Each year, around 750 individuals in the UK are diagnosed chronic myeloid leukaemia (CML), a cancer that causes the bone marrow to produce too many white cells, called granulocytes.

A recent study shows that survival rates for people with CML are now well over 90%.1

Twenty years ago, life expectancy for someone diagnosed with CML was just six years but treatment developed over the last two decades has changed all that. 2018 marks 20 years since the first group of CML patients began clinical trials for new drugs, called tyrosine kinase inhibitors (TKIs).

“The leukaemia is characterised by a single chromosomal abnormality, known as the ‘Philadelphia chromosome’. This single abnormality creates a new gene that is present in the leukaemic cells but not in any other cells in the body,” explains Professor Jane Apperley, Chair of the Centre for Haematology at Imperial College.

This new gene makes a new protein that that is different to any other in the body, so researchers developed TKIs to target those specific proteins and stop the cells from growing and dividing.

 

Patients fight for drug approval

 

The efficacy of the TKIs was immediately apparent. From 1998 onwards, drug companies have continued to develop even more effective treatments.

“A recent study from Scandinavia shows that survival rates for people with CML are now well over 90%1 and many have the same life expectancy as they would have had before they were diagnosed with the condition,” says Apperley.

There are now a whole range of TKI drugs that are taken as a daily tablet. And, because they are focused on tackling a specific gene, the damage that you get with other forms of chemotherapy is not so widespread. “The patient and medical communities worked together and  fought to get all the drugs approved by NICE and to be able to prescribe them in a logical fashion, so now, if you fail to respond to one, you can move to the next,” says Apperley.

 

Treatment-free remission

 

Because CML is a single gene disorder, doctors can measure the amount of disease that’s left in the patient very precisely. A few years ago, a number of brave patients who clearly showed a very positive response to the treatment came off the drugs altogether, with very promising results.

“For people with very deep sustained responses it looks like about 40% could stay off the drugs and may have been cured simply by the tablets, which is phenomenal. We call this treatment-free remission,” says Apperley.

 

Unexpectedly high success rates

 

While the current drugs are hugely effective, there are a number of chronic side effects that mean many patients want to come off them altogether. Three years ago, Professor Richard Clark (University of Liverpool) led a study to see what would happen if patients were first given half the dosage for one year and then stopped completely. Yet, again, the results were unprecedented.

“Our results for the proportion of patients who can stop was much higher – at 70% – for reasons we don’t entirely understand,” says Apperley. The findings will be presented at the European Haematology Association in June and could spark the next wave of research into finding a cure.

Patients are who are effectively able to stop treatment have to achieve such deep remissions that there are virtually no traces of the cancer in their blood cells. They will need to undergo regular blood tests to check there is no relapse, but the importance of this development cannot be understated. Stopping treatment will save the NHS hundreds of thousands of pounds each year and, most importantly, it will give patients their life back.

The success seen by CML patients has sparked a whole range of research into cancer treatments and, while there is always more to be done, it’s clear to see why many are hailing CML drugs as the poster child for cancer treatment.

 


[1] Journal of Clinical Oncology, August 2016