Should I Be Worried About Breast Cancer?
Frederick R. Jelovsek MD, MS
"Should I be worried about breast cancer? I am 26 and my maternal aunt died of breast cancer at the age of 46. I have fibrocystic breast and I am taking Loestrin® 1.5/30 birth control pills?" Joy
Hardly a month goes by that we do not hear about a new risk factor for breast cancer. It is very difficult to know however, how much each factor changes your risk. Is each risk factor additive? Does the risk go up a few percent or by quite a lot? These can be difficult questions to answer.
Most women are aware that a family history of breast cancer can increase your risk but they also think that any type of cancer in the family makes you more at risk. This is not true. Even with breast cancer, it is only 1st degree relatives (sister, mother, daughter) that matter. There is a tendency especially among young women to overestimate their risk of breast cancer and also to overestimate how much their risk can be reduced by screening mammograms (1). They also tend to underestimate their risk for heart disease and this is where such a misperception of risk can harm you (2).
Is the use of birth control pills a risk for breast cancer?
Most studies have not shown a risk of breast cancer with birth control pill use except in older women who took high dose birth control pills before 1975 (3). Oral contraceptives (OCPs) actually decrease the incidence of benign breast disease (4).
In women who have a positive family history of breast cancer, the question of whether taking birth control pills raises cancer risk has been looked at (5). They found that with the advent of lower dose pills, birth control pill use after 1975 was not associated with breast cancer beyond the risk of having a mother, sister or daughter with breast cancer.
How does my family history of breast cancer make me at risk?
Having a grandmother or an aunt with breast cancer does not raise a woman's risk for cancer, believe it or not! Only first degree relatives such as a mother, sister or child with breast cancer raises the risk (6).
If a woman has more than one first degree relative with a history of breast cancer, her risk goes up. With no family history (mother, sister, child) of breast cancer, a woman's overall lifetime risk is about 8%. With one such relative (first degree), the lifetime risk is 14%; with two such relatives the lifetime risk is about 20% (7).
Does fibrocystic breast disease or any other benign breast disease raise my risk of breast cancer?
Benign breast disease has been noted to be a risk factor for breast cancer in some studies (8, 9), but not in others (10). The relationship is complex because fibrocystic disease makes breasts dense. Dense breasts often have hyperplasia of breast cells and sometimes the hyperplasia is atypical in structure. When it is, atypical hyperplasia is a very strong risk.
When you eliminate atypical breast hyperplasia, fibrocystic disease does not seem to be associated with breast cancer (11). In the statistical risk prediction models, the factor that is predictive is how many previous breast biopsies a woman has had. In other words, if fibrocystic breasts end up having suspicious areas requiring a biopsy, then they become a risk factor for breast cancer.
What other factors could put me at risk for breast cancer?
Through various scientific studies, many other factors have been identified as being associated with breast cancer. They are not causes. When looked at in isolation they may turn out to be present more often in women who develop breast cancer than in women who do not.
Increased dietary fat (12), lack of certain vitamins (13) and alcohol (14) on a daily basis have been cited as risks. Reproductive history such as delayed childbearing (15) and age at onset of menses and menopause have for many years been identified with increased incidences of breast cancer (16). Even working at night has been found to raise a woman's breast cancer risk (17).
When all of these factors are lumped together, many turn out statistically not to be predictive because they are somehow related to the other factors (18). Minor risk factors drop out of statistical models when the strong predictors are also in the model. This is a mathematical way of saying what are the important things to worry about.
If I am at increased breast cancer risk, are my chances of developing breast cancer 50%, 80%, 100% or what?
The best estimates for a woman's breast cancer risk come from a mathematical model developed by Dr. Gail (19). While there are many factors that have been associated with increased risk, the ones that give the best estimate are:
- number of 1st degree relatives with breast cancer
- age at first menstrual period
- age at first delivery of a child
- number of previous breast biopsies
- previous history of atypical ductal hyperplasia on breast biopsy
- past history of ductal carcinoma in situ or lobular carcinoma in situ
To assess your own risk, you may want to use the risk assessment software based upon the Gail model. The software asks about 10 questions and gives you an estimate of your risk of cancer of the breast over the next five years and your cumulative, lifetime risk of developing such a cancer.
You will notice that the model does not ask about use of hormonal replacement therapy or birth control pills. It does not ask about aunts, grandmothers or other more distant relatives with breast cancer.
It is not that these factors do not have a very small degree of risk, but rather that when the above Gail model factors are taken into consideration, there is no additional risk prediction from HRT, OCPs or family history of 2nd degree relatives.
Also, remember to perform a self-breast exam every month to ensure that any potential problems can caught before it is too late.
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