Breast cancer screening a waste of time? Not so fast
A new study published in the British Medical Journal (BMJ) suggests mammogram screening is a waste of time and may add fuel to breast cancer screening controversies. The newest report showed annual breast cancer screening leads to high rates of false positive results that in turn can precipitate unnecessary biopsies and stress for women. A previous finding from the same study showed mammography performed yearly did not reduce death rates from the disease for women age 40 to 59, compared to physical exam or usual health care. But there may be more to the story, suggest radiology experts.
Authors for the study found 22 percent of breast cancers were overdiagnosed. In response to the finding, the American College of Radiology (ACR) and Society of Breast Imaging warn women that foregoing yearly breast cancer screening would put them at unnecessary risk for dying. There may indeed be more to the story that women should know.
Is the study flawed?
According to the ACR and Society for Breast Imaging, the Canadian researchers who conducted the study extracted data from women whose breast cancer screening was performed with “second-hand mammography machines” that makes it difficult to detect breast cancer and produces “cloudy” images.
One of the contentions of the new study is that mammograms are a waste of time and cost money.
They also point out the technical quality of the screening was poor due to improper positioning of the women being screened. The ACR also states physician interpreting those mammograms had no special training, which would mean lower detection rates.
Women investigated were part of the Canadian National Breast Screening Study (CNBSS) that is a 25-year follow up from previous 11 and 16 years of tracking the value of breast cancer screening. The new study reports the number of false positive results from mammography, found to be 22 percent and is published for the first time.
The study authors, Anthony B Miller and colleagues, concluded: “Annual mammography in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available. Overall, 22% (106/484) of screen detected invasive breast cancers were overdiagnosed, representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial.”
Substandard techniques used in study
The ACR says the reason breast cancer wasn't detected is poor quality screening that was confirmed by experts called on to review the CNBSS finding. The techniques used were even substandard considering the time of the study, which was in the early 1980s.
Another study flaw cited by the ACR is that the women studied were not randomly chosen, which violates the rules of protocol when conducting a randomized controlled trial (RCT). All of the women had a physical exam prior to being assigned to either a control or screening group. The researchers already knew which women had large tumors and incurable breast cancer prior to carrying out the investigation. But the study authors say the women were assigned randomly without regard to physical findings on breast examination. The ACR thinks it’s likely that a large number of women who already had breast cancer could have been assigned to the group receiving regular breast cancer screening.