Adherence to immunomodulatory drugs in patients with multiple myeloma

Immunomodulatory drugs (thalidomide, lenalidomide and pomalidomide; IMID) are widely used in the treatment of multiple myeloma patients. To date, few data are available on IMID adherence in multiple myeloma patients. The aim of our study was to evaluate IMID adherence and to compare two indirect methods to measure IMID adherence in multiple myeloma patients: a specific questionnaire and the medication possession ratio (MPR). Another aim was to explore this specific questionnaire for the assessment of IMID adherence in multiple myeloma patients.

All consecutive multiple myeloma patients, with at least two consecutive dispensations of thalidomide, lenalidomide or pomalidomide in our hospital were included in this prospective study. IMID adherence was measured using a specific questionnaire and the medication possession ratio. Relationship between the questionnaire scores and variables of interest was evaluated by multiple linear regression with a robust variance estimator.

Sixty-three patients were included in our study. The mean questionnaire score was 8.2±1.2 and the mean medication possession ratio value was 0.97±0.06. A total of 76% of patients were considered adherent according to the questionnaire (i.e. score ≥ 8), 94% according to the medication possession ratio (i.e. MPR ≥ 0.90), and 70% according to the questionnaire and the medication possession ratio. No statistically significant linear association was observed between the questionnaire score and any variables of interest including medication possession ratio. All Cronbach's alpha were relatively low (range 0.0342-0.2443), showing a low correlation of the different questions with the questionnaire score.

Our study is the first prospective study evaluating IMID adherence in multiple myeloma patients in real life. The high adherence to IMIDs reported here, regardless of the drug, is encouraging considering the efficacy, toxicity and elevated cost of IMIDs. The specific questionnaire should be used with caution to evaluate IMID adherence.