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Background: Colorectal cancer screening is universally recommended for adults ages 45 to 75 years. Noninvasive fecal occult blood tests are effective screening tests recommended by guidelines. However, empirical evidence to inform older adults' decisions about whether to continue screening is sparse, especially for individuals with prior screening., Methods: This study used a retrospective cohort of older adults at three Kaiser Permanente integrated healthcare systems (Northern California, Southern California, Washington) and Parkland Health. Beginning 1 year following a negative stool-based screening test, cumulative risks of colorectal cancer incidence, colorectal cancer mortality (accounting for deaths from other causes), and non-colorectal cancer mortality were estimated., Results: Cumulative incidence of colorectal cancer in screen-eligible adults ages 76 to 85 with a negative fecal occult blood test 1 year ago (N = 118,269) was 0.23% [95% confidence interval (CI), 0.20%-0.26%] after 2 years and 1.21% (95% CI, 1.13%-1.30%) after 8 years. Cumulative colorectal cancer mortality was 0.03% (95% CI, 0.02%-0.04%) after 2 years and 0.33% (95% CI, 0.28%-0.39%) after 8 years. Cumulative risk of death from non-colorectal cancer causes was 4.81% (95% CI, 4.68%-4.96%) after 2 years and 28.40% (95% CI, 27.95%-28.85%) after 8 years., Conclusions: Among 76- to 85-year-olds with a recent negative stool-based test, cumulative colorectal cancer incidence and mortality estimates were low, especially within 2 years; death from other causes was over 100 times more likely than death from colorectal cancer., Impact: These findings of low absolute colorectal cancer risk, and comparatively higher risk of death from other causes, can inform decision-making regarding whether and when to continue colorectal cancer screening beyond age 75 among screen-eligible adults., (©2023 American Association for Cancer Research.)

Background: Multiple quality metrics have been recommended to ensure consistent, high-quality execution of screening tests for breast, cervical, colorectal, and lung cancers. However, minimal data exist evaluating the evidence base supporting these recommendations and the consistency of definitions and concepts included within and between cancer types., Methods: We performed a systematic review for each cancer type using MEDLINE, Embase, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) from 2010 to April 2020 to identify guidelines from screening programs or professional organizations containing quality metrics for tests used in breast, cervical, colorectal, and lung cancer screening. We abstracted metrics' definitions, target performance levels, and related supporting evidence for test completeness, adequacy (sufficient visualization or collection), accuracy, and safety., Results: We identified 11 relevant guidelines with 20 suggested quality metrics for breast cancer, 5 guidelines with 9 metrics for cervical cancer, 13 guidelines with 18 metrics for colorectal cancer (CRC), and 3 guidelines with 7 metrics for lung cancer. These included 54 metrics related to adequacy (n = 6), test completeness (n = 3), accuracy (n = 33), and safety (n = 12). Target performance levels were defined for 30 metrics (56%). Ten (19%) were supported by evidence, all from breast and CRC, with no evidence cited to support metrics from cervical and lung cancer screening., Conclusions: Considerably more guideline-recommended test performance metrics exist for breast and CRC screening than cervical or lung cancer. The domains covered are inconsistent among cancers, and few targets are supported by evidence. Clearer evidence-based domains and targets are needed for test performance metrics., Registration: PROSPERO 2020 CRD42020179139., (© The Author(s) 2023. Published by Oxford University Press.)

Background: Cancer screening should be recommended only when the balance between benefits and harms is favorable. This review evaluated how U.S. cancer screening guidelines reported harms, within and across organ-specific processes to screen for cancer., Objective: To describe current reporting practices and identify opportunities for improvement., Design: Review of guidelines., Setting: United States., Patients: Patients eligible for screening for breast, cervical, colorectal, lung, or prostate cancer according to U.S. guidelines., Measurements: Information was abstracted on reporting of patient-level harms associated with screening, diagnostic follow-up, and treatment. The authors classified harms reporting as not mentioned, conceptual, qualitative, or quantitative and noted whether literature was cited when harms were described. Frequency of harms reporting was summarized by organ type., Results: Harms reporting was inconsistent across organ types and at each step of the cancer screening process. Guidelines did not report all harms for any specific organ type or for any category of harm across organ types. The most complete harms reporting was for prostate cancer screening guidelines and the least complete for colorectal cancer screening guidelines. Conceptualization of harms and use of quantitative evidence also differed by organ type., Limitations: This review considers only patient-level harms. The authors did not verify accuracy of harms information presented in the guidelines., Conclusion: The review identified opportunities for improving conceptualization, assessment, and reporting of screening process-related harms in guidelines. Future work should consider nuances associated with each organ-specific process to screen for cancer, including which harms are most salient and where evidence gaps exist, and explicitly explore how to optimally weigh available evidence in determining net screening benefit. Improved harms reporting could aid informed decision making, ultimately improving cancer screening delivery., Primary Funding Source: National Cancer Institute.

Background: Cancer screening is a complex process involving multiple steps and levels of influence (e.g., patient, provider, facility, health care system, community, or neighborhood). We describe the design, methods, and research agenda of the Population-based Research to Optimize the Screening Process (PROSPR II) consortium. PROSPR II Research Centers (PRC), and the Coordinating Center aim to identify opportunities to improve screening processes and reduce disparities through investigation of factors affecting cervical, colorectal, and lung cancer screening in U.S. community health care settings., Methods: We collected multilevel, longitudinal cervical, colorectal, and lung cancer screening process data from clinical and administrative sources on >9 million racially and ethnically diverse individuals across 10 heterogeneous health care systems with cohorts beginning January 1, 2010. To facilitate comparisons across organ types and highlight data breadth, we calculated frequencies of multilevel characteristics and volumes of screening and diagnostic tests/procedures and abnormalities., Results: Variations in patient, provider, and facility characteristics reflected the PROSPR II health care systems and differing target populations. PRCs identified incident diagnoses of invasive cancers, in situ cancers, and precancers (invasive: 372 cervical, 24,131 colorectal, 11,205 lung; in situ: 911 colorectal, 32 lung; precancers: 13,838 cervical, 554,499 colorectal)., Conclusions: PROSPR II's research agenda aims to advance: (i) conceptualization and measurement of the cancer screening process, its multilevel factors, and quality; (ii) knowledge of cancer disparities; and (iii) evaluation of the COVID-19 pandemic's initial impacts on cancer screening. We invite researchers to collaborate with PROSPR II investigators., Impact: PROSPR II is a valuable data resource for cancer screening researchers., (©2022 American Association for Cancer Research.)

