Letters Section Editor: Robert M. Golub, MD, Senior Editor.
In Reply: Drs Lagiou, Trichopoulos, and Adami ask whether the nearly significant 9% lower breast cancer incidence in the intervention group of the WHI Dietary Modification Trial should be attributed to the lower fat intake or to the modest reduction in body weight. To examine the effect of the low-fat dietary pattern intervention on breast cancer risk while controlling for change in body weight, we added change in body weight as a time-dependent control variable (defined in any follow-up year as the change in body weight from randomization to the preceding annual visit) to the Cox regression analyses that generated the original hazard ratio estimate. This analysis generates a hazard ratio of 0.91 (95% confidence interval, 0.83-1.01), identical to that without controlling for change in body weight. Hence, this analysis does not support a role for the lower body weight among intervention vs control group women in explaining the lower breast cancer incidence in the intervention group.
Prentice RL, Caan B, Aragaki A, Chlebowski RT, Patterson R. Low-Fat Diet and Risk of Breast Cancer—Reply. JAMA. 2006;296(3):278-279. doi:10.1001/jama.296.3.279-a