Note: Estimated new cases and deaths from chronic myelogenous leukemia in the United States in 2008:[1]

• New cases: 4,830.
• Deaths: 450

Chronic myelogenous leukemia (CML) is one of a group of diseases called the myeloproliferative disorders. Other related entities include polycythemia vera, myelofibrosis, and essential thrombocythemia. (Refer to the PDQ summary on Chronic Myeloproliferative Disorders Treatment for more information.)

CML is a clonal disorder that is usually easily diagnosed because the leukemic cells of more than 95% of patients have a distinctive cytogenetic abnormality, the Philadelphia chromosome (Ph1).[2,3] The Ph1 results from a reciprocal translocation between the long arms of chromosomes 9 and 22 and is demonstrable in all hematopoietic precursors.[4] This translocation results in the transfer of the Abelson (ABL) on chromosome 9 oncogene to an area of chromosome 22 termed the breakpoint cluster region (BCR).[4] This in turn results in a fused BCR/ABL gene and in the production of an abnormal tyrosine kinase protein that causes the disordered myelopoiesis found in CML. Furthermore, these molecular techniques can now be used to supplement cytogenetic studies to detect the presence of the 9;22 translocation in patients without a visible Ph1 (Ph1-negative).

Ph1-negative CML is a poorly defined entity that is less clearly distinguished from other myeloproliferative syndromes. Patients with Ph1-negative CML generally have a poorer response to treatment and shorter survival than Ph1-positive patients.[5] Ph1-negative patients who have BCR/ABL gene rearrangement detectable by Southern blot analysis, however, have prognoses equivalent to Ph1-positive patients.[6,7] A small subset of patients have BCR/ABL detectable only by reverse transcriptase–polymerase chain reaction (RT–PCR), which is the most sensitive technique currently available. Patients with RT–PCR evidence of the BCR/ABL fusion gene appear clinically and prognostically identical to patients with a classic Ph1; however, patients who are BCR/ABL-negative by RT–PCR have a clinical course more consistent with chronic myelomonocytic leukemia, which is a distinct clinical entity related to myelodysplastic syndrome.[6,8,9] Fluorescent in situ hybridization of the BCR/ABL translocation can be performed on the bone marrow aspirate or on the peripheral blood of patients with CML.[10]

The median age of patients with Ph1-positive CML is 67 years.[11] The median survival is 4 to 6 years, with a range of less than 1 year to more than 10 years. Survival after development of an accelerated phase is usually less than 1 year and after blastic transformation is only a few months.[10]

References:

1. American Cancer Society.: Cancer Facts and Figures 2008. Atlanta, Ga: American Cancer Society, 2008. Also available online. Last accessed February 21, 2008.
2. Kurzrock R, Kantarjian HM, Druker BJ, et al.: Philadelphia chromosome-positive leukemias: from basic mechanisms to molecular therapeutics. Ann Intern Med 138 (10): 819-30, 2003.
3. Goldman JM, Melo JV: Chronic myeloid leukemia--advances in biology and new approaches to treatment. N Engl J Med 349 (15): 1451-64, 2003.
4. Deininger MW, Goldman JM, Melo JV: The molecular biology of chronic myeloid leukemia. Blood 96 (10): 3343-56, 2000.
5. Onida F, Ball G, Kantarjian HM, et al.: Characteristics and outcome of patients with Philadelphia chromosome negative, bcr/abl negative chronic myelogenous leukemia. Cancer 95 (8): 1673-84, 2002.
6. Martiat P, Michaux JL, Rodhain J: Philadelphia-negative (Ph-) chronic myeloid leukemia (CML): comparison with Ph+ CML and chronic myelomonocytic leukemia. The Groupe Français de Cytogénétique Hématologique. Blood 78 (1): 205-11, 1991.
7. Cortes JE, Talpaz M, Beran M, et al.: Philadelphia chromosome-negative chronic myelogenous leukemia with rearrangement of the breakpoint cluster region. Long-term follow-up results. Cancer 75 (2): 464-70, 1995.
8. Oscier DG: Atypical chronic myeloid leukaemia, a distinct clinical entity related to the myelodysplastic syndrome? Br J Haematol 92 (3): 582-6, 1996.
9. Kurzrock R, Bueso-Ramos CE, Kantarjian H, et al.: BCR rearrangement-negative chronic myelogenous leukemia revisited. J Clin Oncol 19 (11): 2915-26, 2001.
10. Sawyers CL: Chronic myeloid leukemia. N Engl J Med 340 (17): 1330-40, 1999.
11. Lee SJ, Anasetti C, Horowitz MM, et al.: Initial therapy for chronic myelogenous leukemia: playing the odds. J Clin Oncol 16 (9): 2897-903, 1998.