by
J. STRAX
New York/ PSA Rising/ Aug 3, 2003. Men who are long-term, heavy smokers face twice the risk of developing aggressive prostate cancer than men who have never smoked, say researchers at Fred Hutchinson Cancer Research Center.
Men under age 65 with a cigarette smoking history of 40 or more "pack-years" face a 100 percent increased risk - or double the risk - of developing more aggressive forms of prostate cancer compared to nonsmokers, said Janet L. Stanford, Ph.D. at Fred Hutchinson's Public Health Sciences Division. That many pack years can mount up from, say, a pack a day for 40 years or two packs a day for 20 years. Men who had smoked this much for this long face a 60 percent increased risk of prostate cancer overall relative to nonsmokers. Compared to nonsmokers, current smokers experienced a 40 percent increase in the risk of prostate cancer.
"This study provides additional evidence that supports a role for smoking as a risk factor for prostate cancer and confirms recent findings that suggest smoking is an even stronger risk factor for more life-threatening forms of prostate cancer," said Stanford, director of Fred Hutchinson's Prostate Cancer Research Program.
Previously, research results regarding smoking and prostate cancer have been mixed, but these results, together with recent findings from investigators at Johns Hopkins University and Harvard University, provide cumulative evidence that smoking - in particular high-dose, long-term cigarette exposure - is an important risk factor for prostate cancer, said Stanford.
"From a public-health perspective, I think we now have enough evidence to suggest that prostate cancer should be added to the long list of malignancies in which smoking plays a role," she said. In additon to lung cancer, other smoking-related cancers include those of the bladder, cervix, esophagus and kidney.
The study involved more than 1,450 Seattle-area men, ages 40 to 64. Half had a history of prostate cancer (diagnosed between 1993 and 1996) and the other half, which did not have a history of prostate cancer, served as a comparison group. Participants completed detailed in-person interviews that assessed a variety of factors, from smoking and alcohol consumption to diet and occupational history.
One of the study's strengths, the researchers say, is that it focused on younger men, for whom the risk factors stand out more starkly. "The contribution of smoking to prostate cancer may have been easier to detect in men under 65, who are at lower absolute risk of the disease," Stanford said, "than in older men, in whom the cumulative effects of numerous risk factors may cloud the picture."
Another strength of this study, according to Stanford and his team, is that it assessed other lifestyle variables - from prostate-cancer screening history to dietary intake - factors which, if unaccounted for during data analysis, might have biased the results.
How Smoking Can Damage the Prostate
Smoking may promote prostate cancer through several mechanism, the study group says. For one thing, it can increase the amount of circulating androgens (male hormones), which fuel the growth of normal and malignant prostate cells.
"Cigarette smoking appears to alter a man's hormonal milieu by tilting the scale toward a hormonal environment that may be conducive to tumor growth," Stanford said.
Then there is cadmium.
"Cadmium has been shown to be concentrated in the prostate, so this may be one chemical exposure from cigarette smoking that could have an adverse biological effect on the prostate," Stanford said.
Another recent study has found that cadmium can mimic estrogen. In female mice it goes to the breast and womb, causing abnormal breast development and speeded up puberty.
So men exposed to cadmium in the workplace can be exposed to even more risk of developing prostate cancer if they are heavy smokers. Cadmium exposure is higher for men who work with phosphate fertilizers, in mining and smelting, and in production and industrial handling of batteries, alloys, and pigments (see sidebar). Cadmium is present also in some de-icer or road salt used on highways in parts of the USA.
On the bright side, while the relative risk of developing prostate cancer increases with the number of pack-years smoked, this risk declines to near that of nonsmokers within about 10 years of quitting, Stanford said.
"When men stop smoking, within a decade their risk of prostate cancer returns to a level that is not substantially different from nonsmokers, so for most men, it's not too late to quit. There are few environmental risk factors for prostate cancer that have been identified, but here's one way that men can take action to reduce their risk," she said.
"Cigarette smoking and risk of prostate cancer in middle-aged men" by Stanford and colleagues, appears in July issue of Cancer Epidemiology, Biomarkers and Prevention, a publication of the American Association for Cancer Research.
Researchers from the University of Washington School of Medicine also collaborated on the study, which was funded by the National Cancer Institute.
The Fred Hutchinson Cancer Research Center, home of two Nobel Prize laureates, is an independent, nonprofit research institution dedicated to the development and advancement of biomedical research to eliminate cancer and other potentially fatal diseases. Fred Hutchinson receives more funding from the National Institutes of Health than any other independent U.S. research center. Recognized internationally for its pioneering work in bone-marrow transplantation, the center's four scientific divisions collaborate to form a unique environment for conducting basic and applied science. Fred Hutchinson, in collaboration with its clinical partners, the University of Washington Academic Medical Center and Children's Hospital and Regional Medical Center, is the only National Cancer Institute-designated comprehensive cancer center in the Pacific Northwest and is one of 39 nationwide. For more information, visit the center's Web site at www.fhcrc.org.
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