The incidence of colorectal cancer (CRC) in adults younger than 55 years has been increasing in recent years ― a "dramatic increase" was noted in the United States in 2017, and an increase in incidence has subsequently been seen in many other countries across Europe, as well as Australia, New Zealand, and Canada.
A new study has identified geographic hot spots across the United States, characterized by distinct patterns of early-onset CRC with worse survival among men. The hot spots primarily include counties in the lower Mississippi Delta, west-central Appalachia, and eastern Virginia/North Carolina.
In these hot spots, young adult non-Hispanic black men were specifically at risk and were more likely to die of the disease as compared to persons of other racial groups.
The study was published online on May 15 in the American Journal of Cancer Research.
These data can help to identify some of the risk factors associated with early-onset CRC/mortality, commented lead author Charles Rogers, PhD, MPH, a researcher at the Huntsman Cancer Institute and assistant professor of public health at the University of Utah, Salt Lake City.
"We noted potential explanations for the hot spots," he told Medscape Medical News. "These include an enduring history of unique challenges, such as inadequate access to care, poor health literacy, and low educational attainment."
Within hot-spot counties there were also higher rates of poverty, a lack of health insurance, and fewer primary care physicians.
"The disproportionate burden of early-onset colorectal cancer among non-Hispanic black men may result from distinctive stressors coupled with cultural and social expectations that impact screening and care behaviors," said Rogers. "And while it's estimated that approximately 14% of all US adults are current smokers, we observed that 24% of the adult population residing in hot-spot counties reported currently smoking and having smoked at least 100 cigarettes in their lifetime."
Lifestyle and Screening
Elements relating to the increase in early-onset CRC include environmental and geographical factors, as well as lifestyle factors, such as diet, obesity, and sedentary behaviors, Rogers commented.
"I think lifestyle factors are huge," he said. "Consumption of high-fructose corn syrup and charred meat, for example, are worth considering and deserve more attention."
He also emphasized the importance of screening. Most health organizations in the United States recommend that screening start at age 50 years, but the American Cancer Society lowered this to 45 years, and the issue has been hotly debated. Rogers said that adults younger than 50 should be having conversations with their clinicians about screening for CRC. He noted that this is particularly important if they have any symptoms of CRC, a family history of the disease, or reside in one of the hot spots that were identified in their study.
An expert who was approached for outside comment agreed. Chyke Doubeni, MBBS, MPH, director of the Center for Health Equity and Community Engagement Research at the Mayo Clinic in Rochester, Minnesota, said that anyone with health concerns should discuss preventive measures with their primary care physician.
"Screening for people younger than the age of 50 is currently controversial, as it is not recommended by some guidelines," he said. "Recommendations for screening are different for people with a family history or certain genetic conditions."
Such people include those younger than 50 years who have a family history of CRC or advanced adenomas. These patients should share that history with their primary care physician in order to determine when to begin screening and how often to be screened.
"People under the age of 50 who have symptoms such as unexplained rectal bleeding or iron deficiency anemia that may suggest the presence of colorectal cancer should be promptly evaluated for that possibility," Doubeni added.
Hot Spots vs Other Counties
The goal of the study was to identify mortality hot spots specific to men with early-onset CRC and to evaluate disparities while controlling for sex-specific differences. Rogers and colleagues identified counties with high early-onset CRC mortality rates using data from the Centers for Disease Control and Prevention (1999–2017) and linked them to data from the Surveillance, Epidemiology, and End Results (SEER) for men aged 15 to 49 years.
The team identified 232 US counties (7% of the total) as hot spots. The majority (214 of 232, 92%) were located in the South, and the remainder (18 of 232, 8%) were in the Midwest P < .01).
As compared to men living in other counties, those residing in hot-spot counties were more likely to be non-Hispanic blacks (30.82% vs 13.06%), less likely to be Hispanic (1.68% vs 16.65%; P < .01), and more likely to be diagnosed with metastatic disease (stage IV CRC) (2.58% vs 1.94%; P < .01).
Among men who lived in hot spots, CRC survival was poorer than was seen elsewhere (113.76 vs 129.04 months, respectively; P < .001). Among those with early-onset CRC, the risk for CRC-specific death was 24% higher (hazard ratio [HR], 1.24) than for men living outside of the hot-spot counties. However, that figure dropped to 12% after adjusting for county-level smoking (HR, 1.12).
With respect to racial/ethnic differences, non-Hispanic black (HR, 1.31) and Hispanic (HR, 1.12) patients had a 31% and 12% increased risk for CRC-specific death as compared to non-Hispanic white men (HR, 1.01) after adjusting for smoking status.
The authors note that among all determinants, "clinical stage explained the largest proportion of the variance" in early-onset CRC survival for men living in hot spots and other locations combined.
In the hot-spot counties, severe tumor grade was associated with greater CRC-specific mortality risk. Among patients with poorly differentiated tumors (HR, 1.87) and undifferentiated tumors (HR, 2.60), the mortality risk was nearly 2 times and 2.6 times greater, respectively, than those with well-differentiated tumors.
Compared to other counties, hot-spot counties were characterized by demographics that have been linked to poorer health outcomes, such as higher poverty rates (26.57% vs 16.77%), greater prevalence of adult obesity (34.94% vs 25.89%), higher adult smoking rates (23.97% vs 15.44%), higher uninsured rates (20.06% vs 17.91%), and fewer primary care physicians (58.28 vs 75.45 per 100,000 population).
Geographic Distribution of CRC
Commenting to Medscape Medical News, Doubeni pointed out that the identified hot spots are similar to previously reported overall CRC hot spots.
"It shows the same patterns of geographic distribution of colorectal cancer in the United States," he said. "These patterns tend to be associated with areas with high levels of poverty, as is the case with other chronic diseases, and may be related to clustering of risk factors and limited access to care in those areas."
The research was supported by the National Cancer Institute of the National Institutes of Health, the Huntsman Cancer Foundation, and the Health Studies Fund of the Department of Family and Preventative Medicine at the University of Utah. The authors and Doubeni have disclosed no relevant financial relationships.
Am J Cancer Res. 2020;10:1592-1607. Full text
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Cite this: Geographical Hot Spots for Early-Onset Colon Cancer - Medscape - Jul 01, 2020.