Eating less fat may help patients with breast Ca live longer

February 1, 2007

Reducing dietary fat intake by about 35% reduced the risk of a relapse event in women with resected, early-stage breast cancer receiving conventional cancer management by about 24%, according to interim efficacy results from the Women's Intervention Nutrition Study, the first large-scale randomized trial to test whether a dietary intervention can improve outcome in women with breast cancer.

Reducing dietary fat intake by about 35% reduced the risk of a relapse event in women with resected, early-stage breast cancer receiving conventional cancer management by about 24%, according to interim efficacy results from the Women's Intervention Nutrition Study, the first large-scale randomized trial to test whether a dietary intervention can improve outcome in women with breast cancer.

Researchers assigned 2,437 women to either a dietary intervention to reduce fat intake or to a control group and followed them for 5 years. Women in the former group consumed approximately 33 fat g/day, while those in the latter about 51 g.

Not quite one tenth (9.8%) of the women in the intervention group had a relapse event, defined as either local, regional, distant, or ipsilateral breast cancer recurrence or new contralateral breast cancer, versus 12.4% in the control group (hazard ratio 0.76; 95% CI, 0.60–0.98; P=0.077 for stratified log-rank analysis and P=0.034 for adjusted Cox model analysis).

In addition, a 6-lb body weight difference existed between the two groups by the end of follow-up. "It is difficult to disentangle the role of dietary fat reduction from that of weight loss on the improved relapse-free survival seen in the dietary intervention group," say the authors of the editorial.

Finally and unexpectedly, sub-group analyses showed a stronger, but statistically insignificant, effect for dietary fat intake reduction on breast cancer recurrence in women with estrogen receptor-negative or progesterone receptor-negative tumors, which may have occurred by chance or which may suggest a possible adjuvant therapy for women with these tumors.

Chlebowski RT, Blackburn GL, Thomson CA, et al. Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women's Intervention Nutrition Study. J Natl Cancer Inst. 2006;98:1767-1776.

Thiébaut AC, Schatzkin A, Ballard-Barbash R, et al. Dietary fat and breast cancer: contributions from a survival trial. J Natl Cancer Inst. 2006;98:1753-1755.