Prescribing pattern of imatinib among chronic phase chronic myeloid leukaemia (CML) patients and its financial impact on Hong Kong

Abstract

Background: Chronic myeloid leukaemia (CML) is a haematological malignant disease involving haematopoietic stem cells. It is caused by a known reciprocal chromosomal t(9;22)(q34;q11) translocation, or known as Philadelphia chromosome. The translocation results in the formation of a chimeric BCR-ABL fusion gene. In the most recent guidelines published by NCCN and European LeukemiaNet in 2013, tyrosine kinase inhibitors (TKI) specifically inhibiting the Bcr-Abl tyrosine kinase, are the first-line therapy for patients with chronic phase CML. Imatinib is the oldest among the 3 TKI, and is the most commonly prescribed. Despite its proven therapeutic role in CML, imatinib is a drug of extreme high cost. Estimated annual drug cost is HKD$223,380for a standard 400mg adult daily dose. Therefore, this study aims to survey on the prescribing pattern of imatinib in CML patients, its funding status, response; and estimate its economic burden on the Hong Kong population. Methodology: This is a retrospective patient chart review study. All patients who were diagnosed with CML from 2003 to 2012 and were managed in QMH or QEH were reviewed. Electronic records were retrieved to see whether imatinib was started as first-line treatment within 6 months of diagnosis. The reasons for not initiating imatinib were also investigated. Patients’ response to imatinib, and funding source for the drug, were documented. Annual drug cost of imatinib was estimated from all CML patients who attended all Hospital Authority institutions in 2012 who were prescribed with the drug. Results: Total 153 patients from the 2 institutions were reviewed. One hundred twenty four (81%) of them started imatinib as first-line therapy within 6 months of diagnosis. Nine patients started second generation TKI as first-line. Among those who did not start TKI, the most common reasons are patient preference (3.9%) and financial difficulties (3.3%). Twelve paediatric patients are identified, and all but one of them started imatinib. Seventy one% patients on imatinib experienced side effects. Most frequently reported adverse reactions are thrombocytopenia, oedema and neutropenia. Twenty eight% switched to second generation TKI due to suboptimal response or intoleranceto imatinib. During their course of treatment, 46.3% patients on imatinib require social subsidy from Samaritan Fund. From the dispensing records, the average drug cost per patient per year is HK$113,902. The estimated annual cost burden on the whole Hong Kong population is HK$43,425,878. Conclusion: The prescribing rate of imatinib in chronic phase CML patients in Hong Kong is comparable to overseas prescribing rate. The drug has become a significant financial burden to patients’ family and the society as a whole.