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Cancer Intervention and Surveillance Modeling Network

Modeling to guide public health research and priorities

Other Achievements: Highlights

What was the contribution of risk factors, screening, and treatment in the 28% decline in colorectal mortality between 1978 and 2000?

To optimally guide cancer control opportunities in the future, it is important to know the degree to which past improvements are responsible for past trends. The University of Minnesota CISNET model (SimCRC) was used to analyze the potential contributors to observed trends in colorectal cancer mortality. The simulation results found that most of the decline (about 80%) was due to increases in screening, with advances in treatment, increased utilization of chemotherapy, and net improvements in risk factors contributing the rest. These results are important in guiding priorities for future cancer control efforts (Knudsen 2005).

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Which quality-of-care measure for colorectal cancer care has the greatest potential for reducing colorectal cancer mortality?

The Cancer Care Quality Measurement Project is an interagency initiative to develop quality-of-care measures for cancer care for evaluation by the National Quality Forum. To assist the National Quality Forum, a simulation model of colorectal cancer care was used to assess the relative contribution of four processes of care for improving cancer outcomes. Increasing appropriate use of chemotherapy in the adjuvant and metastatic settings is likely to provide a substantial reduction in colorectal cancer mortality. Improving colorectal cancer care delivery by increasing the intensity of post-treatment surveillance or chemotherapy subsequent to metastectomy will likely have minimal impact on reducing cancer mortality at the population level.

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What are some of the important public health implications associated with colorectal cancer risk factors?

There are various risk factors related to colorectal cancer, most of which are associated with several diseases or conditions in addition to colorectal cancer. Studying these risk factors in a context that extends beyond colorectal cancer is important from a public health standpoint. Using data from multiple waves of the National Health and Nutrition Examination Surveys, the increased folate intake following the folic acid fortification policy was estimated (Bentley 2006) and the impact on diseases evaluated (Bentley 2008). These surveys were also used to forecast the obesity epidemic in the U.S. population (Wang 2007).

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Does individualizing colonoscopy screening guidelines by gender and race reduce health disparities?

The Memorial Sloan-Kettering group (MISCAN colorectal model) showed only marginal improvements in the costs and effects of individualized screening recommendations on a population level. Individualized recommendations, however, could contribute to decreasing disparities between African-American and white populations. This study informs the discussion on individualization of colorectal cancer screening recommendations by quantifying the potential benefit (Lansdorp-Vogelaar 2008).

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What estimates of fecal occult blood test screening sensitivity and sojourn time best explain trial data?

Estimates of the fecal occult blood test (FOBT) (Hemoccult II) sensitivity differ widely between screening trials and could lead to divergent conclusions on the effects of FOBT screening. Three hypotheses for FOBT sensitivity were tested:

  1. ,sensitivity is the same for all preclinical colorectal cancer stages,
  2. sensitivity increases with each stage of disease, and
  3. sensitivity is higher for the stage in which the cancer would have been diagnosed in the absence of screening than for earlier stages.

The latter hypothesis gave the best fit to results of several randomized controlled trials (those conducted in Minnesota, Nottingham, and Funen).

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At what age do people undergo their first colorectal cancer test? How has this changed over time?

Miglioretti (2008) estimated the age at first fecal occult blood test, first lower endoscopy examination, and first colorectal cancer screening test of either type by using two series of cross-sectional surveys: the National Health Interview Survey (NHIS) and the Behavioral Risk Factor Surveillance System (BRFSS). The model for the national data (NHIS) incorporated birth cohort effects and was linked to state-specific models for BRFSS data. These results will be used to estimate the contribution of stool and endoscopy examinations to observed changes in colorectal cancer incidence and mortality.

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Do individuals with a positive fecal occult blood test receive appropriate follow-up?

Screening for fecal occult blood can be effective in reducing the rate of colorectal cancer mortality only if positive tests are appropriately followed up with complete diagnostic evaluation (i.e., colonoscopy or flexible sigmoidoscopy with double contrast barium enema) and treatment. Changes in the rates of complete diagnostic evaluation were examined within 1 year following a positive fecal occult blood test (FOBT) performed from 1993 to 2005 by Group Health (GH), a large integrated health care organization. In 1998, GH started an electronic registry to track enrollees who had not received a complete diagnostic evaluation within 4 months after a positive FOBT, and in 2003, GH implemented a centralized manual audit system to supplement the electronic system. Rates of complete follow-up increased from 57-64% between 1993 and 1996 to 82-86% between 2000 and 2005. This study demonstrates great improvements in adherence to recommendations for complete diagnostic evaluation after a positive FOBT, and it also showed that it may be possible to reach levels of follow-up that are comparable to those observed in randomized trials through the use of tracking systems and screening recommendations (Miglioretti 2008).

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How prevalent are adenomas, and how does prevalence vary with age?

Adenoma prevalence rates vary widely in the literature, and they depend on the age and sex of the individuals included in the sample and the methods used to measure adenomas. A study was conducted to estimate adenoma prevalence by age and sex by combining information from 14 autopsy studies. All studies reported adenoma prevalence by age. Most also reported adenoma prevalence by sex, and several also reported adenoma counts. A meta-analytic model developed by Group Health Center for Health Studies was used to combine the results across studies, which were consistent with results from recent colonoscopy studies. Adenomas were more prevalent in men than women, and adenoma prevalence and multiplicity both increased with age. For example, the prevalence of adenomas in men was estimated to increase from 32% at age 50 to 40% at age 60; the prevalence of adenomas in women was estimated to increase from 23% at age 50 to 29% at age 60. In addition, 9% of 50-year-old men and 5% of 50-year-old women have three or more adenomas (Rutter 2007). These results are important in understanding the natural history of adenoma initiation and progression.

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