Breast Cancer Risk Factors
 The most important risk factors for breast cancer are:
- Increasing age (risk doubles
between ages 45 and 65)
- Previous breast cancer
in the same patient
- Family history of breast
cancer - particularly breast cancer in a woman's mother, sister,
or daughter
If blood relative (mother,
sister, or daughter) is pre-menopausal and has bilateral breast
cancer - risk is nine-fold
If blood relative is pre-menopausal
and has uni-lateral breast cancer - risk is three-five fold
If blood relative is post-menopausal
and has breast cancer - risk is two-fold
Less significant risk factors for breast cancer are:
- Carriers of genes BRCA1
and BRCA2 are very highly at risk. However, probably fewer than
1 in 20 women with breast cancer have these genes.
- Female descendants of
European Jews have a higher than normal risk
- Women with a family history
of cancer of the cervix, uterus or colon have a slightly increased
risk
- Early menarche (before
age 13)
- Late menopause (over age
52)
- Nulliparity (no pregnancies)
- First pregnancy over age
30 may slightly increase risk
- Obesity is said to be
a risk factor, but it may just obscure and delay discovery of
a breast mass
- Breast augmentation - Does not increase risk of breast cancer and does fall into a higher risk category, however, as a tumour would be more difficult to detect because mammogram cannot be performed as effectively. Strongly advised to have a pre-surgical mammogram as a baseline before having augmentation
- Oral Contraceptives - Most studies have shown no significant increased risk for breast cancer from oral contraceptive use, although there is evidence they may reduce risk for ovarian and uterine cancer. A few recent studies suggest a small increase in risk in specific subgroups of women who have mainly used older types of oral contraceptives which contained more estrogen than those commonly used today. The largest overall analyses show no significant increase in risk of breast cancer for women who take oral contraceptives when compared to women who do not take oral contraceptives. Modern pills contain less estrogen than those commonly prescribed 20 years ago. It may be that there is a very small increase in risk which would have to be balanced against what can for some women be a much greater risk of not taking the pill. Individual women should discuss this with their family physician at the time of renewing their prescription.
- Hormone Replacement Therapy (HRT)
- For menopausal symptoms, osteoporosis, cardiovascular disease, etc: Most studies have shown a 1.5x increased risk for breast cancer from HRT if taken for more than 5-10 years. There is evidence that HRT reduces ovarian cancer risk as well as risk of cardiovascular disease and osteoporosis (not osteoarthritis) in post-menopausal women. Any potential, as yet unproven, increased breast cancer risk from estrogen HRT must be balanced against the positive effects in reducing menopausal symptoms and decreasing risk of cardiovascular disease and osteoporosis.
- For women who have had breast cancer:
Present opinion is that HRT is not recommended for women with a previous history of breast cancer (except for a very few exceptions defined individually between the woman and her doctor).
- An injury to the breast is not associated with increased risk of developing cancer but on occasion draws attention to the mass.
- Calcium deposits
Abortion and Breast Cancer Risk
Delaying a first full term pregnancy, or not becoming pregnant at all, increases a woman's chance of developing breast cancer. A spontaneous or induced abortion does not independently increase a woman's chance of developing breast cancer. Prolonged lactation (breast feeding) seems to offer a weak protection from breast cancer.
Diet and Alcohol Consumption and Breast Cancer Risk
The role of diet in affecting the risk of breast cancer is still inconclusive, however, there are several large studies underway now to examine the importance of dietary fat (which may increase risk). The evidence that alcohol and cancer link is consistently found, however, its effect on increasing risk is not strong - risk is one and one-half to 2 fold.
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