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- Materials and methods
Colorectal cancer (CRC) remains a major source of morbidity and mortality in the US, causing an estimated 51 370 deaths in 2010. CRC incidence and mortality is increased in black individuals relative to whites and blacks are often a younger age at the time of diagnosis. The difference in CRC rates has been further elucidated by the report of a higher prevalence of large polyps in blacks compared to whites, as shown in an analysis of a multicentre endoscopy database.
There is paucity of data regarding the prevalence of adenomas among Hispanics living in the US. Hispanics comprise the largest growing ethnicity in the US, and are estimated to reach a population of greater than 100 million individuals by 2050. There is emerging evidence that colorectal neoplasia rates among Hispanics are similar to or possibly greater than those of whites, although studies to date have been limited to sigmoidoscopy, did not include whites as a comparison group, did not include histology or were limited to symptomatic individuals.
We aimed to compare the prevalence of histologically confirmed adenomas and advanced colorectal neoplasia among Hispanics and blacks as compared to whites among individuals undergoing screening colonoscopy at an urban medical centre that serves a racially and ethnically diverse patient population.
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- Materials and methods
A total of 7459 asymptomatic individuals underwent complete screening colonoscopy during the study period. Due to missing data pertaining to race or ethnicity, 2197 (29%) subjects were excluded. In addition, 187 (3%) reported race other than white, black or Hispanic and were also excluded. In total, 5075 subjects were eligible for analysis and baseline characteristics of the cohort are shown in Table 1.
Table 1. Patient characteristics by race/ethnicity
| ||All (n = 5075)||White (n = 3542)||Hispanic (n = 942)||P valuea||Black (n = 591)||P valuea|
|Age (mean, years)||62.2||62.9||60.0||<0.0001||61.4||0.0005|
|50–59||2288 (45)||1494 (42)||506 (54)||<0.0001||288 (49)||0.0047|
|60–69||1660 (33)||1168 (33)||306 (32)|| ||186 (31)|| |
|≥70||1127 (22)||880 (25)||130 (14)||117 (20)|
|Female gender||2948 (58)||1980 (56)||571 (61)||0.0094||397 (67)||<0.0001|
|Average risk||4606 (91)||3151 (89)||894 (95)||<0.0001||561 (95)||<0.0001|
|Family history||469 (9)||391 (11)||48 (5)|| ||30 (5)|
Of the 5075 eligible subjects, 3542 (70%) were white, 942 (19%) were Hispanic and 591 (12%) were black (Table 1). Fifty eight per cent of subjects were women. The mean age for the entire cohort was 62.2 years (s.d.: ±9.1), where whites were slightly older than Hispanics, 62.9 vs. 60.0 years (P < 0.0001) and blacks (61.4 years, P = 0.0005). Eleven per cent of whites reported a family history of colorectal neoplasia compared to only 5% of Hispanics (P < 0.0001) and blacks (P < 0.0001).
The adenoma prevalence among all subjects was 20% (Table 2). At least one colorectal adenoma was present in 19% of whites, 22% of Hispanics (P = 0.09) and 26% of blacks (P = 0.0001). Among men, adenomas were present in 23% of whites, 26% of Hispanics (P = 0.14) and 32% of blacks (P = 0.002). Among women, adenomas were present in 16% of whites, 19% of Hispanics (P = 0.21) and 23% of blacks (P = 0.002). Overall, the risk of adenoma was higher in men compared with women in all three groups.
Table 2. Prevalence of adenomas by race/ethnicity
| ||White (n = 3542)||Hispanic (n = 942)||P valuea||Black (n = 591)||P valuea|
|Overall prevalence||675 (19)||203 (22)||0.09||153 (26)||0.0001|
|Men||352/1562 (23)||97/371 (26)||0.14||63/194 (32)||0.0021|
|Women||323/1980 (16)||106/571 (19)||0.21||90/397 (23)||0.0023|
|50–59||250/1494 (17)||91/506 (18)||0.52||56/288 (19)||0.26|
|60–69||206/1168 (18)||75/306 (25)||0.0064||52/186 (28)||0.0009|
|≥70||219/880 (25)||37/130 (28)||0.38||45/117 (38)||0.0018|
|Average risk||501/3110 (16)||191/891 (21)||0.0002||144/556 (26)||<0.0001|
|Family history||151/391 (39)||12/48 (25)||0.07||6/30 (20)||0.0421|
Differences in adenoma prevalence among white, Hispanic and black men and women were age-dependent (Figure 1). Among those subjects between 50 and 59 years, neither men nor women demonstrated a statistically significant difference in the prevalence of adenomas among the three groups. In the remaining age strata, the differences among whites, Hispanics and blacks were either significant (men ages 60–69, women ages ≥70), or demonstrated a trend towards statistical significance (men ages ≥70 P = 0.18, women ages 60–69 P = 0.10). The consistent gradient of adenoma prevalence, where whites had the lowest prevalence and blacks had the highest prevalence, illustrates a lack of effect modification of age and gender on the relative differences among these three groups.
