THURSDAY, July 7 (HealthDay News) -- While there has been a significant decline in colon cancer death rates in the past two decades, a new report reveals that the downward trend is not spread evenly across the United States, with the southern part of the nation lagging far behind the north.

Focusing on the time period between 1990 and 2007, the current study found that in certain instances the growing regional gap is quite dramatic: ranging from no drop whatsoever in colon cancer mortality rates in the southern state of Mississippi to a 33 percent plummet in colon cancer deaths across the northern states of Massachusetts, Rhode Island, New York and Alaska.

"There is certainly a clear regional disparity in colorectal cancer death rates in the U.S.," noted study co-author Ahmedin Jemal, vice president for surveillance research at the American Cancer Society. "And there are several factors that might contribute to this."

"One factor may be colorectal screening rates, state-by-state," Jemal observed, "with indications of a much lower utilization of screenings in the southern states. And secondly, although we didn't collect data on treatment for colorectal cancer by states, we already know from previous studies that those who live in poorer neighborhoods and more rural areas are less likely to have insurance coverage, and less likely to receive standard treatment for colorectal cancer."

"And the third factor," he added, "is that smoking and obesity are known risk factors for colorectal cancer. And for both prevalence is much higher in the southern states, compared to other regions."

Jemal and his colleagues report their findings in the July issue of Cancer Epidemiology, Biomarkers & Prevention.

According to a separate report issued by the U.S. Centers for Disease Control and Prevention earlier this week, declining colon cancer death rates have not stripped the disease of its deadly status. The CDC report noted that it currently ranks second among cancers as a killer of American men and women, and the American Cancer Society (ACS) report characterizes it as the nation's number three cancer killer.

Part of the continuing problem, according to the CDC, is that despite the availability of highly effective screening techniques, only two-thirds of Americans got tested for the disease in 2010. And although that figure represents a significant jump in screening rates (52 percent to 65 percent), 22 million men and women still did not get screened.

However, the CDC noted that colon cancer death rates have nonetheless plunged dramatically.

To dig a little deeper into how that breaks down state by state, the ACS authors analyzed 17 years of information reported by the National Center for Health Statistics.

The bottom line: Overall, the northeast saw a far greater drop in colorectal death rates than did the south.

For example, the team noted that northern states such as New York and Massachusetts saw their decline in colorectal cancer death rates pick up significant speed over the study period, from an annual drop of 2.5 percent n the 1990s to a annual drop of between 4 percent and 5 percent in the 2000s.

By contrast, southern states like Mississippi and Alabama saw their annual death rates remain more or less constant over the same timeframe.

Interestingly, the researchers found that over the study period the highest colorectal cancer death rates migrated. While the highest death rates had been found among northeastern states in the 1990s, by the mid-2000s the highest death rates were in states in the Appalachian corridor.

To get at what might be driving these state-by-state trends, Jemal and his associates stressed the marked regional differences in insurance coverage. For example, U.S. Census Bureau numbers for 2007 revealed that while nearly 19 percent of Mississippians and Louisianans lacked coverage at the time, that figure was just 5.4 percent in Massachusetts.

What's more, while the national poverty rate currently hovers at about 13 percent, that figure shoots up to one in five in Mississippi.

In terms of the prevalence of notable disease risk factors, the South has been less quick to kick the smoking habit than either the Northwest or West, the study authors noted, while obesity remains a greater issue in the South than in other regions of the country.

Dr. Felice Schnoll-Sussman, director of research at the Jay Monahan Center for Gastrointestinal Health at New York-Presbyterian Hospital/Weill Cornell Medical Center in New York City, said that while such underlying explanations "make sense," the findings are both "surprising" and "shocking."

"You might expect there might be some difference in the death rate between, say, a state like New York where you can bump into a physician at every corner, and other places where there aren't as many," she said. "You'd think we'd find maybe a 5 or 10 percent difference. But for there to be such a large difference is really what is so shocking and sad."

"And it's really unacceptable," Schnoll-Sussman added. "Because we have already made great strides in getting the word out that colorectal cancer is identifiable and treatable. So, I would say that this study isn't so much focused on trying to answer the question as to why this is happening as it is highlighting a call for action to try and make a difference for those patients for whom likely economic disparities are playing a huge role in all of this. So we need to continue to focus on access to care, education of the patient, education of the internists, open access to endoscopy and bringing down barriers related to the fear of having a screening done. That's where we can make an impact. That's where we can make a difference."

More information

For more on colorectal cancer statistics, visit the U.S. Centers for Disease Control and Prevention.