Treatment Patterns and Adherence Among Patients with Myelodysplastic Syndromes Receiving Deferasirox As Iron Chelation Therapy: A Real World Medicare Database Study

Background: Patients with myelodysplastic syndrome (MDS) may present with anemia and become red blood cell (RBC) transfusion dependent (TD), which increases the risk of iron overload (IO). Iron chelation therapy (ICT) treats IO and has been shown to be associated with improved survival and quality of life among TD MDS patients. Deferasirox (DFX) is an oral ICT used to reduce IO in TD MDS patients. This study aims to assess real-world treatment patterns and adherence among MDS patients on Medicare receiving DFX as ICT.

Methods: This was a retrospective cohort study using 100% Medicare claims data from 2006-2013. Patients were diagnosed with MDS, identified using ICD-9 codes (238.72-238.76), and entered the study cohort when they met a minimum transfusion threshold of either: 10 consecutive weeks with at least 1 unit of RBC transfusion, or 20 total units of RBC transfusions. Treatment patterns, including discontinuation and treatment changes, were assessed among patients who received DFX as initial ICT and who had ≥180 days of follow-up. Discontinuation was defined as a minimum 45-day treatment gap. Adherence was defined as a medication possession ratio (MPR) ≥ 0.8. Treatment discontinuation, overall survival, acute myeloid leukemia (AML)-free survival, and cardiac event-free survival were compared between adherent and non-adherent patients using Kaplan Meier (KM) survival analysis, as well as Cox regressions controlling for time-dependent ICT use and baseline characteristics. Survivals were estimated as time from cohort entry to the event.

Results: Among 6,796 MDS patients who met the minimum transfusion threshold, 591 (8.7%) received ICT. Median weeks of ICT was 15.14 (range=2.29 - 201.43 weeks). 583 (98.6%) initiated with DFX, and 374 DFX patients had a follow-up period of ≥180 days. Of these 374 patients, 213 (57.0%) discontinued DFX treatment within 180 days of initiation. Among the remaining 161 patients, one switched to deferoxamine (DFO), none augmented treatment with DFO, and 160 continued on DFX. The KM-estimated 3-month and 1-year DFX discontinuation rates were 36.5% and 77.4%, respectively, and the average time to discontinuation was 84.4 [Standard Deviation [SD]=48.6] days. Overall, the average 6-month MPR was 0.69 (SD=0.30), and 49.1% of patients were adherent (MPR≥0.8). Adherent patients had similar baseline characteristics compared with non-adherent patients, except that a lower proportion had renal disease (24.2% vs. 38.3%, P<0.01). Patients adherent to DFX had a lower risk of therapy discontinuation (Hazard Ratio=0.07, 95% Confidence Interval, 0.05-0.11) compared with non-adherent patients. Additionally, adherent patients had significantly longer cardiac event-free survival compared with non-adherent patients (1-year rate for cardiac-event/death: 66.1% vs. 76.1%, respectively, P<0.01). There were no statistically significant differences in overall survival and AML-free survival between adherent and non-adherent cohorts. Overall and AML-free survival were longer in the adherent cohort, however this did not reach statistical significance.

Conclusions: DFX was the most commonly used ICT among eligible MDS patients. The majority of patients discontinued DFX within 1 year. Adherence to DFX was associated with statistically significant improved cardiac-event free survival. Further analysis on the long-term impact of the duration of chelation is warranted.