Celeste Robb-Nicholson, M.D.
The release of updated breast cancer screening guidelines from
the United States Preventive Services Task Force (USPSTF) in
November 2009 sparked a heated national debate about how best to
use screening mammography. Many of my patients are still asking
questions about their own breast cancer screening strategies.
The USPSTF asked an expert panel to re-examine the scientific
evidence on the effectiveness of breast cancer screening in women
ages 40 and older who are at average risk for developing breast
cancer. The panel reviewed clinical studies published since
guidelines were last updated, in 2002, and it applied new methods
for analyzing all the data. It concluded that the use of
mammography, clinical breast exam, and breast self-exam should be
scaled back. The most controversial recommendations were to delay
routine screening mammography until age 50 (previous guidelines
recommended mammography screening every one to two years for
women in their 40s) and to screen women in their 50s and 60s only
once every two years, rather than annually, as the earlier
guidelines had advised.
Many physicians, researchers, health organizations, advocacy
groups, politicians, and individual women reacted with concern to
the guidelines, and for good reason. Breast cancer is the second
leading cause of cancer death among women in the United States.
According to the most recent calculations, 192,370 cases of
invasive breast cancer were diagnosed in 2009, and 40,170 women
died from the disease. Mammography screening has been the
foundation of breast cancer prevention in this country since the
1980s. Since 1990, breast cancer mortality has been decreasing at
a fairly steady 2% per year, and many experts attribute that
decrease to a combination of regular screening mammography and
Summary of the USPSTF recommendations on screening for
The USPSTF recommends against routine screening
mammography in women in their 40s who aren’t at
increased risk for breast cancer. The decision to
start mammography before age 50 should be based on a
woman’s risk for breast cancer and personal
preferences about the benefits and harms.
The USPSTF recommends mammography every two years for
women ages 50 to 74.
Current evidence is not sufficient to assess the
effectiveness of screening mammography in women ages
75 and over.
Current evidence is not sufficient to assess the
effectiveness of clinical breast exam in addition to
The USPSTF recommends against clinicians teaching
women breast self-examination.
Current evidence is not sufficient to assess the
additional effectiveness of digital mammography or
breast MRI instead of film mammography for breast
Source: Annals of Internal Medicine, Nov. 17,
2009, pp. 716–726. The recommendations may also be viewed
online, at /brcascreen.
Why review an effective screening program?
The USPSTF is an independent group of experts appointed by the
government to review the evidence for clinical practices such as
screening tests and treatments. A doctor makes decisions based on
what’s best for an individual patient, while decisions about a
general screening program are made on statistical grounds: does
it pay off in saved lives? When the USPSTF reviewed breast cancer
screening in 2002, there already were questions about screening
mammography for women in their 40s, which has been a subject of
debate for decades. The task force was prompted to take another
look by new clinical studies and new statistical methods
developed since 2002.
The panel reviewed all clinical trials of screening mammography
with more than 10 years of follow-up. They found that starting at
age 40, screening mammography reduces breast cancer mortality
overall by 15% — about the same as in 2002. But this time, the
panel also tried to determine how the benefits of screening
(lives saved) stacked up against the harms, such as
false-positive results, which can lead to unnecessary testing,
biopsies, and psychological distress.
Lacking enough clinical data to assess harms, the panel used
statistical models, which suggested that screening women starting
at age 40 would reduce breast cancer deaths by only a modest
amount, compared with screening starting at a later age. The net
benefit for women in their 40s is small because breast cancer is
less common in this age group. These women also show more false
positives, because their breasts are denser, making cancers
harder to spot. To avoid one breast cancer death, 1,904 women in
their 40s would need to be screened. In women in their 50s, one
life would be saved for every 1,339 women screened, and for those
in their 60s, screening just 377 women would yield one life
saved. According to the USPSTF’s model, screening women in their
40s for breast cancer does not make good public health sense
because there is no net benefit: the number of deaths prevented
is too small, and the potential harm from false positive test
results is too great.
