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(Ivanhoe Newswire) -- Body mass and weight gain in middle age may influence a man's risk for prostate cancer, but this risk varies among different ethnic populations, according to a new study.
"The relationship of certain characteristics, such as body size, with cancer risk may vary across ethnic groups due to the combined influence of both genes and lifestyle," lead researcher Brenda Y. Hernandez, Ph.D., M.P.H., assistant professor at the Cancer Research Center of Hawaii, University of Hawaii was quoted as saying.
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While obesity is a risk factor for common cancers like colorectal cancer and breast cancer in post-menopausal women, the influence of body size on prostate cancer risk is not entirely understood. Hernandez and colleagues examined this relationship in a multiethnic population consisting of blacks, Japanese, Hispanics, Native Hawaiians and whites, and compared differences among age groups. They used the Multiethnic Cohort, a study of men, aged 45 to 75 years, in Hawaii and California from 1993 to 1996.
Results showed that of the 83,879 men who participated in this study, 5,554 developed prostate cancer. Overall, men who were overweight or obese by age 21 had a decreased risk of localized and low-grade prostate cancer, according to Hernandez.
Excessive weight gain between younger and older adulthood increased the risk of advanced and high-grade prostate cancers in white men and increased the risk of localized and low-grade disease in black men, but decreased the risk of localized prostate cancer in Japanese men.
"Readers of Cancer Epidemiology, Biomarkers & Prevention might initially look at these results and discount them for being inconsistent across the racial/ethnic groups, but they should not," Elizabeth A. Platz, Sc.D., M.P.H., associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, Baltimore, was quoted as saying.
Platz stressed the strength of this study, including that it was conducted prospectively and consisted of large numbers of men in most of the ethnic groups studied. An estimated 30 percent of prostate cancer cases occurred among Japanese men, 25 percent among white men, 27 percent among Hispanic men, 13 percent among black men, and 7 percent among Native Hawaiian men.
This study underscores the importance of investigating cancer etiology in diverse populations. "There is no reason to think that the differences in results by ethnicity are explained by bias. Different racial and ethnic populations tend to have differing proportions of fat relative to lean mass and carry their fat mass differently. These differences may be used as a launching point for the next line of research: The nature of the weight gain amount of fat gained and distribution of the fat gained in association with prostate cancer risk overall, and by stage and grade," added Platz.
"These results do not warrant a change in the current public health messages about obesity, Platz continued. Men of normal weight in all racial and ethnic groups should be encouraged to avoid weight gain, and men who are overweight and obese should be encouraged to lose weight for good health in general."
SOURCE: Cancer Epidemiology, Biomarkers & Prevention, September 1, 2009
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