Persistence and compliance of deferoxamine versus deferasirox in Medicaid patients with sickle-cell disease

Abstract

Patients with sickle-cell disease (SCD) receiving chronic transfusions of red blood cells are at risk of developing serious adverse effects. Iron chelation therapy (ICT) helps eliminate iron overload by binding with plasma iron to form a non-toxic conjugate that can be safely excreted from the body. Two iron chelating agents are currently available in the United States: Deferoxamine (DFO) is an injectable formulation, and deferasirox (Exjade(®) ) is an oral suspension. This study compared the frequency of hospitalizations, persistence and compliance of patients with SCD from Medicaid programmes treated with DFO vs. deferasirox. Health care claims from Medicaid Florida (1998-2007), Missouri (1993-2008) and New Jersey (1996-2008) were analysed. Patients with continuous enrolment for ≥6months prior to ICT initiation and ≥1 SCD diagnosis were included in the analysis. Patients were divided into four cohorts: patients treated with DFO (any-DFO group) and patients treated with deferasirox (any-deferasirox group); the latter was further divided into patients initiated on DFO and then switched to deferasirox (deferasirox switchers), and patients treated with deferasirox-only (deferasirox-only group). Frequency of hospitalization for crisis conditions related to SCD as well as length of stay pre- and post-ICT treatment initiation were assessed. Persistence was defined as time to drug discontinuation with ≥1 Rx gap, using Kaplan-Meier approach. Compliance was estimated using a medication possession ratio (MPR) based on the drug exposure approach. Adjusted analyses of persistence and compliance were also conducted. A total of 217 (mean age: 19·4years, 39·2 men), 275 (20·1years, 41·5% men), 105 (19·4years, 42·9% men) and 166 (20·4years, 41·6% men) patients were included in the any-DFO, any-deferasirox, deferasirox switchers and deferasirox-only groups, respectively. After ICT initiation, the any-deferasirox and deferasirox-only groups experienced a statistically significant reduction in the frequency of hospitalizations relative to pretreatment [any-deferasirox: from 0·09 to 0·06 hospitalizations per patient per month (pmpm), P=0·0105; deferasirox-only: from 0·11 to 0·07 hospitalizations pmpm, P=0·0188], whereas it remained stable in the any-DFO group at 0·08 hospitalizations pmpm (P=0·9483). The Kaplan-Meier rates of medication persistence assessed at 6 and 12months of follow-up were significantly lower for DFO patients (6 months: 0·34, 12months: 0·21) as compared to all deferasirox (0·51, 0·29, P=0·0002), deferasirox switchers (0·56, 0·37, P=0·0002) and deferasirox-only (0·47, 0·24, P=0·0176) patients. Similarly, compliance to treatment was significantly lower for patients treated with DFO (mean MPR: 0·64) compared with any-deferasirox (0·78, P<0·0001), deferasirox switchers (0·75, P=0·0002) and deferasirox-only (0·80, P<0·0001) patients. Adjusted analyses of persistence and compliance yielded similar results. Based on a Medicaid population, patients treated with deferasirox were more compliant and persistent with their treatment than those treated with DFO. Frequency of hospitalizations was significantly reduced after treatment initiation for the any-deferasirox and deferasirox-only groups. Prospective studies controlling for potential clinical and treatment pattern differences between deferasirox and DFO patients are needed to assess whether the decreased hospitalizations after initiation of deferasirox are related to better treatment compliance.