Background: It is strongly recommended that adults aged 50-75 years be screened for colorectal cancer. Recommended screening options include colonoscopy, sigmoidoscopy, CT colonography, guaiac fecal occult blood testing (FOBT), fecal immunochemical testing (FIT), or the more recently introduced FIT-DNA (FIT in combination with a stool DNA test). Colorectal cancer screening programs can benefit from knowledge of patterns of use by test type and within population subgroups., Methods: Using 2018 National Health Interview Survey (NHIS) data, we examined colorectal cancer screening test use for adults aged 50-75 years ( N = 10,595). We also examined time trends in colorectal cancer screening test use from 2010-2018., Results: In 2018, an estimated 66.9% of U.S. adults aged 50-75 years had a colorectal cancer screening test within recommended time intervals. However, the prevalence was less than 50% among those aged 50-54 years, those without a usual source of health care, those with no doctor visits in the past year, and those who were uninsured. The test types most commonly used within recommended time intervals were colonoscopy within 10 years (61.1%), FOBT or FIT in the past year (8.8%), and FIT-DNA within 3 years (2.7%). After age-standardization to the 2010 census population, the percentage up-to-date with CRC screening increased from 61.2% in 2015 to 65.3% in 2018, driven by increased use of stool testing, including FIT-DNA., Conclusions: These results show some progress, driven by a modest increase in stool testing. However, colorectal cancer testing remains low in many population subgroups., Impact: These results can inform efforts to achieve population colorectal cancer screening goals., (©2021 American Association for Cancer Research.)

The success of fecal occult blood-based colorectal cancer screening programs is dependent on repeating screening at short intervals (ie, every 1-2 years). We conducted a literature review to assess measures that have been used to assess longitudinal adherence to fecal-based screening. Among 46 citations identified and included in this review, six broad classifications of longitudinal adherence were identified: (a) stratified single-round attendance, (b) all possible adherence permutations, (c) consistent/inconsistent/never attendance, (d) number of times attended, (e) program adherence and (f) proportion of time covered. Advantages and disadvantages of these measures are described, and recommendations on which measures to use based on data availability and scientific question are also given. Stratified single round attendance is particularly useful for describing the yield of screening, while programmatic adherence measures are best suited to evaluating screening efficacy. We recommend that screening programs collect detailed longitudinal, individual-level data, not only for the screening tests themselves but additionally for diagnostic follow-up and surveillance exams, to allow for maximum flexibility in reporting adherence patterns using the measure of choice., (© 2021 UICC.)

Objective: To examine whether receiving a fecal occult blood test after a negative sigmoidoscopy reduced mortality from colorectal cancer., Methods: We used a nested case-control design with incidence-density matching in historical cohorts of 1,877,740 50-90-year-old persons during 2006-2012, in an integrated health-system setting. We selected 1758 average risk patients who died from colorectal cancer and 3503 matched colorectal cancer-free persons. Colorectal cancer-specific death was ascertained from cancer and mortality registries. Screening histories were determined from electronic and chart-audit clinical data in the 5- to 10-year period prior to the reference date. We evaluated receipt of subsequent fecal occult blood test within five years of the reference date among patients with negative sigmoidoscopy two to six years before the reference date., Results: Of the 5261 patients, 831 patients (204 colorectal cancer deaths/627 controls) had either negative sigmoidoscopy only ( n  = 592) or negative sigmoidoscopy with subsequent screening fecal occult blood test ( n  = 239). Fifty-six (27.5%) of the 204 patients dying of colorectal cancer and 183 (29.2%) of the 627 colorectal cancer-free patients received fecal occult blood test following a negative sigmoidoscopy. Conditional regressions found no significant association between fecal occult blood test receipt and colorectal cancer death risk, overall (adjusted odds ratio = 0.93, confidence interval: 0.65-1.33), or for right (odds ratio = 1.02, confidence interval: 0.65-1.60) or left-colon/rectum (odds ratio = 0.77, confidence interval: 0.39-1.52) cancers. Similar results were obtained in sensitivity analyses with alternative exposure ascertainment windows or timing of fecal occult blood test., Conclusions: Our results suggest that receipt of at least one fecal occult blood test during the several years after a negative sigmoidoscopy did not substantially reduce mortality from colorectal cancer.

Importance: The US Preventive Services Task Force (USPSTF) is updating its 2016 colorectal cancer screening recommendations., Objective: To provide updated model-based estimates of the benefits, burden, and harms of colorectal cancer screening strategies and to identify strategies that may provide an efficient balance of life-years gained (LYG) from screening and colonoscopy burden to inform the USPSTF., Design, Setting, and Participants: Comparative modeling study using 3 microsimulation models of colorectal cancer screening in a hypothetical cohort of 40-year-old US individuals at average risk of colorectal cancer., Exposures: Screening from ages 45, 50, or 55 years to ages 70, 75, 80, or 85 years with fecal immunochemical testing (FIT), multitarget stool DNA testing, flexible sigmoidoscopy alone or with FIT, computed tomography colonography, or colonoscopy. All persons with an abnormal noncolonoscopy screening test result were assumed to undergo follow-up colonoscopy. Screening intervals varied by test. Full adherence with all procedures was assumed., Main Outcome and Measures: Estimated LYG relative to no screening (benefit), lifetime number of colonoscopies (burden), number of complications from screening (harms), and balance of incremental burden and benefit (efficiency ratios). Efficient strategies were those estimated to require fewer additional colonoscopies per additional LYG relative to other strategies., Results: Estimated LYG from screening strategies ranged from 171 to 381 per 1000 40-year-olds. Lifetime colonoscopy burden ranged from 624 to 6817 per 1000 individuals, and screening complications ranged from 5 to 22 per 1000 individuals. Among the 49 strategies that were efficient options with all 3 models, 41 specified screening beginning at age 45. No single age to end screening was predominant among the efficient strategies, although the additional LYG from continuing screening after age 75 were generally small. With the exception of a 5-year interval for computed tomography colonography, no screening interval predominated among the efficient strategies for each modality. Among the strategies highlighted in the 2016 USPSTF recommendation, lowering the age to begin screening from 50 to 45 years was estimated to result in 22 to 27 additional LYG, 161 to 784 additional colonoscopies, and 0.1 to 2 additional complications per 1000 persons (ranges are across screening strategies, based on mean estimates across models). Assuming full adherence, screening outcomes and efficient strategies were similar by sex and race and across 3 scenarios for population risk of colorectal cancer., Conclusions and Relevance: This microsimulation modeling analysis suggests that screening for colorectal cancer with stool tests, endoscopic tests, or computed tomography colonography starting at age 45 years provides an efficient balance of colonoscopy burden and life-years gained.

