Cancer Taking Unusual Toll on People in the
Southeastern States, Study Seeks Answers
When looking at brain cancer incidence in the
Southeast lights up in red
July 22, 2008 - The South is known for many things
– hot, steamy summers, iced tea laced with sugar and friendly people
with a tendency to welcome strangers. But beneath the veneer of Southern
hospitality and gracious living lurks a silent killer – cancer.
Vanderbilt-Ingram Cancer Center researchers have their own name for the
southern region of the United States – The Cancer Belt.
Brain cancer is one of the most alarming
malignancies disproportionately affecting people who live in this cancer
hot-spot. Glioma, also known as glioblastoma, is lethal. Ninety-five
percent of patients die within two years of diagnosis.
“When you look at a map of brain cancer incidence
in the United States the Southeast just lights up in red,” said Reid
Thompson, M.D., associate professor and vice-chair of the Department of
Neurological Surgery.
“When we found this hot-spot on the National Cancer
Institute’s mortality maps we realized something unusual is going on in
this region.”
Thompson and co-investigator Kathleen Egan, M.P.H.,
Sc.D., formerly of Vanderbilt-Ingram but now on faculty at the H. Lee
Moffitt Cancer Center and Research Institute in Tampa, Fla., have
launched a study to find clues that may explain this southern brain
cancer cluster.
Vanderbilt-Ingram, which sits squarely in the
center of the Cancer Belt, is enrolling as many as 1,000 patients in the
study with the help of four other cancer centers.
“We’re asking patients about their diets, possible
job-related exposure to cancer-causing chemicals, and we’re collecting
DNA samples,” explained Thompson. “We know there are some genetic
markers that are linked to other forms of cancer and they may play a
role in brain cancer, as well.”
Brain cancer isn’t the only cancer taking an
unusual toll on Southern populations. Topping the list is lung cancer.
Despite decades of warnings about the dangers of cigarette smoking,
Southerners continue to smoke more than individuals in other regions of
the country.
But it is less easy to determine why people living
in the South are developing many other types of cancer at higher rates
than folks who live elsewhere. And it doesn’t explain why
African-Americans are more likely to develop some forms of cancer and
are more likely to die from the disease.
So William Blot, Ph.D., professor of Medicine, is
leading the Southern Community Cohort Study (SCCS), the largest
epidemiologic study in history to explore why the South has become the
Cancer Belt and why African-Americans experience higher rates of many
types of cancer.
Starting with a $28 million grant from the National
Cancer Institute, the SCCS hopes to recruit 90,000 people in 12 Southern
states to learn about their lifestyles, their family medical histories
and their risk factors for cancer and other serious diseases. Two-thirds
of the participants will be African-American and many are from rural
areas. Nearly 60,000 people already have enrolled.
The SCCS is a collaborative project among
Vanderbilt-Ingram, Meharry Medical College, Nashville, Tenn., and the
International Epidemiology Institute, Rockville, Md., as well as
participating Community Health Centers across the South.
“The study participants form one of the groups at
highest risk for cancer that has ever been studied,” explained Blot.
“Most other investigations have not included large numbers of
African-Americans and few have included low-income individuals and
people from rural parts of the country.”
The focus on African-Americans is long-overdue
since this group has much higher mortality rates for many forms of
cancer. Even when the incidence of a certain form of cancer is higher
among whites, the survival rate is nearly always lower for blacks.
While lifestyle factors and access to preventive
surveillance and treatment play a role in cancer, scientists
increasingly are finding genetic differences that may explain some of
the disparities. African-American men are far more likely to be
diagnosed with prostate cancer than white men, and the death toll is
even more alarming, with African-Americans more than twice as likely to
die from the disease. Researchers recently found a combination of genes
that appear to play a role in the aggressive forms of the disease often
found among black men.
The skin pigmentation differences associated with
race also may play more than a cosmetic role in some forms of cancer.
Dark pigmentation may hinder and light skin may help the body’s ability
to produce vitamin D.
“It’s been speculated for a number of years that
vitamin D may play a protective role in cancer,” explained Blot.
“Exposure to sunlight helps the body produce vitamin D so it stands to
reason that someone with dark skin may not be getting enough of the
vitamin. Our study in the South found roughly half of the
African-American population had insufficient levels of vitamin D versus
only 10 to 15 percent of the white population.”
This search for genetic variables is just one of
the reasons the Southern Community Cohort Study includes DNA samples.
Each participant is asked for a blood and urine sample. Those who are
unwilling to give blood are asked to use a mouth rinse, from which
researchers can extract DNA. This database of biologic specimens, stored
at Vanderbilt-Ingram, serves as a treasure trove for scientific
investigators.
“Collecting those specimens is absolutely critical
to the success of this project,” Blot explained. “The way biology and
medicine are moving, eventually we’re going to be in a world of
individualized medicine, individualized treatment and individualized
prevention. To do that you really must have biologic information on
patients.”
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