Three Colorectal Cancer Death 'Hotspots' Identified in U.S.

Graphic Courtesy of the American Cancer Society

Graphic Courtesy of the American Cancer Society

Though colorectal cancer death rates in the U.S. have declined greatly in the past 40 years, researchers have identified three distinct areas (hotspots) where “progress has lagged.”

The hotspots were identified in the lower Mississippi Delta, west central region of Appalachia and northeastern North Carolina/southeastern Virginia.

“Although we’ve made great strides against colorectal cancer in a fairly short time period, there are a lot of vulnerable populations that aren’t benefiting,” lead study author Rebecca Siegel said in a statement. “Now that these groups have been identified, there is a moral obligation to do something about it.”

Poverty, Obesity and Access

Siegel is the director of surveillance information in the Surveillance and Health Services Research Program at the American Cancer Society. For this study, she and her research colleagues analyzed data from the Surveillance, Epidemiology, and End Results (SEER) Program, which collects information on all deaths in the U.S. from the National Center for Health Statistics and population estimates from the Population Estimates Program of the U.S. Census Bureau.Socioeconomics play a large role in the development of these hotspots, according to the researchers. Both the Delta and Appalachia hotspots have been characterized by “high unemployment, low levels of education and health literacy and inadequate access to health care.”

Colorectal cancer survival rates are typically lower among low-income patients due to higher prevalence of comorbidities, more advanced disease stage and a lower likelihood of surgery and additional treatment. The authors noted a factor that could be limiting access to care: As of March 2015, only six of the 12 states with higher-risk counties have taken advantage of Affordable Care Act funding.

Overall health greatly impacts the risk of developing and dying from colorectal cancer. Obesity is correlated with an increased risk of colorectal cancer by twofold in men and 50 percent in women. With the exception of Virginia, all of the hotspots are in the upper quartile of adult obesity prevalence. Anecdotally, the highest obesity rates in Mississippi are concentrated in the Delta region. Study authors also noted that individuals in Mississippi and West Virginia are least likely to take part in leisure-time physical activity, which has been shown to be beneficial in protecting against colorectal cancer.

Colorectal cancer screening is effective in reducing the risk of death — by means of removing precancerous lesions and detecting disease at an early and more treatable stage. Though screening rates have been increasing in the U.S. since 1987, the authors wrote, “uptake has not been equally distributed and disparities by race, ethnicity and socioeconomic status remain.”

Though preventing colorectal cancer with lifestyle changes is preferred, the authors wrote, such changes could take generations to benefit an entire population.

Screening, conversely, has been shown to reduce and cut out disparities in a short amount of time. In point of fact, Siegel said in a statement, statewide screening was implemented in Delaware and “effectively eliminated disparities in less than a decade.”

Progress … but Disparities Remain

“Promoting and improving access to screening […] offers a more immediate return on investment,” the authors wrote.In 1970, the age-standardized colorectal cancer death rate per 100,000 Americans was 29.2. Over the next four decades, that rate declined to 15.1 (a 48 percent decrease).

Due to increased population screening, changing patterns in risk factors and improvements in treatment, the magnitude of this decline accelerated each decade. In the 1970s, the colorectal cancer death rate declined by 4 percent; by the 2002, it had declined by 27 percent.

Different regions saw improvements at different times. Before 1990, rates were lowest in the South and highest in the mid-central region and the Northeast. By 2000 though, rates were similar across the country with the exception of the three hotspots.

The lower Mississippi Delta hotspot had a population of 3.7 million across 94 counties in 2011. This area spreads across sections of Arkansas (17 counties), Illinois (16), Kentucky (3), Louisiana (6), Mississippi (27), Missouri (15) and Tennessee (10).

In this region, colorectal cancer death rates were 18 percent lower compared with non-hotspots from 1970-1972 but were 40 percent higher than non-hotspots from 2009-2011. This crossover occurred around 1990 for both blacks and whites. The race-specific disparity in 2011 was not as pronounced for whites compared with blacks, the study authors wrote, but the difference was not statistically significant.

The second hotspot, the west central region of Appalachia, had a population of 6.2 million across 107 counties in 2011. The area spreads across sections of Indiana (6 counties), Kentucky (60), Ohio (22) and West Virginia (19).

Unlike the Delta region, this region had colorectal cancer death rates higher than national rates in the 1970s — a disparity that widened through the 1980s, 1990s and 2000s. Study authors noted this region was 89 percent white from 2009-2011.

The third hotspot consisted of 11 counties in northeastern North Carolina and 26 counties in southeastern Virginia. Its colorectal cancer death rate pattern and racial distribution were similar to that of the Delta, according to the study, which is being published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.