Transfusion Independence in Lower-Risk, Non-del5(q) Myelodysplastic Syndromes (LR-MDS) Among Patients (pts) Initiating Hypomethylating Agents (HMAs) While Receiving Red Blood Cell (RBC) Transfusions

Background: HMAs were approved in the U.S. for treatment of MDS in 2004 (azacitidine) and 2006 (decitabine), and are used for upfront management higher risk disease and in LR-MDS at progression or after failure or low likelihood to respond to erythropoiesis stimulating agents (ESAs). Clinical trial data suggest that 24-50% of LR-MDS pts achieve RBC transfusion independence (TI) from prior transfusion dependence (TD) with HMA therapy. Response among older pts with LR-MDS treated with HMA in a real-world setting is unclear. We have previously shown that survival of higher risk MDS pts treated with HMAs in real-life setting is much shorter than clinical trial data. We therefore examined rates of achieving TI in LR-MDS pts receiving HMAs.

Methods: We identified adults >65 years old diagnosed with LR-MDS (WHO categories RA, RARS, and RCMD) in 2004-2013 from the Surveillance Epidemiology and End Results Medicare claims data. Exclusion criteria include: pts with MDS diagnosed on autopsy report or death certificate, absence of continuous Medicare Part A and B coverage or presence of HMO enrollment from 12 months prior to diagnosis through death or end of study (12/31/2014). Pts had to initiate at least one cycle of HMA, defined as 3 to 10 doses of HMA within 28 days. A gap in treatment between 14 to 28 days indicates a new cycle. Pts were assessed for their transfusion status each week throughout the study period. We measured weekly transfusion status based on receipt of RBC transfusions (observed in Medicare claims) during the current and prior 7 weeks (8 weeks total). Transfusion status was defined as: transfusion receiving (TR), pts received at least one transfusion in each period; TD, patient received ≥2 transfusions over 8 weeks, with ≥2 transfusions ≥2 weeks apart; TI, no transfusions within the 8-week period. We required pts to be at least TR at HMA initiation. We censored observations one month prior to death and 4 weeks after the end of the last HMA cycle. TI duration is defined as number of weeks between last transfusion before achieving TI and first transfusion after TI. TI ends the week that the pt receives a transfusion. Time to achieve TI as well as duration of TI were assessed with Kaplan-Meier and Cox models, adjusting for patient's demographics, health status at HMA initiation, prior hospitalization for bleeding and infection, and prior erythropoiesis-stimulating agent and transfusion use. Analysis was also conducted among the subset of pts who were TD at time of first HMA.

Results: Among 336 pts with LR-MDS who initiated HMA while RBC TR, median age was 76 years (interquartile range [IQR]: 71-81) and 87.2% were non-Hispanic white. Median time to HMA initiation from diagnosis of MDS was 44.3 (IQR: 13-117) weeks. 136 (40.5%) pts achieved RBC TI, with median time of 23 (95% confidence interval [CI]: 18-28) weeks (Figure 1a). Multivariate Cox model showed pts receiving ≥3 transfusions in the 8 weeks before HMA initiation were less likely to achieve TI (HR: 0.46, p<.01). Geographic region of residence also affected time to TI, with pts in the Northeast and West having lower probability of achieving TI compared to pts in the Midwest (hazard ratio [HR]: 0.44, 95% CI: 0.24-0.80 and HR: 0.56, 0.36-0.87 respectively). Medicaid dual coverage also had a positive association with achieving TI (HR: 1.92, p=.03). Median TI duration was 50 (95% CI:26-76) weeks (Figure 1b). Among 192 pts who were TD at HMA initiation, 64 (33.3%) achieved TI, with a median time to TI of 32 (95% CI: 24-71) weeks. Median TI duration was 60 (95% CI: 23-87) weeks. TD pts of older age (>85 years) showed a higher tendency of losing TI over younger pts (age 66-69) (HR: 4.50, p=.04).

Conclusions: Achieving TI is an important quality of life outcome for MDS pts. Our results indicate that a substantial portion of HMA recipients who were RBC TD or TR at initiation achieved TI status, with slightly shorter time to achieve TI for those who initiated while TR compared to TD, and no significant difference in duration of TI. Our results are limited by inability to assess for lenalidomide use and lack of ascertainment of reason of HMA initiation (progression of LR-MDS versus ESA failure). Observed rates of achieving RBC TI in LR-MDS pts utilizing HMA were consistent with clinical trials.

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