Cancer cells can lie dormant, avoiding the effects of chemotherapy, and then 'wake up' decades later, according to a new study.
Scientists at the Institute of Cancer Research believe this could explain why cancers come back, many years after they seem to have been eradicated.
The research, published in the journal Leukemia, looked at a patient whose leukemia had come back after two decades in remission.
%VIRTUAL-AFCSponserAds%Scientists found that the 'awakened' cancer cells were similar to those that pre-dated the first incidence of the disease but had also gone through several genetic changes. This suggests that the cancer cells had become dormant, resisted chemotherapy and then 'woke up' many years later.
Because chemotherapy kills rapidly dividing cells, experts believe the original cancer cells may have survived because they were growing much more slowly than the others.
Lead researcher Professor Mel Greaves, director of the Centre for Evolution and Cancer at The Institute of Cancer Research in London, said: "It provides striking evidence of cancer evolution in action, with cancer cells able to lie dormant to avoid treatment, and then to accumulate new mutations capable of driving a new bout of disease.
"Blood stem cells regularly fluctuate between being dormant or 'asleep' and dividing very quickly, so it seems cancer cells are just borrowing this trick to avoid being killed by chemotherapy."
He added: "In future it might be possible to speed up the growth of these pre-cancerous dormant cells so that they can be targeted and killed using chemotherapy, to reduce the risk of relapse even further."