Chronic blood cancers that eventually worsen may carry detectable genetic warning signs years before patients develop serious symptoms — and some people currently diagnosed with blood cancer may instead be showing normal aging, a new study finds.

Published in Cancer Discovery and led by the Wellcome Sanger Institute, the research tracked 30 patients with myeloproliferative neoplasms (MPNs) — rare, long-lasting bone-marrow cancers affecting around 40,000 people in the UK — for up to 25 years, combining whole-genome sequencing with nearly 8,000 blood test results. By reconstructing genetic 'family trees' of blood cells from more than 450 samples, the team found that patients whose disease remained stable had genetically 'steady' blood cell populations, while those who progressed accumulated new DNA changes over time. The results suggest progression may be biologically 'encoded' years before it becomes clinically visible.

The study also examined the roughly 10% of MPN patients lacking the common JAK2, CALR or MPL mutations. Their blood cells showed patterns consistent with normal aging rather than cancer — challenging the assumption that everyone with certain unusual bone-marrow features has true blood cancer. New British Society for Haematology guidelines already recommend describing some of these patients as having thrombocytosis without the mutations, rather than immediately diagnosing cancer.

'We've been able to watch how the genetic code of their disease evolves in advance of clinical changes,' said senior author Jyoti Nangalia. The findings support regular genomic monitoring to spot high-risk patients years earlier — and to spare others unnecessary treatment.

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