(CNN) Cancer deaths in the United States dropped over 20% between 1980 and 2014, but a new study shows that some places are being left behind.
Looking at death records from the National Center for Health Statistics, the study in the Journal of the American Medical Association pinpoints cancer clusters where deaths have not come down. In fact, some places have gotten worse.
"It makes you wonder: How could this happen in a country like ours, when we spend more money on health than any other country in the world?" said Ali Mokdad, the lead author of the study and a professor at the University of Washington's School of Public Health.
Of the 19.5 million cancer deaths on record during the 24-year period, nearly half came from three cancers: Cancer of the lungs and airways took the lion's share, followed by colorectal and breast cancers.
Based on 2014 data, lung cancer deaths bunched across the state of Kentucky, though Union County, Florida, had the highest in the nation with 231 deaths per 100,000 people that year. Breast cancer, on the other hand, lit up the map along the Mississippi River and Southern belt. It was highest in Madison County, Mississippi, with 52 deaths per 100,000 people.
Summit County, Colorado, which has fewer than 30,000 residents, had the lowest incidences of both lung and breast cancers, at 11 deaths per 100,000 people for each cancer.
Liver cancer increased by almost 88% nationwide over the 24 years, from 3.6 to 6.8 deaths per 100,000 people. The authors pointed out clusters along Texas' border with Mexico and in several counties in states with large Native American populations: New Mexico, Alaska and South Dakota. However, the researchers did not examine the reasons for the increase.
Overall, the counties with the cancer highest mortality rates were in Kentucky and the South (per 100,000 people):
The lowest rates of all cancers were seen in these counties (per 100,000 people):
Because the data end at 2014, Mokdad said, the numbers do not show how the Affordable Care Act, which expanded coverage to millions of Americans, might have impacted these disparities. Other recent studies have described an increase in mammograms among older women and coverage for the chronically ill under the act.
Mokdad cautioned that even his study, which is more detailed than the statewide data that are often reported, can still be broad enough to hide pockets where people are dying at high rates. Some counties may show declines in cancer, but examining each ZIP code may tell another story, he said.
His own county, King County, includes parts of Seattle that are wealthy and well-resourced, home to companies like Starbucks and Amazon. But it also includes neighborhoods that are chronically underserved, he said.
"We can't just look at the big picture," he said.
"At the county level, you see huge disparities," Mokdad said. "Many counties are falling behind while the rest of the country benefits."
These disparities may exist for any number of reasons, he said. For one, risk factors for cancer, such as smoking and obesity, might be more prevalent in certain places.
Prevention and screening in some counties can lag behind others, which may cause fatal cases of cancers that are normally easily detected and treated. Low awareness of cancer risks and symptoms, as well as poor access to health care, can impact the quality of cancer treatment and how soon patients receive it.
Even in cancer research, multiple studies have showed that participants are largely white and male, which may impact how effective treatments are for all populations.
"There is an added element of difficulty in engaging in research and education from folks who are considered to be from the outside," said Dr. LeeAnn Bailey, who develops diversity training and community outreach programs with the Center to Reduce Cancer Health Disparities. She was not involved in the study.
According to Bailey, going out into the community is key. One of these programs, the Geographic Management of Cancer Health Disparities Program, organizes the country into six "hubs," each served by a major cancer center, that sends health workers into communities.
"Those are our feet on the ground," Bailey said.
Despite being the second-smallest state, Delaware had the second-highest rate of cancer deaths in the country during the early 1990s, according to a report by Delaware Health and Social Services (PDF). That disparity struck the African-American community the hardest.
"This is not a top-10 list you want to be on," said Dr. Nicholas J. Petrelli, medical director of the state's Christiana Care Health System's Helen F. Graham Cancer Center & Research Institute.
But that all started to change in the early 2000s, Petrelli said. Largely due to an initiative called the Delaware Cancer Consortium, African-American deaths from colorectal cancer were lowered by 42% over seven years -- nearly equal to their white counterparts by 2009.
By 2011, Delaware had dropped from second place to 14th in cancer deaths from all causes.
Petrelli, who served on the advisory council for the consortium, said it was a "pretty dramatic change."
The consortium increased screening rates among minorities, funded a program to treat cancer for the uninsured and sent nurses and other health workers out into communities. These outreach staffers went to churches, farmers markets and other community events in an effort to recruit African-Americans who might have not otherwise taken advantage of cancer screening and care. Radio, newspaper and billboard ads cropped up across the state, Petrelli said.
Slowly, he said, members of the African-American community began to visit the Graham Cancer Center.
"From my perspective, it ran like a well-tuned clock," he said.
Colorectal cancer screening rates for African-Americans in Delaware jumped from 48% in 2002 to 74% in 2009, according to a paper published in the Journal of Clinical Oncology. Screening rates for all Delaware adults over 50 rose from 57% to 74% in the same period.
Parallel outreach programs targeted other types of cancers and populations, such as breast cancer in the Chinese community.
The report also spotlighted millions of dollars in savings: The colorectal screening program cost $1 million per year and was estimated to save $8.5 million annually, which would have otherwise been spent largely on costly cancer treatments.
Mokdad, who used to work for the Centers for Disease Control and Prevention, said public health officials need to prove that their health programs are effective on the community level to receive grants, highlighting the importance the small-scale data in the new study.
"Giving a number for a county is very important so they can act on it," he said.
Though both researchers stressed the need for continuing research on health disparities, Petrelli believes his state's model is widely adaptable.
"This model in Delaware can be done in any state in the country," he said.