The number, size, location and histology of adenomas are shown in Table 3. The number of adenomas per patient was fewer in whites (0.26) than in Hispanics (0.30, P = 0.11) and blacks (0.39, P < 0.0001). Blacks were more likely to have ≥3 adenomas (4.1%) as compared to Hispanics (1.2%, P = 0.0003) or whites (1.6%, P < 0.0001).
Table 3. Adenoma size, location and histology in white, Hispanic and black patients
| ||White (n = 3542)||Hispanic (n = 942)||P valuea||Black (n = 591)||P valuea|
|Number of adenomas per patient||0.26||0.30||0.11||0.39||<0.0001|
|Number with ≥1 adenoma||675 (19)||203 (22)||0.09||153 (26)||0.0001|
|≥10 mm||96 (2.7)||55 (5.8)||<0.0001||24 (4.1)||0.07|
|Villous, tubulovillous, or HGD||74 (2.1)||16 (1.7)||0.45||17 (2.9)||0.23|
|Any advanced features||132 (3.7)||61 (6.5)||0.0002||32 (5.4)||0.05|
|≥3 adenomas||57 (1.6)||11 (1.2)||0.32||24 (4.1)||<0.0001|
|Isolated proximal adenomas||301 (9)||101 (11)||0.03||66 (11)||0.03|
|Isolated proximal advanced adenomasb|
|≥10 mm||31 (0.9)||20 (2.1)||0.0013||10 (1.7)||0.09|
|Villous, tubulovillous, or HGD||22 (0.6)||9 (1.0)||0.27||6 (1.0)||0.28|
|Any advanced features||45 (1.3)||23 (2.4)||0.009||14 (2.4)||0.04|
Advanced lesions based on increased polyp size and/or advanced histology were present in 3.7% of whites, 6.5% of Hispanics (P = 0.0002) and 5.4% of blacks (P = 0.05). Isolated proximal adenomas, as defined by proximal adenomas in the absence of any distal adenoma, were present in 9% of whites, 11% of Hispanics (P = 0.03) and 11% of blacks (P = 0.03). Similarly, isolated proximal advanced adenomas, was present in 1.3% of whites, 2.4% of Hispanics (P = 0.009) and 2.4% of blacks (P = 0.04).
On multivariate analysis, Hispanic ethnicity and black race were associated with an increased risk of adenomas and advanced adenomas, once adjusting for age, gender and presence of a family history of colorectal neoplasia (Table 4). Increasing age, male gender and family history were associated with an increased adenoma rate and the presence of an advanced adenoma. Compared to whites, adenoma rate was highest in blacks (RR: 1.76, 95% CI: 1.52–2.04) but was also elevated in Hispanics (RR: 1.37, 95% CI: 1.20–1.57). The odds of an advanced adenoma were greatest among Hispanics (OR compared to whites 2.25, 95% CI: 1.62–3.11) but were also increased among blacks (OR: 1.91, 95% CI: 1.27–2.86). When adjusting for medical insurance status as a surrogate for SES (Medicaid insurance vs. other), the adenoma rates remained similarly elevated in Hispanics (RR: 1.35, 95% CI: 1.12–1.63, P = 0.002) and blacks (RR: 1.76, 95% CI: 1.51–2.04, P < 0.0001) as compared to whites. Similarly, when adjusting for the participation of a trainee in the colonoscopy, the adenoma rates remained elevated in Hispanics (RR: 1.21, 95% CI: 1.05–1.40, P = 0.01) and blacks (RR: 1.70, 95% CI: 1.46–1.97, P < 0.0001).
