Medication Adherence Among Adults With Comorbid Chronic Conditions Initiating Oral Anticancer Agent Therapy for Multiple Myeloma

PURPOSE: Increased use of oral anticancer agents (OAAs) has empowered adults with multiple myeloma (MM) to manage their oncolytic therapy, but such a shift may result in issues with medication use, particularly among patients being concurrently treated for pre-existing, multiple chronic conditions. METHODS: This retrospective cohort study used 2013-2018 commercial and Medicare claims data to assess medication use in adults with MM. To be included, adults (18 years and older) must have been diagnosed with and had 2+ claims for an OAA, had continuous enrollment for 12 months before and after OAA initiation, and have been previously diagnosed with and had prescription fills for 2+ select chronic conditions. The proportion of days covered metric assessed medication adherence and was compared for 12 months before and after the OAA initiation by Wilcoxon signed-rank tests, McNemar's tests, and difference-in-differences models. RESULTS: The mean OAA adherence in the first year of therapy was 58.3% (standard deviation: 24.5) and 65.1% (standard deviation: 27.01) for commercial and Medicare patients, respectively. Adherence and the proportion adherent (proportion of days covered ≥ 80%) to comorbid therapies generally declined in the first year after OAA initiation. Changes in medication use were particularly noticeable among those on antihypertensive therapy: adjusted analyses uncovered a 2.5% (Medicare) and 5.2% (commercial) difference in adherence to these medications between those initially adherent and nonadherent to OAA therapy (both P < .05). CONCLUSION: Initiating OAA therapy in adults with MM may complicate an already complex treatment regimen, resulting in poor overall medication adherence in patients with multiple comorbid conditions.