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The goal of cancer screening is to reduce disease-related death through the detection and effective treatment of precursor or early invasive lesions without undue harm. The effectiveness of colorectal cancer (CRC) screening is well established, but less is known about its impact at the population level.[1] In the United States, CRC screening has been practiced since the 1960s or earlier and began to be tracked by the National Health Interview Survey (NHIS) in 1987 (Fig. 1).[2, 3] Although national surveys overestimate the true prevalence of screening,[4] in combination with other data systems, they demonstrate a steady increase in the use of CRC testing over the years in tandem with declines in both disease incidence and mortality rates since the mid-1980s.[3] In men, CRC incidence dropped by 2.6% during 1992 to 1995 and by 4.2% during 2008 to 2010, and similar changes were observed in women.[5] Remarkably, there has also been a decline in the absolute number of CRC cases over the years. For instance, there will be approximately 136,830 new CRC cases in 2014 compared with 145,290 in 2005.[6] The reasons for this decline have been speculated; and, naturally, many are apt to attribute it to the increased uptake of screening. However, little empirical data exist to support that view.

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Figure 1. Colorectal cancer test use rates for adults aged ≥50 years are illustrated according to race/ethnicity (National Health Interview Survey [NHIS], 1987-2010). The colorectal cancer use rate is defined as the combined percentage of individuals who have received a home fecal occult blood test in the prior 2 years or who have ever had a lower endoscopy. Data were age adjusted to the 2000 US standard population. Source: NHIS. National Center for Health Statistics/Centers for Disease Control and Prevention, with permission from the National Cancer Institute, Cancer Trends Progress Report.

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In this issue of Cancer, Yang et al present an ecological study of the public health impact of CRC screening in the United States.[3] Their study analyzed over 3 decades of Surveillance, Epidemiology, and End Results data on CRC diagnosis and NHIS data on CRC screening use from 1987 to 2010. The incidence data from 1976 to 1978 served as the baseline for disease rate in the absence of screening to derive the number of prevented cancers. The authors report that approximately 250,000 to 500,000 CRC cases were averted during the period from 1979 to 2009. These estimates were based on 2 scenarios. First, the authors assumed that the CRC incidence rate did not change between 1979 and 2009. The second more realistic estimates incorporated a 0.4% annual percentage incidence increase over the base rate. In contrast to screening for other cancers, there was no evidence of over-diagnosis bias.[7] There was a decrease in incidence for both early and late-stage disease. Not surprisingly, the greatest number of averted cancers was in the left colon/rectum. In the right colon, which is less effectively screened by fecal occult blood testing (FOBT) or sigmoidoscopy, there was a slight increase in early stage cancers but a decrease in the rate of incident advanced cancers. The inclusion of in situ lesions, which are precursor lesions, in the analysis may have led to an underestimate of the number of averted cancers. The authors also excluded unstaged cancer, which may have led to an underestimate of the total number of observed incident cancers.

Although no direct causal conclusions can be drawn from an ecological analysis, increased use of screening seems to be the most plausible explanation for the decreased incidence. This hypothesis is strongly supported by results from randomized trials indicating that screening with sigmoidoscopy reduced the incidence of CRC within the reach of the sigmoidoscope by 50%.[8] Case-control studies also have demonstrated that screening colonoscopy substantially reduces the risk of late-stage disease.[9] By using microsimulation modeling, Edwards et al observed that a substantial portion of the decrease in CRC death in the United States was because of increased uptake of screening.[10] Furthermore, the favorable trends in CRC disease burden have occurred during a period of continued increases in risk factors in the United States. Approximately 70% of CRC cases in the United States are believed to be attributable to unhealthful lifestyles.[11] In the United States, these risk factors, particularly obesity, are highly prevalent, with high calorie intake and only modest improvements in physical activity levels.[12] The prevalence of obesity among individuals ages 20 to 74 years increased from 15.1% between 1976 and 1980 to 35.3% between 2007 and 2010. In some countries, increased westernization has been accompanied by an increase in the incidence of CRC.[13] However, CRC rates are lower among Hispanics than among non-Hispanic whites, but so are their screening rates. Thus, alternative explanations are possible. Increasing use of drugs with chemopreventive properties, such as nonsteroidal anti-inflammatory agents, may contribute to the observed CRC incidence trends.[14]

Before we celebrate, the report by Yang et al also underscores that a substantial portion of the current cases of CRC is attributable to nonuse of screening. In particular, some groups have not equally realized the public health benefits of screening. Substantial uptake of screening did not occur in the United States until the start of the 21st century in tandem with the ascendancy of interest in colonoscopy. Unfortunately, even with overestimation in national surveys,[4] screening rates remain below the public health goal of 70.5%, and progress has been particularly slow in some minority populations.[15] For instance, the screening rates of African Americans lag about 2 years behind those of non-Hispanic whites, and their incidence and mortality rates are higher. For the period from 2001 to 2010, the CRC incidence rate was 50.5 per 100,000 white men and 62.5 per 100,000 black men, and the percentage decreases in incidence were 4% and 2%, respectively, with similar mortality trends.[5] In addition to race/ethnicity, low income and geography and a lack of insurance coverage, a regular place of health care, or a physician recommendation for screening are significant barriers to the receipt of CRC screening.[16] Increasing the use of screening in these underserved populations, who also have disproportionally high disease rates, will have great impact on progress toward the HealthyPeople 2020 screening goal.