Table 4. Multivariate analysis of factors independently associated with adenoma rate and the presence of an advanced adenoma
| ||Rate Ratio for adenoma (95% CI)||P value||Odds Ratio for advanced adenoma (95% CI)||P value|
|60–69||1.27 (1.12–1.44)||0.0002||1.01 (0.72–1.40)||0.98|
|≥70||1.70 (1.50–1.94)||<0.0001||1.62 (1.16–2.25)||0.0046|
|Male gender||1.58 (1.42–1.75)||<0.0001||2.04 (1.55–2.69)||<0.0001|
|Family history||2.08 (1.81–2.40)||<0.0001||2.87 (2.02–4.10)||<0.0001|
|Hispanic||1.37 (1.20–1.57)||<0.0001||2.25 (1.62–3.11)||<0.0001|
|Black||1.76 (1.52–2.04)||<0.0001||1.91 (1.27–2.86)||0.0019|
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- Materials and methods
This study is the first to describe the comparative prevalence of histologically confirmed colorectal adenomas among asymptomatic white, Hispanic and black individuals undergoing screening colonoscopy in the US. We found that the prevalence of adenomas among Hispanics and blacks exceeds that of whites and this difference is similar between men and women. Hispanics had the highest prevalence of large adenomas ≥10 mm and blacks had multiple (≥3) adenomas which represent advanced colorectal neoplasia that require more frequent endoscopic surveillance for CRC prevention. Most notably, Hispanics and blacks had an increased prevalence of proximal neoplasms in the absence of any distal pathology compared to whites. These lesions can only be detected if colonoscopy is the chosen screening modality.
To date, the issue of racial and ethnic disparities in the prevalence of colorectal adenomas has focused predominantly on comparisons drawn from studies involving only whites and blacks. Using data from the Clinical Outcomes Research Initiative (CORI), Lieberman and colleagues found that blacks had a higher prevalence of polyps >9 mm compared to whites (7.7% vs. 6.2%), although polyp histology was not available. This difference was more pronounced among women and individuals older than 60 years. Our study, which provides histological review to include only adenomatous lesions, confirms the aforementioned findings of an increased risk of colorectal neoplasia among blacks as compared to whites, especially after the age of 60 years but equally among men and women.
Similar studies assessing the risk of adenomas in whites as compared to Hispanics in the US are sparse. A recent report on 647 patients in Puerto Rico undergoing screening colonoscopy found an overall adenoma prevalence of 25.1%, similar to the reported prevalence of 22% in the present study. In a CORI-based study ascertaining the prevalence of large (>9mm) neoplasia among individuals receiving colonoscopy for screening, surveillance or evaluation of symptoms, Hispanics undergoing colonoscopy for any reason had a similar risk of large polyps compared to whites (RR: 1.03, 95% CI: 0.94–1.12), although histological confirmation of adenomatous polyps was unavailable. A recent study using the same database but limiting the analyses to only those asymptomatic individuals undergoing screening colonoscopy, found no difference in the prevalence of large polyps between Hispanics and whites. However, these results should be interpreted with caution as histological confirmation of adenomatous polyps was not conducted.
The CRC incidence and mortality is currently reported to be lower in Hispanics as compared to whites and blacks. However, there is emerging evidence that the risk of CRC among Hispanics may be increasing with acculturation and some studies report increased rates of CRC among some Hispanic subpopulations in the US compared with their countries of origin.[10, 11] It is not unexpected for immigrants to gradually acquire the disease profile of the host population with increased risks seen in subsequent generations.[11, 12] Our study may support the impact of acculturation over time among Hispanics who have relocated to the US, as the prevalence of adenomas and advanced lesions exceeded that of whites, particularly in individuals over the age of 60 years. However, the number of colonic adenocarcinomas in this study was highest among whites (1%) and was similar among blacks (0.3%) and Hispanics (0.2%). Given the overall small number of CRCs among the three groups, we cannot interpret this data in a meaningful way. We suspect that additional CRC cases among blacks and Hispanics were likely excluded by the indication for colonoscopy where these patients may have presented for diagnostic colonoscopy to evaluate for signs or symptoms associated with CRC. Whether or not our findings represent differences in a biological predisposition to colorectal neoplasia among blacks and Hispanics is not known. Future collaborative studies are necessary to also explore the possibility of an interaction between race and acculturation as well as socio-economic status.
