Architect of U.K. mammo program says projected harm often ignored

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The debate about breast cancer screening is not limited to the U.S.

In a commentary published online last week in BMJ, Michael Baum, a professor emeritus of surgery at the University College London, questions the conclusions made last fall of a U.K. panel led by Sir Michael Marmot, a professor of epidemiology and public health and director of the Institute of Health Equity at University College London, that determined that the benefits of screening outweigh the harms, despite the potential for overdiagnosis. Baum was an architect of the original U.K. breast cancer screening program, and has since had a change of heart about its effectiveness. In a radio interview with BBC Radio 4 in October 2011, Baum described what prompted his reversal of course.

"As the evidence changes, one should, as a clinical scientist, be prepared to change one's position, and I have watched with increasing alarm as evidence has accumulated that suggests the initial estimates of benefit were exaggerated and the initial estimate of harm was, frankly, ignored," he said in the interview. "What has gone wrong is that we would never have predicted how many of these cancers detected at screening lack the potential to threaten the woman's life."

In the BMJ piece, Baum said that while screening may help avoid some deaths from breast cancer, benefits from screening will be outweighed by deaths due to the long term adverse effects of treatment for breast cancer.

"Does screening improve length of life? Sadly, the Marmot committee chose to duck that one and rely on another surrogate outcome measure, cause specific mortality, with the rather lame excuse that the trials weren't powered to detect any impact on all cause mortality," Baum said. "Well shame on them, I say."

Baum estimates that for every 10,000 women screened for breast cancer, three or four deaths are avoided, while 2.72 to 9.25 deaths are caused by the long-term toxicity associated with radiotherapy.

To learn more:
- read the commentary in BMJ (subscription required)
- listen to the radio interview on BBC 4

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