A fairly stringent low-fat diet in women with early-stage breast cancer resulted in a very impressive 42% risk reduction in cancer recurrence or death in women with hormone receptor-negative tumors, according to the second follow-up data analysis from the Women's Intervention Nutrition Study (WINS) presented at the December 2006 29th Annual Breast Cancer Symposium held in San Antonio.

The study was started in 1994 and is the first large scale randomized clinical trial which, so far, shows that dietary changes can strongly affect outcomes in women with breast cancer who also receive conventional treatment. The findings are very exciting, and are holding up through a second interim analysis, but plans call for three more years of follow-up to confirm the results. The next planned re-analysis of the data is scheduled towards the end of 2007. In addition, another confirmatory study is planned to start in early 2007 by the Canadian National Cancer Institute and other smaller studies are underway.

WINS was a multi-center trial involving almost 2500 women, ages 48 to 79, who were randomized either to a dietary intervention arm or a control group who ate their usual diet. The randomization was performed after patients underwent standard treatment for early-stage breast cancer. The intervention arm was closely directed by physicians and dieticians, and involved reducing fat consumption from about 57 grams per day in the regular diet control group to an average of 24 grams per day in the intervention arm. The intervention arm resulted in an average 6 pound weight loss after 5 years. Follow-up for this study is now approaching 6 years.

The recurrence and death rate amongst the entire group reached only borderline statistical significance with an approximate 15% risk reduction. However, among the 362 patients who had hormone receptor (estrogen and progesterone) negative breast cancer, the overall mortality was 6% in the intervention arm and 17% in the control group. Similarly, the combined death or recurrence rate was 9.8% in the intervention arm, compared to 24% in the control group. This represents a 42% risk reduction of recurrence or death.

Although the mechanism by which this occurs is not clear, the most likely reason is an effect on insulin, insulin-like growth factors and moderation of the inflammatory cascade. In other words, it is likely related to how sugars are processed and inflammation is handled by your body.

At this time, although confirmation of these results is pending, a motivated woman could consider following the WINS diet as published in J. Am. Diet. Assoc. 2004;104:551. It is not clear if partial benefit is derived from a low fat diet that is not quite as stringent as the one tested. Therefore, in order to approach the reported results, one has to be very committed to a very significant dietary modification.

If these results are confirmed in breast cancer, it is very tempting to speculate that this effect may be true in other cancers as well, especially hormonally related or mediated cancers like endometrial and ovarian cancer.