“Liquid biopsy” for cancer screening

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 …