While more than half of women aged 75 years and older receive annual mammograms, they do not see a reduced risk of death from breast cancer, compared with women who have stopped regular screening, according to a study published in Annals of Internal Medicine.
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The lack of benefit is not because older women’s cancer risk is low; a third of breast cancer deaths occur in women diagnosed at or after age 70 years, according to study author Xabier García-Albéniz, MD, PhD, of Harvard University in Boston, and colleagues.
The lack of benefit is not because mammography is less effective in women older than 75 years; indeed, it becomes a better diagnostic tool as women age, said Otis Brawley, MD, of Johns Hopkins University, Baltimore, the author of an editorial related to the study. Rather, the lack of benefit is because breast cancer treatment in older women is less successful, he clarified.
Study details
Dr. García-Albéniz and colleagues looked at data from 1,058,013 women enrolled in Medicare across the United States during 2000-2008. All subjects were aged 70-84 years and had a life expectancy of at least 10 years, at least one recent mammogram, and no history of breast cancer.
There are little randomized trial data available on mammography and breast cancer deaths for women in their early 70s and none for women older than 75 years. To compensate for this, the researchers aimed to emulate a prospective trial by looking at deaths over an 8-year period for women aged 70 and older who either continued annual screening or stopped it. The investigators conducted separate analyses for women aged 70-74 years and those 75-84 years of age.
Diagnoses of breast cancer were, not surprisingly, higher in the continued-screening group, but this did not translate to serious reductions in death.
In the continued-screening group, the estimated 8-year risk for breast cancer was 5.5% in women aged 70-74 and 5.8% in women aged 75-84 years. Among women who stopped screening, the estimated 8-year risk for breast cancer was 3.9% in both age groups.
Among women aged 70-74 years, the estimated 8-year risk for breast cancer death was slightly reduced with continued screening: 2.7 deaths per 1,000 women, compared with 3.7 deaths per 1,000 women for those who stopped screening. The risk difference was –1.0 deaths per 1,000 women, and the hazard ratio was 0.78.
Among women aged 75-84 years, there was no difference in estimated 8-year risk for breast cancer death. Women treated under a continued screening protocol had 3.8 deaths per 1,000, while the stop-screening group had 3.7 deaths per 1,000. The risk difference was 0.07 deaths per 1,000 women, and the hazard ratio was 1.00.
Interpreting the results
In the editorial accompanying this study, Dr. Brawley praised its design as “especially useful in breast cancer screening,” as “prospective randomized studies of mammography are not feasible and are perhaps no longer ethical in older women … because mammography is so widely accepted.”
In an interview, Dr. Brawley stressed that the findings do not argue for denying women aged 75 years and older mammography screening. Decisions about screening require a value judgment tailored to each individual patient’s perceived risks and benefits, he said.
Dr. Otis W. Brawley
In the absence of randomized trial evidence, “the jury will always be out” on the benefits of regular mammography for women 75 and older, Dr. Brawley said. “A clinical trial or a modeling study always tells you about an average person who doesn’t exist,” he added. “I predict that, in the future, we will have more parameters to tell us, ‘this is a person who’s 80 years old who is likely to benefit from screening; this is a person who is 75 years old who is unlikely to benefit.’ ”
And focusing too much on screening, he said, can divert attention from a key driver of breast cancer mortality in older women: inadequate treatment.
In the United States, Dr. Brawley said, “There’s a lot of emphasis on screening but fewer people writing about the fact that nearly 40% of American women get less than optimal treatment once they’re diagnosed.”
Dr. Brawley cited a 2013 modeling study showing that improvements in delivering current treatments would save more women even if screening rates remained unaltered (Cancer. 2013 Jul 15;119[14]:2541-8).
Among women in their 70s and 80s, Dr. Brawley said, some of the barriers to effective breast cancer care aren’t related to treatment efficacy but to travel and other logistical issues that can become more pronounced with age. “Unfortunately, there’s very little research on why, for women in their 70s and 80s, the treatments don’t work as well as they work in women 20 years younger,” he said.
Dr. García-Albéniz and colleagues’ study was funded by the National Institutes of Health. One coauthor reported financial ties to industry. Dr. Brawley discloses no conflicts of interest related to his editorial.
SOURCE: García-Albéniz X et al. Ann Intern Med 2020. doi: 10.7326/M18-1199.