Background: Colonoscopy follow-up recommendations depend on the presence or absence of polyps, and if found, their number, size, and histology. Patients may be responsible for conveying results between primary and specialty care or providing medical information to family members; thus, accurate reporting is critical. This analysis assessed the accuracy of self-reported colonoscopy findings., Methods: 3,986 participants from the Study of Colonoscopy Utilization, an ancillary study nested within the Prostate, Lung, Colorectal, and Ovarian Screening Trial, were included. Self-reports of polyp and adenoma were compared to medical records, and measures of sensitivity and specificity were calculated. Correlates of accurate self-report of polyp were assessed using logistic regression and weighted to account for study sampling., Results: The sensitivity and specificity of self-reported polyp findings were 88% and 85%, respectively, and for adenoma 11% and 99%, respectively. Among participants with a polyp, older age was associated with lower likelihood while polyp severity and non-white race were associated with increased likelihood of accurate recall. Among participants without a polyp, having multiple colonoscopies was associated with lower likelihood while family history of colorectal cancer was associated with increased likelihood of accurate recall. Among both groups, longer time since colonoscopy was associated with lower likelihood of accurate recall., Conclusions: Participants recalled with reasonable accuracy whether they had a prior polyp; however, recall of histology, specifically adenoma, was much less accurate., Impact: Identification of strategies to increase accurate self-report of colonic polyps are needed, particularly for patient-provider communications and patient reporting of results to family members., (©2020 American Association for Cancer Research.)

Background: Cancer screening is a complex process encompassing risk assessment, the initial screening examination, diagnostic evaluation, and treatment of cancer precursors or early cancers. Metrics that enable comparisons across different screening targets are needed. We present population-based screening metrics for breast, cervical, and colorectal cancers for nine sites participating in the Population-based Research Optimizing Screening through Personalized Regimens consortium., Methods: We describe how selected metrics map to a trans-organ conceptual model of the screening process. For each cancer type, we calculated calendar year 2013 metrics for the screen-eligible target population (breast: ages 40-74 years; cervical: ages 21-64 years; colorectal: ages 50-75 years). Metrics for screening participation, timely diagnostic evaluation, and diagnosed cancers in the screened and total populations are presented for the total eligible population and stratified by age group and cancer type., Results: The overall screening-eligible populations in 2013 were 305 568 participants for breast, 3 160 128 for cervical, and 2 363 922 for colorectal cancer screening. Being up-to-date for testing was common for all three cancer types: breast (63.5%), cervical (84.6%), and colorectal (77.5%). The percentage of abnormal screens ranged from 10.7% for breast, 4.4% for cervical, and 4.5% for colorectal cancer screening. Abnormal breast screens were followed up diagnostically in almost all (96.8%) cases, and cervical and colorectal were similar (76.2% and 76.3%, respectively). Cancer rates per 1000 screens were 5.66, 0.17, and 1.46 for breast, cervical, and colorectal cancer, respectively., Conclusions: Comprehensive assessment of metrics by the Population-based Research Optimizing Screening through Personalized Regimens consortium enabled systematic identification of screening process steps in need of improvement. We encourage widespread use of common metrics to allow interventions to be tested across cancer types and health-care settings., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Flexible sigmoidoscopy and colonoscopy are both recommended colorectal cancer screening options, but their relative effectiveness needs clarification. The aim of this study was to compare the effectiveness of colonoscopy and flexible sigmoidoscopy for reduction of colorectal cancer incidence., Methods: We conducted a case-control study within the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Cases were subjects age 70-85 years in the SEER-Medicare database diagnosed with CRC during 2004-2013. Up to 3 controls were matched to each case by birth year, sex, race, and SEER region. Receipt of screening colonoscopy or flexible sigmoidoscopy was ascertained from Medicare claims. Conditional logistic regression models were developed to estimate the odds ratios (ORs) and 95% confidence intervals (CI) for a history of screening in cases vs. controls. We conducted secondary analyses by sex, race, endoscopist characteristics, and with varying timing and duration of the look-back period., Results: Receipt of screening colonoscopy and sigmoidoscopy was associated with a 59% (OR 0.41, 95%CI 0.39, 0.43) and 22% reduction (OR 0.78, 95%CI 0.67, 0.92) in colorectal cancer incidence, respectively. Colonoscopy was associated with greater reduction in the distal colorectal cancer incidence (OR 0.22, 95%CI 0.20, 0.24) than proximal colorectal cancer incidence (OR 0.62, 95%CI 0.59, 0.66). Sigmoidoscopy was associated with a 52% reduction in distal colorectal cancer incidence (OR 0.48, 95%CI 0.37, 0.63), but with no reduction in proximal colorectal cancer incidence. These associations were stronger in men than in women. No differences by race or endoscopist characteristics were observed., Conclusion: Both screening colonoscopy and sigmoidoscopy were associated with reductions in overall colorectal cancer incidence, with a greater magnitude of reduction observed with colonoscopy., Competing Interests: Michael J. Barrett is an employee of Information Management Systems, Inc., the information technology contractor of the National Cancer Institute. This company assists researchers with creation of SEER-Medicare data files and assistance with data analyses, and does not have a commercial interest in any products or publications resulting from this database. This commercial affiliation does not alter adherence to all PLOS ONE policies on sharing data and materials.

Purpose: Colonoscopy and flexible sigmoidoscopy are both recommended colorectal cancer (CRC) screening strategies, but their relative effectiveness is unclear. We sought to evaluate the ability of each of these two modalities to reduce CRC mortality., Methods: We conducted a case-control study using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Cases were persons aged 70-85 years who died of CRC and were matched to up to three non-CRC controls. Receipt of endoscopy was ascertained from Medicare claims and endoscopy indication assigned using a validated algorithm. Conditional logistic regression models were developed to estimate the association between screening colonoscopy or sigmoidoscopy and CRC mortality. We conducted secondary analyses by race, sex, and endoscopist characteristics, and with varying duration of the look-back period., Results: In the initial analysis using all available look-back years, screening flexible sigmoidoscopy was associated with a 35% reduction in CRC mortality (OR 0.65, 95% CI 0.48, 0.89), while screening colonoscopy was associated with a 74% reduction (OR 0.26, 95% CI 0.23, 0.30). Sigmoidoscopy was not associated with any reduction in proximal CRC mortality. The association between colonoscopy and reduced CRC mortality was stronger in the distal than the proximal colon. Results were similar in analyses using a 5-year look-back period., Conclusions: Screening colonoscopy was associated with greater reductions in CRC mortality than screening sigmoidoscopy, and with a greater reduction in the distal than the proximal colon. These results provide additional information on the relative benefits of screening for CRC with sigmoidoscopy and colonoscopy.

