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Screening for Colorectal Cancer in the Elderly Population: How Much Is Enough?

Screening for Colorectal Cancer in the Elderly Population: How Much Is Enough? The reality of any cancer screening at any age is that benefits accrue to the few at the expense of the many. Benefits include longer life expectancy and less morbidity, while expenses include the risks of false-positive test results and cancer overdiagnosis, the burdens and risks of downstream tests and treatments, monetary costs to both individual patients and the health care system, and lost opportunity costs from diverted resources. This tension crescendos in the case of colorectal cancer (CRC) screening in elderly persons. On the one hand, the dramatic increases in CRC incidence and mortality appeal directly to our sense of responsibility as clinicians to detect and eradicate it with the goal of improving the quality and quantity of life; on the other hand, several realities interfere with this logic, such that the mission of “detect and eradicate” may not translate into improving either quantity or quality of life. Older patients have less life expectancy to save. Many elderly persons have comorbid conditions that further dilute the benefits of screening. Elderly adults incur more burdens and complications from colonoscopy and its downstream tests and treatments.1-4 Given the tension between the benefits and burdens of CRC screening, it behooves clinicians to find the right balance—explicitly and quantitatively if possible—for each patient. Another factor in the equation is that, unlike for other cancers, there are several screening tests, each with its own set of benefits and burdens. While guideline organizations recommend any one of them,5-7 the clinical reality is that 2 dominate CRC screening in 2011: colonoscopy every 10 years and fecal occult blood testing (FOBT) annually. How are these 2 tests and strategies being used in older patients? Studies of screening colonoscopy in the elderly population have focused on its yield for cancer and advanced adenomas (which has been high) but have not reported downstream outcomes such as subsequent colonoscopies, other tests, surgery, and chemotherapy. Studies of FOBT indicate that not all persons with a positive FOBT result have a total colon evaluation (TCE). Two Veterans Affairs (VA) based studies of FOBT screening in persons aged 70 years or older8,9 have shown that receipt of TCE is unrelated to the degree of comorbidity, suggesting some inappropriate use of CRC screening. Another VA-based study showed underuse of screening among elderly persons with life expectancy of more than 5 years and overuse among those with life expectancy of less than 5 years.10 In none of these studies were downstream outcomes described. Knowing these outcomes might provide opportunity to improve how screening decisions are made by clinicians and patients by helping us understand how much screening is enough. Two observational studies in this issue of the Archives that look at downstream outcomes identify areas for improving clinical decision making and for subsequent investigation.11,12 The study by Goodwin and colleagues11 examined use of colonoscopy in average-risk Medicare patients. Among elderly patients with a negative result and no indication other than screening, colonoscopy was repeated in 24.6% and 46.2% at 5 and 7 years, respectively. Although the true proportion of overutilization may have been overestimated because of inclusion of surveillance and high-risk screening, these results appear consistent with some degree of overuse, given the guideline-recommended 10-year interval for a negative colonoscopy.13 Why would this occur? Several reasons are possible. First, evidence for the 10-year interval following a negative colonoscopy is indirect, consisting of case-control studies of sigmoidoscopy, analyses of large administrative databases for the number of observed vs expected CRCs, and limited knowledge of growth rates of colorectal adenomas and their progression to CRC. And while the indirect data are consistent in showing a reduced risk of subsequent CRC, this evidence is not as high quality as having the direct evidence that comes from observing a large cohort with a negative index screening colonoscopy for 10 years and either repeating the colonoscopy at that time or identifying who developed and died from CRC. Furthermore, the 10-year interval, which applies to all average-risk persons aged 50 to 80 years, may not apply to elderly patients in whom faster adenoma progression to CRC has been described.14,15 And endoscopists do not want to miss CRC. Missing