Factors such as breast
density and women's values should be considered when deciding frequency
of mammograms
Mammograms should not be done on a one-size
fits all basis, but instead should be personalized based on a woman's
age, the density of her breasts, her family history of breast cancer
and a number of other factors including her own values. That's the
conclusion of a new study in the July 5 issue of the Annals of Internal
Medicine.
The study is likely to be controversial as it challenges the current
guidelines from groups such as the American Cancer Society and the
US Preventive Task Force which recommend one frequency - screening
every 1 or 2 years ? for all women.
No one doubts that mammograms save lives but there is disagreement
over when women should begin getting mammograms and how often they
should get them: should they be done every two years starting at
50 or every year starting at age 40?
"Most guidelines use age as the determining factor in when,
and how often, a woman should get a mammogram," says Steve
Cummings, M.D., of the San Francisco Coordinating Center at the
California Pacific Medical Center Research Institute - part of the
Sutter Health network - and the lead author of the study. "What
our study shows is that other factors, particularly breast density,
are just as important, if not more so, in helping a woman decide
what is most appropriate for her. We show that mammography should
be personalized. The best interval for you depends on your age,
breast density, and other risk factors for breast cancer."
Many studies have shown that the denser a woman's breast on a mammogram,
the greater her risk of breast cancer. Low density or fatty breasts
means a low risk of breast cancer while high density or less fatty
breasts means a higher risk.
Using data from the Breast Cancer Surveillance Consortium and Surveillance
Epidemiology and End Results of the National Cancer Institute. The
researchers developed a model to compare the lifetime costs and
health benefits for women who got mammograms every year, every two
years, every three to four years, or who never got a mammogram.
The women all had different risk factors for breast cancer and the
model assumed that they all began as healthy but could subsequently
fall into one of six different categories: remain healthy, develop
ductal carcinoma in situ (DCIS), develop localized invasive breast
cancer, regional invasive breast cancer, distant invasive breast
cancer, die from invasive breast cancer, or die from causes other
than breast cancer.
The authors used the data to estimate how many extra mammograms
over 10 years would be needed to prevent one death from breast cancer
in those having mammograms once every three to four years compared
to no mammograms, and in those having mammography every two years
compared to once every three to four years. They also estimated
the costs for each frequency of mammography for each year of quality
life gained.
"Our analysis suggests that women with a first-degree relative
with breast cancer or with a history of a breast biopsy should have
an initial screening mammography at age 40,'' said study co-author
Karla Kerlikowske, M.D., MS, an expert in mammography at the University
of California, San Francisco.
"For women age 40 to 49 with high breast density and with
either a first-degree relative with breast cancer or a prior breast
biopsy, the benefits versus harm for performing mammography every
two years is similar to screening an average-risk woman in her 50s.
This amounts to about 20 percent of women in their 40s. For women
age 40 to 49 without these risk factors, it is reasonable to wait
until age 50 to start mammography screening."
Lead author Dr. John Schousboe of the Park Nicollet Institute and
the University of Minnesota in Minneapolis, Minnesota, noted that
yearly mammography was not cost-effective in that it was expensive
and yielded little additional health benefits compared to mammography
once every 2 years, regardless of breast density or other risk factors.
The frequency of mammography is not just a clinical decision, he
said, it also has a strong emotional component. "Feelings matter
too. For example some mammograms produce a 'false positive' result
and these can cause a lot of worry for a woman. The effect of mammograms
on a woman's quality of life should be considered in her decision
about when to be screened. If mammograms reassure you, then more
often is ok. If they worry or bother you, then less frequent may
be ok."
Dr. Susan Love, President of the Dr. Susan Love Research Foundation
commented that "this is exactly the type of analysis that we
need if we are going to help women and doctors figure out the best
schedule of screening for them. Personalized medicine extends beyond
treatment to risk definition and appropriate screening schedules.
"
The study was supported by grants from Eli Lilly and Co. and the
Da Costa Family Foundation for Research in Breast Cancer Prevention
at CPMC. However, the sponsors had no role in the design, data collection,
analysis or interpretation of the study.
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