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Life expectancy and colorectal cancer screening
Life expectancy and colorectal cancer screening
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Cary P Gross, MD yale, Cary P. Gross, Gail McAvay, Mary Tinetti
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cary.gross{at}yale.edu Cary P Gross, et al.
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The authors reply to Dr. Burack Colorectal cancer screening can benefit patients through two mechanisms. First, a screening colonoscopy will increase the likelihood of early stage diagnosis among patients with prevalent disease.(1) Because of the slow-growing nature of colorectal cancer, clinical benefits of this “stage-shift” take years to accrue.(1, 2) This is because the colorectal cancer survival benefit is due to detection and treatment of early stage cancers – cancers that otherwise would not have resulted in death for at least 5 years. Hence, further understanding of life expectancy after early stage diagnosis should inform decision making about screening by identifying patients unlikely to live long enough to receive this benefit.(3) Second, as Dr. Burack emphasizes, colorectal cancer screening can also benefit patients by removing pre-cancerous lesions, and decreasing the incidence of colorectal cancer. However, it is important to note that the interval between onset of an adenoma and the clinical diagnosis of cancer has been estimated to be as long as 20 years.(4) Trial data support these estimates. The Minnesota Colon Cancer Control Study randomized over 46,000 patients to fecal occult blood testing (FOBT) or a control group.(1) Patients randomized to the annual FOBT group experienced significantly lower colorectal cancer mortality (0.59% vs.0.88% in the control group) after 13 years of follow-up; patients in the FOBT were more likely to be diagnosed with early stage disease.(1) Yet differences in incidence took longer to accrue. While there was no significant difference in incidence rates at 13 years, after 18 years there was a significantly lower incidence rate in the annual FOBT group (3.2%) than in the control group (3.9%; P<0.001).(5) Given that the clinical benefits of ‘stage shift’ may be noted in as little as 5 yeaRs, while that of adenoma removal may take 15 years or longer, we feel that the shorter-term interval should guide decision-making. We agree further work is needed to explore factors associated with life expectancy in the cancer-free population. While this analysis was beyond the scope of our study, it is notable that the relative survival of early stage colon cancer approaches 90%.(6) Therefore, although one would not expect substantial differences in life expectancy estimates between early stage colorectal cancer patients and those without cancer, empiric analyses should validate this assumption. - Cary Gross, Gail McAvay, Mary Tinetti. 1. Mandel J, Bond J, Church T. Reducing mortality from colorectal cancer by screening for fecal occult blood. N Engl J Med. 1993;328:1365- 71. 2. Kronborg O, Fenger C, Olsen J, Jorgensen OD, Sondergaard O. Randomised study of screening for colorectal cancer with faecal-occult-blood test. Lancet. 1996;348(9040):1467-71. 3. Gross CP, McAvay GJ, Krumholz HM, Paltiel AD, Bhasin D, Tinetti ME. The effect of age and chronic illness on life expectancy after a diagnosis of colorectal cancer: implications for screening. Ann Intern Med. 2006;145(9):646-53. 4. Loeve F, Boer R, van Oortmarssen GJ, van Ballegooijen M, Habbema JD. The MISCAN-COLON simulation model for the evaluation of colorectal cancer screening. Comput Biomed Res. 1999;32(1):13-33. 5. Mandel JS, Church TR, Bond JH, et al. The effect of fecal occult-blood screening on the incidence of colorectal cancer. N Engl J Med. 2000;343(22):1603-7. 6. Ries L, Eisner M, Kosary C, et al. (National Cancer Institute). SEER Cancer Statistics Review, 1975-2000. 2003. Conflict of Interest:None declared |
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Robert C Burack, MD, MPH Wayne State University
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rburack{at}med.wayne.edu Robert C Burack
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To the editor: Gross et al provide important information demonstrating the anticipated reduction in life expectancy that accompanies advancing age and higher co-morbidity burden among patients newly diagnosed with colorectal cancer.(1) While their observations may be particularly informative in considering treatment options following the diagnosis of colorectal cancer, the direct relevance of their observations to decision- making about screening is somewhat more complex. If the benefit of endoscopic screening for colorectal cancer derives from earlier diagnosis of cancer, then life expectancy at the time of diagnosis is particularly relevant. However, to the extent that the endoscopy offers benefit through the identification and removal of colorectal polyps among patients free of colorectal cancer, decisions about screening might better reflect consideration of life expectancy among individuals without colorectal cancer. While the issues of advancing age and co-morbidity are still quite relevant (2;3) it would be of interest to know the extent to which the estimates of Gross et al are sensitive to the presence of colorectal cancer. References (1) Gross CP, McAvay GJ, Krumholz HM, Paltiel AD, Bhasin D, Tinetti ME. The effect of age and chronic illness on life expectancy after a diagnosis of colorectal cancer: implications for screening. Ann Intern Med. 2006;145:646-53. (2) Lin OS, Kozarek RA, Schembre DB, Ayub K, Gluck M, Drennan F et al. Screening colonoscopy in very elderly patients: prevalence of neoplasia and estimated impact on life expectancy. JAMA. 2006;295:2357-65. (3) Walter LC, Covinsky KE. Cancer screening in elderly patients: a framework for individualized decision making. JAMA. 2001;285:2750-2756. Conflict of Interest:None declared |
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