A new chronic myeloid leukemia (CML) staging system was proposed

08-15-2006

"Several staging classification systems, all of which were designed in the preimatinib era, are used for CML. The World Health Organization (WHO) recently proposed a new classification system that has not been validated clinically. The authors investigated the significance of the WHO classification system and compared it with the classification systems used to date in imatinib trials ('standard definition') to determine its impact in establishing the outcome of patients after therapy with imatinib," scientists in the United States reported.

"In total, 809 patients who received imatinib for CML were classified into chronic phase (CP), accelerated phase (AP), and blast phase (BP) based on standard definitions and then were reclassified according to the new WHO classification system," explained J.E. Cortes and colleagues, M.D. Anderson Cancer Center. "Their outcomes with imatinib therapy were compared, and the value of individual components of these classification systems was determined. With the WHO classification, 78 patients (10%) were reclassified: 45 patients (6%) were reclassified from CP to AP, 14 patients (2%) were reclassified from AP to CP, and 19 patients (2%) were reclassified from AP to BP.

"The rates of complete cytogenetic response for patients in CP, AP, and BP according to the standard definition were 72%, 45%, and 8%, respectively. After these patients were reclassified according to WHO criteria, the response rates were 77% (p=.07), 39% (p=.28), and 11% (p=.61), respectively. The 3-year survival rates were 91%, 65%, and 10%, respectively, according to the standard classification and 95% (p=.05), 63% (p=.76), and 16% (p=.18), respectively, according to the WHO classification."

"Patients who had a blast percentage of 20-29%, which is considered CML-BP according to the WHO classification, had a significantly better response rate (21% vs. 8%; p=.11) and 3-year survival rate (42% vs. 10%; p=.0001) compared with patients who had blasts {{>=}}30%. Different classification systems had an impact on the outcome of patients, and some prognostic features had different prognostic implications in the imatinib era.

"The authors believe that a new, uniform staging system for CML is warranted, and they propose such a system," the researchers concluded.

Cortes and colleagues published their study in Cancer (Staging of chronic myeloid leukemia in the imatinib era - An evaluation of the World Health Organization proposal. Cancer, 2006;106(6):1306-1315).

For more information, contact J.E. Cortes, University of Texas, M.D. Anderson Cancer Center, Dept. Leukemia, Unit 428, 1515 Holcombe Blvd., Houston, TX 77030, USA.