UK Panel: Breast Cancer Screening Programs Reduce Deaths

Women who undergo routine breast cancer screening have a lower risk of dying from breast cancer, according to an independent British panel.

Over the past several years, there has been much debate regarding the use of breast cancer screening and the possible result of overdiagnosis and treatment for disease that may not have caused illness if not detected. To address this issue, a panel of physicians in the United Kingdom performed an independent review of the evidence for the benefits and harms of breast cancer screening in the UK. In the UK, women aged 50 to 70 are invited for breast cancer screening every three years.

The panel, led by Prof. Sir Michael Marmot, director of the Institute of Health Equity at University College in London, performed a meta-analysis of 11 randomised controlled trials to determine if breast cancer screening resulted in fewer deaths due to the disease, compared to when no screening took place.

The researchers found that the women who underwent regular breast cancer screening did have a lower relative risk of death from breast cancer (20 percent less) than did the women who were not screened. Although the studies did take place more than 20 years ago, the panel felt that the evidence was still valid.

Researchers found only three trials that looked at overdiagnosis from breast cancer screening. From these numbers, the panel found that among the approximately 307,000 women, aged 50 to 52, who were invited to be screened every year, only 1 percent would have an overdiagnosed cancer within the following 20 years.

“If these figures are used directly, for every 10,000 UK women aged 50 years invited to screening for the next 20 years, 43 deaths from breast cancer would be prevented and 129 cases of breast cancer, invasive and non-invasive, would be overdiagnosed,” the panel wrote in the study published in this week’s The Lancet . “That is one breast cancer death prevented for about every three overdiagnosed cases identified and treated.”

Further research is necessary, however, given the uncertainties of all the estimates, the panel noted. According to Marmot, “The reduction in risk of death from breast cancer screening corresponds to one breast cancer death prevented for every 235 women invited to screening, and one death averted for every 180 women who attend screening.” The UK every-three-year breast screening programs probably prevent about 1,300 breast cancer deaths and about 4,000 women each year are overdiagnosed as a result of the screening program, he added.

“For each woman, the choice is clear,” Marmot concluded. “On the positive side, screening confers a reduction in the risk of mortality of breast cane 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 that would never have caused problems if she had not been screened. Clear communication of these harms and benefits to women is essential, and the core of how a modern health system should function.”