Diet and Breast Cancer Prevention Trial

The long term goal of this trial is to determine if intervention in subjects with extensive mammographic densities (a risk factor for breast cancer) with a low fat-high carbohydrate diet will reduce the incidence of breast cancer by 37%. We propose to meet this goal by carrying out a randomized multi-centre trial of dietary intervention in subjects at increased risk of breast cancer that is now in progress. The method used is to recruit subjects with extensive mammographic densities and enrol them in a randomized trial in which they receive one of two kinds of dietary counselling. A control group receives general advice about nutrition but is not counselled to change their intake of dietary fat or carbohydrate, and an intervention group is given intensive counselling to reduce their intake of total fat to a target of 15% of calories and increase intake of carbohydrate to maintain intake of total calories. Recruitment to this trial has been in progress in Toronto, Hamilton, London and Windsor since 1991, and in Vancouver since 1994, and all of the 4,615 subjects required for the trial were recruited by November 1998. The trial is explanatory in that it seeks to determine if there is a biological effect of dietary fat reduction in terms of a reduction in breast cancer incidence. To meet this goal we will select as participants highly motivated subjects who are at increased risk of breast cancer, provide them with a high level of assistance in making a dietary alteration, follow them carefully to ensure the correct identification of subjects who develop breast cancer, and analyse the results both according to intention to treat and dietary compliance. This trial does not attempt to assess directly the possible effects of dietary counselling on the health of the general public. II Specific Aims 1. To recruit 4,615 Canadian women with extensive mammographic density and to enrol them in a randomized trial of dietary fat reduction and follow up until 2006. 2. To compare in the control and intervention groups of this trial the incidence of breast cancers, as well as other histological changes in the breast tissue of patients undergoing surgical biopsy of the breast. 3. To determine if a reduction in dietary fat intake will reduce either the proportion of the breast area occupied by radiological signs of density or the total quantity of density.