CRC is bad for everyone except malpractice attorneys, and constitutes a common cause for malpractice suits.14 In addition, the quality of the index colonoscopy may have been compromised by a less-than-adequate colon preparation, which was not assessed in the study. Less-than-adequate preparation quality leads to earlier repeated colonoscopy16 and is particularly problematic in the right colon, a location where the effectiveness of colonoscopy has been questioned.17 Furthermore, while Goodwin et al11 considered only “complete” examinations (presumably to the cecum), it is unclear how completeness was ensured. If it was done by excluding all colonoscopies with coding modifiers that indicated an incomplete examination, then it is likely that some incomplete examinations were included because these modifiers are not always applied properly. While these reasons preclude a valid use of the term overutilization, it is likely that colonoscopy is overused in some proportion of the elderly population that stands to benefit less from CRC screening to begin with, and much less from repeated examinations following a negative index colonoscopy. Without knowing preparation quality and examination completeness, however, we cannot ascertain the true magnitude of clinical overuse from this study. The study by Kistler and colleagues12 quantifies 7-year outcomes in a cohort of 212 veterans aged 70 years or older with a positive FOBT finding. After determining who did and who did not undergo colonoscopy within a year of the positive FOBT result, the authors examined downstream outcomes, including subsequent testing, CRC diagnosis and treatment, complications, and mortality. Based on age and comorbidity at the time of the FOBT, each patient was categorized as having a life expectancy of more than 10 years, 5 to 10 years, or less than 5 years and as having net benefit, net burden, or indeterminate results from screening. Just over half of the patients with a positive FOBT result underwent colonoscopy. As expected, the yield for advanced neoplasia was high; so too was the 10% complication risk from colonoscopy or cancer treatment. Among the 44% of patients who did not have colonoscopy, nearly half of them died of other causes within 5 years, suggesting some degree of appropriate withholding of further testing. Not surprisingly, patients with the shortest life expectancy were more likely to experience net burden from screening than were those with the longest life expectancy. The novelty of this study includes the long-term follow-up for relevant clinical outcomes and the classification of each patient's life expectancy by net burden or benefit of screening. A study limitation is the arbitrary way net benefits and burdens were decided. For 94 of the 149 patients who were determined to have had net burden (63%) (recall that most persons who undergo CRC screening at any age will have net burden), the burden may be considered small, consisting of completing only the 1 FOBT or just repeating it, in which case there was no chance for benefit because colonoscopy was never done. However, in other instances, there was a large net burden; some of this was due to inappropriate use of surveillance colonoscopy. No data were collected on patient preferences to know what role these may have played in how and why FOBT screening was done in the first place and why further testing was or was not pursued. While both studies have limitations that keep us from understanding how much screening is enough, how can they help improve decision making for CRC screening in older adults or target the agenda for research? One way is by reminding us to carefully consider the potential benefits and burdens of screening for each patient and, in the process, include informed patient preferences for whether and how to be screened. Second, consideration of life expectancy, using the combination of age and comorbid conditions, may help guide decisions about screening. Third, greater attention to previous test results will likely decrease some of the screening burden. Patients whose colonoscopy showed no neoplasia require neither screening FOBT for at least 5 years—and perhaps 10 years or longer—nor a surveillance colonoscopy for distal hyperplastic polyps. If a rescreening colonoscopy is thought to be necessary prior to 10 years, then the reason for the early repeated examination should be clearly documented. Fourth, the data from both studies may be used to refine costs and outcomes in cost-effectiveness analyses. Areas for research include obtaining more direct evidence for the protective duration of a negative colonoscopy in older patients; more precise prognostication