Use of mammograms in older women questionable, say UCSF researchers

December 05, 1999

A new study using a computer model questions the value of screening for breast cancer in elderly women, according to researchers at the University of California, San Francisco.

Although several organizations recommend mammograms for women after age 69, no data show that screening will avert deaths from breast cancer among elderly women, the study found. The UCSF study, published in the December 8 issue of the Journal of the American Medical Association, reports that mammography screening after age 69 results in only a small gain in life expectancy and is moderately cost-effective.

"There are downsides to mammograms as women get older and only a small gain in life expectancy from continuing screening," said Karla Kerlikowske, MD, UCSF assistant professor of medicine and epidemiology and biostatistics who directs the Women Veterans Comprehensive Health Care Center at the SF Veterans Administration Medical Center.

The researchers developed a computer model using population-based cancer and mortality data to compare the life expectancy of 10,000 hypothetical 65-year-old women undergoing one of three breast cancer screening strategies. They assumed that screening mammography would reduce breast cancer mortality by 27 percent as it does in women aged 50 to 69 years old, as reported in the medical literature.

According to the model, if women underwent biennial screening until age 69, 148 would die of breast cancer by age 85. If screening were continued until age 79 in women with high bone mineral density - which is a good predictor of breast cancer risk - 9.4 breast cancer deaths would be averted and would add, on average, 2.1 days to life expectancy among the women screened. Expanding the mammography screening program for all women up to age 79, including those women with low bone mineral density, would avert 1.4 additional deaths and add, on average, 0.3 days of life per woman screened.

Looked at another way, ten more years of biennial screening -- from age 69 to 79 -- averts only 10.8 breast cancer deaths and adds, on average, 2.5 days to a woman's life.

A shortened life expectancy coupled with the high risk of death from other causes explains why continuing screening after age 69 does not have a greater impact on life expectancy, say the researchers.

"As you get older, you are more likely to die of cardiovascular disease than breast cancer," said Kerlikowske.

Other reasons to consider discontinuing screening after age 69 are the potential harms and annoyances associated with mammography, said Kerlikowske. Older women may be bothered by medical tests, physician visits, and waiting for test results. Contending with abnormal results, about 90 percent of which will be false-positives, also adds worry and anxiety, she said.

In addition, mammograms often detect ductal carcinoma in situ (DCIS), a breast lesion contained within the milk ducts which are often surgically removed despite the fact that the risk of death from DCIS is low and will likely not affect mortality in elderly women.

"Women's preferences for a small gain in life expectancy and the potential harms of screening should play an important role when elderly women are deciding about screening," said Kerlikowske.

Mammograms in general have only a moderate effect on life expectancy, said Kerlikowske. For example, women aged 50 to 69 who undergo biennial screening increase their life expectancy by only 12 days, on average. Despite the fact that screening mammography appears to have a small impact on life expectancy among elderly women, many organizations, including Medicare, recommend annual screenings, said Kerlikowske.

"Women who want to maximize the potential benefits they may get from undergoing screening mammograms and minimize the harms of having the test done should have mammograms biennially between the ages of 50 and 69, or ten mammograms in their lifetime," said Kerlikowske.
In addition to Kerlikowske, co-authors include Peter Salzmann, MD, Stanford University Graduate School of Business; Kathryn Phillips, PhD, UCSF associate professor of health economics and health services research; Jane Cauley, DrPH, professor of epidemiology, Graduate School of Public Health, University of Pittsburgh; and Steve Cummings, MD, UCSF professor of medicine and epidemiology.

This work was funded by the National Cancer Institute's Breast Cancer Surveillance Consortium co-operative agreement and the National Cancer Institute's Breast Cancer SPORE grant.

University of California - San Francisco

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