Trial Information

An Explanatory Clinical Trial of Breast Cancer Prevention

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.