The present analysis suggests that 8-yearly uniform and individualized colonoscopy recommendations by gender and race on a total population level are comparable in costs and effects: the overall (total population) benefit of individualization is limited (0.0002 additional life-years gained, $9.09 lower costs per person). This is explained by the fact that the African American population constitutes no more than approximately 20% of the population. For African Americans, the increase in life-years gained was more substantial (0.0078 life-years, approximately 14% of total life-years saved with screening), decreasing the disparity in incidence and mortality compared to whites. Our results were robust for changes in model assumptions. In 1,000 simulations with different model parameter values, the 8-yearly uniform and individualized strategies remained equivalent in costs and effects. We found that with individualizing screening, African Americans are screened with a one-year shorter interval than whites and start screening 6 years earlier, whereas the recommended screening ages and frequency for men and women remain similar.
Our findings support the recommendation of the American College of Gastroenterology to begin screening 5 years earlier in African Americans than whites. Starting screening at an earlier age without increasing the number of screenings, results in saving 0.0052 additional life-years in African Americans (data not shown). Also increasing the number of screens as recommended from our study, significantly further increases the additional life-years gained to 0.0078. Individualization can therefore play a significant role in reducing disparities between African Americans and whites. Our results are in line with other studies that have shown that the average cost-effectiveness of CRC screening is better in African American men than in other population subgroups.60, 61
Based on these results, the authors advocate earlier screening in African Americans. However, basing individualized guidelines on average cost-effectiveness does not necessarily lead to efficient use of resources. In the present analysis, we determined individualized guidelines based on incremental cost-effectiveness and hence ensuring efficient use of resources.33, 34
Besides the current recommendation of four screenings every 10 years from age 50 to age 80, we also used another uniform colonoscopy strategy as a comparator to enable a fair comparison between uniform and individualized screening. We could not use the exact recommendation for that purpose, because it was not optimally cost-effective, although it was close. The current guidelines were not based on a formal decision analysis, but on studies on colonoscopic efficiency1
and on simplicity and clarity. Individualized guidelines are more complex than uniform ones, and one could therefore argue that recommendations should not be individualized unless benefits are substantial. Individualized screening guidelines may confuse providers and consumers to the point of decreasing adherence. A decrease in adherence will easily offset the gains from individualization. Currently, 40% of African American men and 32% of African American women aged 50 years and older reported having had either a Fecal Occult Blood Test (FOBT) within the past year or a colorectal endoscopy within the past 5 years.62
Based on these figures much can be gained from increased adherence to screening guidelines. On the other hand, individualization of screening guidelines must be considered in the context of a general trend towards personalized medical care.63, 64
As a result, screening adherence might improve because individuals appreciate that the recommendation is based on their personal risk profile. In any case, in a situation where individualization of medical care and especially of screening, becomes the standard, it would be only natural to account also for race and gender differences, given the expected benefit and regardless of its size. To avoid too much complexity, one could recommend not changing the guidelines for whites but changing screening for African Americans to every 9 years from age 45 years onward (a similar change as the results of this study). Compared with the current screening guidelines, this recommendation would result in 0.0076 more life-years gained for blacks, comparable with the 0.0078 found in this study.
In this analysis, we assumed that all disparities in cancer incidence are caused by differences in adenoma incidence. This assumption is supported by results from the Clinical Outcomes Research Initiative (CORI), showing a higher percentage of adenoma patients with polyps of size > 9mm in African Americans than in whites.65
Furthermore, observational studies show that CRC risk factors have a similar effect on adenoma prevalence as on CRC incidence.66-71
Theoretically, higher CRC incidence could also be caused by more rapid adenoma and cancer progression. In this case, development of adenomas into CRC would have a shorter duration in blacks than in whites. When we assumed faster progression for blacks, with a strongly reduced average preclinical disease duration, the benefit of individualization slightly reduced.
We assumed that differences in observed CRC incidence and stage distribution between African Americans and whites reflect true differences in risk and are not due to differences in screening utilization. However, considering that screening rates are lower for African Americans than for whites,62
the risk difference between African Americans and whites may be smaller. The sensitivity analysis shows that with a lower CRC risk in African Americans (i.e. smaller difference with whites), the benefit of individualization was reduced. Furthermore, we only considered life-years gained and not quality adjusted life-years. The reason for this is that the effect of CRC screening on quality of life has hardly been studied. There has been one study estimating quality of life 30 days before and after colonoscopy, which found that mental health and vitality domains of quality of life significantly improved after colonoscopy.72
However, quality of life at the moment of colonoscopy was not assessed. In population screening large numbers of individuals undergo colonoscopy and even a minor effect of colonoscopy on quality of life will have a large impact on quality adjusted life-years gained. Our results are only influenced by adjusting for quality of life when this differs between population subgroups. Crimmens has shown that African Americans and whites not only differ in life-expectancy (for which we accounted in the present analysis) but also in the proportion of healthy life-years,73
due to the fact that African Americans have more comorbidities at older ages. Therefore, intensive colonoscopy screening at older ages may be less feasible in African Americans and also less beneficial in terms of quality adjusted life years gained, reducing the potential benefit of individualization.
Age-specific CRC incidence and mortality in men reaches levels of risk comparable to women four to eight years later in life.74
Also, more women than men need to be screened for the detection of one advanced neoplasia.22, 65, 75
Therefore, one may have expected that men need earlier and more intensive screening than women. However, our results show that the cost-effective individualized policies for men and women are comparable. This is due to longer life-expectancy of women. Although women have fewer advanced adenomas than men, more of those adenomas can evolve into CRC during the longer lifetime. This means that the number needed to screen to detect one advanced adenoma in women may be higher than in men, but that the number of detected adenomas needed to prevent one case of CRC is lower. This makes the number needed to screen to prevent one CRC case similar for men and women. Our finding of similar screening strategies is supported by the fact that the absolute number of CRC cases in men and women is comparable.76
This study aimed to explore the cost-effectiveness of individualization of screening guidelines. We restricted ourselves to colonoscopy, the preferred method of screening according to the American College of Gastroenterology.77
Fortunately, the results can be generalized to other screening modalities. The costs per life-year gained will be different for other screening modalities, but the conclusion that individualization is cost-effective will remain, as well as the result that it is more cost-effective for African Americans to be screened over a wider age range and with greater frequency than whites. We focused the analysis on African American and white (including Hispanics) population subgroups. In a more extensive study Hispanics and non-Hispanics could be considered separately and Asians, Pacific Islanders, American Indians and Alaskan Natives could be included to explore further benefit of individualization. However for these groups, incidence and mortality data will be based on small numbers. CRC incidence and mortality tend to be lower in Hispanics, Asians, Pacific Islanders, American Indians and Alaskan Natives than in whites.78
When these data are confirmed, a less intensive screening schedule for these groups could be considered.
In conclusion, our study suggests that 8-yearly uniform and individualized colonoscopy screening are comparable in costs and effects in the total population. However, individualized guidelines could contribute to decreasing disparities between African Americans and whites. The acceptability and feasibility of individualized guidelines should therefore be explored.