of life expectancy based on age, comorbidity and functional status; a way to stratify risk for CRC and advanced adenomas; and determining how immunochemical FOBT (iFOBT) screening may be used quantitatively. With iFOBT, the threshold for a positive result could be adjusted to detect cancer and advanced adenomas or both and would decrease the false-positive risk. Accomplishing this agenda would improve the appropriateness and efficiency of screening older patients. Until then, it is up to the clinician and informed patient to consider benefits, burdens, and preferences in deciding whether and how screening should be performed. Back to top Article Information Correspondence: Dr Imperiale, Regenstrief Institute Inc, 1050 Wishard Blvd, Fifth floor, Indianapolis, IN 46202. Financial Disclosure: None reported. Funding/Support: This work was supported in part by grant R01 CA 104459 from the National Cancer Institute. References 1. Gatto NM, Frucht H, Sundararajan V, Jacobson JS, Grann VR, Neugut AI. Risk of perforation after colonoscopy and sigmoidoscopy: a population-based study. J Natl Cancer Inst. 2003;95(3):230-23612569145PubMedGoogle ScholarCrossref 2. Naef M, Käsemodel GK, Mouton WG, Wagner HE. Outcome of colorectal cancer surgery in the early fast-track era with special regard to elderly patients. Int Surg. 2010;95(2):153-15920718323PubMedGoogle Scholar 3. Köhne CH, Folprecht G, Goldberg RM, Mitry E, Rougier P. Chemotherapy in elderly patients with colorectal cancer. Oncologist. 2008;13(4):390-40218448553PubMedGoogle ScholarCrossref 4. Warren JL, Klabunde CN, Mariotto AB, et al. Adverse events after outpatient colonoscopy in the Medicare population. Ann Intern Med. 2009;150(12):849-857, W15219528563PubMedGoogle Scholar 5. U.S. Preventive Services Task Force. Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008;149(9):627-63718838716PubMedGoogle Scholar 6. Levin B, Lieberman DA, McFarland B, et al; American Cancer Society Colorectal Cancer Advisory Group; US Multi-Society Task Force; American College of Radiology Colon Cancer Committee. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology. 2008;134(5):1570-159518384785PubMedGoogle ScholarCrossref 7. Rex DK, Johnson DA, Anderson JC, Schoenfeld PS, Burke CA, Inadomi JM.American College of Gastroenterology. American College of Gastroenterology guidelines for colorectal cancer screening 2009 [corrected]. Am J Gastroenterol. 2009;104(3):739-75019240699PubMedGoogle ScholarCrossref 8. Garman KS, Jeffreys A, Coffman C, Fisher DA. Colorectal cancer screening, comorbidity, and follow-up in elderly patients. Am J Med Sci. 2006;332(4):159-16317031239PubMedGoogle ScholarCrossref 9. Carlson CM, Kirby KA, Casadei MA, Partin MR, Kistler CE, Walter LC. Lack of follow-up after fecal occult blood testing in older adults: inappropriate screening or failure to follow up? Arch Intern Med. 2011;171(3):249-25620937917PubMedGoogle ScholarCrossref 10. Walter LC, Lindquist K, Nugent S, et al. Impact of age and comorbidity on colorectal cancer screening among older veterans. Ann Intern Med. 2009;150(7):465-47319349631PubMedGoogle Scholar 11. Goodwin JS, Singh A, Reddy N, Riall TS, Kuo Y-F. Overuse of screening colonoscopy in the Medicare population. Arch Intern Med. 2011;171(15):1335-1343Google ScholarCrossref 12. Kistler CE, Kirby KA, Lee D, Casadei MA, Walter LC. Long-term outcomes following positive fecal occult blood test results in older adults: benefits and burdens. Arch Intern Med. 2011;171(15):1344-1351Google ScholarCrossref 13. Winawer SJ, Zauber AG, Fletcher RH, et al; US Multi-Society Task Force on Colorectal Cancer; American Cancer Society. Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society. Gastroenterology. 2006;130(6):1872-188516697750PubMedGoogle ScholarCrossref 14. Feld AD. Malpractice risks associated with colon cancer and inflammatory bowel disease. Am J Gastroenterol. 2004;99(9):1641-164415330895PubMedGoogle ScholarCrossref 15. Brenner H, Hoffmeister M, Stegmaier C, Brenner G, Altenhofen L, Haug U. Risk of progression of advanced adenomas to colorectal cancer by age and sex: estimates based on 840,149 screening colonoscopies. Gut. 2007;56(11):1585-158917591622PubMedGoogle ScholarCrossref 16. Rex DK, Imperiale TF, Latinovich DR, Bratcher LL. Impact of bowel preparation on efficiency and cost of colonoscopy. Am J Gastroenterol. 2002;97(7):1696-170012135020PubMedGoogle ScholarCrossref 17. Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L. Association of colonoscopy and death from colorectal cancer. Ann Intern Med. 2009;150(1):1-819075198PubMedGoogle Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Internal Medicine American Medical Association

