Avoiding Mammograms in Elderly May Boost Breast Cancer Mortality: Study

April 12, 2013

By Fran Lowry

NEW YORK (Reuters Health) Apr 12 - Holding off on screening mammograms in older women might increase their risk of dying from breast cancer, researchers concluded from an observational analysis of data from the Women's Health Initiative.

Among women diagnosed with breast cancer at age 75 or older, those whose last mammogram was more than five years ago had three times the odds of dying of their cancer compared to women with a mammogram in the last six to 12 months.

It's not clear whether mammography affected their overall survival rates, however.

The researchers presented their study April 7 at the annual meeting of the American Academy for Cancer Research (AACR) in Washington, D.C.

In their presentation, Dr. Michael S. Simon, from the Barbara Ann Karman's Cancer Institute in Detroit, Michigan, and his colleagues noted that more than 60% of breast cancers diagnosed between ages 70 to 79 were moderately or poorly differentiated. "Older women in the WHI did get aggressive breast cancer," Dr. Simon told Reuters Health, "so we decided to do this analysis to see whether mammography interval had an influence on the death rate from breast cancer."

He and his colleagues looked at data on 8,663 women who were diagnosed with breast cancer during an average of 12.2 years of follow-up.

The interval from screening mammogram to breast cancer diagnosis was six to 12 months in roughly a third of the women, one to two years in 47%, two to five years in 17%, and more than five years (or never) in 5.8%.

Records showed the incidence of advanced disease at diagnosis was 23% in women with an interval of five or more years since their last mammography, compared to 20% in women who reported an interval of six months to a year since their last mammogram (p=0.05).

Overall, there were 437 deaths from any cause among the 8,340 women in the final analysis (5.2%) and 116 in the 2,381 women over 75 (4.9%), according to Dr. Simon.

After adjusting for age, race, ethnicity, participation in the observational study or clinical trial of the WHI, health insurance, marital status, Charlson co-morbidity index, and body mass index, mammography timing was linked with breast cancer mortality in women aged 75 and older.

Among these older women, those with an interval of five years or more between mammogram and diagnosis had a three-fold risk of breast cancer death compared with women whose last mammogram was six to 12 months before their diagnosis (hazard ratio 3.17; p for trend=0.0001). And women with an interval of more than two years but less than five years had almost a two-fold increased risk.

These relationships were not found among younger women, however. In those aged 50 to 74 years, the HR was 1.28 for an interval of five years or more and 1.05 for an interval of more than two but less than five years (p for trend = 0.43).

"I am not sure why we are seeing these results particularly for older women," Dr. Simon said.

"Tumors of younger women were more likely to be a little more unfavorable overall," he said. "It is possible that the differences in the relationship between screening interval and mortality in older versus younger women may be related to the more aggressive nature of the tumors in younger women, which might obliterate the effects of more screening."

Women with a longer interval between mammogram and diagnosis were also more likely to have estrogen receptor negative disease, however (22% vs 16%, p=0.03), which could also have affected survival in that group.

Did more frequent mammography actually save lives? Dr. Simon told Reuters Health he didn't have information on overall mortality rates broken down by age. But, he said, a competing risks analysis "showed that the relationship between mammography interval and the likelihood of dying from breast cancer was stronger than that of the likelihood of dying from other causes for the group of women over 75."

The caveat, Dr. Simon added, is that his study was retrospective. "We tried to adjust for what we thought would be related to the risk of dying but we did not have information on treatment."

Dr. Simon said the study was done "in reaction to the U.S. Preventive Services Task Force (USPSTF) recommendation back in 2009 that said that women over 75 should not get screening mammograms, based on the premise that the disease would be indolent or that they would die of other causes."

But Dr. Michael LeFevre, co- chair of the USPSTF, told Reuters Health the panel didn't specifically recommend against screening mammography in older woman - nor did the panel recommend in favor of it.

"In 2009 the USPSTF concluded that the science was not clear about the balance of benefits and harms of mammography screening after age 75, and did not recommend either for or against screening in this age range," said Dr. LeFevre, who is also the Future of Family Medicine Professor and Vice-Chair in the Department of Family and Community Medicine at the University of Missouri in Columbia.

"In the absence of good evidence, a woman should work with a trusted health care provider to decide whether continuing regular mammography makes sense for her personally," Dr. LeFevre said.

Dr. Simon believes the study shows a role for screening mammography in older women. "Physicians should discuss the risks and benefits of mammography with older patients and encourage them to continue to be screened, but always in light of the overall health of the individual woman," he said.

Commenting on the study for Reuters Health, Dr. Shicha Kumar from Roswell Park Cancer Institute in Buffalo, New York, acknowledged that optimal surveillance for aging women has been controversial.

"While some may recommend cessation of screening with increasing age, if a woman is otherwise in good health, and can tolerate the treatment should a cancer be found, early diagnosis is important," Dr. Kumar said. "Cancers diagnosed at earlier stages have better survival rates and can sometimes be managed with less invasive treatment. This study confirms that our aging population also derives benefit from early diagnosis. Clinicians should advise elderly women in otherwise good health to continue mammographic screening for breast cancer."

Dr. LeFevre, however, says, "As a family physician with many patients in this age range, I can attest that personal values and preferences vary a great deal between women, and a blanket recommendation to continue screening is hard to support."

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