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It has long been known that smoking contributes to more than just lung cancer. The U.S. Centers for Disease Control and Prevention says, for example, that smoking leads to higher rates of bladder, pancreas and kidney cancer. But a new study by a UC Davis researcher shows a much more dramatic link, at least among African American men.
The findings of Dr. Bruce Leistikow suggest that tobacco smoke exposure is responsible for more than half the non-lung cancer death rate in African American men and up to two-thirds of their overall cancer death rate.
"It looks like we badly underestimated the risks of smoking," said Leistikow, an epidemiologist whose study results will be published in the May issue of the journal Preventive Medicine. "And that if we want to address cancer in this population, we ought to greatly increase our efforts to reduce smoking and secondhand smoke exposure."
The death rate from cancer for African American men is 39 percent higher than it is for white males in the United States. Leistikow's is the first study to clearly demonstrate that the higher cancer burden is linked to smoking.
Because almost all lung cancer is caused by exposure to smoke - either firsthand or secondhand, Leistikow used lung cancer death rates as a measure of smoke exposure for his study.
He then analyzed the correlation between smoke exposure and non-lung cancer death rates for African American males for the years from 1969 through 2000. He found that the non-lung cancer death rate moved in near-perfect lock step with changes in the smoke exposure rate over the 31-year period.
When the smoke exposure rates surged in the the 1970s and 1980s, so rose the non-lung mortality rates. When smoking declined, from 1990 through 2000, so dropped the non-lung cancer rates.
"Up to this point, the CDC has linked over 11 percent of non-lung cancer deaths in men in the U.S. to smoking. My result says there is a very good chance that the true burden, at least in African Americans, is over four times as high."
Leistikow said his findings cannot be extrapolated to other populations such as whites or African American women. He said the finding suggest that smoking's risks may have been widely underestimated across the board, but need to be further analyzed.
Leistikow said he chose African American men to study because they were the easiest group to analyze. Their cancer death rate increases were steepest. In addition, because of well-documented disparities in timely access to good health care, he said African Americans were also less likely to be affected by improvements in cancer treatment. He focused on men because unlike women, they have not benefited from recent decreases in death rates from female cancers due to treatment improvements.
Finally, Leistikow did not include stomach cancer in his grouping of non-lung cancers because of across-the-board drops in stomach cancer deaths.
"Almost all the change in non-lung cancer seems to be from changes in smoking rates, not from cancer treatment," he said. "It tells us that we likely underestimated some of the cancer harm from smoking in this group. It also tells us that access to treatment for deadly cancers may not have improved much."
Leistikow's findings caught the attention of Dr. Jim Boggan, a UC Davis neurosurgeon and an African American who admits being a smoker.
Boggan, who is helping organize a program to reduce cancer risk among African Americans, said the findings that smoking raises risk of death from all cancers should further motivate people such as himself to quit.
"I think it has a tremendous prevention message in the African American community," he said.
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