Disclosures: The Federal Office of Rural Health Policy and American Cancer Society supported the study. Zahnd reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
November 25, 2020
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Early-onset colorectal cancer incidence higher among rural vs. urban populations

Disclosures: The Federal Office of Rural Health Policy and American Cancer Society supported the study. Zahnd reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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Residents of rural areas demonstrated higher rates of early-onset colorectal cancer and greater increases in incidence than residents of urban areas, according to study results published in Cancer.

Rates appeared highest among Black and American Indian/Alaska Native rural populations, researchers wrote.

Residents of rural areas demonstrated higher rates of early-onset colorectal cancer than residents of urban areas.
Residents of rural areas demonstrated higher rates of early-onset colorectal cancer than residents of urban areas.

“Colorectal cancer incidence among people younger than 50 years has increased in recent years, which is concerning. Colorectal cancer rates, regardless of age, are also consistently higher in rural populations,” Whitney E. Zahnd, PhD, research assistant professor at University of South Carolina, told Healio. “We initiated this study because it is important to understand among which populations early-onset colorectal cancer is increasing to inform interventions and policies. We also looked at the intersection of rurality and race/ethnicity because too few studies examine this intersection, even though one in every 25 Americans is a rural minority.”

Whitney E. Zahnd, PhD
Whitney E. Zahnd

Zahnd and colleagues used SEER data to evaluate combined rural and urban and racial/ethnic trends and disparities in incidence of early-onset colorectal cancer, occurring among those aged 20 to 49 years, and average-onset colorectal cancer, occurring among those aged 50 years and older.

According to study results, incidence of early-onset colorectal cancer increased by 34.9% between 2000 and 2016 among rural populations (10.44 per 100,000 to 14.09 per 100,000; annual percent change [APC], 2.09; P < .05) compared with a 19.4% increase among urban populations (9.37 per 100,000 to 11.2 per 100,000; APC, 1.26; P < .05).

“Our study underscores the importance of the new USPSTF draft recommendation changing the recommended age of colorectal cancer screening [initiation] from 50 years to 45 years to reduce both the overall rates of colorectal cancer in younger populations and geographic and racial/ethnic disparities,” Zahnd said.

Researchers observed decreases in average-onset colorectal cancer rates among both rural and urban populations; however, the improvement was greater for urban populations. Incidence of average-onset colorectal cancer decreased from 185.62 per 100,000 to 123.92 per 100,000 among rural populations (percent change, –33.42) compared with a decrease of 185.07 per 100,000 to 108.4 per 100,000 among urban populations (percent change, –41.42).

Rural populations experienced a 56.22% increase in early-onset rectal cancer during the period (APC, 2.63; P < .05) compared with a 26.26% increase among urban populations (APC, 1.79; P < .05).

Black (15.73 per 100,000) and American Indian/Alaska Native (16.61 per 100,000) rural populations had the highest incidence of early-onset colorectal cancer of any group studied.

Rural Black women had a 53% higher incidence of early-onset disease than their urban counterparts (19.25 per 100,000 vs. 12.54 per 100,000), driven primarily by higher colorectal cancer rates (rate ratio = 1.62; 95% CI, 1.3-1.99).

“Rural and racial/ethnic disparities in colorectal cancer incidence often have been thought to be largely due to less access to and utilization of colorectal cancer screening. However, when we identify disparities in colorectal cancer among those who are too young to be recommended for screening, it indicates that other factors are at play,” Zahnd said. “A myriad of potential etiological factors have been hypothesized as playing a role in the increase of early-onset colorectal cancer, including antibiotic exposure, birth by cesarean and other lifestyle and chronic disease risk factors. ... However, our study did not examine causality. It was purely descriptive and may be hypothesis-generating.”

Future research should involve assessment of possible etiological factors contributing to the increased rates of early-onset disease and rural and racial/ethnic disparities, Zahnd added.

“Additional research should also examine whether disparities exist in delayed diagnosis or outcomes,” she said. “Although rates of early-onset colorectal cancer are increasing, it is relatively rare. Clinicians may initially diagnose patients with another gastrointestinal disease, not fully considering the possibility of a cancer diagnosis. Delayed diagnosis is a concern, and it would be important to see if this is a greater problem among rural patients, particularly Black and Native American populations. Timely diagnosis is important among all populations, but particularly among those with early-onset colorectal cancer, which tends to be more aggressive.”

For more information:

Whitney E. Zahnd, PhD, can be reached at University of South Carolina, 220 Stoneridge Drive, Suite 204, Columbia, SC 29210; email: zahnd@mailbox.sc.edu.