Screening for Colorectal Cancer in the Elderly Population: How Much Is Enough?

Archives of Internal Medicine , Volume 171 (15) – Aug 8, 2011

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References (24)

Publisher
American Medical Association
Copyright
Copyright © 2011 American Medical Association. All Rights Reserved.
ISSN
0003-9926
eISSN
1538-3679
DOI
10.1001/archinternmed.2011.364
Publisher site
See Article on Publisher Site

Abstract

The reality of any cancer screening at any age is that benefits accrue to the few at the expense of the many. Benefits include longer life expectancy and less morbidity, while expenses include the risks of false-positive test results and cancer overdiagnosis, the burdens and risks of downstream tests and treatments, monetary costs to both individual patients and the health care system, and lost opportunity costs from diverted resources. This tension crescendos in the case of colorectal cancer (CRC) screening in elderly persons. On the one hand, the dramatic increases in CRC incidence and mortality appeal directly to our sense of responsibility as clinicians to detect and eradicate it with the goal of improving the quality and quantity of life; on the other hand, several realities interfere with this logic, such that the mission of “detect and eradicate” may not translate into improving either quantity or quality of life. Older patients have less life expectancy to save. Many elderly persons have comorbid conditions that further dilute the benefits of screening. Elderly adults incur more burdens and complications from colonoscopy and its downstream tests and treatments.1-4 Given the tension between the benefits and burdens of CRC screening, it behooves clinicians to find the right balance—explicitly and quantitatively if possible—for each patient. Another factor in the equation is that, unlike for other cancers, there are several screening tests, each with its own set of benefits and burdens. While guideline organizations recommend any one of them,5-7 the clinical reality is that 2 dominate CRC screening in 2011: colonoscopy every 10 years and fecal occult blood testing (FOBT) annually. How are these 2 tests and strategies being used in older patients? Studies of screening colonoscopy in the elderly population have focused on its yield for cancer and advanced adenomas (which has been high) but have not reported downstream outcomes such as subsequent colonoscopies, other tests, surgery, and chemotherapy. Studies of FOBT indicate that not all persons with a positive FOBT result have a total colon evaluation (TCE). Two Veterans Affairs (VA) based studies of FOBT screening in persons aged 70 years or older8,9 have shown that receipt of TCE is unrelated to the degree of comorbidity, suggesting some inappropriate use of CRC screening. Another VA-based study showed underuse of screening among elderly persons with life expectancy of more than 5 years and overuse among those with life expectancy of less than 5 years.10 In none of these studies were downstream outcomes described. Knowing these outcomes might provide opportunity to improve how screening decisions are made by clinicians and patients by helping us understand how much screening is enough. Two observational studies in this issue of the Archives that look at downstream outcomes identify areas for improving clinical decision making and for subsequent investigation.11,12 The study by Goodwin and colleagues11 examined use of colonoscopy in average-risk Medicare patients. Among elderly patients with a negative result and no indication other than screening, colonoscopy was repeated in 24.6% and 46.2% at 5 and 7 years, respectively. Although the true proportion of overutilization may have been overestimated because of inclusion of surveillance and high-risk screening, these results appear consistent with some degree of overuse, given the guideline-recommended 10-year interval for a negative colonoscopy.13 Why would this occur? Several reasons are possible. First, evidence for the 10-year interval following a negative colonoscopy is indirect, consisting of case-control studies of sigmoidoscopy, analyses of large administrative databases for the number of observed vs expected CRCs, and limited knowledge of growth rates of colorectal adenomas and their progression to CRC. And while the indirect data are consistent in showing a reduced risk of subsequent CRC, this evidence is not as high quality as having the direct evidence that comes from observing a large cohort with a negative index screening colonoscopy for 10 years and either repeating the colonoscopy at that time or identifying who developed and died from CRC. Furthermore, the 10-year interval, which applies to all average-risk persons aged 50 to 80 years, may not apply to elderly