San Antonio Breast Cancer Symposium
December 2006

The Conference, held December 14-17, 2006, provided good news for women, including a reported 7 percent decrease in breast cancer incidence in the United States in 2003. News of the decrease was presented at the conference by medical oncologist Peter Ravdin, MD, PhD. Researchers indicated the decline may be related to a number of factors, including a significant decrease in hormone replacement therapy (HRT) use that took place in 2002, along with changes in mammography screening use. Most concur that more observation needs to be made over the next several years to put this in context. Figures on breast cancer incidence in 2004 will be released in early 2007.

Another finding reported at the San Antonio meeting on December 16th builds on an earlier study, the Women's Intervention Nutrition Study (WINS), and extends and confirms the finding that a low-fat diet reduces the risk of breast cancer recurrence, in postmenopausal women treated for early-stage breast cancer. The Breast Cancer Research Foundation funded the Women's Intervention Nutrition Study through multi-year support of the Institute for Cancer Prevention. Here is a summary of the newly-presented findings, taken from a December 16th press release from the National Cancer Institute:

Postmenopausal women who reduce their consumption of dietary fat and have been treated for early-stage breast cancer may reduce their chances for breast cancer recurrence or a second breast cancer, according to results from the Women's Intervention Nutrition Study (WINS). WINS was the first large-scale randomized trial to show that a change in diet can improve breast cancer outcomes in women who are receiving conventional treatment for early-stage breast cancer. Results of this study, which was sponsored by the National Cancer Institute (NCI), appear in the December 20, 2006, issue of the Journal of the National Cancer Institute.

This report is based on an interim analysis of the trial data. The WINS study investigated a subset of women who have already been diagnosed with breast cancer and who were willing to enroll in a study to see if lowering fat in their diet would reduce the risk of their cancer recurring. Earlier in 2006, the Women's Health Initiative (WHI), which examined the effect of a low-fat diet on breast cancer risk, showed a trend toward a modest benefit of a reduced-fat diet on the incidence of invasive breast cancer. "The relationship between dietary fat and breast cancer has been unclear," said NCI Director John E. Niederhuber, M.D. "Certainly there is accumulating evidence that a healthy lifestyle -- reduced fat consumption and exercise -- is a worthy goal to decrease risk and to optimize long-term therapy outcome."

WINS enrolled 2,437 women between 1994 and 2001 who had been treated for early-stage breast cancer. The women, ages 48 to 79, were randomly assigned to a lower-fat dietary intervention group or a control group who ate their regular diet. At the start of the study, both groups consumed similar amounts of calories from fat; about 57 grams of fat per day or close to 30 percent of daily caloric intake. At the end of the first year of observation, the women in the dietary intervention group had reduced their fat intake by an average of 24 grams per day compared with only a 5 gram per day drop in the control group. The difference between the two groups was maintained throughout the trial. By the fifth year of the trial the women in the intervention group weighed an average of 6 pounds less than the women in the control group.

Three more years of follow-up are currently being planned. After a median of five years of follow-up, breast cancer recurrence or new breast cancers occurred 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 relative risk of recurrence for the women on the low-fat diet. The largest risk reduction -- 42 percent -- appeared to be among women on the low-fat diet whose tumors did not respond to the presence of the hormone estrogen. The risk reduction was 15 percent in women who did respond to estrogen. Breast cancer that doesn't respond to estrogen is called estrogen receptor negative (ER-negative) and usually has a poorer outcome than ER-positive disease.

"These results suggest that an intervention aimed at reducing dietary fat consumption can reduce the risk of breast cancer recurrence," said principal investigator Rowan T. Chlebowski, M.D., Ph.D, of the Los Angeles Biomedical Research Institute in California. "Although further confirmation is needed, a low-fat diet may offer other health benefits, such as modest weight loss." Scientists note the difficulty of conducting clinical trials where very dramatic lifestyle changes are involved, but conclude that WINS produced very important results for future consideration. Funding for this study was provided by the NCI's Division of Cancer Prevention, The Breast Cancer Research Foundation and the American Institute for Cancer Research.