Treatment patterns and prognostic indicators of response to therapy among patients with chronic myeloid leukemia in Australia, Canada, and South Korea

Objective: Given the multiple options for treatment of chronic-phase chronic myeloid leukemia (CML) with tyrosine kinase inhibitors, our objective was to understand treatment patterns in routine practice and prognostic indicators of response.

Research design and methods: We conducted a retrospective medical record review of 681 patients with CML in Australia, Canada, and South Korea. Eligible patients had a diagnosis of chronic-phase CML, were Philadelphia chromosome– and/or BCR-ABL–positive, were aged 18 years or older, and had been treated with first-line imatinib therapy between January 2005 and September 2010. Data on patient demographics, medical history (e.g., comorbidities, Sokal score), and treatment characteristics (e.g., time to initiation, therapy duration) were abstracted. Descriptive analyses were stratified by country and therapy line. Prognostic indicators of response to imatinib were evaluated using multivariable logistic regression, adjusting for country, patient demographics, medical history, treatment characteristics, and side effects.

Main outcome measures: Hematologic, cytogenetic, and molecular responses at 3, 6, 12, and 18 months following initiation of each therapy line.

Results: Patients’ average age was 57 years, and 59% were male. Overall, imatinib was initiated approximately 4 months following CML diagnosis. Complete or major molecular response (C/MMR) at 6 months following imatinib initiation was 54% in Australia, 22% in Canada, and 38% in South Korea. At 18 months, over 60% of patients achieved C/MMR. Approximately 30% of patients discontinued imatinib primarily due to intolerance and lack of response. Among patients who received second-line treatment, dasatinib was used more frequently than nilotinib. Multivariable regression results indicated Sokal score was identified as a prognostic indicator of response to imatinib therapy at several time points.

Limitations: There are several limitations to this study. First, we selected a convenience sample of patients and physicians and therefore results may not be representative of the true population of patients with chronic-phase CML. Second, data were entered by the selected physician and could be subject to data entry error or inaccuracies. Third, limited information was collected from the patient records, and it is possible that we did not capture additional prognostic or confounding factors related to the measured outcomes. Next, because this was an analysis of previously documented data (i.e., retrospective), we were unable to provide a priori definitions of response. Finally, multivariable analyses were limited to imatinib-related outcomes.

Conclusions: Treatment patterns and prognostic indicators differed by country. Health care providers, payers, and patients can utilize these results to inform treatment and policies aimed at improving the effectiveness of care for patients with chronic-phase CML.