Philadelphia Chromosome positive acute lymphoblastic leukemia (Ph+ALL) is a rare subtype of the most common childhood cancer, acute lymphoblastic leukemia (ALL). Like ALL, Ph+ ALL is a cancer of a type of white blood cell called lymphocytes. It has a well-known mutation
in its genetic code that fuses two genes together (the BCR and ABL
genes) that do not normally fuse together. This BCR-ABL gene, also known
as the Philadelphia Chromosome, can cause the white blood cells to
become cancerous. While this Philadelphia chromosome is rare in pediatric ALL, it is much more common in adult ALL. It’s also the main cause of another much more common adult leukemia called chronic myelogenous leukemia (CML).
The
signs and symptoms of Ph+ ALL are the same as standard ALL, which
include: enlargement of the liver or spleen, enlarged lymph nodes,
paleness, fevers, bruising, weight loss, bone pain, and abnormal blood
cell counts. These symptoms are nonspecific and can occur in more common
viral illnesses, as well.
Historically, pediatric Ph+ ALL patients had been very difficult to cure with standard chemotherapy.
Survival rates were only around 30 percent, compared to survival rates
of most pediatric ALL patients of more than 85 percent. It was not until
recently, when a new class of drugs that directly target the Philadelphia Chromosome were developed, that that survival rates doubled to about 70 percent.
These
drugs are called tyrosine kinase inhibitors. The most well-known drug
in this class is called imatinib (or Gleevec). Using imatinib,
in combination with chemotherapy, is now the recognized
standard-of-care treatment for kids with Ph+ ALL. In fact, the next
large US clinical trial that will attempt to improve the outcomes in
children with Ph+ ALL will use imatinib in combination with
chemotherapy.
Research
is going into developing new types of drugs to directly target the
Philadelphia Chromosome. Other research is also focused on trying to use
alternative therapies to cure those 30 percent of patients who don’t
respond to treatment with imatinib (or similar drugs in its class).
Explore more about Hematology this July at Rome, Italy. For more information, PS: WORLD HEMATOLOGY 2019
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