Geographic Variation in Women’s Colorectal Cancer Survival

Geographic Variation in Women’s Colorectal Cancer Survival
A first look into where early onset mortality spikes among U.S. women.

Women with early onset colorectal cancer have a greater risk of dying from the disease depending upon their county of residence, according to a study published in Clinical and Translational Gastroenterology.

“Our study sought to define regions in the United States with a disproportionate burden of colorectal cancer mortality among young women, and to understand individual and community-level features that may be contributing to these geographic differences in survival,” said Andreana Holowatyj, Ph.D., first and corresponding author on the study and an assistant professor of medicine and cancer biology at Vanderbilt University Medical Center. 

The study is the first to pinpoint geographic areas in the United States where women diagnosed with colorectal cancer before age 50 have higher mortality rates.

Linking Hot Spots and Health Data

To define ‘hot spots’ of high early onset colorectal cancer mortality among women, the researchers created a composite hot spot map with three geospatial analyses using national mortality data from the Centers for Disease Control and Prevention. About 1 in every 16 counties (191 of 3,108) were identified as hot spots across the contiguous U.S., with 52.9 percent of hot spot counties among women located in the South.

To understand patterns of community health behaviors that may be linked to survival disparities, the researchers used Surveillance, Epidemiology and End Results (SEER) data to identify 28,790 female early-onset colorectal cancer cases between 1999 and 2016 and then linked these cases to hot spots, county and demographic data.

Physical inactivity and fertility were county level features that modestly correlated with hot spot residence. The proportion of non-Hispanic Black individuals also modestly correlated with hot spot residence. Non-Hispanic Black individuals comprised 19.3 percent of the population in hot spot counties compared to 11.5 percent in non-hot spot counties.

Uncovering Sex Disparities

The hot spots identified in the new study differ geographically from an earlier study by Holowatyj and colleagues. The prior study examining early onset colorectal cancer mortality among men and women found that 92 percent of hot spot counties were in the South. For hot spot counties specifically among women, nearly half of the counties were in the Midwest and Northeast.

“In our study published earlier this year, Nashville is not an area of high mortality for both men and women diagnosed with early onset colorectal cancer, but when you take a step back and look at only women, now Davidson County and Nashville emerge,” Holowatyj said.

“These results emphasize the need to understand these pronounced disparities in early onset colorectal cancer burden not only by geographic region, but also by sex and race/ethnicity.”

“These results emphasize the need to understand these pronounced disparities in early onset colorectal cancer burden not only by geographic region, but also by sex and race/ethnicity.”

Addressing the Unexplained Variance

Despite overall reductions in colorectal cancer morbidity and mortality, incidence rates are rising at an alarming rate in younger adults less than 50 years of age, and survival disparities by sex persist among this patient population.

“Further study of community health behaviors and healthcare access, as well as modifiable colorectal cancer risk factors, is critical to elucidate the unexplained variance in early onset colorectal cancer survival among women,” the researchers wrote.