Medical costs associated with imatinib (IM) non-compliance in chronic myeloid leukemia (CML) patients (pts)

Abstract

17514 Background: Not adhering to treatment (tx) may lead to suboptimal outcomes. This study examined associations between medical costs and IM compliance in CML pts. Methods: CML pts under age 65 were identified with ICD-9 diagnosis code (205.1X) using MarketScan Commercial Claims data between 1/1/02–12/31/05. Pts were required to be continuously enrolled in the 4 months prior to (baseline) and the 6 months following (study period) IM initiation. CML severity was categorized into 3 groups by diagnosis of CML and related comorbidities. Compliance was defined by medication possession ratio (MPR=total days of IM supply in the study period divided by 180), and stratified into 3 groups (low: <65%, medium: 65–95%, high: 95–100%). Tx interruption was defined as tx gap of 30 or more consecutive days in the study period. Costs for inpatient (IP), ER, outpatient (OP) services and OP drugs during the study period were adjusted to 2005 dollars. Costs, the number of IP admissions and hospital days were compared across different levels of tx compliance using Wilcoxon tests. A generalized linear model (GLM) was also used to compare costs controlling for age, sex, CML severity, Charlson comorbidity index, year of IM start, etc. Results: The study sample consisted of 404 pts. Compared to the high MPR group, pts in the low MPR group incurred 1.6 times the average total health care costs (p <.001), 5.9 times the IP costs (p<.001), 2.6 times the OP costs (p=.722), 2.1 times the non-IM drug costs (p<.001), and 0.39 times the IM drug costs (p<.001). Compared to the high MPR pts, low MPR pts had on average 3.8 times the IP admissions (p<.001), and 7.3 times the IP days (p<.001). Comparing costs of pts interrupting tx versus those who did not showed similar trends. GLM regression showed that 6-month total health care costs per patient in the low MPR group were 1.4 times (p<.01) those of the high MPR group. Pts who had tx interruption had 1.3 times the total health care costs (p<.01) compared to those who did not. Conclusions: This study shows that better IM compliance was associated with significantly lower health care costs in CML pts, especially for IP costs. Further analyses will be conducted to confirm whether lower compliance leads to more hospitalizations. No significant financial relationships to disclose.