Women's Health

Breast cancer – to screen or not to screen – Part 2


This is the second of a two-part Monday note on breast cancer screening. The research was initiated by an invitation to breast screening that I received. The invitation presented the trade-off “for every 1 woman who has her life saved from breast cancer, about 3 women are diagnosed with a cancer that would never have become life threatening.” I wanted to understand quantifiable benefit vs harm to make my personal decision – to screen or not to screen.

Last week we looked at two reports from 2013, one led by Michael Marmot (Ref 1) and the other by Peter Gøtzsche (Ref 2), to try to answer my question. We found that the two reviews had located the same trials (as should have happened) and they agreed on data extraction, and Risk Ratios. They disagreed on which trials were robust enough to be pooled in meta-analysis. Marmot included nine; Gøtzsche evaluated only four as robust enough to be considered. This difference was the crux of the differing conclusions. Pooling the weak trials suggested that screening provides some benefit (before factoring in harms). Pooling only the robust trials suggested that screening provides no benefit (and thus there is only harm).

This week we cover the answer to my original question about life extension (still not a complete answer). We cover where the one life ‘saved’ comes from. I question the one life saved numbers. I contacted Peter Gøtzsche while doing this research and he kindly sent me the manuscript to the update of his mammography book. I will also share some insights from this – for example on lump size – which I had not thought about. We need to cover all-cause mortality and not just breast cancer mortality. Finally, I will share the decision that I have made on screening.

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