Case-control studies evaluating a screening test's efficacy in reducing cancer mortality require accurate classification of test indication to obtain a valid result. However, for analogous studies of cancer incidence, determination of test indication is not as critical because, to define exposure, we need consider only tests that can identify precursor lesions whose treatment might prevent cancer, not tests leading to cancer diagnosis. This study utilizes US Surveillance, Epidemiology, and End Results (SEER)-Medicare data, which do not include information about colonoscopy indication, to evaluate the efficacy of colonoscopy in preventing colorectal cancer (CRC) incidence. Cases were Medicare enrollees diagnosed with CRC between 1996 and 2013; up to 3 controls were matched to each case. Colonoscopy receipt prior to presumed onset of occult cancer was associated with an approximately 60% reduction in CRC incidence (odds ratio = 0.41, 95% confidence interval: 0.40, 0.42). The association was robust to differing exposure windows and estimates of occult cancer duration and is similar to those from CRC incidence studies in which exam indication was available. Our results suggest that, when it is impractical/impossible to determine whether tests were conducted for screening, the efficacy of a test in preventing cancer incidence can still be estimated using a case-control study design., (Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health 2019.)

Background: To reduce colorectal cancer incidence and mortality, experts recommend surveillance colonoscopy 3 years after advanced adenoma removal. Little is known about adherence to that interval., Methods: We describe patterns of and factors associated with subsequent colonoscopy among persons with ≥3 adenomas and/or ≥1 adenoma with villous/tubulovillous histology in four U.S. integrated healthcare delivery systems. We report Kaplan-Meier estimators of the cumulative percentage of patients undergoing colonoscopy 6 months to 3.5 years after an index colonoscopy with high-risk findings. Combining data from three healthcare systems, we used multivariable logistic regression with inverse probability of censoring weights to estimate ORs and 95% confidence intervals (CI) for associations between patient characteristics and receipt of subsequent colonoscopy., Results: Among 6,909 persons with advanced adenomas, the percent receiving a subsequent colonoscopy 6 months to 3.5 years later ranged from 18.3% (95% CI: 11.7%-27.8%) to 59.5% (95% CI: 53.8%-65.2%) across healthcare systems. Differences remained significant in the multivariable model. Patients with ≥3 adenomas were more likely than those with 1 to 2 villous/tubulovillous adenomas to undergo subsequent colonoscopy. Subsequent colonoscopy was also more common for patients ages 60-74 and less common for patients ages 80 to 89 compared with those ages 50 to 54 years at their index colonoscopy. Sex, race/ethnicity, and comorbidity index score were generally not associated with subsequent colonoscopy receipt., Conclusions: Colonoscopy within the recommended interval following advanced adenoma was underutilized and varied by healthcare system, age, and number of adenomas., Impact: Strategies to improve adherence to surveillance colonoscopy following advanced adenomas are needed., (©2018 American Association for Cancer Research.)

Background: Microsimulation models synthesize evidence about disease processes and interventions, providing a method for predicting long-term benefits and harms of prevention, screening, and treatment strategies. Because models often require assumptions about unobservable processes, assessing a model's predictive accuracy is important., Methods: We validated 3 colorectal cancer (CRC) microsimulation models against outcomes from the United Kingdom Flexible Sigmoidoscopy Screening (UKFSS) Trial, a randomized controlled trial that examined the effectiveness of one-time flexible sigmoidoscopy screening to reduce CRC mortality. The models incorporate different assumptions about the time from adenoma initiation to development of preclinical and symptomatic CRC. Analyses compare model predictions to study estimates across a range of outcomes to provide insight into the accuracy of model assumptions., Results: All 3 models accurately predicted the relative reduction in CRC mortality 10 years after screening (predicted hazard ratios, with 95% percentile intervals: 0.56 [0.44, 0.71], 0.63 [0.51, 0.75], 0.68 [0.53, 0.83]; estimated with 95% confidence interval: 0.56 [0.45, 0.69]). Two models with longer average preclinical duration accurately predicted the relative reduction in 10-year CRC incidence. Two models with longer mean sojourn time accurately predicted the number of screen-detected cancers. All 3 models predicted too many proximal adenomas among patients referred to colonoscopy., Conclusion: Model accuracy can only be established through external validation. Analyses such as these are therefore essential for any decision model. Results supported the assumptions that the average time from adenoma initiation to development of preclinical cancer is long (up to 25 years), and mean sojourn time is close to 4 years, suggesting the window for early detection and intervention by screening is relatively long. Variation in dwell time remains uncertain and could have important clinical and policy implications., (© The Author(s) 2016.)

Importance: The US Preventive Services Task Force (USPSTF) is updating its 2008 colorectal cancer (CRC) screening recommendations., Objective: To inform the USPSTF by modeling the benefits, burden, and harms of CRC screening strategies; estimating the optimal ages to begin and end screening; and identifying a set of model-recommendable strategies that provide similar life-years gained (LYG) and a comparable balance between LYG and screening burden., Design, Setting, and Participants: Comparative modeling with 3 microsimulation models of a hypothetical cohort of previously unscreened US 40-year-olds with no prior CRC diagnosis., Exposures: Screening with sensitive guaiac-based fecal occult blood testing, fecal immunochemical testing (FIT), multitarget stool DNA testing, flexible sigmoidoscopy with or without stool testing, computed tomographic colonography (CTC), or colonoscopy starting at age 45, 50, or 55 years and ending at age 75, 80, or 85 years. Screening intervals varied by modality. Full adherence for all strategies was assumed., Main Outcomes and Measures: Life-years gained compared with no screening (benefit), lifetime number of colonoscopies required (burden), lifetime number of colonoscopy complications (harms), and ratios of incremental burden and benefit (efficiency ratios) per 1000 40-year-olds., Results: The screening strategies provided LYG in the range of 152 to 313 per 1000 40-year-olds. Lifetime colonoscopy burden per 1000 persons ranged from fewer than 900 (FIT every 3 years from ages 55-75 years) to more than 7500 (colonoscopy screening every 5 years from ages 45-85 years). Harm from screening was at most 23 complications per 1000 persons screened. Strategies with screening beginning at age 50 years generally provided more LYG as well as more additional LYG per additional colonoscopy than strategies with screening beginning at age 55 years. There were limited empirical data to support a start age of 45 years. For persons adequately screened up to age 75 years, additional screening yielded small increases in LYG relative to the increase in colonoscopy burden. With screening from ages 50 to 75 years, 4 strategies yielded a comparable balance of screening burden and similar LYG (median LYG per 1000 across the models): colonoscopy every 10 years (270 LYG); sigmoidoscopy every 10 years with annual FIT (256 LYG); CTC every 5 years (248 LYG); and annual FIT (244 LYG)., Conclusions and Relevance: In this microsimulation modeling study of a previously unscreened population undergoing CRC screening that assumed 100% adherence, the strategies of colonoscopy every 10 years, annual FIT, sigmoidoscopy every 10 years with annual FIT, and CTC every 5 years performed from ages 50 through 75 years provided similar LYG and a comparable balance of benefit and screening burden.

