An independent panel was convened to review breast cancer practices in the UK to look at two things – was the screening preventing deaths and was breast cancer being overdiagnosed?
The panel found that screening does save lives, but it also results in overdiagnosis in about 1 percent of the women screened.
The review concluded that the benefits of breast cancer mammography should continue, but that women should be informed about the pros and cons of the procedure.
"Develop a breast cancer screening plan with your doctor."
The panel included five experts and one former breast cancer patient and was commissioned by Cancer Research UK and the Department of Health.
The panel was charged with looking at the deaths screening mammography prevents and the incidence of overdiagnosis.
Currently, in the UK, women ages 50-70 are “invited” to receive screening mammography every three years.
Review panel members examined previous studies on breast cancer screening and talked to screening experts from around the UK.
Eleven of the trials, with follow-up times of up to 13 years, looked at how long women with breast cancer lived after the disease was detected by mammography.
Screening reduced the relative risk of breast cancer deaths by about 20 percent for women who were screened compared to women who weren't. Looking at it another way, mammography prevented the deaths of 43 women for every 100,000 women who had received mammography.
Determining overdiagnosis, the panel admitted, was a great deal trickier. By changing the parameters of the trials being evaluated, it was determined that overdiagnosis ranged from 0 - 36 percent of the studies.
“The frequency of overdiagnosis was of the order of 11 percent from a population perspective, and about 19 percent from the perspective of a woman invited to screening,” the panel wrote in its report.
From still another perspective, the panel found that of the estimated 681 breast cancers detected in every 100,000 women screened, 129 of those would not have needed to be treated, while 43 deaths would have been prevented.
So what does all this mean? The authors concluded that breast cancer screening offers significant benefit and should continue.
They wrote, “But for each woman, the choice is clear: on the plus side, screening confers a likely reduction in mortality from breast cancer because of early detection and treatment. On the negative side, is the knowledge that she has perhaps a 1 percent chance of having a cancer diagnosed, and treated with surgery and other modalities, that would never have caused problems had she not been screened. “
The panel was chaired by Sir Michael Marmot, professor of epidemiology and public health and Director of the Institute of Health Equity at University College, London.
He said in a press release, “It is now vital to give women information that is clear and accessible before they go for a mammogram so they can understand both the potential harms and benefits of the process.”
The Independent Breast Screening Review report was published October 29 in The Lancet.