My Doctor’s Explanation

Question: “Why was my diagnosis changed to Chronic Myelogenous Leukemia (CML) in Bilineal Blast Crisis?”

Doctor’s response: Let’s focus on the bilineage part first. White blood cells can be of myeloid or lymphoid origin. When [Kurt] came to the hospital he had a high white blood cell count with mostly lymphoid cells. The high white count favored an acute leukemia. The first and most likely diagnosis is acute lymphoblastic leukemia (ALL). We then performed a bone marrow biopsy and flow cytometry that showed that 77% of his bone marrow cells were of lymphoid origin and that 1-2% that appeared to be of myeloid origin. This meant there were two lineages – lymphoid and myeloid, although the myeloid population was very tiny. In these cases, we design a therapy that targets both lineages. For lymphoid leukemias we treat with a lymphoid induction chemotherapy regimen, which in your husband’s case was E2993. For myeloid leukemias, we can treat with myeloid induction chemotherapy or for patients that are Philadelphia chromosome positive, we can treat with a tyrosine kinase inhibitor such as Imatinib (also known as Gleevac) or Desatinib (also known as Sprycel). Because [Kurt] was Philadelphia chromosome positive, the chemotherapy plan we designed for [him] was E2993 induction with Desatinib. I want to emphasize that if [Kurt] had simply Philadelphia chromosome positive ALL (in other words no myeloid cells) we would still use the exact same regimen of E2993 induction with Desatinib.

Now let me explain in more detail the diagnosis of chronic myelogenous leukemia (CML) in blast crisis. The pathologists emphasized to us that this was a challenging case. When the pathologists first gave us their analysis of the bone marrow, they also saw basophils and increased myeloid growth which suggested CML in blast crisis. CML is at first a slow growing disease but goes through 3 phases: chronic (slow), accelerated (medium), and blast phase (fast). Some people with CML to get from chronic phase to blast phase; others and we suspect, for [Kurt], this shift from slow to fast occurred over months at most. In blast phase (the fast growing phase), CML can make either or both myeloid or lymphoid blasts which is consistent with what we saw for [Kurt]. The definitive tests to prove CML are molecular tests and cytogenetic test in which we analyze [his] chromosomes. These tests confirmed the presence of the Philadelphia chromosome and also that the size of the BCR-Abl product was the p210 product. You can read more about this, but this p210 product is found in CML not ALL.

I want to emphasize, however, that we were thinking about both diagnoses from the start of [Kurt’s] care and that for both diagnoses, our treatment plan was exactly the same. Even though the p210 test was pending when we started treatment, we were confident that the chemotherapy plan we outlined would be the best treatment for both diagnoses. Our goal is to cure [Kurt], and the current plan of E2993/desatinib and transplantation is the best strategy for defeating his leukemia.