patients in whom faster adenoma progression to CRC has been described.14,15 And endoscopists do not want to miss CRC. Missing CRC is bad for everyone except malpractice attorneys, and constitutes a common cause for malpractice suits.14 In addition, the quality of the index colonoscopy may have been compromised by a less-than-adequate colon preparation, which was not assessed in the study. Less-than-adequate preparation quality leads to earlier repeated colonoscopy16 and is particularly problematic in the right colon, a location where the effectiveness of colonoscopy has been questioned.17 Furthermore, while Goodwin et al11 considered only “complete” examinations (presumably to the cecum), it is unclear how completeness was ensured. If it was done by excluding all colonoscopies with coding modifiers that indicated an incomplete examination, then it is likely that some incomplete examinations were included because these modifiers are not always applied properly. While these reasons preclude a valid use of the term overutilization, it is likely that colonoscopy is overused in some proportion of the elderly population that stands to benefit less from CRC screening to begin with, and much less from repeated examinations following a negative index colonoscopy. Without knowing preparation quality and examination completeness, however, we cannot ascertain the true magnitude of clinical overuse from this study. The study by Kistler and colleagues12 quantifies 7-year outcomes in a cohort of 212 veterans aged 70 years or older with a positive FOBT finding. After determining who did and who did not undergo colonoscopy within a year of the positive FOBT result, the authors examined downstream outcomes, including subsequent testing, CRC diagnosis and treatment, complications, and mortality. Based on age and comorbidity at the time of the FOBT, each patient was categorized as having a life expectancy of more than 10 years, 5 to 10 years, or less than 5 years and as having net benefit, net burden, or indeterminate results from screening. Just over half of the patients with a positive FOBT result underwent colonoscopy. As expected, the yield for advanced neoplasia was high; so too was the 10% complication risk from colonoscopy or cancer treatment. Among the 44% of patients who did not have colonoscopy, nearly half of them died of other causes within 5 years, suggesting some degree of appropriate withholding of further testing. Not surprisingly, patients with the shortest life expectancy were more likely to experience net burden from screening than were those with the longest life expectancy. The novelty of this study includes the long-term follow-up for relevant clinical outcomes and the classification of each patient's life expectancy by net burden or benefit of screening. A study limitation is the arbitrary way net benefits and burdens were decided. For 94 of the 149 patients who were determined to have had net burden (63%) (recall that most persons who undergo CRC screening at any age will have net burden), the burden may be considered small, consisting of completing only the 1 FOBT or just repeating it, in which case there was no chance for benefit because colonoscopy was never done. However, in other instances, there was a large net burden; some of this was due to inappropriate use of surveillance colonoscopy. No data were collected on patient preferences to know what role these may have played in how and why FOBT screening was done in the first place and why further testing was or was not pursued. While both studies have limitations that keep us from understanding how much screening is enough, how can they help improve decision making for CRC screening in older adults or target the agenda for research? One way is by reminding us to carefully consider the potential benefits and burdens of screening for each patient and, in the process, include informed patient preferences for whether and how to be screened. Second, consideration of life expectancy, using the combination of age and comorbid conditions, may help guide decisions about screening. Third, greater attention to previous test results will likely decrease some of the screening burden. Patients whose colonoscopy showed no neoplasia require neither screening FOBT for at least 5 years—and perhaps 10 years or longer—nor a surveillance colonoscopy for distal hyperplastic polyps. If a rescreening colonoscopy is thought to be necessary prior to 10 years, then the reason for the early repeated examination should be clearly documented. Fourth, the data from both studies may be used to refine costs and outcomes in cost-effectiveness analyses. Areas for research include obtaining more direct evidence for the protective duration of a negative colonoscopy in older patients; more precise