According to this study:
* Reducing dietary fat may reduce the risk of breast cancer recurrence.
* It may be even more effective in women with hormone-receptor negative tumors.
Postmenopausal women receiving conventional treatment for early-stage breast cancer may decrease their risk of disease recurrence if they lower their dietary fat intake, according to the Women's Intervention Nutrition Study.
Researchers studied 2,437 women with early-stage breast cancer who'd undergone appropriate surgical tumor removal, radiotherapy or chemotherapy (or both), and when appropriate, therapy with tamoxifen. Investigators randomized participants to a dietary intervention (n = 975) or a control group (n = 1,462). The primary end point was relapse-free survival, with relapse defined as any recurrence of breast cancer, including in the other breast.
The goal for the intervention group was to reduce fat intake to 20% of total calories consumed. They were given an eating plan that "included self-monitoring, [horizontal ellipsis] goals setting, modeling, social support, and relapse prevention and management." Women in the control group had one visit with a dietitian and contact with a dietitian every three months.
Women in both groups originally consumed about 57 g of fat per day. At 12 months, those in the intervention group had cut fat intake by an average of 24 g per day, compared with 5 g per day in the control group. Women kept their fat intake consistent throughout the rest of the trial. After five years of follow-up, intervention-group participants weighed an average of 6 lbs. less than those in the control group.
Relapse occurred in 9.8% (n = 96) of the intervention group, compared with 12.4% of controls (n = 181). For those in the intervention group, the risk of relapse was 24% lower than for those in the control group.
A 42% risk reduction occurred among women on the low-fat diet whose tumors were estrogen-receptor (ER) negative, compared with a 15% reduction in those with ER-positive tumors, although there was no difference in the rate of overall survival.
An accompanying editorial points out possible study limitations: the possibility of variations in treatment between the two groups, as well as the benefit that might be conferred by the lower level of adiposity in the women who had controlled their fat intake. However, the authors of the editorial concluded that the study contributes valuable data to the ongoing controversy over dietary fat's impact on breast cancer. -HL
Chlebowski RT, et al. J Natl Cancer Inst 2006;98(24):1767-76; Thiebaut ACM, et al. J Natl Cancer Inst 2006;98(24):1753-4.