LIFESTYLE CHANGES CLINICALLY EFFECTIVE IN PREVENTING CANCER

PHOENIX – Though the concept of healthy living has long included such recommendations as diet and exercise, clinical evidence suggests that these activities may be more powerful in preventing cancer than previously thought, according to research presented today at the American Association for Cancer Research Second Annual International Conference on Frontiers in Cancer Prevention Research.

“These studies provide us with evidence about the mechanisms by which modest changes in daily habits can alter the risk of cancer,” said John Potter, M.D., Ph.D., of the Fred Hutchison Cancer Research Center, Seattle, Wash.

“Here, for instance, are some quite specific data on the way in which weight loss and exercise can alter body chemistry, so as to favor a reduction in risk. This adds to the empirical findings of lower risk of cancer with healthier lifestyles that can act as a spur to those who need to know how it works before they are willing to change,” he added.

The Effects of Weight Loss and Weight Gain on Biomarkers of Breast Cancer Risk (Abstract 1451)

Pre-menopausal weight gain is associated with an increased risk of post-menopausal breast cancer, according to researchers from Manchester, England, who examined a weight-loss program to identify the link between weight loss and risk of developing cancer. Results showed that even a small weight loss, just five percent of an individual's body weight, may lower the risk of developing breast cancer.

In the trial, 79 women with a family history of breast cancer who had gained significant amounts of weight as adults were divided into two different diet regimens: a calorie-restricted/exercise, weight-loss program; and a standard diet with only exercise advice.

Changes were measured by body weight, waist circumference, percent body fat, total subcutaneous and intrabdominal fat, insulin, testosterone and SHGB (sex hormone binding globulin), which impacts levels of bioavailable estrogen. The effects of losing more than five percent, or between zero and five percent of body weight, were examined. Only women losing more than five percent of their body weight experienced notable declines in waist circumference; percent body fat; total, subcutaneous and intra-abdominal fat; testosterone and insulin levels; and increases in SHBG.

Biomarkers for breast cancer risk pointed to positive benefits from a weight loss of five percent when compared to the standard trend of weight gain among overweight women with a family history of breast cancer.

“Until now, the general perception suggested that weight loss had to be significant in order to make a difference in disease prevention,” said Michelle Harvie, Ph.D., of the South Manchester University Hospitals in Manchester and lead author of the study.

“We hope this study will prove to women that a small effort can go a long way.”

Researchers are currently examining the effects of this weight loss intervention over a 12-month period, in order to determine the potential long-term benefits.

The Association Between Physical Activity Levels and Mammographic Breast Density in Pre- and Post-Menopausal Women: The Health, Eating, Activity and Lifestyle (HEAL) Study (Abstract 1481)

Women with dense breast tissue are at an increased risk of breast cancer when compared to women with less dense breast tissue. In this study of 1,223 women, researchers found that lower amounts of dense breast tissue were associated with higher physical activity levels in premenopausal women with a BMI (body mass index) less than 30, providing further evidence that exercise may protect against breast cancer.

Participants were enrolled in the Health, Eating, Activity and Lifestyle (HEAL) study, a multicenter study designed to examine the associations between physical activity, diet, weight, hormones, breast density, and other influences on breast cancer prognosis among newly diagnosed breast cancer survivors. Physical activity levels and breast density for this analysis were determined from information and mammographic films from the year prior to diagnosis.

After adjusting for age, ethnicity, education, BMI, study site, number of children, and hormone-replacement use, a statistically significant 17 percent difference in breast tissue density was observed between the least active and most active pre-menopausal women with a BMI less than 30. Researchers found the association between physical activity and breast density only among leaner pre-menopausal women, and not among heavier pre-menopausal women or post-menopausal women in any BMI category.

“We're pleased that we observed an association between physical activity and breast density. We've known that breast density is related to breast cancer risk, and that breast density may change throughout a lifetime. Factors that change breast density may also change breast cancer risk,” said Melinda Irwin, Ph.D., MPH, of Yale University, and lead author of the study.

“This information provides further evidence of the many benefits of regular exercise that could be used to motivate women to be more physically active,” she added.

Dietary Fat and Carbohydrates: Role in Prevention of Prostate Cancer Progression and TRAMP Mice (Abstract 1217)

Previous studies have suggested a link between the amount of saturated fat in the diet and the risk of progression to advanced prostate cancer. This study, led by Ada Elgavish, Ph.D., at the University of Alabama at Birmingham, compared the relative risk of developing advanced prostate cancer with a low-carbohydrate or a low-fat diet provided ad libitum (as much as wished), beginning before tumors developed and continuing until middle age.

“In the low-fat versus low-carbohydrate debate, we're finding that under conditions in which diet is provided ad libitum, a diet with fewer carbohydrates may be more effective in preventing progression to advanced, lethal prostate cancer than a diet with low fat content,” said Dr. Elgavish, the lead author of the study.

“However, the results of this study are preliminary. Men should talk to their doctors before changing their diets,” she added.

The study was carried out in TRAMP mice, a TRA nsgenic M ouse model of P rostate cancer developed by Dr. Greenberg and associates at Baylor College of Medicine in Houston. These mice are biologically engineered to develop prostate cancer after puberty. The objective of the present study was to test the possibility of delaying progression to advanced prostate cancer by diet modifications.

Two groups of genetically compromised TRAMP mice were fed diets containing the same amount of calories, with either 10 percent or 45 percent fat (mostly lard); 17 and 13 mice, respectively. Carbohydrates, mostly corn starch and sucrose, replaced fat in the low fat diet. Researchers measured food intake and body weight throughout the 23-week study. After the onset of middle age, mice fed the 45 percent fat diet had a consistently higher body weight and the increase was due to higher body fat. When the study ended, 95 percent of the mice fed the 45 percent fat diet had survived, as compared with only 68.2 percent of those fed with the 10 percent fat diet. In addition, the percentage of mice with advanced prostate cancer in the 45 percent fat group was one-third of that in the group fed the 10 percent fat diet.

Diet and Risk of Breast Cancer in Shanghai, China (Abstract 1274)

International incidence rates of breast cancer vary drastically, and recent studies have shown dramatically increased cancer risk levels in women migrating from China to Hong Kong to the United States. This information suggests that environmental differences may contribute to breast cancer risk, including extremely different dietary intakes in various regions of the world.

In this study, 378 women in Shanghai, China, who were diagnosed with breast cancer were compared with 1,070 age-matched, unaffected control women. Dietary intake was determined through the completion of an in-depth food frequency questionnaire, which recorded such factors as food group and caloric intake.

Researchers found that consumption of four or more servings of fruits and vegetables per day was associated with a significantly lower breast cancer risk. However, no association was seen between intake of soy or soy products and breast cancer risk. The results provide support for the benefits of eating fruits and vegetables to prevent cancer, and also offer one of the first analyses between different botanical groups and breast cancer risk.

“The study provides further support suggesting that low fruit and vegetable intake in the Western diet may be a major factor in the risk of developing breast cancer,” said Jackelin Shannon, Ph.D., R.D., assistant professor of public health and preventive medicine in the Oregon Health and Science University School of Medicine, member of the OHSU Cancer Institute, and lead author of the study.

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Founded in 1907, the American Association for Cancer Research is a professional society of more than 21,000 laboratory, translational, and clinical scientists engaged in cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's annual meetings - next year in Orlando, Fla., March 27-31 - attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings like this one, held throughout the year, focus on the latest developments in all areas of cancer research.