Hormone therapy at menopause, too much alcohol, obesity, late pregnancy, absence of pregnancy or early puberty are all lifestyle-related factors that increase the risk of developing breast cancer.
A new study published in The Lancet says that genes are responsible for only a small proportion of breast cancers and lifestyle has a greater influence.
Research was done on 7,160 women with breast cancer and 10,196 women in good health at Oxford University, UK. It ignored two known genes, BRCA 1 and BRCA 2, which increase the risk of cancer.
The study looked at whether various factors related to lifestyle interfered with genetic variations in disease development.
Study co-author Dr. Jane Green commented: "This study provides another piece in the jigsaw, helping us to understand how genes and lifestyle affect breast cancer risk. Genes account for only a small proportion of breast cancers and for most women the main risk factors remain the lifestyle factors such as childbearing, use of HRT, obesity and alcohol consumption. The good news is that some of these are modifiable, so by changing their behaviour women can alter their risk of breast cancer."
Dr. Steven A. Narod, Women’s College Research Institute, Toronto, said: "The challenge of breast cancer prevention remains with us and new approaches are sorely needed."