New Study Implicates Healthcare Utilization Rates, More than Biology, in Colorectal Cancer Disparities
Higher rates of colorectal cancer incidence and mortality experienced by African-Americans may be driven largely by differences in health care utilization, and less by biology, according to a new study led by researchers from the National Cancer Institute (NCI), part of the National Institutes of Health.
In a study involving more than 60,000 people who were screened for colorectal cancer, researchers found that blacks and whites were equally likely to need a follow-up colonoscopy after a screening sigmoidoscopy, but blacks were less likely to actually receive the follow-up.
Lower rates of follow-up could lead to delayed diagnosis and treatment and higher mortality. The results of this study were published online April 6, 2010, in the Journal of National Cancer Institute (JNCI) and will appear in the April 21, 2010, print edition.
Our research suggests that the biology of colorectal cancer may not differ by race, at least in the early stages of tumor development, said author Adeyinka O. Laiyemo, M.D., M.P.H., from NCIs Division of Cancer Prevention. Instead, health care utilization differences among races may play a more important role in colorectal cancer disparities.
In the United States, colorectal cancer disproportionally affects blacks, who have higher incidence and mortality rates compared to whites. From 2002 to 2006, the average annual incidence rate for colorectal cancer was 48.6 per 100,000 for white men and women combined, compared to 59.9 per 100,000 for black men and women. The annual mortality rates for the same time period were 17.7 per 100,000 for white men and women, and 25.4 per 100,000 for black men and women. Several studies have found that blacks are more likely than whites to be diagnosed with advanced colorectal cancer, which is more difficult to treat and has worse survival outcomes.
Participants in this study were part of the ongoing Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), a multi-center, randomized, controlled screening trial designed to evaluate the effect of screening on cancer mortality. At the start of the colorectal cancer part of the study, participants were offered a screening flexible sigmoidoscopy, which is used to examine the lower, or sigmoid, portion of the colon. Subjects who had polyps or lesions detected during the sigmoidoscopy were referred to their personal physician for follow-up colonoscopy, the cost of which was not covered by the study.
In a colonoscopy, the entire colon, which is about five feet in length, is examined. During a sigmoidoscopy, only about the last two feet of the colon closest to the rectum is viewed. The records of the follow-up colonoscopies were collected and reviewed to determine which subjects had received them. Those results were analyzed to determine whether utilization of follow-up colonoscopy and likelihood of adenomas (pre-cancerous lesions) or colorectal cancer varied by race. In their analysis, to reduce the possibility that other factors were influencing the outcome of the study, the researchers documented age, education, sex, body mass index, smoking, family history of colorectal cancer, colon cancer screening within the previous three years, personal history of polyps, and center where the participant was screened.