Breast Cancer – Risk Factors
Please keep in mind when reading about or discussing risks of anything, that none of it is cast in stone. Depending on which studies you read, you can often find two that will contradict each other and say completely different things. Avoidance of known or suspected risks is no guarantee that you will live your life disease- or cancer-free. Life is not like that.
A woman’s lifetime risk of developing breast cancer is 1 in 8, or 12.3%. This should be further clarified by breaking it down as to risk at different ages, because the risk of developing breast cancer increases with advancing age. Breast Cancer risk in US women has been calculated by age group as follows:
Age 30 0.44% (1 in 227)
Age 40 1.47% (1 in 68)
Age 50 2.38% (1 in 42)
Age 60 3.56% (1 in 28)
Age 70 3.82% (1 in 26)
Data from www.cancer.gov/cancertopics/factsheet/detection/probability-breat-cancer
There have been many factors identified as associated with a higher risk of developing breast cancer. Inheritance of the genes BRCA1 and BRCA2 significantly increase ones’ risk; only 5 to 6 % of all breast cancers are caused by the inheritance of these susceptibility genes, however. The risk of breast cancer is doubled by having a first-degree relative with breast cancer, and tripled if one has two affected first-degree relatives. The risk is higher if the affected relative was diagnosed before menopause. Having had breast cancer yourself increases your risk of developing cancer in the other breast.
Having dense breasts increases the risk of breast cancer. This is a factor that is difficult to measure, however, because mammography reports rarely report an estimate of density outside of a qualitative comment. Hormone therapy may be related to an increase in density of breasts, although medical research is not conclusive about breast cancer risk in women with naturally higher estrogen levels.
Established risk factors for breast cancer include those above, as well as being female (women have breast cancer 100 times more frequently than men), being white in the US (although research hasn’t teased out how much of this is genetic as opposed to due to lifestyle factors and access to health care), and obesity in postmenopausal women. Premenopausal women who are obese (BMI>30 kg/m2) have been found to have a lower risk of breast cancer, the explanation of which remains unclear to researchers. Being taller has been found to be associated with a higher risk of breast cancer.
Having an early menarche (start of periods) or a late menopause has been related to higher risk of breast cancer, as has never having children. These are all related to having more menstrual cycles over a lifetime. Having your first baby when older than 30 increases risk; this is said to be due to the proliferative stimulation place on the breast cells that are fully developed and possibly more prone to damage than a younger women’s breast cells. The news has recently been trumpeting that taller women have a higher risk of breast and other cancers. There are theories involving various growth factors of why this is so, but time will tell if this association noted in data from the Women’s Health Initiative in the 1990s is confirmed.
Lifestyle factors are associated with an increased risk of breast cancer and other disease. Alcohol consumption, starting with amounts as low as three to six drinks per week, has been shown to increase breast cancer risk. Night shift work has been shown to be a probable risk factor for cancer. Some studies have shown smoking is a risk factor, especially in younger women and long-term smokers.
What’s the good news in all of this? Well, physical activity has been shown to lower risk. A healthy lifestyle of nutritious food, minimal alcohol, regular exercise can lower risk. There are no guarantees in life, but living as well as we can, physically and mentally, means our quality of life today is the best we can make it.