Oral antineoplastic agents: how do we care about adherence?

Oral therapies, including hormone-based or targeted therapies, have recently taken an increasing place in cancer treatment. In this context, a state of the art of the available studies dealing with the adherence of adult patients to oral anticancer treatment is warranted. The purpose of this review is to address (i) the association between assessment methods and measured adherence, (ii) the putative factors related to adherence and (iii) new ways of improving adherence to oral cancer therapies.

We conducted a literature-based narrative review of studies obtained from Pubmed using medical subject heading terms and free-text terms combining concepts related to oral anticancer medication and adherence.

The analysis is based on 48 studies published since 1990, mostly assessing hormone-based therapy in breast cancer and targeted therapies in chronic myeloid leukaemia. Various methods of adherence were reported including self-report, medication measurement or combinations of methods. Adherence rates were found to vary from 14% to 100%. Beside patient related-factors, adherence rate discrepancies were found to be dependent on the method used. Furthermore, there was no consensual definition of adherence even regarding the same methods, some of them tolerating a period of interruption during the treatment period. Finally, several studies addressing persistence found a progressive decrease in adherence with time.

Adherence to novel oral therapies is a major issue and further research is warranted to standardize adherence assessment in clinical studies better and to define better the most appropriate approaches to improve long term adherence in oncology practice.