Preventing breast cancer with “Polish Diet” insight

Family history and genetic mutations can increase breast cancer risk profoundly – women in Ontario with a BRCA1 genetic mutation have up to 80 per cent risk of developing breast cancer at some point.

But a recent WCRI study suggests that diet and lifestyle factors can modify a woman’s risk of breast cancer, even if she has a genetic predisposition. The scientists compared the breast cancer risk of Polish and North American women who carry BRCA1 mutations. They found that the breast cancer risk for Polish women is about half that of the women in North America.

“Polish women with BRCA1 mutations still have a higher risk of breast cancer compared to women without mutations, but their risk is substantially lower than for North American women with the same mutation,” says Dr. Steven Narod, who led the study.

“It’s an exciting finding because it suggests that the choices women make can lengthen their lives and prevent cancer,” Narod says. “It means that genetic predisposition does not totally dictate whether a woman will develop cancer.”

Published in the International Journal of Cancer, the finding resulted from a collaborative study with Poland’s Pomeranian Medical University. The strongest of Narod’s many international collaborators, the partnership has yielded over 100 peer-reviewed articles on hereditary breast and ovarian cancer.

This productivity – and the insights it generates – is the result of the power of Narod’s patient data, extracted from a database of nearly 12,000 women with BRCA1/2 mutations.

“The volume of our patient data is unprecedented,” explains Narod. “Poland is very informed and proactive about the health benefits of genetic testing, and through our work, Ontarians are benefitting.”

Dr. Joanne Kotsopoulos

Dr. Joanne Kotsopoulos, an expert in modifiable risk factors for breast cancer, hopes to pinpoint the nutritional or lifestyle factor that reduces breast cancer risk in Polish BRCA1 carriers.

“We don’t yet know why Polish women have lower breast cancer risk, but we hope to find out,” says Kotsopoulos. “Then we’ll be able to give North American women more options, and less invasive options, to reduce their risk.”

If a woman has a BRCA mutation, prophylactic surgeries like mastectomy and removal of the ovaries are her best options to prevent cancer.

“Not every woman is going to choose surgery,” says Kotsopoulos, “particularly a woman who learns about her mutations at a very young age.”

Kotsopoulos is leading a separate study to examine diindolylmethane (DIM), a nutrient found in cruciferous vegetables, including broccoli, cauliflower and cabbage.

“The BRCA1 gene protects against breast and ovarian cancer, but in mutation carriers it’s not fully expressed,” says Kotsopoulos. “DIM seems to be protective, because it increases the gene expression, so it can do its job properly.”

“Cabbage is a staple in the Polish diet, and it’s naturally rich in DIM, so we’re excited to clarify the role of DIM in lowering breast cancer risk in Polish women.”

Dr. Steven Narod is a Tier 1 Canada Research Chair in Breast Cancer. With more than 550 peer-reviewed publications and an H-index of 84, he is amongst the world’s most influential breast cancer researchers. Narod is a senior scientist at WCRI and a University of Toronto professor in the Dalla Lana School of Public Health and the Department of Medicine.

Dr. Joanne Kotsopoulos was trained at Harvard, and holds a Cancer Care Ontario Research Chair in Population Studies. She is a scientist at WCRI and an assistant professor in the Dalla Lana School of Public Health at the University of Toronto.