Screening mammography can reduce the risk of advanced breast cancer in elderly
women, according to a University of California, San Francisco study.
The study, published in the February 2000 issue of the American Journal of
Medicine, found that women who undergo screening mammography in their 70s had a
43 percent less chance of developing metastatic or advanced breast cancer than
women who were not screened, suggesting that mammography is effective in these
women. The reason: screening catches the cancer in the early stages, said
Rebecca Smith-Bindman, MD, lead author and UCSF assistant professor of
radiology, epidemiology and biostatistics. Metastatic or advanced cancer means
that the tumors have spread to other parts of the body.
“No one really knows when to stop screening,’ Smith- Bindman said. “This study
provides the first evidence that mammography is beneficial for these women and,
given what we know about mammography, it’s not surprising.”
Although mammography has been shown to be effective in women ages 50 to 69
years old, there has been little evidence that is effective in older women.
Though eight randomized trials of the effectiveness of screening mammography
have been conducted in the past, only two included women older than 69 years
old. Both trials were small, lacking statistical power to provide meaningful
results, according to the study. In addition, women 75-years or older were not
included in any of the trials.
The study looked at 690,993 women, aged 66 to 79 years old, who were California
Medicare beneficiaries from January 1992 to December 1993. It found that among
the 300,000 plus women who were screened, their rates of advanced breast cancer
were 43 percent lower than the rates of women who were not screened.
“Metastatic breast cancer reflects a missed opportunity to treat the disease
early before it spreads,” Smith-Bindman said. “Screening finds the disease
early when it is potentially curable. That’s the whole point of screening.”
Breast cancer mortality rates have declined in the past decade for women ages
50 to 69 years old, in part because of an increase in the use of mammography,
she said. However, women ages 70 to 79 years old have not seen the same kind of
improvement in breast cancer mortality rates. For example, in California, women
aged 70 to 79 years old experienced a 10 percent decrease in breast cancer
mortality from 1989 to 1993, Smith-Bindman said. Women ages 50 to 69-years old
experienced a 19 percent drop in breast cancer mortality during those same
“Women in their 70s undergo screening mammography less often than younger
women, and it may be why these women have not had the same decline in breast
cancer mortality, since they do not undergo screening as often,” Smith-Bindman
While breast cancer screening can reduce the rates of metastatic breast cancer
in elderly women, it can also uncover early stage, non-invasive tumors in women
who would have remained symptom free even in the absence of screening, she
said. But since it’s impossible to tell which of these early stage tumors will
be dangerous, most are surgically removed. Elderly women should weigh their
treatment options, Smith Bindman said. For example, a patient with early stage
cancer most likely wouldn’t need a mastectomy, but could need a lumpectomy. A
lumpectomy is the surgical removal of a lesion. A mastectomy involves removing
In addition to Smith-Bindman, co-authors include: Karla Kerlikowske, MD, UCSF
assistant professor of medicine and epidemiology and biostatistics; Tebeb
Gebretsadik, MPH; California Medical Review Inc.; and Jeffrey Newman, MD, MPH,
UCSF assistant clinical professor of medicine.
This study was funded by a National Cancer Institute Breast Cancer SPORE grant,
the Health Care Finance Administration and a Breast Cancer Surveillance
Consortium Cooperative agreement.