Epidemiology and Prevention of Breast Cancer
Our research is concerned with the development of strategies to prevent breast cancer. Breast cancer is the most common cause of death from any cancer in women in most of the Western world, and the leading cause of death from all causes among women aged less than 50. Several factors have been identified that influence risk of the disease, including the characteristics of breast tissue on either mammography or histology, the number of pregnancies, alcohol, and body weight.
Mammographic density has consistently been shown to be one of the strongest known risk factors for breast cancer. Research is designed to improve our understanding of this risk factor, its measurement, its causes, and its significance as a biomarker of breast cancer risk. Current methods of measuring mammographic density are based on the 2-dimensional image. In collaboration with Dr M Yaffe (Medical Biophysics and Imaging Research, Sunnybrook Health Sciences Centre) we are now evaluating novel methods of measurement that assess the volume of the tissues in the breast that contribute to radiological density. Data collection has been completed and final calibration of the measurements and data analysis is in progress.
The breast is especially susceptible to carcinogenic events at early ages. In collaboration with Dr. M Bronskill (Imaging Research, Sunnybrook Health Sciences Centre), the goal of this research is to use magnetic resonance (MR) imaging to generate quantitative estimates of breast tissue composition in young women, and to examine factors likely to be associated with variation in these measurements, in particular the relationship between lifestyle factors and genes, hormones and growth factors that influence the growth and development of breast tissue.
Striking differences exist between countries in the incidence of breast cancer. The causes of these differences are unknown, but because incidence rates change in migrants, they are thought to be due to differences in lifestyle. The goal of this research is to identify the factors responsible for international differences in breast cancer risk, and to determine whether differences in breast tissue composition, and the hormonal and growth factors associated with them contribute to differences in risk.
Previous twin studies have shown that mammographic density is highly heritable. In collaboration with Drs Rommens and Paterson at the Hospital for Sick Children, we are now carrying a large scale multicentre family-based linkage study with whole genome scanning to identify the genetic variants that influence density.
In collaboration with Dr. L Martin, we have recently completed a multicentre randomized trial in women with high risk mammographic changes that tests the hypothesis that a 25% dietary reduction of calories from fat, with isocaloric replacement of carbohydrate, will reduce the incidence of breast cancer by approximately 35% over 10 years. The trial is now under analysis. Additional studies will examine the effect of this dietary intervention on plasma hormones and growth factors that may mediate environmental influences on risk of breast cancer.
Selected References:Link to Pubmed Publications
Boyd NF, Guo H, Martin LJ, Sun L, Stone J, Fishell E, Jong RA, Hislop G, Chiarelli A, Minkin S, Yaffe MJ.Mammographic density and the risk and detection of breast cancer. N Engl J Med. 2007 Jan 18;356(3):227-36.
Boyd NF, Martin LJ, Sun L, Guo H, Chiarelli A, Hislop G, Yaffe M, Minkin S. Body size, mammographic density, and breast cancer risk. Cancer Epidemiol Biomarkers Prev. 2006 Nov;15(11):2086-92.
Martin LJ, Greenberg CV, Kriukov V, Minkin S, Jenkins DJ, Boyd NF. Intervention with a low-fat, high-carbohydrate diet does not influence the timing of menopause. Am J Clin Nutr. 2006 Oct;84(4):920-8.
Boyd NF, Dite GS, Stone J, Gunasekara A, English DR, McCredie MR, Giles GG, Tritchler D, Chiarelli A, Yaffe MJ, Hopper JL. Heritability of mammographic density, a risk factor for breast cancer.. N Engl J Med. 2002 Sep 19;347(12):886-94.