Colon Cancer Screening in North Carolina

Colon Cancer Prevention Screening

Colonoscopy is currently the gold standard for preventive screening, and its greatest benefit lies in its ability to remove polyps. Indeed, other screening methods ultimately achieve their cancer-preventive benefit by referring patients for colonoscopy when the initial screening test is positive. It is important to note, however, that colonoscopy is an imperfect test. One study noted that colonoscopy has a 12% miss rate for large adenomas (1 cm or greater), and others have noted a miss rate for colon cancer of around 4% [9, 10]. Some recent studies have suggested that, although colonoscopy is a very important part of the CRC screening picture, its protective effect is lower than the 76–90% decreased risk of CRC noted in the 1993 National Polyp Study; a follow-up to the National Polyp Study found only 53% reduction in CRC mortality [6]. In addition to missed polyps, another risk of colonoscopy is the small but nonzero risk of perforation; a study using Medicare claims data estimated this rate at 5–7 perforations per 10,000 procedures [11].

CT colonography has also been shown to be effective in screening for CRC. One study showed 94% sensitivity for polyps 1 cm or greater [12], such that 1 in 13 patients screened would subsequently have been referred for a colonoscopy to remove the polyps. Issues related to CT colonography include how to address small polyps, the undetermined risk associated with radiation exposure, and the possibility for extracolonic findings that may lead to additional procedures and testing. The USPSTF has concluded that there is insufficient evidence to recommend for or against CT colonography at this time. Currently, Medicare does not cover CT colonography for routine screening, but it is often covered if prior colonoscopy has failed.

Flexible sigmoidoscopy and barium enema are 2 additional options for preventive screening, although they have been used with less frequency in the United States in recent years. In flexible sigmoidoscopy, only the lower half of the colon is evaluated, and this procedure is often performed without sedation. The disadvantages are that it does not evaluate the right side of the colon, an area of increased neoplasia (particularly in later life); patients are often uncomfortable due to the lack of sedation; and there is a small risk of perforation, estimated at less than 1 per 20,000 procedures [13]. A barium enema can evaluate the whole colon, but it requires a colon preparation, and enthusiasm for this test is often limited due to patient discomfort, reduced sensitivity for polyps as compared to colonoscopy or CT colonography, and the need for a follow-up colonoscopy (including another colon preparation) if the test is positive.

Colon Cancer Detection Tests

Other options for screening include various stool tests: FOBT, FIT, and fecal DNA testing. Although these tests may detect premalignant adenomatous polyps, their main goal is the detection of CRC; thus the opportunity for prevention of CRC is more limited [7]. FOBT relies on the detection of blood in the stool through measurement of pseudoperoxidase activity of heme or hemoglobin [7]. Trials of FOBT have shown a CRC mortality reduction of 15–33%, with a range of sensitivity for cancer—from 37% for rehydrated Hemoccult II to 79% for Hemoccult II SENSA, although other studies have shown a much lower sensitivity [7]. However, FOBT performed on a sample collected by digital rectal exam at the time of a medical appointment, which is still widely performed today, is highly inaccurate and not recommended. This method was shown to have 5% sensitivity for detection of advanced neoplasia and 9.5% sensitivity for cancer [14].

FIT relies on the detection of human globin, a part of hemoglobin. One advantage of FIT is that, unlike with FOBT, patients do not have to adhere to dietary restrictions prior to testing. In one study, the sensitivity for FIT to detect advanced neoplasia was 40% for distal lesions and 28% for proximal colon lesions, with an overall sensitivity of 55% and a negative predictive value for CRC of 99.8% [15].

Stool DNA testing looks for tumor-specific alterations in the DNA shed in the stool. One study showed 92% sensitivity for detecting CRC and 42% sensitivity for detecting advanced neoplasia with stool DNA testing [16]. One important question that has been raised is whether a patient with a negative colonoscopy in the setting of a positive stool DNA test truly has a negative result, or whether the positive DNA test is a harbinger of future malignancy or indicative of upper gastrointestinal malignancy. Stool DNA testing shows great promise and is a reasonable option for screening, but it is not endorsed by all organizations or covered by all insurance companies at this time.

Colon Cancer Screening in North Carolina

Historically, CRC death rates were highest in the Northeast and Mid-Central United States and lowest in the South [3]. However, a recent study noted that rates had become fairly even across the United States by the 2000s, with the exception of 3 hot spots—the Lower Mississippi Delta, west-central Appalachia, and eastern North Carolina/Virginia—all of which are primarily rural areas [3]. This fits with the finding of increased risk of death from CRC among patients from rural areas and the shift of CRC burden to low-income individuals, who have higher CRC incidence, morbidity, and mortality [3]. This closely mirrors findings in countries with more limited health resources [3]. This study thus highlights the need to increase CRC screening, especially among the rural population of North Carolina.

In North Carolina, African Americans have a higher rate of CRC, are more likely to be diagnosed at an advanced stage, and have a higher mortality rate than whites [17]. This disparity is possibly due to higher screening rates among whites; the North Carolina Behavioral Risk Factor Surveillance System indicated that the rate of sigmoidoscopy or colonoscopy among whites was 69% in 2008, versus 62% for African Americans; in 2014, these rates were 75% and 71%, respectively [18]. North Carolina needs to make concerted efforts to increase CRC screening rates in the state's African American population.

Overall, a comprehensive approach to screening cannot rely exclusively on colonoscopy. There are many counties in North Carolina that do not have an endoscopy unit, and there are also social, economic, and cultural factors that impede colonoscopy screening in North Carolina's population. Based on 2007 estimates, 6.5% of households in North Carolina have no vehicle, 14% of the population has less than a high school education, 14% of households earn less than $15,000 per year, and roughly 9.6% of the population speaks a language other than English at home [19]. Also, part of North Carolina's population is transient, due to movements in the agricultural workforce. These are all factors that may hinder access to screening colonoscopy.

The Patient Protection and Affordable Care Act of 2010 requires coverage of CRC screening for health plans that started on or after September 23, 2010. Medicare covers screening colonoscopy at no cost; if a polyp is removed, however, Medicare then labels the procedure as diagnostic and the patient becomes responsible for the coinsurance and/or copayment. There is a legislative push at the national level to change this rule with the Removing Barriers to Colorectal Cancer Screening Act [20].

A comprehensive CRC screening approach for North Carolina also cannot rest solely on physicians referring patients for colonoscopy, as many patients do not have access to primary care or do not see a physician regularly; in a 2014 survey, only 62% of respondents indicated having a personal physician [18]. Despite data showing a considerable benefit to screening, approximately 1 in 3 Americans aged 50–75 years still have not been screened for CRC. In 2014, the National Colorectal Cancer Roundtable, a collective action of multiple organizations, announced its goal to increase screening by any method to 80% by 2018 [21]. This is an important goal for the people of North Carolina, and a strategy for reaching this goal will need to be creative and must factor in patients' preferences, local expertise, and social and economic variables.