Biphenotypic acute leukaemia (BAL) is a mixture of both types of acute leukaemias, acute myeloid leukaemia (AML) and acute lymphoblastic leukaemia (ALL).
Biphenotypic (bye-fee-no-tip-ik) just means ‘both types’. There are several tests that help to determine each type of leukaemia. One test looks for special ‘markers’ on the outside of the cells and other tests look at the chromosomes in the leukaemia cells. The particular markers on a cell give it its ‘phenotype’. So, this testing is called immunophenotyping. In biphenotypic leukaemia the leukaemia cells have markers for two different types of cells on their surface. They have markers for lymphoid cells, which are usually found in acute lymphoblastic leukaemia (ALL). They also have markers for myeloid cells, which are usually found in acute myeloid leukaemia. The leukaemia is therefore called biphenotypic because it has markers for two different types of cells. Researchers studying the chromosomes of people with BAL report structural abnormalities including a high incidence of the Philadelphia chromosome, chromosome rearrangements and other abnormalities.
Who does it commonly affect?
BAL is an uncommon type of leukaemia. It is estimated that around 5% of people with acute leukaemia have biphenotypic leukaemia. Based on this incidence rate, we estimate that about 65 cases would be diagnosed in Australia among the over 1300 cases of acute leukaemias.
BAL can affect people of any age but it’s more common in adults than in children.
Do we know what causes it?
BAL can develop for no known reason, or after another cancer treatment.
How is it treated?
BAL can be difficult to treat and people who get into remission have a high risk of relapse. Generally treatment is chosen according to the most common type of immature blood cells or blasts (AML or ALL) present in the leukaemia and so may use the chemotherapy for ALL or for AML. It is likely to be an intensive approach with chemotherapy, followed by a bone marrow transplant if appropriate. Your doctor will discuss with you what treatment is likely to be best for you.
What is the prognosis?
Unfortunately biphenotypic leukaemia has a poor prognosis but there are some good prognostic features emerging from the limited research that has been conducted. The most important emerging factors indicating good prognosis are:
- people under the age of 60
- absence of the Philadelphia chromosome
- achievement of complete remission after treatment.