Background: Preclinical and observational studies suggest a relationship between dietary
fat intake and breast cancer, but the association remains controversial. We carried out a
randomized, prospective, multicenter clinical trial to test the effect of a dietary intervention
designed to reduce fat intake in women with resected, early-stage breast cancer receiving
conventional cancer management. Methods: A total of 2437 women were randomly
assigned between February 1994 and January 2001 in a ratio of 40: 60 to dietary …

Chleblowski et al.(1) recently reported an interim analysis of the Women's Intervention
Nutrition Study trial and concluded that a reduction in dietary fat intake may influence
relapse-free survival following breast cancer. This effect was observed mainly in the
subgroup of patients with previously diagnosed hormone receptor–negative tumors. The
accompanying Editorial (2) noted that the study's conclusion is contrary to much of the
literature and raised the possibility that the analysis may have been confounded by either …