Dr Nicholas Goulden, Great Ormond Street Hospital

The aim of the first stage of treatment for acute lymphoblastic leukaemia (ALL) is to induce remission by eradicating the majority of leukaemia cells and allow the bone marrow to resume its normal function. A child is said to have achieved remission when it is no longer possible to detect leukaemia cells in samples of their bone marrow viewed through a microscope.

However, every child will have some leukaemia cells remaining in their bone marrow when they achieve remission. This is known as minimal residual disease – or MRD. The number of remaining leukaemia cells is minute - often less than one leukaemia cell in 10,000 normal cells – which is why it isn’t possible to detect them under the microscope.

A new technique has been developed which enables scientists to accurately measure the level of MRD in a child’s bone marrow, and it has been shown that the precise level of MRD, which varies widely from child to child, is a good indicator of relapse risk.

Doctors and scientists are now working together to establish whether children’s treatment regimes can be individually tailored according to their MRD status. They aim to establish whether relapse can be avoided in children with a high level of MRD after stage one of treatment by intensifying their chemotherapy at this early stage; and whether children with a lower level of MRD can receive lower doses of chemotherapy, minimising their risk of treatment-related side-effects without compromising their chance of a cure.

Scientists in four laboratories around Britain (in Bristol, Glasgow, London and Sheffield) have been trained in the use of the molecular techniques which enable them to measure the level of MRD in bone marrow. As the current national clinical trial for ALL, all children diagnosed with ALL are asked to participate in the trial. Samples are collected from children at diagnosis and then at the relevant time-points during treatment and sent to one of these four centres for analysis.

Around 1,000 children have now commenced treatment under the trial, now in its fifth year. Even at clinical trial stage, it is likely that this technique has already saved young lives. We expect that, within the next three years, this technique will become part of standard NHS practice.

This project has been acclaimed as the most promising way forward in improving the prognosis and reducing harm in children with leukaemia.

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