The Key:
Early Detection
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The key to finding breast cancer is early detection, and the key to
early detection is screening: looking for cancer in women who have no
symptoms of disease. The best available tool is a regular screening
mammogram--x-ray
of the breast--coupled with a clinical
breast exam--by a doctor or nurse.
Mammography A mammogram
is an x-ray of the breast. Cancers that are found
on mammograms but
that cannot be felt (nonpalpable
cancers) usually are smaller than cancers that can be felt, and
they are less likely to have spread.
Mammography
is not foolproof. Some breast changes, including lumps that can be felt,
do not show up on a mammogram. Changes can be especially difficult to spot
in the dense, glandular breasts of younger women. This is why women of all
ages should have their breasts examined every year by a physician or
trained health professional.
~ A lump should never be
ignored just
because it is not visible on a mammogram.~
Two Kinds of Mammography:
Diagnostic and Screening
If a woman visits her doctor because of
unusual breast changes such as a lump, pain, nipple thickening or
discharge, or changes in breast size or shape, or has a suspicious
screening mammogram, the doctor often asks her to have a diagnostic
mammogram: an x-ray of the breast to help assess her symptoms. A
diagnostic mammogram is a basic medical tool, and it is appropriate for
women of any age.
This booklet discusses screening mammograms: x-rays that are used to
look for breast changes in women who have no signs of breast cancer. (Even
though the woman has no symptoms of breast disease, a diagnosis of breast
cancer can begin with a doctor checking a screening mammogram.)
What Are the Benefits of
Screening Mammography?
High-quality mammography is the most
effective tool now available to detect breast cancer early, before
symptoms appear--often before a breast lump can even be felt. Regularly
scheduled mammograms can decrease a woman's chance of dying from breast
cancer. For some women, early detection may prevent the need to remove the
entire breast or receive chemotherapy.
Who Benefits From Screening
Mammography?
Studies done over the past 30 years clearly show
that regular screening mammography significantly reduces the death rate
from breast cancer in women over the age of 50. Recent results from
studies show that regular mammography also reduces death rates from breast
cancer in women who begin screening in their forties.
The effectiveness of mammography seems to increase as a woman ages, and
the time it takes for benefits to emerge appears to take longer in younger
women.
Who Is at Average Risk for
Breast Cancer?
Simply being a woman and getting older puts you
at average risk
for developing breast cancer. The older you are, the greater your chance
of getting breast cancer. No woman should consider herself too old to need
regular screening mammograms.
Who Is at Higher Than
Average Risk for Breast Cancer?
One or more of the following
conditions place a woman at higher than average risk for breast
cancer:
- personal history of a prior breast cancer
- evidence of a specific genetic change that increases susceptibility
to breast cancer (See Gene Testing for Breast Cancer Susceptibility,
page 18.)
- mother, sister, daughter, or two or more close relatives, such as
cousins, with a history of breast cancer (especially if diagnosed at a
young age)
- a diagnosis of a breast condition that may predispose a woman to
breast cancer (i.e., atypical
hyperplasia), or a history of two or more breast biopsies for
benign breast disease (See Benign Breast Conditions and the Risk for
Breast Cancer, page 26.)
Also playing a role in a heightened risk
for breast cancer is breast
density. Women ages 45 or older who have at least 75 percent dense
tissue on a mammogram are at elevated risk. And a slight increase in the
risk of breast cancer is associated with having a first birth at age 30 or
older.
In addition, women who receive chest irradiation for conditions such as
Hodgkin's disease at age 30 or younger remain at higher risk for breast
cancer throughout their lives. These women require meticulous surveillance
for breast cancer.
These factors that increase cancer risk--risk
factors--do not by themselves cause cancer. Having one or more
does not mean that you are certain or even likely to develop breast
cancer. Even among women with no other risk factors except a strong family
history--for example, both a mother and a sister or two sisters with early
onset breast cancer--three-fourths will not develop the disease.
Clearly, there is much yet to be learned about what causes breast
cancer.
~ On the other hand, not
having any of the known risk factors
does not mean that you are "safe."
Most women who develop
breast cancer do not have a strong family
history of breast
cancer or fall into any special higher risk
category. ~
What Are the Limitations of
Screening Mammography?
Early detection by mammography does not
guarantee that a woman's life will be saved. It may not help a woman who
has a fast-growing cancer that has spread to other parts of her body
before being detected. Also, about half of the women whose breast cancers
are detected by mammography would not have died from cancer, even if they
had waited until the lump could be felt, because their tumors are
slow-growing and treatable.
False Negative Mammograms
Breasts of
younger women contain many glands and ligaments. Because their breasts
appear dense on mammograms, it is difficult to see tumors or to
distinguish between normal and abnormal breast conditions. As a woman
grows older, the glandular and fibrous tissues of her breasts gradually
give way to less dense fatty tissues. Mammograms can then see into the
breast tissue more easily to detect abnormal changes. About 25 percent of
breast tumors are missed in women in their forties, compared to about 10
percent of women older than age 50. These are called false
negatives. A normal mammogram in a woman with symptoms does not
rule out breast cancer. Sometimes a clinical breast exam by a doctor or
nurse can reveal a breast lump that is missed by a mammogram.
False Positive Mammograms
Between 5 and
10 percent of mammogram results are abnormal and require more testing
(more mammograms, fine needle aspiration,
ultrasound,
or biopsy),
and most of the followup tests confirm that no cancer was present. It is
estimated that a woman who has yearly mammograms between ages 40 and 49
would have about a 30 percent chance of having a false
positive mammogram at some point in that decade, and about a 7 to
8 percent chance of having a breast biopsy within the 10-year period. The
estimate for false positive mammograms is about 25 percent for women ages
50 or older.
Increased Cases of Ductal Carcinoma In Situ
(DCIS)
The increased use of screening mammography has increased
the detection of small abnormal tissue growths confined to the milk ducts
in the breast, called ductal
carcinoma in situ (DCIS). Doctors don't know which, if any, cases
of DCIS may become life threatening. Usually, the growth is removed
surgically, and radiation
treatment is often given.
How Mammograms Are
Made Mammography is a simple procedure. It uses a
"dedicated" x-ray machine specifically designed for x-raying the
breast and used only for that purpose (in contrast to machines used to
take x-rays of the bones or other parts of the body). The standard
screening exam includes two views of each breast, one from above and one
angled from the side. A registered technologist places the breast between
two flat plastic plates. The two plates are then pressed together. The
idea is to flatten the breast as much as possible; spreading the tissue
out makes any abnormal details easier to spot with a minimum of radiation.
The technologist takes the x-ray, then repeats the procedure for the
next
view.
The pressure from the plates may be uncomfortable, or even somewhat
painful. It helps to remember that each x-ray takes less than one
minute--and it could save your life. It also helps to schedule mammography
just after your period, when your breasts are least likely to be tender,
or at the same time each year, if you no longer have your period.
Although some women are concerned about radiation exposure, the risk of
any harm is extremely small. The doses of radiation used for mammography
are very low and considered safe. The exact amount of radiation needed for
a specific mammogram will depend on several factors. For instance, breasts
that are large or dense will require higher doses to get a clear image.
Federal mammography guidelines limit the radiation used for each exposure
of the breast to 0.3 rad.
(A "rad" is a unit of measurement that stands for radiation
absorbed dose.) In practice, most mammograms deliver just a
small fraction of this amount.
Specialized mammography facilities have experienced personnel as well
as modern equipment that is custom designed for mammograms. The
combination of good technology and expertise makes it possible to obtain
good-quality x-ray images with very low doses of radiation.
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