Background: Primary care providers and health systems have prominent roles in guiding effective cancer screening., Objective: To characterize variation in screening abnormality rates and timely initial follow-up for common cancer screening tests., Design: Population-based cohort undergoing screening in 2011, 2012, or 2013 at seven research centers comprising the National Cancer Institute-sponsored Population-based Research Optimizing Screening through Personalized Regimens (PROSPR) consortium., Participants: Adults undergoing mammography with or without digital breast tomosynthesis (n = 97,683 ages 40-75 years), fecal occult blood or fecal immunochemical tests (n = 759,553 ages 50-75 years), or Papanicolaou with or without human papillomavirus tests (n = 167,330 ages 21-65 years)., Intervention: Breast, colorectal, or cervical cancer screening., Main Measures: Abnormality rates per 1000 screens; percentage with timely initial follow-up (within 90 days, except 9-month window for BI-RADS 3). Primary care clinic-level variation in percentage with screening abnormality and percentage with timely initial follow-up., Key Results: There were 10,248/97,683 (104.9 per 1000) abnormal breast cancer screens, 35,847/759,553 (47.2 per 1000) FOBT/FIT-positive colorectal cancer screens, and 13,266/167,330 (79.3 per 1000) abnormal cervical cancer screens. The percentage with timely follow-up was 93.2 to 96.7 % for breast centers, 46.8 to 68.7  % for colorectal centers, and 46.6 % for the cervical cancer screening center (low-grade squamous intraepithelial lesions or higher). The primary care clinic variation (25th to 75th percentile) was smaller for the percentage with an abnormal screen (breast, 8.5-10.3 %; colorectal, 3.0-4.8 %; cervical, 6.3-9.9 %) than for the percentage with follow-up within 90 days (breast, 90.2-95.8 %; colorectal, 43.4-52.0 %; cervical, 29.6-61.4 %)., Conclusions: Variation in both the rate of screening abnormalities and their initial follow-up was evident across organ sites and primary care clinics. This highlights an opportunity for improving the delivery of cancer screening through focused study of patient, provider, clinic, and health system characteristics associated with timely follow-up of screening abnormalities., Competing Interests: The authors declare no conflicts of interest. Funders This work was supported by the National Cancer Institute (NCI)-funded Population-based Research Optimizing Screening through Personalized Regimens (PROSPR) consortium (grant numbers U01CA163304 to M.T., W.B.; U54CA163303 to D.L.W., B.S.; U54CA163307 to A.N.A.T., T.O., J.H.; U54CA163313 to K.A., M.S.; U54CA163308 to C.S.S., E.H.; U54CA163308-04S1 to C.S.S., J.A.T.; U54CA163261 to C.R.; U54CA163261-04S1 to J.C., A.K.; U54CA163262 to A.G.Z., D.C., C.D., T.L.; U54CA163262-04S1 to D.C., M.S.; and U54CA164336 to C.W.). The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the Department of Veterans Affairs or the United States government.

Objective: To examine the rates of colorectal cancer (CRC) following a negative screening sigmoidoscopy., Design: Cohort study., Setting: An integrated healthcare delivery organisation in California, USA., Participants: 72,483 men and women aged 50 years and above who had a negative screening sigmoidoscopy between 1994 and 1996. Those at elevated risk of CRC due to inflammatory bowel disease, prior polyps or CRC, or a strong family history of CRC were excluded., Main Outcome Measures: Incidence rates of distal and proximal CRC. Standardised Incidence Ratios were used to compare annual incidence rates of distal and proximal CRC in the cohort to expected rates based on Surveillance, Epidemiology, and End Results data. Additionally, rate ratios (RR) and rate differences (RD) comparing the incidence rate of distal CRC in years 6+ postscreening with that in years 1-5 were calculated., Results: Incidence rates of distal CRC were lower than those in the San Francisco Bay area population at large during each of the first 10 years postsigmoidoscopy screening. However, the incidence of distal CRC rose steadily, from 3 per 100,000 in the first year of follow-up to 40 per 100,000 in the 10th year. During the second half of follow-up, the rate of distal CRC was twice as high as in the first half (RR 2 .08, 95% CI 1.38 to 3.16; RD 14 per 100,000 person-years, 95% CI 6 to 22)., Conclusions: Though still below population levels, the incidence of CRC during years 6-10 following a negative sigmoiodoscopy is appreciably higher than during the first 5 years., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Aims: Screening colonoscopy's effectiveness in reducing risk of death from right colon cancers remains unclear. Methodological challenges of existing observational studies addressing this issue motivated the design of 'Effectiveness of Screening for Colorectal Cancer in Average-Risk Adults (SCOLAR)'., Methods: SCOLAR is a nested case-control study based on two large integrated health systems. This affords access to a large, well-defined historical cohort linked to integrated data on cancer outcomes, patient eligibility, test indications and important confounders., Results: We found electronic data adequate for excluding ineligible patients (except family history), but not the detailed information needed for test indication assignment., Conclusion: The lessons of SCOLAR's design and implementation may be useful for future studies seeking to evaluate the effectiveness of screening tests in community settings.

