Factors Predicting Intentional Non-Adherence In Chronic Myeloid Leukemia: A Multivariate Analysis On 2546 Patients By The CML Advocates Network

Adherence to the prescribed dose of tyrosine kinase inhibitors (TKIs) is critical to maximize treatment effectiveness in chronic myeloid leukemia (CML). While patient-centered outcome studies are lacking in this area, literature has shown that a significant proportion of patients report both intentional and unintentional non-adherence.

The main objective of this multivariate analysis was to identify risk factors that might predict intentional non-adherence to TKIs in CML.

The CML Advocates Network, connecting 79 CML patient groups from 63 countries, conducted an international project investigating patterns of medication-taking behaviors of CML patients, supported by CML investigator groups in Germany, Italy and France. We sought to demonstrate the relationship between 16 factors and adherence in this multinational cohort. A web-based survey was launched in 12 languages, enrolling CML patients from Sept 2012 to Jan 2013. The identical questionnaire was provided to a cohort of patients recruited in clinics in France, Germany and Italy, returned by patients in a pre-stamped envelope to an independent data center. Questions included potential factors associated with non-adherence as well as on patients' perception of disease and treatment burden.

Based on previous literature and on clinical relevance, a pool of 16 candidate factors, potentially predicting intentional non-adherence, was selected for analysis. These included: frequency of CML medication, co-payment for CML treatment, and current TKI therapy. Patients who reported having skipped intentionally one or more doses over the last year were considered as “intentional non-adherers”. Univariate logistic regression analysis was performed to examine the impact of pre-selected candidate factors on the probability of intentional non-adherence. Two multivariate models were fitted based on line of therapy received by patients (i.e. first line and second or greater lines of therapy).

This patient-led study is the largest study conducted to date on the influencers of non-adherence in CML. Overall, 2546 adult CML patients (47.6% female) under TKI treatment from 79 countries responded to the survey. 2151 patients responded online, 395 questionnaires were returned on paper. No significant difference on intentional non-adherence was observed between paper or online responses. Median age of patients was 51 years (range 18-96) and median time from diagnosis was 4 years (0-27). Overall, 51.6% of all respondents reported having missed at least one dose unintentionally over the last year, and 19.5% did so intentionally. This analysis regards the intentional non-adherent population (n=490). Of those, 60% were on imatinib, 20% on nilotinib, 14% on dasatinib, 6% on other TKIs.

Several factors predicted intentional non-adherence in univariate analysis, including education level (P=0.016) and co-payment for TKIs (P=0.005). For patients on first line TKI (n=1551), the following factors independently predicted a higher likelihood of being intentional non-adherers: younger age (P=0.015), longer time since diagnosis (P<0.001), lower satisfaction with information received from healthcare providers (P=0.002), higher burden on social life (P<0.001) and not being fully informed on the importance of adherence (P=0.042). Non-adherence was lower when patients were told every dose was important to make the treatment work (P=0.042). Overall, intentional non-adherers intended to avoid fatigue (13%), diarrhea and GI issues (11%), nausea (10%) and muscle pain (9%). For patients in second or greater lines of therapy (n=985) all of the above factors were still statistically significant except for satisfaction with information received. Being female (P<0.001) also increased the likelihood of intentional non-adherence in this group.

Despite there is clear evidence that survival is close to that of the general population when CML is treated effectively in chronic phase with current therapies, every fifth CML patient deliberately skips doses. Key factors predicting intentional non-adherence can potentially help physicians and patient organisations to identify patients early who should be monitored more closely and informed about the importance of adherence. Managing side effects proactively also reduces reasons for intentional non-adherence.

Geissler:Novartis: Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Pfizer: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees. Efficace:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy. Bombaci:Ariad: Consultancy; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy. de Jong:Novartis: Membership on an entity’s Board of Directors or advisory committees. Gavin:Celgene: Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees. Daban:Ariad: Membership on an entity’s Board of Directors or advisory committees; Pfizer: Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees. Pelouchová:Bristol-Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees. Sharf:Pfizer: Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees.