One out of every 7 cases of screen-detected breast cancer are over diagnosed, new data suggest.
That’s according to research recently published in the Annals of Internal Medicine that examined a large cohort of cancer screenings and diagnosis records from Breast Cancer Surveillance Consortium (BCSC) facilities. After retrospectively examining the data on women aged 50 to 74 who had their mammography screenings between 2000-2018, the researchers used a natural history likelihood model to estimate the rate of overdiagnoses.
In this setting, overdiagnosis is defined as screen-detected cancer that would not have caused signs or symptoms in women if left alone for their remaining lifetime.
A total of 82,677 mammograms from 35,986 average-risk women were included in the researchers’ model. From those, 718 breast cancers were diagnosed. Experts estimated that 15.4% of cancers were overdiagnosed.
Indolent preclinical cancer findings were responsible for 6.1% of the overdiagnoses, while progressive preclinical cancer in women who would have died of another, unrelated cause before clinical diagnosis accounted for 9.3%
"Given that approximately 7 in 1,000 women will be diagnosed with invasive or noninvasive breast cancer on the basis of a screening mammogram, women should be told that approximately 1 in 1,000 women who undergo mammography will be found to have a cancer that would never have caused problems," Felippe O. Marcondes, MD, and Katrina Armstrong, MD, both with Massachusetts General Hospital in Boston, explained in an editorial published alongside the study.
Encouragingly, those numbers are down from older, widely cited studies that estimated overdiagnosis of breast cancer to occur in up to 30% of mammography screenings. This is important, the authors explain, because overdiagnosis can lead to unnecessary and invasive procedures and treatments, such as biopsies and lumpectomies.
“This information clarifies the risk for breast cancer overdiagnosis in contemporary screening practice and should facilitate shared and informed decision making about mammography screening,” corresponding author Marc D. Ryser, PhD, with the department of population health sciences at Duke University Medical Center, and co-authors suggested.
The detailed study, Estimation of Breast Cancer Overdiagnosis in a U.S. Breast Screening Cohort, can be viewed in Annals of Internal Medicine.
More on breast cancer screenings:
Breast MRI screening cuts cancer mortality rates in half for women with lesser-known gene mutations
Combining neural network with breast density measurements boosts interval cancer detection rates
Mammograms should not be delayed after COVID vaccine, research shows
DBT plus synthesized mammography drops patients’ dosage without losing imaging quality
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She joined Innovate Healthcare in 2021 and has since put her unique expertise to use in her editorial role with Health Imaging.