Blood Test Improves Treatment for Acute Myeloid Leukemia

A simple blood test has been developed that is capable of detecting trace levels of leukemia cells remaining after intensive chemotherapy. The test can predict which patients with acute myeloid leukemia (AML) are at risk of their cancer returning in the future, helping to guide doctors on what further treatment is needed.

AML is a type of blood cancer diagnosed in around 2,400 people each year in the UK and survival rates are extremely poor, with fewer than 2 in 10 patients surviving for more than five years. The leukemia can be cured in patients who are able to tolerate intensive treatment and the prognosis is better in these patients.

A large team of scientists led by those at the UK National Institute for Health Research (London, UK) enrolled patients in a trial from April 6, 2009, to December 31, 2014. Centralized molecular screening identified patients with nucleophosmin (NPM1) mutations. Follow-up samples were scheduled to be obtained at the time of blood-count regeneration after each cycle of treatment and then quarterly until 24 months after consolidation therapy. Samples that were obtained at early time points (i.e., on regeneration after induction and consolidation cycles) were mostly samples of peripheral blood, since the evaluation of bone marrow was prioritized for flow cytometry.

The team detected minimal residual disease (MRD) on reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) using a mutation-specific primer with a common primer and probe. Assays were run in triplicate on the ABI 7900 platform (Applied Biosystems; Foster City, CA, USA) and mutated transcript levels were compared to expression of a reference gene with the use of plasmid standards with the difference-in-cycle-thresholds method used for rare mutations. High-throughput sequencing with the use of HaloPlex Target Enrichment (Agilent Technologies; Santa Clara, CA, USA) was performed on the HiSeq 2000 (Illumina; San Diego, CA, USA).

The scientists found that MRD testing was far superior at predicting relapse compared to current methods, which mainly rely on analysis of genetic abnormalities within individual patients' cancer cells that influence whether they are “high risk” or “low risk” at the start of treatment. The MRD test can determine if a patient is in “molecular remission,” which means there are no signs of the faulty genes indicative of leukemia cells in their blood. In 82% of cases in which the MRD test detected the presence of the NPM1 cancer gene in a blood sample taken after initial treatment, the patient had relapsed within three years. Only 30% of patients who had no detectable leukemia cells in their blood at this stage went on to relapse within that time.

David Grimwade, PhD, a professor and principal investigator of the study said, “Conventional methods for guiding treatment for this aggressive type of leukemia are inadequate. The MRD test is an invaluable tool to assess treatment response and identify those patients for whom chemotherapy is not sufficient and require stem cell transplantation or new treatments.” The study was published on January 20, 2016, on the journal the New England Journal of Medicine (NEJM).

Related Links:
UK National Institute for Health Research
Applied Biosystems
Agilent Technologies