Exploring chronic myeloid leukemia patients’ reasons for not adhering to the oral anticancer drug imatinib as prescribed

Abstract

Nonadherence has been shown to be frequent amongst chronic myeloid leukemia (CML) patients prescribed imatinib, which results in reduced clinical response and increased healthcare costs. However, little is known about the reasons why CML patients frequently do not take their imatinib as prescribed. The current study explored CML patients’ experience of taking, or not taking, imatinib therapy through in-depth interviews with twenty-one patients. Their adherence had been previously measured using a medication events monitoring device. The interviews were recorded, transcribed and analysed in accordance with established techniques. Patients revealed a variety of reasons for their nonadherence. Major themes that emerged from the data were the intentional and unintentional reasons for nonadherence. Furthermore, as a result of information received from health care professionals, several patients felt inappropriately reassured that their nonadherence would not have a detrimental effect on their clinical response. Factors that seemed to favour adherence were finding ways to deal with side effects and using prompts as reminders to take the medicine. This study forms a basis on which to build future adherence research and may help to develop interventions designed to ensure that patients with CML and other cancers adhere optimally to their oral drugs treatment.

Introduction

Adherence has been defined by the WHO as the extent to which a person's behaviour corresponds with agreed recommendations of a healthcare provider [1]. The adherence rates to oral anticancer therapies vary greatly; for example, a review of 6 studies investigating adherence to oral anticancer treatments in adults reported nonadherence rates between 0% and 83% [2]. This variation in the reported nonadherence rates can be partly explained by differences in measurements and definitions of nonadherence; the average nonadherence rate to oral anticancer treatments has been estimated as 21% [3].

Imatinib (Gleevec^® in US/Canada/Israel; Glivec^® elsewhere; Novartis, Basel, Switzerland) has transformed chronic myeloid leukemia (CML) from an inexorably fatal illness to a chronic illness that can be managed by the patient at home; nevertheless several recent studies have shown that lack of adherence to imatinib is frequent and may have a significant impact on a patient's outcome [4], [5]. For example a Belgian study found that one third of 169 patients were nonadherent, and only 14% took all of their prescribed imatinib; this nonadherence was associated with reduced clinical response [4]. We have reported that 26% of the patients on long term imatinib therapy have an adherence rate lower than 90% and that the adherence rate is the most important factor determining the achievement of molecular responses [5]. In addition, a US study found that nonadherence to imatinib in CML patients led to increased health care costs; 31% of 267 patients were identified as having treatment interruptions of at least 30 consecutive days during a 365 days follow-up period [6].

Nonadherence to potentially lifesaving therapy seem counterintuitive and very little is known of the reasons why CML patients are nonadherent to imatinib therapy. This paper reports a qualitative study that explored the experience of CML patients of taking, or not taking, their imatinib as prescribed. The interviews reported here complemented the results of a UK clinical trial reported previously that investigated the relationship between imatinib adherence and clinical response [5].