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

Abstract

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 errors 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.

Key words::

• BCR-ABL positive
• Chronic
• Dasatinib
• Imatinib
• Leukemia
• Myelogenous
• Nilotinib

Transparency

Declaration of funding

This study was funded by Pfizer.

S.I. and J.A.K. were the primary developers of the study design. S.D.C. had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. All authors assisted in interpreting the study findings and drafting the manuscript text, and served as the primary reviewers of the manuscript text. All authors were responsible for approving the manuscript and its contents.

Declaration of financial/other relationships

J.A.K. and S.D.C. have disclosed that they are employees of RTI Health Solutions, a company that received research funding from Pfizer for this study and for the development of this manuscript. J.W. and S.I. have disclosed that they are employees of Pfizer. The publication of this study’s results is not contingent upon the sponsor’s approval or censorship of the manuscript.

CMRO peer reviewers on this study have no relevant financial or other relationships to disclose.

Acknowledgments

The authors thank Debanjali Mitra and Peter Trask for their contributions to the original study design and analyses, and Samantha K. Kurosky, an employee of RTI Health Solutions, for her assistance with preparing this manuscript which was funded by Pfizer.

Previous presentation: Portions of the data reflected in this manuscript were presented in poster format at the 15th Annual European Congress of the International Society for Pharmacoeconomics and Outcomes Research, 3–7 November 2013, Berlin, Germany.