One of the great successes in the war on cancer has been the steep decline in the death rate from colorectal cancer.

Since 1970, the colorectal cancer death rate per 100,000 Americans has been cut in half, falling to 15.1 in 2011 from 29.2 in 1970.

Increased screening, improvements in treatment and changes in risk factors (such as a drop in smoking) have contributed to the dramatic reduction.

Even so, colorectal cancer remains the third biggest cancer killer. The American Cancer Society estimates there will be 49,700 deaths from colorectal cancer this year.

It's also the case that progress against the disease has been uneven.

Researchers at the American Cancer Society analyzed colorectal cancer death rates by county and identified three geographic hot spots: the Lower Mississippi Delta, west central Appalachia, and a swath of counties in eastern Virginia and North Carolina.

"There are areas in the South that pop out with particularly high rates," epidemiologist Rebecca Siegel tells Shots. While the colorectal cancer death rate has declined nationally since 1970, the rates in the hot spots were either stagnant or rose, she says.

Poverty, a lack of health insurance and low levels of education and health literacy are factors that may help explain what's happening in the hot spots, Siegel says. People in rural area may also have more difficulty getting screening and treatment.

The discrepancy in death rates is highest in the Delta, about 40 percent higher than the national average. And colorectal death rates for black men there haven't begun to decline, she says.

Once a disparity like this is identified, Siegel says, "there's an obligation to do something about it. "We know the disparities can be eliminated because we saw it in Delaware." In less than a decade there, a statewide initiative got more people screened, coordinated follow-up and paid for treatment for people who needed help. Racial disparities in screening and care were eliminated.

Ideally, it's best to prevent colorectal cancer by cutting the risks, such as weight control and physical activity, Siegel says. But colonoscopies can make a big dent in colorectal cancer by finding precancerous polyps that can be removed before they become a threat and also identifying the disease itself at an early, treatable stage.

The findings were published online Wednesday by Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

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