prognostication of life expectancy based on age, comorbidity and functional status; a way to stratify risk for CRC and advanced adenomas; and determining how immunochemical FOBT (iFOBT) screening may be used quantitatively. With iFOBT, the threshold for a positive result could be adjusted to detect cancer and advanced adenomas or both and would decrease the false-positive risk. Accomplishing this agenda would improve the appropriateness and efficiency of screening older patients. Until then, it is up to the clinician and informed patient to consider benefits, burdens, and preferences in deciding whether and how screening should be performed. Back to top Article Information Correspondence: Dr Imperiale, Regenstrief Institute Inc, 1050 Wishard Blvd, Fifth floor, Indianapolis, IN 46202. Financial Disclosure: None reported. Funding/Support: This work was supported in part by grant R01 CA 104459 from the National Cancer Institute. References 1. Gatto NM, Frucht H, Sundararajan V, Jacobson JS, Grann VR, Neugut AI. Risk of perforation after colonoscopy and sigmoidoscopy: a population-based study. J Natl Cancer Inst. 2003;95(3):230-23612569145PubMedGoogle ScholarCrossref 2. Naef M, Käsemodel GK, Mouton WG, Wagner HE. Outcome of colorectal cancer surgery in the early fast-track era with special regard to elderly patients. Int Surg. 2010;95(2):153-15920718323PubMedGoogle Scholar 3. Köhne CH, Folprecht G, Goldberg RM, Mitry E, Rougier P. Chemotherapy in elderly patients with colorectal cancer. Oncologist. 2008;13(4):390-40218448553PubMedGoogle ScholarCrossref 4. Warren JL, Klabunde CN, Mariotto AB, et al. Adverse events after outpatient colonoscopy in the Medicare population. Ann Intern Med. 2009;150(12):849-857, W15219528563PubMedGoogle Scholar 5. U.S. Preventive Services Task Force. Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008;149(9):627-63718838716PubMedGoogle Scholar 6. Levin B, Lieberman DA, McFarland B, et al; American Cancer Society Colorectal Cancer Advisory Group; US Multi-Society Task Force; American College of Radiology Colon Cancer Committee. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology. 2008;134(5):1570-159518384785PubMedGoogle ScholarCrossref 7. Rex DK, Johnson DA, Anderson JC, Schoenfeld PS, Burke CA, Inadomi JM.American College of Gastroenterology. American College of Gastroenterology guidelines for colorectal cancer screening 2009 [corrected]. Am J Gastroenterol. 2009;104(3):739-75019240699PubMedGoogle ScholarCrossref 8. Garman KS, Jeffreys A, Coffman C, Fisher DA. Colorectal cancer screening, comorbidity, and follow-up in elderly patients. Am J Med Sci. 2006;332(4):159-16317031239PubMedGoogle ScholarCrossref 9. Carlson CM, Kirby KA, Casadei MA, Partin MR, Kistler CE, Walter LC. Lack of follow-up after fecal occult blood testing in older adults: inappropriate screening or failure to follow up? Arch Intern Med. 2011;171(3):249-25620937917PubMedGoogle ScholarCrossref 10. Walter LC, Lindquist K, Nugent S, et al. Impact of age and comorbidity on colorectal cancer screening among older veterans. Ann Intern Med. 2009;150(7):465-47319349631PubMedGoogle Scholar 11. Goodwin JS, Singh A, Reddy N, Riall TS, Kuo Y-F. Overuse of screening colonoscopy in the Medicare population. Arch Intern Med. 2011;171(15):1335-1343Google ScholarCrossref 12. Kistler CE, Kirby KA, Lee D, Casadei MA, Walter LC. Long-term outcomes following positive fecal occult blood test results in older adults: benefits and burdens. Arch Intern Med. 2011;171(15):1344-1351Google ScholarCrossref 13. Winawer SJ, Zauber AG, Fletcher RH, et al; US Multi-Society Task Force on Colorectal Cancer; American Cancer Society. Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society. Gastroenterology. 2006;130(6):1872-188516697750PubMedGoogle ScholarCrossref 14. Feld AD. Malpractice risks associated with colon cancer and inflammatory bowel disease. Am J Gastroenterol. 2004;99(9):1641-164415330895PubMedGoogle ScholarCrossref 15. Brenner H, Hoffmeister M, Stegmaier C, Brenner G, Altenhofen L, Haug U. Risk of progression of advanced adenomas to colorectal cancer by age and sex: estimates based on 840,149 screening colonoscopies. Gut. 2007;56(11):1585-158917591622PubMedGoogle ScholarCrossref 16. Rex DK, Imperiale TF, Latinovich DR, Bratcher LL. Impact of bowel preparation on efficiency and cost of colonoscopy. Am J Gastroenterol. 2002;97(7):1696-170012135020PubMedGoogle ScholarCrossref 17. Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L. Association of colonoscopy and death from colorectal cancer. Ann Intern Med. 2009;150(1):1-819075198PubMedGoogle Scholar

Journal

Archives of Internal MedicineAmerican Medical Association

Published: Aug 8, 2011

Keywords: older adult,colorectal cancer screening,colonoscopy

There are no references for this article.