Background: It is unclear whether the higher rate of colorectal cancer (CRC) among non-Hispanic blacks (blacks) is due to lower rates of CRC screening or greater biologic risk., Objective: We aimed to evaluate whether blacks are more likely than non-Hispanic whites (whites) to develop distal colon neoplasia (adenoma and/or cancer) after negative flexible sigmoidoscopy (FSG)., Design: We analyzed data of participants with negative FSGs at baseline in the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial who underwent repeat FSGs 3 or 5 years later. Subjects with polyps or masses were referred to their physicians for diagnostic colonoscopy. We collected and reviewed the records of diagnostic evaluations., Participants: Our analytic cohort consisted of 21,550 whites and 975 blacks., Main Measures: We did a comparison by race (whites vs. blacks) in the findings of polyps or masses at repeat FSG, the follow-up of abnormal test results and the detection of colorectal neoplasia at diagnostic colonoscopy., Key Results: At the follow-up FSG examination, 304 blacks (31.2 %) and 4183 whites (19.4 %) had abnormal FSG, [adjusted relative risk (RR) = 1.00; 95 % confidence interval (CI), 0.90-1.10]. However, blacks were less likely to undergo diagnostic colonoscopy (76.6 % vs. 83.1 %; RR = 0.90; 95 % CI, 0.84-0.96). Among all included patients, blacks had similar risk of any distal adenoma (RR = 0.86; 95 % CI, 0.65-1.14) and distal advanced adenoma (RR = 1.01; 95 % CI, 0.60-1.68). Similar results were obtained when we restricted our analysis to compliant subjects who underwent diagnostic colonoscopy (RR = 1.01; 95 % CI, 0.80-1.29) for any distal adenoma and (RR = 1.18; 95 % CI, 0.73-1.92) for distal advanced adenoma., Conclusions: We did not find any differences between blacks and whites in the risk of distal colorectal adenoma 3-5 years after negative FSG. However, follow-up evaluations were lower among blacks.

Background: Accurate indication classification is critical for obtaining unbiased estimates of colonoscopy effectiveness and quality improvement efforts, but there is a dearth of published systematic classification approaches. The objective of this study was to evaluate the effects of data-source and adjudication on indication classification and on estimates of the effectiveness of screening colonoscopy on late-stage colorectal cancer diagnosis risk., Methods: This was an observational study in members of four U.S. health plans. Eligible persons (n = 1039) were age 55-85 and had been enrolled for 5 years or longer in their health plans during 2006-2008. Patients were selected based on late-stage colorectal cancer diagnosis in a case-control design; each case patient was matched to 1-2 controls by study site, age, sex, and health plan enrollment duration. Reasons for colonoscopies received in the 10-year period before the reference date were collected from three medical records sources (progress notes; referral notes; procedure reports) and categorized using an algorithm, with committee adjudication of some tests. We evaluated indication classification concordance before and after adjudication and used logistic regressions with the Wald Chi-square test to compare estimates of the effects of screening colonoscopy on late-stage colorectal cancer diagnosis risk for each of our data sources to the adjudicated indication., Results: Classification agreement between each data-source and adjudication was 78.8-94.0% (weighted kappa = 0.53-0.72); the highest agreement (weighted kappa = 0.86-0.88) was when information from all data sources was considered together. The choice of data-source influenced the association between screening colonoscopy and late-stage colorectal cancer diagnosis; estimates based on progress notes were closest to those based on the adjudicated indication (% difference in regression coefficients = 2.4%, p-value = 0.98), as compared to estimates from only referral notes (% difference in coefficients = 34.9%, p-value = 0.12) or procedure reports (% difference in coefficients = 27.4%, p-value = 0.23)., Conclusion: There was no single gold-standard source of information in medical records. The estimates of colonoscopy effectiveness from progress notes alone were the closest to estimates using adjudicated indications. Thus, the details in the medical records are necessary for accurate indication classification.

Objective: To estimate the expected magnitude of error produced by uncontrolled confounding from health behaviours in observational medical record-based studies evaluating effectiveness of screening colonoscopy., Methods: We used data from the prospective National Institutes of Health American Association of Retired Persons (NIH-AARP) Diet and Health Study to assess the impact of health behaviour related factors (lifestyle, education, and use of non-steroidal anti-inflammatory drugs [NSAID]) on the association between colonoscopy and colorectal cancer (CRC) mortality. We first examined the difference between adjusted and unadjusted results within the cohort data, and then estimated a broader range of likely confounding errors based on the Breslow-Day approach that uses prevalence of confounders among persons with and without exposure, and the rate ratio reflecting the association between these confounders and the outcome of interest. As dietary factors and habits are often inter-correlated, we combined these variables (physical activity, body mass index, waist-to-hip ratio, alcohol consumption, and intakes of red meat, processed meat, fibre, milk, and calcium) into a "healthy lifestyle score" (HLS)., Results: The estimated error (a ratio of biased-to-true result) attributable to confounding by HLS was 0.959-0.997, indicating less than 5% departure from the true effect of colonoscopy on CRC mortality. The corresponding errors ranged from 0.970 to 0.996 for NSAID, and from 0.974 to 1.006 for education (all ≤3% difference). The results for other CRC screening tests were similar., Conclusion: Health behaviour-related confounders, either alone or in combination, seem unlikely to strongly affect the association between colonoscopy and CRC mortality in observational studies of CRC screening.

Background: The effectiveness of screening colonoscopy in average-risk adults is uncertain, particularly for right colon cancer., Objective: To examine the association between screening colonoscopy and risk for incident late-stage colorectal cancer (CRC)., Design: Nested case-control study., Setting: Four U.S. health plans., Patients: 1039 average-risk adults enrolled for at least 5 years in one of the health plans. Case patients were aged 55 to 85 years on their diagnosis date (reference date) of stage IIB or higher (late-stage) CRC during 2006 to 2008. One or 2 control patients were selected for each case patient, matched on birth year, sex, health plan, and prior enrollment duration., Measurements: Receipt of CRC screening 3 months to 10 years before the reference date, ascertained through medical record audits. Case patients and control patients were compared on receipt of screening colonoscopy or sigmoidoscopy by using conditional logistic regression that accounted for health history, socioeconomic status, and other screening exposures., Results: In analyses restricted to 471 eligible case patients and their 509 matched control patients, 13 case patients (2.8%) and 46 control patients (9.0%) had undergone screening colonoscopy, which corresponded to an adjusted odds ratio (AOR) of 0.29 (95% CI, 0.15 to 0.58) for any late-stage CRC, 0.36 (CI, 0.16 to 0.80) for right colon cancer, and 0.26 (CI, 0.06 to 1.11; P = 0.069) for left colon/rectum cancer. Ninety-two case patients (19.5%) and 173 control patients (34.0%) had screening sigmoidoscopy, corresponding to an AOR of 0.50 (CI, 0.36 to 0.70) overall, 0.79 (CI, 0.51 to 1.23) for right colon late-stage cancer, and 0.26 (CI, 0.14 to 0.48) for left colon cancer., Limitation: The small number of screening colonoscopies affected the precision of the estimates., Conclusion: Screening with colonoscopy in average-risk persons was associated with reduced risk for diagnosis of incident late-stage CRC, including right-sided colon cancer. For sigmoidoscopy, this association was seen for left CRC, but the association for right colon late-stage cancer was not statistically significant.