This study has a number of strengths. The practice setting is unique for this comparative study given the diverse racial and ethnic makeup of the patient population. In addition, the endoscopy unit at Columbia University Medical Center employs a patient navigator programme that has resulted in increased screening rates among traditionally underserved minority groups. Furthermore, this is the first study of histologically confirmed data on adenoma prevalence and advanced lesions to include Hispanics as well as whites and blacks, so as to yield comparative data. In previous studies, polyp size was used as a surrogate for advanced histology; however, size estimates during colonoscopy are subject to inter-observer variability and advanced histology can occur in small polyps.
There are several limitations to this study. It is possible that some examinations may have been misclassified as first-time screening procedures where patients included in this analysis may have had a previous colonoscopy. To minimise this, all patients in which the indication included a personal history of colorectal polyps were excluded, as were diagnostic examinations such as those with an indication of gastrointestinal bleeding or anaemia. It is unlikely that any residual misclassification would have been differentially distributed among whites, Hispanics and blacks.
Second, race or ethnicity was available as a single-entry field in the medical record where 2197 patients were excluded from analysis due to a missing entry for race/ethnicity. The exclusion of such patients may limit the generalisability of our findings. It is possible that the excluded subjects may have been systematically different from those subjects included in the analysis. However, the overall prevalence of ≥1 adenoma in the excluded patients was 23%, which falls in between the adenoma prevalence of whites (who had the lowest prevalence) and blacks (who had the highest prevalence). This suggests that the excluded subjects were likely of various races/ethnicities and that they were not especially high or low-risk for colorectal neoplasia. In addition, categorisation of race and ethnicity may have been misclassified. Our institution does not conform to the NIH Policy on Reporting Race and Ethnicity Data, where both race and ethnicity are assigned to each patient. However, this variable was self-identified and significant misclassification would bias the results towards the null; the consistent disparity of adenoma prevalence among multiple age groups and both genders suggests that such misclassification was minor and lends credence to the association found between race/ethnicity and risk of colorectal neoplasia.
Another potential limitation is that the results of this study, as they pertain to Hispanics, may not be generalisable. The Hispanic population in the US is genetically heterogeneous and the results reported on the Hispanic population residing in Northern Manhattan, which is composed primarily of individuals of Dominican and other Caribbean descent, may not necessarily be applicable to all Hispanics. Lastly, there are several potential confounders for which we were unable to adjust in our analyses. Information on medication use (including aspirin and non-steroidal inflammatory drugs), smoking status, body mass index and history of diabetes, which are all associated with variable risk on colorectal neoplasia, were unavailable and may have been differentially distributed between the three patient populations. Similarly, SES, which may not have been comparable among the three groups, may be associated with risk factors for colorectal neoplasia independent of race or ethnicity. For this reason, we included Medicaid enrolment as a surrogate for SES in the multivariate analysis.
The findings of this study may have important implications for determining the preferred CRC screening modality among black and Hispanic individuals. Given the increased number of isolated right-sided neoplasia, including adenomas greater than 10 mm, among both Hispanics and blacks as compared with whites, a full structural endoscopic examination using colonoscopy may be favoured over other CRC screening tests. In addition, our findings may support the development of programmes that will educate patients on the importance of endoscopic surveillance in those individuals with previously detected adenomas. To date, there are no studies that examine adherence to endoscopic surveillance for colorectal neoplasia in either black or Hispanic individuals. This study's findings may also impact the overall utilisation of colonoscopy and the capacity needed once factoring in the increased need of endoscopic surveillance among diverse patient populations at increased risk for advanced adenomas.
In conclusion, asymptomatic black and Hispanic individuals who undergo age-appropriate CRC screening have a higher risk of colorectal adenomas. Hispanics appear to have a greater prevalence of large (≥10 mm) adenomas, while blacks are at greater risk for multiple adenomas. Both patient populations had an equally high risk of having proximal advanced neoplasia in the absence of distal lesions, as compared to whites. Upon validation of these results, the use of colonoscopy may be the preferred screening modality among Hispanics as well as blacks for CRC prevention and control. Presently, continued efforts to improve the uptake of CRC screening are necessary among both black and Hispanic patients.