Dietary change and reduced breast cancer events among women without hot flashes after treatment of early-stage breast cancer: subgroup analysis of the Women's Healthy Eating and Living Study.

Background: A diet high in vegetables, fruit, and fiber and low in fat decreased additional risk of secondary breast cancer events in women without hot flashes (HF-) compared with that in women with hot flashes (HF+), possibly through lowered concentrations of circulating estrogens.

Objective: The objective was to investigate the intervention effect by baseline quartiles of dietary pattern among breast cancer survivors in the HF- subgroup of the Women's Healthy Eating and Living Study.

Design: A randomized controlled trial compared a putative cancer prevention diet with a diet of 5 servings of vegetables and fruit daily in early-stage breast cancer survivors. Participants did not experience hot flashes at baseline (n = 896). We confirmed cancer status for 96% of participants approximately 7.3 y after enrollment.

Results: The study intervention achieved a large between-group difference in dietary pattern that, at 4 y, was not significantly different across baseline quartiles of dietary pattern. The intervention group experienced fewer breast cancer events than did the comparison group for all of the baseline quartiles. This difference was significant only in upper baseline quartiles of intake of vegetables, fruit, and fiber and in the lowest quartile of fat. A significant trend for fewer breast cancer events was observed across quartiles of vegetable-fruit and fiber consumption.

Conclusions: The secondary analysis showing the decreased risk in the HF- subgroup was not explained by amount of change in dietary pattern achieved. The difference was strongest in the quartile with the most putatively cancer-preventive dietary pattern at baseline.