SAN ANTONIO – (FRONTLINE MEDICAL NEWS) Losing weight and exercising may be an important key to good outcomes in some women with breast cancer – especially those with hormone receptor–negative tumors.

For women with tumors that are both estrogen and progesterone receptor negative, losing at least 5 pounds or 5% of total body weight decreased the 10-year risk of all-cause mortality by 64%, Dr. Rowan T. Chlebowski said at the San Antonio Breast Cancer Symposium.

Although it was a post hoc exploratory analysis, the subgroup findings suggest that a lifestyle intervention program could be an effective way to help increase a woman’s chances of surviving, said Dr. Chlebowski, chief of medical oncology at the UCLA Medical Center, Los Angeles.

“From a scientific standpoint, others will have to look at this post hoc analysis and decide whether the data warrant further investigation in a trial to confirm the findings,” he said. “But, on an operational basis, for a woman with breast cancer, there are so many other health benefits associated with this kind of weight loss. For example, this has been shown to significantly reduce the risk of progression from prediabetes to diabetes – and that is a very important health consideration for women with breast cancer.”

And obviously, he added, losing weight and getting active carry a myriad of other health benefits, all of which exert their own positive influences.

Dr. Chlebowski reported long-term follow-up data from the Women’s Intervention Nutrition Study ( WINS ). It enrolled 2,437 women from 1994 to 2001 who had been treated for early-stage breast cancer. The women, aged 48-79 years, were randomly assigned to a lower-fat dietary intervention group or to a control group that ate their regular diet. The intervention group met monthly with a registered dietitian and provided food journals. They were also encouraged to increase physical activity.

At the start of the study, both groups consumed similar amounts of calories from fat, about 57 g/day or 30% 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 g/day, compared with only a 5-gram/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 did the women in the control group.

But at the current follow-up (maximum of 20 years), there was no significant between-group difference in disease-free survival (17% deaths in the control groups vs. 13.6% in the intervention group), either in the entire group or in the subgroup of those with estrogen and progesterone receptor–positive tumors.

However, in the subanalysis of those who were hormone receptor negative, the difference was significant, with a 2-year survival advantage in the intervention group (14 vs. 12 years; hazard ratio, 0.64; P = .045).

The findings may be particularly important for women with triple-negative tumors, since, Dr. Chlebowski noted, data suggest that about 73% of women with ER/PR-negative cancers are anticipated to be triple negative.

He said the protective mechanism is not entirely clear, but may be due more to total calorie decrease than to decreasing fat alone – despite fat’s proclivity to increase total estrogen levels.

“Estrogen does not seem to be the driver here,” he said. Instead, the benefit may have more to do with controlling growth factors, inflammation, and glucose levels.

He did point out that the data are a bit old, and that only 6% of women in the study received tamoxifen. But he stressed that further investigation could refine the results and that, in any case, controlling weight confers a multitude of benefits.

Dr. Chlebowski had no disclosures. The WINS study was sponsored by the National Cancer Institute.

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