Besides false positives, the USPSTF panel also considered another
sort of harm: the possibility of detecting and treating early
breast cancer that wouldn’t adversely affect a woman during her
lifetime. In older women, breast cancer may not shorten life span
— as, for example, in many cases where a woman has another
life-threatening condition, such as cardiovascular disease. These
women could suffer the harms of undergoing unnecessary breast
cancer treatment. The USPSTF recommended that the decision about
mammography in an older woman should be based on her overall
health, other illnesses, and her willingness to have more tests
and treatments for a breast cancer that may not shorten her life.
The panel also re-evaluated the recommended interval for breast
cancer screening, which was previously set at one year. The panel
found that mammography every two years in women in their 50s and
60s would avert 70% to 90% of breast cancer deaths averted with
annual screening, which is twice as expensive and causes twice as
many harms. So the USPSTF concluded that mammography every two
years in this age group maximizes the potential benefits and
minimizes the harms.
The panel concluded that there weren’t enough data to determine
whether clinical breast exam (examination of the breasts by a
clinician) is useful. It also determined that breast
self-examination is not worth teaching to patients, because it’s
not standardized and leads to many false-positive tests. Digital
mammography is gradually replacing film mammography, and breast
MRI is increasingly used to screen high-risk women. However, the
panel concluded that there weren’t enough studies to justify a
recommendation for more general use of these methods in breast
Debate not over
The 2009 guidelines were released without much warning in the
middle of a public health care debate. To many people, that made
questioning the wisdom of yearly mammograms in women in their 40s
seem like a political decision. It created a sense of mistrust
and fears of rationing. But this is a medical issue, not a
political one. Researchers and scientists constantly re-evaluate
clinical practices as evidence accumulates. That’s how science is
done, and we need scientific evidence to determine how best to
use technology to improve women’s health.
Breast cancer and imaging experts have weighed in for and against
the revised guidelines. Advocates welcome a more cost-effective
approach to breast cancer screening and emphasize the potential
to reduce unnecessary biopsies and psychological stress.
Opponents point to a falling breast cancer death rate that’s due,
in part, to annual screening mammography. Some reject the
statistical models used by the USPSTF. Others worry that
increasing the screening interval will cause some women to
neglect routine screening altogether. For some, the harms of
screening simply do not outweigh the fears of missing a breast
cancer. The debate will surely continue.
For now, this is what I’m telling my patients:
Talk to your clinician about the implications of the
recommendations for you. Physicians are not obliged to
discontinue or cut back on screening.
The revised guidelines apply to women at average
risk of developing breast cancer. Know your own risks and
work with your clinician to develop a screening strategy
that’s right for you.
If you’re in your 40s, you’re not prohibited from having
screening mammography. The USPSTF recommends that you make an
informed decision based on your personal preferences and
medical history as well as the increased risk of a
false-positive result and further testing.
If you’re in your 70s, have a frank discussion with your
clinician about the benefits and harms of breast cancer
screening. If you’re healthy and active, it may be in your
best interest to continue screening. But if you have a
limiting chronic illness, it may not be worth your time,
energy, and resources to find or treat a cancer that may well
not affect how long you live.
I think breast self-examination is still a good idea. You
should be familiar with the architecture of your breasts,
since you may be the first person to detect a change.
The USPSTF guidelines remind us that where breast cancer
screening is concerned, one size (or frequency) doesn’t fit all.
As we learn more about the molecular and genetic basis of breast
cancer, we will improve our ability to identify the women most
likely to benefit from screening as well as those for whom the
risks outweigh the benefits. The balance between benefits and
harms may also shift as digital mammography takes the place of
The practice of annual mammography in women starting at age 40 is
unlikely to change overnight, and many organizations will
continue to recommend it. But we should be prepared for an
ongoing debate that includes public discussion about what we
expect from breast cancer screening, how much disease we want to
detect and treat, what we think about disease that “may not
matter” in terms of longevity — and how much, individually and as
a society, we are willing to pay for screening.