Real-World Survival in Elderly Patients with Myelofibrosis in the United States: Ruxolitinib Exposed Versus Unexposed

Context: Patients with myelofibrosis (MF) have reduced overall survival (OS) versus the general population. Ruxolitinib, a Janus kinase (JAK) 1 and 2 inhibitor, is FDA-approved for treatment of intermediate-/high-risk MF. Ruxolitinib improved OS in patients with MF in the COMFORT trials; however, real-world data are limited. Objective: To compare OS of elderly patients newly diagnosed with MF who were ever exposed vs never exposed to ruxolitinib. Design, Setting, and Patients: The Medicare Fee-for-Service claims database (100% sample Parts A/B/D) from Jan 2012–Dec 2017 was used to identify patients age ≥65 years (intermediate-1 or higher risk MF due to age) with ≥1 inpatient or ≥2 outpatient claims with a diagnosis of MF (index was date of first qualifying MF claim). Patients diagnosed with MF ≤12 months pre-index or other malignancies 12 months pre- or any time post-index were excluded. Continuous medical and pharmacy enrollment was required for ≥12 months pre-index. The sample was stratified into ruxolitinib-exposed vs -unexposed groups based on prescription fills for ruxolitinib during follow-up. Main Outcomes and Measures: OS (time from index date to death) was assessed using Kaplan-Meier and Cox regression analyses adjusting for demographic and clinical characteristics; patients without a death date were categorized as alive until end of data availability. Results: A total of 1,399 beneficiaries (272 ruxolitinib-exposed; 1,127 ruxolitinib-unexposed) with an MF diagnosis met inclusion criteria: median age was 77 years, 42% were male, and 88% were white. Median OS was not reached (95% CI, 51.0–not reached; mean [SD] follow-up, 18.2 [15.0] months) for ruxolitinib-exposed patients and 44.4 months (95% CI, 37.3–62.0; mean [SD] follow-up, 15.9 [16.2] months) for ruxolitinib-unexposed. The 1-year survival rate (95% CI) was 82.3% (76.7%–86.7%) for ruxolitinib-exposed patients and 72.5% (69.5%–75.2%) for ruxolitinib-unexposed patients; 2-year survival was 76.1% (69.2%–81.7%) and 60.6% (56.9%–64.0%), respectively. Patients in the ruxolitinib-exposed group had a significantly lower risk of mortality compared with the ruxolitinib-unexposed group (adjusted HR, 0.61; 95% CI, 0.45–0.82; P=0.0016). Conclusions: In this real-world study, patients who were exposed to ruxolitinib after MF diagnosis had prolonged survival and a 39% lower risk of mortality vs unexposed patients.