Background and Study Aim: Inadequate colorectal cancer screening wastes limited endoscopic resources. We examined patients factors associated with inadequate flexible sigmoidoscopy (FSG) screening at baseline screening and repeat screening 3-5 years later in 10 geographically-dispersed screening centers participating in the ongoing Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial., Methods: A total of 64,554 participants (aged 55-74) completed baseline questionnaires and underwent FSG at baseline. Of these, 39,385 participants returned for repeat screening. We used logistic regression models to assess factors that are associated with inadequate FSG (defined as a study in which the depth of insertion of FSG was <50 cm or visual inspection was limited to <90% of the mucosal surface but without detection of a polyp or mass)., Results: Of 7084 (11%) participants with inadequate FSG at baseline, 6496 (91.7%) had <50 cm depth of insertion (75.3% due to patient discomfort) and 500 (7.1%) participants had adequate depth of insertion but suboptimal bowel preparation. Compared to 55-59 year age group, advancing age in 5-year increments (odds ratios (OR) from 1.08 to 1.51) and female sex (OR = 2.40; 95% confidence interval (CI): 2.27-2.54) were associated with inadequate FSG. Obesity (BMI > 30 kg/m(2)) was associated with reduced odds (OR = 0.67; 95% CI: 0.62-0.72). Inadequate FSG screening at baseline was associated with inadequate FSG at repeat screening (OR = 6.24; 95% CI: 5.78-6.75)., Conclusions: Sedation should be considered for patients with inadequate FSG or an alternative colorectal cancer screening method should be recommended., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Purpose: We designed this study to evaluate the association of colonoscopy with colorectal cancer (CRC) death in the United States by site of CRC and endoscopist specialty., Methods: We designed a case-control study using Surveillance, Epidemiology, and End Results (SEER)-Medicare data. We identified patients (cases) diagnosed with CRC age 70 to 89 years from January 1998 through December 2002 who died as a result of CRC by 2007. We selected three matched controls without cancer for each case. Controls were assigned a referent date (date of diagnosis of the case). Colonoscopy performed from January 1991 through 6 months before the diagnosis/referent date was our primary exposure. We compared exposure to colonoscopy in cases and controls by using conditional logistic regression controlling for covariates, stratified by site of CRC. We determined endoscopist specialty by linkage to the American Medical Association (AMA) Masterfile. We assessed whether the association between colonoscopy and CRC death varied with endoscopist specialty., Results: We identified 9,458 cases (3,963 proximal [41.9%], 4,685 distal [49.5%], and 810 unknown site [8.6%]) and 27,641 controls. In all, 11.3% of cases and 23.7% of controls underwent colonoscopy more than 6 months before diagnosis. Compared with controls, cases were less likely to have undergone colonoscopy (odds ratio [OR], 0.40; 95% CI, 0.37 to 0.43); the association was stronger for distal (OR, 0.24; 95% CI, 0.21 to 0.27) than proximal (OR, 0.58; 95% CI, 0.53 to 0.64) CRC. The strength of the association varied with endoscopist specialty., Conclusion: Colonoscopy is associated with a reduced risk of death from CRC, with the association considerably and consistently stronger for distal versus proximal CRC. The overall association was strongest if colonoscopy was performed by a gastroenterologist.

Background: Among randomized trials evaluating flexible sigmoidoscopy (FSG) for its effect on colorectal cancer mortality, only the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial screened its participants more than one time. We report outcomes from the PLCO screening FSG program and evaluate the increased yield produced by a second FSG., Methods: Participants were screened by 60-cm FSG in 10 regional screening centers at study entry and 3 or 5 years later, depending on the time of random assignment. Results from subsequent diagnostic intervention were tracked and recorded in a standardized fashion, and outcomes were compared according to sex and age. The protocol discouraged repeat FSG in persons with colorectal cancer or adenoma diagnosed after the initial FSG., Results: Of 77 447 enrollees, 67 073 (86.6%) had at least one FSG and 39 443 (50.9%) had two FSGs. Diagnostic intervention occurred in 74.9% after a positive first FSG and in 78.7% after a positive repeat FSG. The second FSG increased the screening yield by 32%: Colorectal cancer or advanced adenoma was detected in 37.8 per 1000 persons after first screening and in 49.8 per 1000 persons after all screenings. The second FSG increased the yield of cancer or advanced adenoma by 26% in women and by 34% in men. Of 223 subjects who received a diagnosis of colorectal carcinoma within 1 year of a positive FSG, 64.6% had stage I and 17.5% had stage II disease., Conclusions: Repeat FSG increased the detection of colorectal cancer or advanced adenoma in women by one-fourth and in men by one-third. Screen-detected carcinomas were early stage (stage I or II) in greater than 80% of screened persons. Colorectal cancer mortality data from the PLCO, as the definitive endpoint, will follow in later publications.

Background: It is unclear whether the disproportionately higher incidence and mortality from colorectal cancer among blacks compared with whites reflect differences in health-care utilization or colorectal cancer susceptibility., Methods: A total of 60, 572 non-Hispanic white and black participants in the ongoing Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial underwent trial-sponsored screening flexible sigmoidoscopy (FSG) without biopsy at baseline in 10 geographically dispersed centers from November 1993 to July 2001. Subjects with polyps or mass lesions detected by FSG were referred to their physicians for diagnostic workup, the cost of which was not covered by PLCO. The records of follow-up evaluations were collected and reviewed. We used log binomial modeling with adjustment for age, education, sex, body mass index, smoking, family history of colorectal cancer, colon examination within previous 3 years, personal history of polyps, and screening center to examine whether utilization of diagnostic colonoscopy and yield of neoplasia differed by race., Results: Among 57 561 whites and 3011 blacks who underwent FSG, 13,743 (23.9%) and 767 (25.5%) had abnormal examinations, respectively. A total of 9944 (72.4%) whites and 480 (62.6%) blacks had diagnostic colonoscopy within 1 year following the abnormal FSG screening. When compared with whites, blacks were less likely to undergo diagnostic evaluation (adjusted risk ratio = 0.88, 95% confidence interval = 0.83 to 0.93). Overall, among subjects with diagnostic colonoscopy (n = 10 424), there was no statistically significant difference by race in the prevalence of adenoma, advanced adenoma, advanced pathology in small adenomas (high-grade dysplasia or villous histology in adenomas <10 mm), or colorectal cancer., Conclusions: We observed a lower follow-up for screen-detected abnormalities among blacks when compared with whites but little difference in the yield of colorectal neoplasia. Health-care utilization may be playing more of a role in colorectal cancer racial disparity than biology.

