy undertaken by skilled endoscopists. In a recent population-based screening pilot program using CTC, we found a good level of participation and high degree of acceptability for this technique.
In this study, we wished to provide a comparison of CTC and colonoscopy as population-based primary screening tests, and to evaluate whether a choice of tests influenced participation. Specifically, the study was designed to determine whether providing a choice of screening by CTC or colonoscopy increased participation. The other objectives were to compare CTC and colonoscopy in relation to participation, acceptability, and yield of advanced CRN and, in doing so, to also provide novel data on colonoscopy-based population screening.
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