Noam Z. Drazin (Hematologist & Oncologist, Cedars-Sinai Medical Group) gives expert video advice on: What causes chronic leukemia? and more...
What causes chronic leukemia?
Chronic leukaemias are caused by similar mechanisms to those that cause the acute leukaemias. It usually involves a mutation or a defect in the genetic material of the stem cells in the bone marrow. I think the general outline is that any particular haematologic malignancy can be caused by damage to the stem cell. Whether it's the primordial stem cell that leads to the production of every single cell in your body, or the particular cell that leads to the white blood cell formatinon, or the stem cell that leads to the red blood cell formation; in any case it's damage to a precusor cell that ultimately leads to the production of an abnormal population, or abnormal set of cells, that don't do the right job for your body.
What is "chronic myelogenous leukemia" (CML)?
CML, Chronic Myelogenous Leukaemia is a type of leukaemia, but also what we call a myeloproliferative syndrome. It is a syndrome that doesn't necessarily need to be malignant or cancerous, but can be benign that is as a result of bone marrow making too many white blood cells. In CML, this chronic type of leukaemia, you make too many white blood cells; not one time, not two times, but every single white blood cell is made in great degrees and amounts. You end up having the extensive population of white blood cells that are normally in the bone marrow and normally supposed to be in the bone marrow, circulating in the peripheral blood. So, taking a blood smear or a blood sample from somebody with CML or Chronic Myelogenous Leukaemia looks very much like looking at someone's bone marrow. This particular disease has a specific genetic mutation called the Philadelphia Chromosome; the 922 translocation so chromosomes 9 and 22 have some problem with them leading to this translocation, and is referred to as the Philadelphia Chromosome. This particular chromosome has been studied by multiple pharmaceutical companies and labs and research departments across the entire world and successfully came up with a targeted therapy. Now, we have two targeted therapies directed specifically to this particular genetic mutation.
What is the "Philadelphia chromosome"?
The Philadelphia chromosome is a genetic mutation identified in certain malignancies. Specifically, 95% of CMLs, or chronic myelogenous leukemia, as well as a certain percentage of acute lymphoid leukemias, have the presence of the Philadelphia chromosome. The Philadelphia chromosome is defined as having the presence of the translocation of chromosome 9 and 22. What does that mean? It means that a portion or a piece of the chromosome number 9 moves to the chromosome number 22. The Philadelphia chromosome, 9-22 translocation, and BCR-ABL are all synonymous with the genetic mutation responsible for the diagnosis of chronic myelogenous leukemia as well as a certain population of acute lymphoid leukemia.
What is "chronic lymphocytic leukemia" (CLL)?
Chronic lymphocytic leukaemia is another one of the chronic leukaemias that we treat. Similar to the differentiation between acute leukaemias being either myeloid or lymphoid, the chronic leukaemias have the same differentiation. So, the CLL or chronic lymphoid leukaemia involves a defect involving the lymphocytes; a type of white blood cell that help fight infection but in an indirect way. Additionally, CLL is on a spectrum of disease similar to SLL; small lymphocytic lymphoma or a type of non-Hodgkin's lymphoma. It makes it very interesting to treat patients with CLL because they can either be presenting with a leukaemic form of their disease (which means that the abnormal cells which happen to be lymphocytes are floating around in their bloodstream) or they can be presenting more like a non-Hodgkin's lymphoma as in SLL or small lymphocytic lymphoma (at which time you would see more lymph node groups or lymph node enlargements similar to how people present or are diagnosed with lymphoma). So, the challenge in treating patients with CLL is differentiating whether or not you are dealing mostly with a leukaemia or mostly with a lymphoma, and the treatment can differ between the two.