Epidemiologic studies of hormone therapy (HT) and colorectal cancer incidence consistently show an inverse association; however, few studies have considered prediagnostic use of HT on mortality among colorectal cancer patients. We evaluated the relationship of HT and survival among a population-based cohort of women with large bowel cancer. Cases (n=1,297) were newly diagnosed with invasive cancer of the colon or rectum, aged 40-74 years at diagnosis, who were identified by Wisconsin's statewide registry (1988-1991; 1997-2001) for two case-control studies. Information on HT use and other colorectal cancer risk factors was collected by standardized interview. There were 507 deaths (274 of these attributable to colorectal cancer) over 8.4 years of follow-up through December 2005. Hormone use was not associated with colorectal cancer mortality (adjusted hazard rate ratio=1.09, confidence interval=0.81-1.47). Colorectal cancer specific mortality was not associated with HT when considered separately by preparation type. Stage did not modify this relationship. Long-term HT was weakly positively associated with increased mortality after diagnosis of proximal colon, but not distal colon cancer. Because we detected no differences in survival among users of HT compared to non-users, the results suggest that HT use may affect only the incidence of some colorectal tumors.

Current users of postmenopausal hormones (PMH) have approximately 30% to 40% lower risk of colorectal cancer (CRC), although associations with specific types of hormones have been inconsistent. Further, it is not clear whether some tumor types have a different risk. We conducted a case-control study to examine the relationship between PMH and CRC. Cases (n = 1,004), ages 50 to 74 years, were identified from the Surveillance Epidemiology and End Results registry in Washington from 1998 to 2002; controls (n = 1,062) were randomly selected from population lists. Case tissue samples were obtained for microsatellite instability (MSI) analyses. Interviews collected risk-factor data for CRC, including detailed information on PMH. Multivariable logistic regression models estimated odds ratios (OR) and 95% confidence intervals (95% CI). Current use of any PMH was associated with a 20% reduction in CRC risk (95% CI 0.6-0.9). This reduction in risk was limited to women who had taken estrogen plus progestin (EP) preparations only (OR = 0.6, 95% CI 0.5-0.9); there was no association with estrogen-only (E alone) use (OR = 0.9, 95% CI 0.7-1.1). For women with MSI-low or MSI-stable tumors, there was a statistically significant 40% reduction in CRC risk associated with EP use (95% CI 0.4-0.9); there was no clear association with MSI-high tumors. EP use was associated with a decreased risk of CRC; however, there seemed to be no association with E alone data that are consistent with the recent Women's Health Initiative findings. Progestin may enhance the estrogenic effect of conjugated estrogen so the combination may be more biologically active in the colon than E alone.

Objectives: Although overweight body mass is an established risk factor for colorectal cancer incidence, few studies have examined the association between body mass index (BMI) and mortality after colorectal cancer diagnosis. We examined survival in a group of postmenopausal women according to BMI., Methods: Using the Wisconsin Cancer Reporting System we identified and enrolled 633 postmenopausal women aged 38-74 years who were diagnosed with colorectal cancer in 1988-1991. These women were interviewed by telephone; vital status was ascertained via Wisconsin death certificates. Cox proportional hazards regression was used to estimate multivariate risks of colorectal cancer-specific and all-cause mortality., Results: Both underweight (BMI <20.0 kg/m2) (Hazard Ratio (HR) 2.3, 95% Confidence Interval (CI) 1.0-5.4) and obese (BMI > or = 30.0 kg/m2) women (HR 2.1, 95% CI 1.1-3.8) were at increased risk of colon cancer death, as compared to normal weight women (BMI 20.0-24.9 kg/m2). No association was observed for those with rectal cancer. Approximately 50% increases in all-cause mortality were observed among underweight and obese women with colorectal cancer. Postmenopausal hormone use did not appear to modify these associations., Conclusions: Underweight and obese postmenopausal women with colon cancer were at increased risk of death, though comorbidities may partially account for this risk.

Background: Several previous studies have found that females and older individuals are at greater risk of having incomplete flexible sigmoidoscopy. However, no prior study has reported the subsequent risk of colorectal cancer (CRC) following incomplete sigmoidoscopy., Methods: Using data from 55 791 individuals screened as part of the Colon Cancer Prevention (CoCaP) programme of Kaiser Permanente of Northern California, we evaluated the likelihood of having an inadequate (<40 cm) examination by age and sex, and estimated the risk of distal CRC according to depth of sigmoidoscope insertion at the baseline screening examination. Multivariate estimation of risks was performed using Poisson regression., Results: Older individuals were at a much greater risk of having an inadequate examination (relative risk (RR) for age 80+ years compared with 50-59 years 2.6 (95% confidence interval (CI) 2.3-3.0)), as were females (RR 2.3 (95% CI 2.2-2.5)); these associations were attenuated but remained strong if Poisson models were further adjusted for examination limitations (pain, stool, and angulation). There was an approximate threefold increase in the risk of distal CRC if the baseline sigmoidoscopy did not reach a depth of at least 40 cm; a smaller increase in risk was observed for examinations that reached 40-59 cm., Conclusions: Older individuals and women are at an increased risk of having inadequate sigmoidoscopy. Because inadequate sigmoidoscopy results in an increased risk of subsequent CRC, physicians should consider steps to maximise the depth of insertion of the sigmoidoscope or, failing this, should consider an alternative screening test.

Background & Aims: Current guidelines recommend a 5-year interval for colorectal cancer (CRC) screening by sigmoidoscopy. However, the optimal screening interval is uncertain. We estimated the annual incidence of distal and proximal CRC in the first 5 years following a negative sigmoidoscopy examination to gauge the potential benefit of rescreening in <5 years., Methods: A cohort of 72,483 participants in the Colon Cancer Prevention program of Kaiser Permanente of Northern California (KP) was defined using computerized databases. Men and women aged 50 years and older who had a negative screening flexible sigmoidoscopy examination between 1994 and 1996 and were considered not to be at high risk for developing CRC were included. Subjects were censored at the time of diagnosis (for cases), death, termination of KP membership, or subsequent colon examination., Results: Thirty cases of distal and 80 cases of proximal CRC occurred. Age-adjusted incidence rates of distal CRC ranged from a low of 2.8 per 100,000 person-years in the first year of follow-up to a high of 13.0 per 100,000 in the fourth year (rate difference, 10.2; 95% confidence interval, 1.1-19.3). However, for the entire follow-up period, incidence of distal CRC remained much lower than age-adjusted rates of 70.6 in the general population (Surveillance, Epidemiology, and End Results registry). The incidence of proximal CRC was also decreased modestly over population rates of disease., Conclusions: Screening by sigmoidoscopy more frequently than every 5 years would likely lead, at best, to only modest improvements as compared with a 5-year screening interval.