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Weight gain associated with prostate cancer risk
Source: (cancerfacts.com)
Tuesday, September 01, 2009
PHILADELPHIA – Sept. 1, 2009 – Men who pack on the pounds between early adulthood and older age may be at greater risk for prostate cancer compared to men who gain weight more slowly, or stay lean during those years, a new study shows.
Led by Dr. Brenda Y. Hernandez, assistant professor at the Cancer Research Center of Hawaii, University of Hawaii, the researchers also found that this risk varies among different ethnic populations. The results of their study appear in the September issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
"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," Hernandez said in a prepared statement.
Obesity is a risk factor for common cancers like colorectal cancer and breast cancer in post-menopausal women. However, the influence of body size on prostate cancer risk is not entirely understood. Hernandez and colleagues used the Multiethnic Cohort, a longitudinal study of men aged 45 to 75 years old established in Hawaii and California from 1993 to 1996 to examine this relationship in a multiethnic population consisting of blacks, Japanese, Hispanics, Native Hawaiians and whites. They also compared differences among age groups.
Results showed that of the 83,879 men who participated in this study, 5,554 were diagnosed with prostate cancer. Overall, men who were overweight or obese before age 21 had a decreased risk of localized and low-grade prostate cancer, according to Hernandez.
Being overweight in older adulthood, however, was associated with increased risk of prostate cancer among white and Native Hawaiian men, but a decreased risk among Japanese men. 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," said Dr. Elizabeth A. Platz, associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, Baltimore.
Platz stressed the strengths of this study, including that it followed men from the start of the study over time and it consisted of large numbers of men in most of the ethnic groups studied. Of the 5,554 men diagnosed with prostate cancer, an estimated 30 percent of prostate cancer cases occurred among the 25,275 Japanese men enrolled, another 25 percent of the cases occurred among the 21,311 white men in the study, while 27 percent occurred among the 20,448 Hispanic men, and 13 percent occurred among the 10,934 black men in the study, and lastly, 7 percent of the cases were diagnosed among the 5,921 Native Hawaiian men.
"There is no reason to think that the differences in results by ethnicity are explained by bias," added Platz, who is also an editorial board member for Cancer Epidemiology, Biomarkers & Prevention. "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."
Platz added that this study alone does not warrant a change in health policy, but instead underscores the need for multi-ethnic research.
"These results do not warrant a change in the current public health messages about obesity: Men of normal weight in all racial/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," Platz added.
SOURCE: adapted from press materials provided by the American Association for Cancer Research
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