In a recent article, Gupta and colleagues provided 4 key multilevel recommendations to boost the use of screening in underserved populations.[16] The first was to avoid a colonoscopy-only screening policy in clinical settings and provide ‘CRC screening’, actively promote the message that, “The best test is the 1 that gets done well.” Currently, the US Preventive Services Task Force recommends highly sensitive FOBT annually, flexible sigmoidoscopy every 5 years with midinterval FOBT, or optical colonoscopy every 10 years as equally acceptable screening strategies.[1] Since 2001, colonoscopy has rapidly become the most commonly used screening test and is considered the preferred test by some national groups, even as we wait for studies to determine whether it is superior to other strategies. Studies demonstrated that 1 size does not fit all and that providing choice in screening can boost screening rates. Second, it is critical to develop and implement strategies to efficiently identify screen-eligible individuals in both clinical settings and outreach programs to maximize use and minimize overuse or misuse. Thus, as adoption of health information technology, including electronic medical record systems, gains momentum, greater collaboration across existing health care delivery silos through health information exchanges can make it possible to document screening use across delivery systems and health plans. Third, it is critical to assure provision of the entire CRC screening continuum, including timely diagnostic testing for abnormal screening and treatment when cancer is diagnosed. Quality metrics for CRC screening, such as Healthcare Effectiveness Data and Information Set (HEDIS) measures, should be updated not only to quantify the receipt of a CRC test but also to separately document the proportion of tests used for screening purposes and the timely (within 90 days) receipt of diagnostic testing for positive screens. This will allow us to identify failures in the screening process to target for appropriate interventions.

Fourth, there is now strong evidence that organized screening strategies are effective in increasing use.[16, 17] Newer FOBT technologies do not require dietary restrictions and can be sent in the mail and tested using high-throughput systems. It is feasible to implement organized programs in many health care systems or practices through local or regional collaborations to gain economies of scale and reduce implementation cost while freeing up health care providers for other tasks. Therefore, visit-based approaches should no longer be used as the sole approach to provide screening.

These recommendations provide a framework for hastening the public health benefits of CRC screening in the United States. Programs in New York City and the state of Delaware are examples of successful public health efforts.[16] They dovetail into provisions in the Patient Protection and Affordable Care Act of 2010 for broadening access to preventive care services. The recommendations are “back to the future.” Screening for CRC dates back to the 1800s, when proctoscopy was first used to observe the rectum and sigmoid.[18] Guaiac-based FOBT (gFOBT) was developed in the 1950s, and immunochemical FOBT (FIT) was developed in the 1970s.[19] The introduction of colonoscopy in 1969 made it possible to observe the colon beyond the reach of the sigmoidoscope.[20] These 3 tests remain central to efforts to prevent premature death from CRC even as technologies and testing patterns continue to evolve. The concept of home-based screening was first introduced by Greegor in 1967.19 Improvements in FIT technology now make it possible to realize the ideals of increasing access to screening with large-scale, population-based screening programs, particularly for those who do not seek care or for whom screening was not provided during the course of a medical care visit.[17] However, all screening programs need adequate colonoscopy capacity, and it is critical to identify and address variations in performance characteristics for all CRC tests.

Finally, the study by Yang and colleagues suggests that we can reduce the public health burden of CRC through increased CRC screening. However, current practices of opportunistic screening delivery in most health care systems deprive many individuals of the benefits of screening, either because they do not receive regular health care or because their preventative care needs are crowded out by competing economic, social, medical, and administrative needs of both the patient and/or the provider. Fortunately, technologies have advanced to the point that opportunistic screening during a visit with a health care provider need not be relied on as the sole approach to deliver CRC screening. US health care systems should adopt programs of population-based delivery through screening outreach and facilitated in-reach by leveraging population health capabilities in health information technology systems. It is also important for public health programs and the medical community to develop more effective ways of communicating both the importance of and the options for CRC screening to the public. Capitalizing on opportunities for provider recommendation of appropriate CRC screening can boost screening rates. All said, our success in maintaining sustained decreases in CRC incidence will be defined by our ability to improve delivery to underserved populations.

FUNDING SUPPORT

  1. Top of page
  2. FUNDING SUPPORT
  3. CONFLICT OF INTEREST DISCLOSURES
  4. REFERENCES

Dr. Doubeni's time is supported by grants U01CA151736 and U54CA163262 from the National Institutes of Health/National Cancer Institute, which played no role in the current work.

CONFLICT OF INTEREST DISCLOSURES

  1. Top of page
  2. FUNDING SUPPORT
  3. CONFLICT OF INTEREST DISCLOSURES
  4. REFERENCES

Dr. Doubeni reports personal fees from Exact Sciences outside the submitted work.

REFERENCES

  1. Top of page
  2. FUNDING SUPPORT
  3. CONFLICT OF INTEREST DISCLOSURES
  4. REFERENCES
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