MUST READ: Why cancer can return even after a patient is cured

It is the news all cancer survivors fear - their disease has reared its ugly head once more and returned to ravage their body a second time.

In rare cases, cancers are known return even when patients have been free of the disease for so long that doctors regard them as cured.

And now, scientists believe they have explained the reason some cancers recur years, sometimes decades later.

Genetic evidence shows cancer cells can 'go to sleep', therefore avoiding the....
effects of treatment, only to 'wake up' years later.

Researchers at The Institute of Cancer Research in London said today their findings could suggest ways of rooting out dormant cancer cells.

Such treatment could eradicate the small risk that the disease will return after appearing to be cured, they said.

The study is unique in that researchers had access to blood and bone marrow samples from a patient with a rare form of leukaemia, which spanned 20 years.

They analysed the samples taken when the patient was diagnosed at four years old, as well as those taken when he relapsed as a 25-year-old, after 22 years in remission.
Professor Mel Greaves, who led the study, said: 'We have always known that in rare cases leukaemia can relapse when it appears to be cured, but what we've lacked is firm evidence that cancer cells can lie dormant for long periods of time.

'Our study shows a common genetic lineage linking the original leukaemia and relapsing disease decades later.

'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.

'In future it might be possible to speed up the growth of these precancerous dormant cells so that they can be targeted and killed using chemotherapy, to reduce the risk of relapse even further.'

The research team identified a specific DNA mutation, in which two genes called BCR and ABL1 fuse together, in cancer cells from both blood samples, taken 22 years apart.

This shows a common lineage between the original and relapsing leukaemia – implying that cancer cells had resisted chemotherapy by becoming dormant, and then ‘woken up’ after decades of slumber.

Scientists have long suspected dormant cells from original cancer were responsible for relapse, but evidence to support the theory.

This study has now suggested the cells that trigger a relapse survived because they were growing at a much slower rate than other cancer cells, resisting chemotherapy which attacks rapidly dividing cells.

It gives researchers important insights that might help them root out the cells, for example by 'waking them up' to enable chemotherapy to kill them.

The scientists found the reawakened cancer cells bore similarities to a group of cancer pre-cursor cells that pre-dated even the original bout of the disease. 

Researchers also found many new genetic changes had occurred in the cancer cells when the patient relapsed.

Dr Matt Kaiser, head of research at Leukaemia & Lymphoma Research, said: 'Despite impressive cure rates for the most common form of childhood leukaemia, there are still too many children whose cancer ends up coming back.

'If we can build up a picture of what causes rare cases of late relapse and how we can detect and prevent it, we may be able to deliver more true cures for this terrible disease.'

The research was funded by Leukaemia & Lymphoma Research, with additional support from the European Haematology Association, The Kay Kendall Leukaemia Fund and The Wellcome Trust.


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