Intended for healthcare professionals


“Liquid biopsy” for cancer screening

BMJ 2021; 372 doi: (Published 04 January 2021) Cite this as: BMJ 2021;372:m4933
  1. Stephen H Bradley, clinical research fellow1,
  2. Matthew E Barclay, statistician2
  1. 1Leeds Institute of Health Sciences, University of Leeds, Leeds, UK
  2. 2The Healthcare Improvement Studies Institute (THIS), University of Cambridge, Cambridge, UK
  1. Correspondence to: S H Bradley medsbra{at}

Careful evaluation must consider harms as well as potential benefits

While outcomes for several cancers have transformed over recent decades, survival remains poor for some common malignancies such as lung and pancreatic cancer. Meanwhile, comparative evaluations of cancer outcomes have generated much reflection in the UK’s NHS and other healthcare systems that are perceived to be lagging behind comparable systems in other countries.12 Detecting cancers at earlier stages of disease, when treatment is more likely to result in improved survival, has therefore become a strategic priority in cancer planning in the UK and globally.

The NHS is committed to diagnosing 75% of all cancers at stage I or II by 2028, from around 50% currently.3 Achieving such progress in less than a decade would be highly ambitious, even without disruption caused by the covid-19 pandemic. In this context, considerable hope has been expressed that blood tests for circulating free DNA—sometimes known as liquid biopsy—could help achieve earlier detection of cancers.

A case-control study of the technology behind one such test (the Galleri) was published earlier this year.4 …

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