Obligate overdiagnosis rates of mammographic screening depend on age
According to a study recently published in Radiology and conducted by radiologist R. Edward Hendrick, PhD, from the University of Colorado School of Medicine, obligate overdiagnosis rates of mammographic screenings are strongly dependent on a women's age at the time of the noninvasive breast exam.
Two types of overdiagnosis may occur with mammographic screening, explained R. Edward Hendrick, PhD, from the University of Colorado School of Medicine.
Obligate overdiagnosis (Type 1) is defined as a female patient who dies of causes other than cancer before it progresses to be clinically evident during her lifetime. Nonobligate overdiagnosis (Type 2) is when a mammographic screening exam detects breast cancer that never progresses, or perhaps regresses, and never becomes clinically apparent during a women's lifetime without screening.
For his research, Hendrick focused on Type 1 regarding ductal carcinoma in situ (DCIS), invasive breast cancer and all breast cancers (DCIS plus invasive). Specifically, obligate overdiagnosis rate for breast cancer is defined in Hendrick's work as the percentage of women with a screen-detected breast cancer diagnosis who wouldn't have shown symptoms of that cancer during their lifetime. This is especially important for advising older women about the potential risks of screening mammography, Hendrick wrote.
For his study, Hendrick obtained and analyzed all-cause mortality rates from the Human Mortality Database, age-specific breast cancer incidence and mortality rates from Surveillance, Epidemiology, and End Results data, and estimates of mean lead times and lead time distributions from breast cancer screening trials to estimate obligate overdiagnosis rates for DCIS, invasive breast cancer and all breast cancers for U.S. women undergoing screening mammography.
Hendrick's post-analysis results included the following:
Obligate overdiagnosis rates depend strongly on the age at which a woman is screened, ranging from less than 1 percent at age 40 years to 30 percent, 21 percent and 22.5 percent at age 80 years for DCIS, invasive breast cancer and all breast cancers, respectively.
Type 1 overdiagnosis rates among screened women in the U.S. are estimated to be 9 percent for DCIS and approximately 7 percent for both invasive breast cancer and all breast cancers.
Screening of women ages 40-49 years (or premenopausal women, as determined from patient history, starting at age 40 years) adds little to obligate overdiagnosis rates (0.15 percent for DCIS and less than 0.1 percent for invasive breast cancer and all breast cancers).
Mammographic screening of women ages 40–49 years (or pre- menopausal women starting at age 40 years) makes a negligible contribution of 0.1 percent to the total obligate overdiagnosis rate.
A recent graduate from Dominican University (IL) with a bachelor’s in journalism, Melissa joined TriMed’s Chicago team in 2017 covering all aspects of health imaging. She’s a fan of singing and playing guitar, elephants, a good cup of tea, and her golden retriever Cooper.