Impact of Initiating Oral Anticancer Agent Therapy for Chronic Myelogenous Leukemia Among Adults with Multiple Chronic Conditions

Abstract

Background: The availability of oral anticancer agents (OAA) has facilitated adults’ ability to manage independently their treatment for chronic myelogenous leukemia (CML). However, pre-existing chronic disease is common among patients with cancer and initiating OAA therapy increases treatment burden on adults with both CML and multiple chronic conditions (MCC). The objective of this research was to examine adherence to OAAs in adult patients with CML who were treatment naïve and initiating an OAA and to assess whether such initiation affected adherence to medications for existing chronic conditions. Methods: This was a retrospective cohort study that used MarketScan commercial claims and a 20% sample of Medicare claims for 2013-2018 to assess medication use in adults with CML. To be included in the analysis, patients must have met the following criteria: 1) at least 18 years old; 2) diagnosed with and had 2+ claims for an OAA indicated for CML; 3) continuously enrolled 12 months before and after OAA initiation; and 4) treated for (2+ fills before and after OAA initiation) at least 2 select chronic conditions (diabetes, hypertension, or hyperlipidemia plus at least 1 other chronic condition). The proportion of days covered (PDC) metric determined medication adherence for all included medication classes and was compared for the 12 months before and after OAA initiation by Wilcoxon signed-rank tests and McNemar's tests. Multivariable logistic regression identified predictors of OAA adherence in the first year following initiation while controlling for available demographic and clinical characteristics. Difference-in-differences models assessed changes in adherence to select comorbid chronic disease medications prior to and following OAA initiation. Results: The final analysis included 256 and 658 adults with CML and MCC with commercial or Medicare coverage, respectively. Mean first-year OAA adherence was 84.5% (SD: 15.8) and 80.1% (SD: 20.1) for commercial and Medicare patients, respectively, and these corresponded to 78.1% and 67.1% of commercially insured adults and Medicare members being deemed adherent to their OAA (PDC > 80%). An increase in comorbidity burden was associated with a lower odds of OAA adherence and was the sole significant predictor in the Medicare models: OR=0.92 (95% CI: 0.87-0.97) in Medicare; OR=0.78 (95% CI: 0.67-0.90) in commercial. Among those with commercial insurance, the odds of initial OAA adherence were higher among those with any ED visit (OR=2.49; 95% CI: 1.07-5.84), but lower among those with an inpatient admission (OR=0.46; 95% CI: 0.22-0.94). Compared to the year before OAA initiation, average adherence to statins declined in the subsequent year among Medicare members on statins, but significant improvements were observed among those commercially insured on antihypertensives or antidiabetics (Figure Panel A). However, compared to the first 6 months post-OAA initiation, mean PDCs in the second half of the year post-OAA initiation were noticeably lower, irrespective of comorbidity or payer cohort, with PDC declines ranging from 4.2 (antihypertensives, Medicare) to 10.1 (antidiabetics, commercial) percentage points (Figure Panel B). Conclusion: Using nationally representative claims data, this study found that initial OAA adherence was generally good among adults with CML, and a majority of patients reached accepted thresholds of adequate OAA use. Using a range of patients’ characteristics, few differences in OAA adherence were observed in multivariable analyses, but consistent evidence pointed to poorer adherence as comorbidity burden increased. Additionally, limited changes in adherence to oral antidiabetic, antihypertensive, or lipid-lowering agents were observed over the first year following OAA initiation, but results suggest this pattern may not be maintained over the entire year post-OAA initiation. Consequently, these findings imply a need for careful monitoring of medication use in patients with CML and MCC over the course of time given the risk for eventual declines in comorbid chronic disease medication adherence. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal