CHICAGO — As women get older, the precision of breast cancer screening with mammography increases because the rate of false-positive results decreases and the detection of cancer increases significantly, according to new research presented here at the Radiological Society of North America 2016 Annual Meeting.
This calls into question the recommendation of the US Preventive Services Task Force (USPSTF) that women undergo screening every 2 years only until age 74, said Cindy Lee, MD, from the University of California at San Francisco.
"Age 75 seems to be an arbitrary cutoff," Dr Lee told Medscape Medical News.
The decision to stop mammography screening should be made on the basis of individual patient values, comorbidities, and health status — not some random cutoff age, she asserted.
Dr Lee and her colleagues examined almost 5.7 million screening mammograms from about 2.6 million women older than 40 years from the American College of Radiology National Mammography Database, which is the largest national mammography registry in the United States.
"Randomized controlled trials to date have excluded women older than 75, limiting available data in this age group to mostly small, observational studies," she reported.
"We needed a large enough number of patients to study the relation between age and screening mammography performance," she explained.
The mean national cancer detection rate was 3.74 per 1000 screening exams. The mean recall rate — the rate of screenings leading to a call-back for additional workup — was 10%. The rate of cancers found in cases recommended for biopsy was 20%. And the rate of cancers found in women who underwent biopsy was 29%.
When the researchers stratified the women into 5-year age groups, they found that the recall rate decreased progressively every decade, and was only 6% in women 90 years and older. At the same time, rates of cancer detection increased progressively with increasing age.
The team hypothesized that screening would work equally well in young and older women. "We were surprised to see that screening performance gets better with increase in age," Dr Lee said.
On the basis of these results, the researchers conclude that doctors should continue to recommend mammograms for women older than 75 years.
This shouldn't be a policy decision," Dr Lee explained. "Women have the right to get a screening mammogram if it is medically appropriate."
Breast cancer is the second most common cancer in women in the United States, and more than 290,000 new cases were diagnosed in 2015.
"Breast cancer screening is as important as any other screening," said Dr Lee. "You don't see an age limit on prostate screening."
The only limitation on screening for prostate cancer is in consideration of life expectancy. According to the American Cancer Society, if a patient is expected to live less than 10 years, prostate cancer screening is not recommended.
Similarly, factors that can affect life expectancy should be taken into account when decisions about breast cancer screening are made, said Dr Lee.
For example, the presence of comorbidities such as diabetes, stroke, or coronary artery disease would have more weight than age "because previous studies have shown that screening only benefits you if you are expected to live 10 years or more," she explained.
But if a 95-year-old woman is probably going to live to 105, "we need to provide screening for her," she added. And a 75-year-old woman should not have to "doctor shop" to find someone who supports her getting a screening mammogram. The final decision has to be made by both the doctor and the patient
"Starting screening at age 40 and continuing after age 75 would save the most lives," said Dr Lee. She said she believes that the USPSTF recommendation to discontinue screening is related more to the cost of public healthcare than to a concern about saving lives.
"Can you equate a life saved with a dollar amount saved? As a physician, I believe in saving the most number of lives," she said.
"It's like throwing Grandma over the cliff," said Stephen Feig, MD, from the University of California, Irvine in Orange.
"Excessive restriction is healthcare rationing," he told Medscape Medical News.
According to the actuarial life table, an average 75-year-old American woman has 12.8 years left, which is beyond the 10-year American Cancer Society recommendation for screening for other cancers, he explained. And "a woman in good health could live even longer," he pointed out.
It is also easier to detect the cancer in older women. "Women have better sensitivity because they have more fatty breast tissue, making it easier to see cancers," Dr Feig said. In addition, the rate of false-positive results is lower because we have more previous mammograms to compare.
"People are getting older, and they are healthy. As long as they are healthy, it makes sense to find cancer early," said Christiane Kuhl, MD, PhD, from the University of Aachen in Germany.
The absence of evidence is not evidence of absence. "We need to stop using outdated information from cohorts several decades old," Dr Kuhl said.
Dr Lee said she supports the guidelines from the American College of Radiology, which state that "screening with mammography should continue as long as a woman has a life expectancy of ≥5 to 7 years on the basis of age and health status, is willing to undergo additional testing including biopsy, if indicated by findings on mammography, and would be treated for breast cancer if diagnosed" (J Am Coll Radiol. 2010;7:18-27).
"Our study suggests that there is no clear age cutoff to inform the decision of when to stop screening," she said.