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What Is Philadelphia Chromosome Positive ALL?

February 20, 2017
4 min read
What is Ph+ALL?

Dr. Gordon Cohen is a St. Baldrick’s Fellow at the John Hopkins Children’s Center. He’s testing new drugs for patients with Ph+ALL who relapse or fail to respond to treatment. He explains Ph+ALL symptoms, treatment options, and how your support is moving clinical trials forward to help kids with this disease.

What is Ph+ALL?

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. What makes it different from standard ALL is that 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).

What are the signs and symptoms of Ph+ALL?

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. For example, patients presenting with mononucleosis can have many of these same symptoms and sometimes it can take specialized testing to distinguish the two diseases.

How is Ph+ALL diagnosed?

Once a patient is diagnosed with ALL there are specialized tests that are performed to look inside the cancer cells at their specific genes. These tests try to identify if there are any known mutations that may make the cancer more or less susceptible to cancer fighting drugs. The Philadelphia Chromosome is one of the many genetic mutations that can be identified with these diagnostic tests. In fact, patients do not typically discover that they have the Ph+ ALL subtype until a week or two after they are diagnosed with ALL, and the more advanced testing has been performed.

What treatment options are available to patients with Ph+ALL?

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.

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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.

How is research helping kids with Ph+ALL?

As noted above, Ph+ ALL cure rates are improving, but they still lag behind most pediatric patients who are diagnosed with ALL. Some of the research is going into developing new types of drugs to directly target the Philadelphia Chromosome. Other research is 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) — which is a particularly difficult group of patients to cure.

Our research falls into the latter group. We are attempting to understand why some pediatric Ph+ ALL patients relapse or don’t respond to imatinib, and how we can use another class of medication in combination with imatinib to help to improve cures.

Has your child been touched by childhood cancer or do you know a child that has been diagnosed? St. Baldrick’s Honored Kids, who have been affected by cancer, inspire fundraising participants to be part of the Foundation’s mission — to fund lifesaving research.

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