Better breast cancer survival for postmenopausal women who are less overweight and eat less fat. The Iowa Women's Health Study.

Background: The authors sought to determine whether prediagnosis obesity, body-fat distribution, and dietary intake of fats, antioxidants, and fiber may be related to survival after the diagnosis of breast cancer.
Methods: The mortality rates of 698 postmenopausal patients with unilateral breast cancer in a large cohort study were analyzed. Body-mass index, waist-to-hip ratio, and food-frequency data were collected by questionnaire within 6 years before breast cancer was diagnosed.
Results: Adjusted for age, women in the highest tertile of body mass index had a 1.9-fold higher risk (95% confidence interval = 1.0-3.7) of dying after breast cancer than those in the lowest tertile; adjusted for other prognostic variables (age, smoking, education level, extent of breast cancer, and tumor size), this relative risk was 1.5 (95% CI = 0.7 to 2.9). Waist-to-hip ratio was not related to risk of dying nor was intake of fiber or several dietary antioxidants. Independent of other prognostic variables, risk of death after breast cancer was statistically significantly elevated, with a relative risk greater than 2.0 for the highest tertiles of total fat, saturated fat, and monounsaturated fat intake, expressed as grams per day. An adjustment for energy intake, which also was associated positively with fatality, weakened these associations somewhat.
Conclusions: Although clinical trials are required, these findings support the hypothesis that a high fat intake is associated with reduced survival of postmenopausal women with breast cancer and suggest that women with breast cancer should consider limiting their intake of fat.