Workshop report: identification of research needs breast cancer etiology

A workshop to evaluate the scientific evidence for the etiologic associations between modifiable lifestyle and environmental risk factors and to identify areas for future research in breast cancer etiology was sponsored jointly by the Canadian Breast Cancer Initiative and the Canadian Breast Cancer Research Initiative in May, 2001. Reviews of the scientific evidence in these topics were commissioned and an expert panel convened to consider the reviews and make recommendations for research. The panel concluded that there was substantial evidence to proceed with additional research in several areas of breast cancer etiology. Particular support for future research for several lifestyle and environmental risk factors including alcohol, diet, physical activity, anthropometric factors, hormonally active agents and occupational exposures was identified. Several emerging hypotheses for breast cancer etiology were also considered and recommendations made in these areas. Specific areas for future consideration included: insulin-like growth factors, pharmaceuticals, viruses, psychosocial factors, and functional polymorphisms. The panel also identified common themes for future research including: studies of exposures across the life cycle; research in populations with unusual exposure levels; consideration of effect modification; development of improved exposure assessment methods and use of intermediate endpoints; separation of disease subtypes by hormone receptor status, stage and tumour markers; and consideration of biological mechanisms in breast cancer etiology.