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Discoveries

The effect of color on colorectal cancer

By Jennifer Durgin

Soneji joined the DMS faculty earlier this year.

Over the past 45 years, death rates from colorectal cancer have dropped steadily among white Americans, but among black Americans a very different story has unfolded. Mortality from colorectal cancer has decreased only slightly among black women and has actually increased during that period among black men, according to a study led by Samir Soneji, Ph.D., a demographer who joined the DMS faculty earlier this year.

Rates: The study, published in the American Journal of Public Health, showed that between 1960 and 2005, annual death rates from colorectal cancer dropped 54% for white women (from 241 to 111 deaths per million), but just 14% for black women (from 203 to 174 per million). The disparity was even more dramatic among men. Death rates declined 39% for white men (from 273 to 166 per million), but rose 28% for black men (from 201 to 258 per million).

Colorectal cancer is one of the few cancers where there have been major advances in screening, treatment, and care, says Soneji, who gathered the data for this study when he was at the University of Pennsylvania as a Robert Wood Johnson Health and Society Scholar. Screening tests for colorectal cancer are widely accepted and effective, unlike tests for some cancers. And recent advances in surgery, chemotherapy, and radiation therapy have made it very treatable if found early.

It's known that "blacks receive less colorectal screening, and their cancer is detected at more advanced stages" than is the case for whites, Soneji and his coauthors wrote. But they found that racial disparities in survival persisted even after eliminating those variables. Black men and women with colorectal cancer are more likely to die from the disease than white patients of the same age group, gender, and stage at diagnosis. And the differential has been growing. The study found that blacks were 22% more likely to die than whites in the 1980s, 26% more likely in the 1990s, and 33% more likely in the 2000s.

Death rates rose 28% for black men between 1960 and 2005.

But Soneji and his coauthors suggest that race itself may not be the driving factor in this widening gap. "Race is an important proxy for all sorts of other socioeconomic factors," Soneji says, such as differences in income, wealth, educational attainment, employment, insurance coverage, and access to health care.

While the factors underlying the colorectal cancer disparities remain unclear, the "most likely" causes, the researchers wrote, are "differences in access to care or the quality of that care."

Disparities: When advances are made in the detection and treatment of particular diseases, Soneji explains, "the most resourced groups will benefit more than the least resourced groups, [because] the distribution and delivery of health care is quite inequitable." That's how disparities can widen over time—and how two very different narratives can unfold for the same disease.


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