Medication adherence to oral anticancer drugs: systematic review.

Many studies have demonstrated that non-adherence to oral anticancer drugs (OACDs) has challenged treatment efficacy. Otherwise, few validated tools exist to measure patients' adherence to medication regimen in clinical practice. To synthesize previous studies on adherence by cancer patients taking OACDs, especially in targeted therapy, a systematic search of several electronic databases was conducted. We analyzed existing scales' contents for various cancer patients and outcomes of studies assessing adherence. However, a well-validated scale designed particularly for OACD adherence is still lacking. Most adherence scales used in the studies reviewed contain items focused on measuring patients' medication-taking behavior more than their barriers to medication compliance and beliefs. However, non-adherence to OACDs is a complex phenomenon, and drug-taking barriers and patient beliefs significantly affect patients' non-adherence. To understand the key drivers and predisposing factors for non-adherence, we need to develop a well-validated, multidimensional scale.