The harms and benefits of modern screening mammography

The Swiss Medical Board, an independent health technology assessment consortium, recently reviewed the evidence for breast cancer screening and made recommendations to its government. The board noted that the current debate on the benefits and harms of mammography screening is based on outdated randomised controlled trials (RCTs) and that it was “non-obvious” that the benefits outweighed the harms.1 They recommended that no new mammography screening programmes should be introduced in Switzerland and that the existing ones should be phased out.1

The Swiss Medical Board relied on a review by another panel: the Independent United Kingdom Panel on Breast Cancer Screening.2 Using data from the published RCTs, the UK panel estimated that for every 10 000 women aged 50 invited to screen for the next 20 years, about 43 would avoid a death from breast cancer and the remaining 9957 would receive no mortality benefit. About 129 women would be treated unnecessarily as a result of overdiagnosis, a ratio of three women with overdiagnosed cancers to one woman with a breast cancer death avoided.

As both panels noted, data from older RCTs are not ideal for determining the benefits and harms of modern day screening. Instead, observational studies such …