Adherence enhancing interventions for oral anticancer agents: a systematic review

Background: The use of oral anticancer agents has increased in the last decades. Adherence is a crucial factor for the success of oral anticancer agent therapy. However, many patients are non-adherent.

Objective: The objective was to evaluate the effectiveness of adherence interventions in patients taking oral anticancer agents.

Methods: A systematic literature search was performed in Medline and Embase. Titles and abstracts and in case of potential relevance, full-texts were assessed for eligibility according to the predefined inclusion criteria. The study quality was evaluated. Both process steps were carried out independently by two reviewers. Relevant data on study design, patients, interventions and results were extracted in standardized tables by one reviewer and checked by a second reviewer.

Results: Six controlled studies were included. Only one study was randomized. The study quality was moderate to low. One study showed statistically significant results in favor of the adherence intervention, two studies showed a tendency in favor of the intervention, one study showed an inconsistent result depending on the adherence definition and one study showed almost identical adherence rates in both groups. One study showed a tendency in favor of the control group.

Conclusions: Although most of the interventions are not very effective, it appears that certain adherence enhancing interventions could have a promising effect. One crucial point is the consideration of the baseline adherence when choosing patients to avoid ceiling effects. The evidence is limited due to lack of sufficient studies and partly inconsistent results. Further high quality studies are needed.