Impact of Treatment Strategies on Clinical Outcomes In Chronic Phase Chronic Myeloid Leukemia (CP-CML) Patients In Canada

New treatment options in chronic myeloid leukemia (CML) have become available in the past years. However, there is a scarcity of published data documenting how patients are treated as well as the impact of the treatment of CP-CML in Canada.

To describe current treatment patterns and clinical outcomes of CP-CML patients receiving treatment in Canada.

Treatment data on CP-CML patients was extracted from a cancer patient treatment summary database, ONCO-CAPPS. The database is comprised of treatment summaries of over 12,000 Canadian cancer patients from across the country. For the study, CP-CML patients aged 18 years or older, who received 400mg of imatinib as 1^st-line treatment, and who completed at least 4 continuous weeks of this treatment between October 1, 2008 and December 31, 2009, were eligible for study inclusion.

A total of 301 patients met the selection criteria. At the time of review, 62% of patients had a confirmed diagnosis of CP-CML for 2 years or more.

Of the CP-CML patients in the study who were prescribed 400mg of imatinib as their initial CP-CML treatment, 51% (155/301) received a 2^nd line treatment option, either a dose modification or a change of therapy. Of those requiring 2^nd line treatment, 32% (50/155) of patients received an increase in their imatinib dose, resulting in an average daily dose of 664 mg, and representing a 66% increase in the dose of imatinib. Average response times for patients who received an increase in imatinib dose for Complete Hematological Response (CHR) was 183 days, for Complete Cytogenetic Response (CCyR) was 671 days, and for Major Molecular Response (MMR) was 971 days. These response times exceed both Canadian Consensus Guidelines as well as the 2009 ELN (European Leukemia Network) recommendations.

Furthermore, 45% (69/155) of patients receiving a 2^nd line CML treatment experienced intolerance to imatinib 400 mg resulting in dose decrease or treatment interruption. Switching to second generation tyrosine kinase inhibitor agents (dasatinib or nilotinib) due to inadequate response, loss of response or intolerance to imatinib occurred in 20% of the population.

Analysis of Canadian patients over time revealed that 51% of CP-CML patients initiated on 400mg imatinib received 2^nd line treatment. The most frequent modification was due to intolerance. Of note, 32% received a dose escalation, which was more common than switching to a second generation tyrosine kinase inhibitor. Furthermore, response times observed amongst patients in this study whose imatinib dose was escalated exceeded timelines for treatment response determination as noted in both internationally and locally recognized treatment guidelines. Published research demonstrates that delays in achieving response are associated with increased risk of progression among patients with CML.

Cribb:Drug Intelligence Inc.: Research Funding. Merali:Bristol-Myers Squibb Canada: Research Funding. Donato:Drug Intelligence Inc.: Research Funding.