Researchers in England are reporting that use of a sensitive test they developed to detect a genetic abnormality in persons with acute myeloid leukemia (AML) after treatment may help predict a relapse (return of cancer), so that more intensive therapy can be administered before the relapse occurs.
Acute myeloid leukemia is characterized by the presence of cancer cells in the blood and bone marrow. AML is sometimes associated with cell genetic abnormalities, the most common of which involves the switching of 2 chromosomes, chromosome 8 and chromosome 21. This abnormality, referred to as translocation 8:21 or t(8:21), produces an abnormal gene, called a fusion gene. Treatment for AML is usually systemic chemotherapy, with more intensive drugs being used if and when a relapse occurs. Persons with AML who have the t(8:21) genetic abnormality have a better outcome than those who do not; however, 20 to 30% still have a relapse, usually within 3 to 18 months of diagnosis. Therefore, tests to measure the presence of leukemia cells left after treatment would be highly useful in determining which persons need further therapy.
The researchers in England developed a sensitive new type of already existing test, called a reverse transcriptase-polymerase chain reaction (RT-PCR) assay, to detect the specific fusion gene produced because of the t(8:21) abnormality. They then sought to use this new test to track the number of leukemia cells remaining after treatment for persons with the t(8:21) abnormality by tracking the number of fusion genes still present. After treatment, 5 of the 20 patients had detectable amounts of the abnormal fusion gene, and all 5 of these persons had a relapse of disease within 3 to 6 months. Other patients, who no longer had any detectable amount of the fusion gene, did not suffer a relapse.
The researchers concluded that the use of the new RT-PCR assay to detect the abnormal fusion gene in patients who have AML with t(8:21) may help identify which persons have leukemia cells remaining after treatment and are therefore likely to relapse. Identifying the likelihood of relapse may allow more intensive chemotherapy to be provided (perhaps with a procedure such as stem cell transplantation) and the anticipated relapse prevented. (Blood, Vol 95, No 3, pp 815-819, 2000)