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May 17, 2005

Low-Fat Diet May Reduce Risk of Breast Cancer Relapse In Post Menopausal Women With Estrogen Receptor Negative Disease

Topics: Medicine

Except for nonmelanoma skin cancers, breast cancer is the most common cancer in women. It's estimated that in 2005 more than 211,000 women in the United States will be diagnosed with invasive breast cancer. As a result of earlier detection and better initial treatments, more women are surviving an initial diagnosis of breast cancer, but many of them remain at risk for a recurrence. Numerous in-vitro and in-vivo studies have strongly suggested that a high-fat diet contributes to the development of breast cancer in postmenopausal women.

Until recently, however, subsequent large prospective studies have failed to show that reducing dietary fat led to a reduction in breast cancer risk, although a positive association has been observed in an in-vivo study among smokers at baseline (Using Western-diet pattern, relative risk = 1.44, comparing top to bottom quintiles; 95% CI = 1.02-2.03; p for trend = 0.03). An inverse association was observed between the prudent pattern and estrogen receptor-negative cancer (relative risk = 0.62; 95% CI = 0.45-0.88; p for trend = 0.006). Among the major food groups, higher consumptions of fruits (relative risk for 1 serving/day increase = 0.88; 95% CI = 0.80-0.97; p = 0.009) and vegetables (relative risk = 0.94; 95% CI = 0.88-0.99; p = 0.03) were significantly associated with decreased risk for ER(-) breast cancer. An in-vitro study has demonstrated that an omega-3 fatty acid enriched diet proved to be a safe means for retarding tumor growth and vascularization. Interestingly, conjugated docosahexaenoic acid and docosahexaenoic acid, omega-3 fats, have been shown to inhibit human breast cancer cell growth in vitro and in vivo via apoptosis and involved downregulation of Bcl-2 protein.

The Study(methods)
On May 16, 2005 at the American Society of Clinical Oncology annual meeting in Orlando, Florida, investigators reported the results of a study that suggests an intervention aimed at reducing dietary fat consumption can reduce the risk of breast cancer recurrence. But as encouraging as the results are, the reliability of the study's outcome is questionable owing to factors such as the modest weight loss seen in the low-fat group or increased consumption of fruit and vegetables, may have contributed to the outcome, and an even more important variable that could make a difference is that some, but not all of the women in both study groups, were treated with chemotherapy following surgery. The researchers have not yet analyzed whether chemotherapy was associated with improved survival. That difference alone could have affected the outcome of the study. No statistical data was provided in the non-scientific review.

The "Women's Intervention Nutrition Study" was a large, prospective, randomized phase III study to investigate whether a low-fat diet could reduce breast cancer recurrence rates in postmenopausal women who had been treated for early-stage breast cancer. Between 1994 and 2001, the study enrolled 2,437 women who in the previous year had had breast cancer surgery followed by therapy appropriate to their particular cancer. The women, whose average age was 62 were randomly assigned to one of two dietary groups. One group was asked to follow their standard diet. Women in this group met with a nutritional counselor periodically but were not urged to change their diet, which contained an average of about 51 grams of fat a day.

Women in the second group were asked to modify their diet to reduce their consumption of dietary fat to 20 percent of total calories. This group received nutritional advice about reducing dietary fat consumption by, for example, using less oil when cooking, increasing intake of fruit and vegetables, controlling portion sizes, and so on. The diet eaten by women in the low-fat group contained an average of 33 grams of fat a day.

After a median of five years of follow-up, breast cancer had come back in 9.8 percent of the women on the low-fat diet and 12.4 percent of those on the standard diet. This amounted to a 24 percent reduction in the risk of recurrence for the women on the low-fat diet. The largest risk reduction, 42 percent, was observed among women on the low-fat diet whose tumors did not respond to the presence of the hormone estrogen (estrogen receptor negative disease, usually poorer outcome than ER-positive disease). Postmenopausal women whose tumors do respond to estrogen are candidates for anti-estrogen drugs such as tamoxifen or letrozole (used in postmenopausal women with hormone receptor positive breast cancer who have   been on tamoxifen for the currently recommended dose of five years), which help reduce the risk of relapse. Although weight loss was not a goal of the study, the investigators reported that women who followed the low-fat diet lost an average of four pounds. Monitoring was conducted every three months, which is far better than in many trials, and the NCI seems to have a lot of faith in this study.

Related readings
Dietary factors modifying breast cancer risk and relation to time of intake.

Dietary omega-3 fatty acids and ionizing irradiation on human breast cancer xenograft growth and angiogenesis.

Omega-3 fatty acids improve liver and pancreas function in postoperative cancer patients.

Opposing effects of prepubertal low and high fat n-3 polyunsaturated fatty acid diets on rat mammary tumorigenesis.

High-fat corn oil diet promotes the development of high histologic grade rat DMBA-induced mammary adenocarcinomas, while high olive oil diet does not.

Other coverage: Bill at INDC Journal belives that making a distinction about what type of fat needs to be reduced is vital before doling out dietary recommendations with confidence, as a low, low fat diet (that cuts all fats, including the anti-inflammatory variety) can jack up the risks of other maladies. He's right on, research data supports his assumption.

Cross posted at NewHopeBlog

Posted by Hyscience at May 17, 2005 8:28 PM

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