There is insufficient evidence to suggest breast cancer screening should be stopped at a specific age. This is the conclusion of the largest study to date of mammography outcomes in the United States.
Study co-author Dr. Cindy Lee, assistant professor in residence at the University of California-San Francisco, and team recently presented their findings at the Radiological Society of North America (RSNA) annual meeting, held in Chicago, IL.
According to the American Cancer Society, around 246,660 new cases of invasive breast cancer will be diagnosed in the U.S. this year, and more than 40,000 women will die from the disease.
Despite these grim statistics, breast cancer death rates have been falling in the U.S. since the late 1980s – a trend that has been partly attributed to earlier detection as a result of screening.
Mammography is considered the gold standard of breast cancer screening. The technique involves the use of X-rays to identify early signs of breast cancer, such as calcifications or tumors in breast tissue.
Guidelines issued by the U.S. Preventive Services Task Force (USPSTF) in 2009 recommend that women aged 40-49 at average risk of breast cancer should make an individual, informed decision as to whether they undergo mammography, while women aged 50-74 should undergo mammography every 2 years.
For women aged 75 and older, however, the USPSTF state that there is insufficient evidence to “assess the balance of benefits and harms of screening mammography.”
Such guidelines are at odds with those from the American Cancer Society, which recommend that women aged 55 and older should undergo mammography every 2 years, and “screening should continue as long as a woman is in good health and is expected to live 10 more years or longer.”
Dr. Lee notes that the conflicting guidelines surrounding the age at which mammography should be stopped have led to much confusion.
“There has been a lot of controversy, debate and conversation regarding the different breast cancer screening guidelines, even among major national organizations, over the past few years,” she adds.
Dr. Lee points out that previous randomized, controlled trials assessing mammography outcomes have excluded women aged 75 and older, meaning the available data have been based on results of small, observational studies.
With this in mind, Dr. Lee and team analyzed data from the National Mammography Database. The researchers assessed more than 5.6 million screening programs that took place at 150 facilities across 31 U.S. states between January 2008 and December 2014.
All in all, the team gathered data from more than 2.5 million women aged 40 and older. The women were divided into age groups by 5-year intervals up to the age of 90 – aged 40-44, 45-49, 50-54, 55-59, and so on.
In order to determine mammography outcomes for the women in each age group, the researchers applied four standard performance measures: cancer detection rate, recall rate – the percentage of mammograms that require follow-up testing – and positive predictive value for biopsy recommended (PPV2) and biopsy performed (PPV3).
Positive predictive value represents the number of cancers identified through mammography that result in biopsy or recommended biopsy.
According to the researchers, a higher cancer detection rate, higher PPV2 and PPV3, and a low recall rate reflect an optimal mammography performance.
For every 1,000 patients, the team identified an overall mean cancer detection rate of 3.74, a 10 percent recall rate, a 20 percent PPV2 rate, and a 29 percent PPV3 rate.
With increasing age, the researchers identified an increase in cancer detection rate, a gradual rise in PPV2 and PPV3 rates, and a fall in recall rates – meeting the criteria for ideal screening performance.
“The continuing increase of cancer detection rate and positive predictive values in women between the ages of 75 and 90 does not provide evidence for age-based mammography cessation.”
Dr. Cindy Lee
The researchers conclude that their findings suggest it should be a woman’s individual choice – based on health status and personal preferences – as to whether she wants to cease or continue breast cancer screening at the age of 75 or older.
While further investigation is needed, the new research indicates that the benefits of breast cancer screening after the age of 74 may outweigh the risks.