High Intake of Dietary Lignans Improves Breast Cancer Survival

Roxanne Nelson

April 25, 2008

April 25, 2008 (San Diego, California) — A high consumption of lignans is associated with better survival in postmenopausal women with breast cancer. Although the dietary intake of lignans did not have any effect on breast cancer survival in premenopausal women, postmenopausal women with a high intake of plant lignans were approximately 70% less likely to die from their breast cancer, according to study data presented here at the American Association for Cancer Research 2008 Annual Meeting.

"We can draw fewer conclusions about lignan intake in terms of overall mortality because, since this was a breast cancer study, most of the patients died from breast disease," lead author Susan E. McCann, PhD, from the division of cancer prevention and population sciences at Roswell Park Cancer Institute, in Buffalo, New York, told Medscape Oncology. "But a high intake of lignans was associated with about a 50% reduction in mortality from all causes. This included cardiovascular disease and other cancers."

Lignans are distributed in seeds, whole grains, berries, fruit, vegetables, and nuts, and have been studied for a possible effect on breast cancer risk. Several epidemiologic studies have found that the dietary intake of lignans is associated with a lower risk for breast cancer but, to date, there have not been any clinical trials evaluating the effect of lignan intake on breast cancer survival.

Dr. McCann and colleagues examined the association between dietary lignan intake and breast cancer survival in 1122 women with primary incident histologically confirmed breast cancer. All of the women were participants in the Western New York Exposures and Breast Cancer (WEB) study, a population-based case-control study of women living in Erie and Niagara counties in Western New York between 1996 and 2001. The women were followed through December 31, 2004.

Study participants completed an extensive food-frequency questionnaire, which assessed their diet in the 12 to 24 months before their cancer diagnosis. The researchers calculated dietary lignan intake using published food-composition data, and associations between dietary lignan intake and all-cause, total cancer, and breast cancer mortality were estimated using the Cox proportional hazards models after adjustment for confounders such as age, tumor stage, and body mass index.

By the end of the follow-up period, 130 patients had died —94 from cancer(of which 84 were breast cancer) and 36 from other causes. "The women who died from breast cancer tended to be older, tended to have a more advanced stage of cancer, and were more likely to be nonwhite," said Dr. McCann. "They were also more likely to be estrogen-receptor negative, but it wasn't statistically significant."

There was no association between the consumption of dietary lignans and all-cause, total cancer, or breast cancer mortality among premenopausal women. However, postmenopausal women with the highest intake of lignans showed a statistically significant reduction in the risk for all-cause mortality (hazard ratio, 0.48) and a significantly lower risk for breast cancer mortality (hazard ratio, 0.35).

"In this study, lignan intake was derived primarily from dark bread, peaches, apricots, broccoli, winter squash, oranges, strawberries, onions, coffee, and tea," said Dr. McCann.

The researchers did not find an association between mortality and the intake of fruits and vegetables, although a high intake of lignans might be a marker of a plant-based diet.

"This study is evidence that a healthy diet can contribute to improved survival in breast cancer and other chronic diseases," she said. "It provides more evidence that a plant-based diet may help survival in cancer patients."

American Association for Cancer Research (AACR) 2008 Annual Meeting: Abstract 4162. Presented April 15, 2008.


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