"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?"
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:
age
race
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
These factors seem to predict a woman's rest fairly
accurately (20, 21).
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.
Download the Gail Model Breast Cancer Risk Assessment
Calculator (note - this may take from 2-10 minutes
(964 KB) depending upon your connection speed and
Internet traffic.
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. |
