Cancer cells can reactivate after decades

A new study, published in the journal Leukemia and reported on the BBC News website, suggests that cancer cells can go to sleep and then reawaken years later – completely avoiding the effects of chemotherapy whilst dormant.

The new findings by the Institute of Cancer Research may explain why some cancers return years after they appear to have been cured, but also present the possibility of identifying the dormant cancer cells and killing them before they become a problem.

 The study was based on analysis of a patient whose leukaemia had returned after 20 years in remission. Blood and bone marrow samples had been taken from the patient at the age of four, when he was diagnosed with a rare form of leukaemia, and these were then compared to samples taken when the cancer returned at the age of 25. It was found that the cancer cells which “woke up” in the patient were similar to a group of cancer cells that pre-dated the original incidence of the disease.

Researchers identified a specific DNA mutation in cancer cells from both blood samples, in which two genes called BCR and ABL1 fuse together, and which establish a common link between the original and the relapsing leukaemia. But they also found many new genetic changes had occurred in the cancer cells when the patient relapsed. This implies that cancer cells had become dormant, resisted chemotherapy and then “woken up” after many years of rest. Chemotherapy is designed to attack rapidly dividing cells, and it is suggested that slowed rate of growth of the “sleeping” cancer cells is what allowed them to survive treatment.

In the BBC report, study leader Professor Mel Greaves, director of the Centre for Evolution and Cancer at The Institute of Cancer Research in London, says: “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.”

Gordon Wishart, Professor of Cancer Surgery and Medical Director of Check4Cancer, comments: “This could be a very significant breakthrough for those who have suffered cancer and are in remission. If it proves possible to speed up the growth of pre-cancerous dormant cells so that they can be targeted and killed using chemotherapy, as the researchers suggest, this could greatly reduce the risk of future relapse.”