Real-World Clinical Outcomes of Patients with Myelofibrosis Treated with Ruxolitinib: Evidence from a Multinational Medical Record Review

Introduction: Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by cytopenia, splenomegaly, and debilitating constitutional symptoms, such as fatigue, night sweats, weight loss, bone pain, and pruritus. Prior to the approval of the selective Janus kinase-2 (JAK2) inhibitor fedratinib for adults with Intermediate (Int)-2 or High-risk MF in 2019, ruxolitinib (RUX) was the only FDA-approved JAK inhibitor and considered standard of care; treatment (tx) options after RUX were limited. Furthermore, although about 60% of pts carry JAK2 mutations, not all patients respond to RUX. The aim of this study was to describe real-world tx patterns and determine unmet need in pts with MF treated with RUX. Methods: We report interim data collected from the UK and USA as part of a global retrospective medical chart review of adult pts with Int-1, Int-2, or High-risk MF who started RUX tx between Jan 2012 and Dec 2016 in the USA, UK, Germany, Spain, Canada, and France, Pts were required to have discontinued RUX prior to data abstraction (Apr-May 2020). Prior tx was allowed, except for allogeneic hematopoietic cell transplantation or JAK2 inhibitor trial participation. Study measures included pt and tx characteristics at RUX initiation, tx patterns, dose modifications (DMs), and clinical outcomes. The rate of DMs (decrease or increase) during the first 6 months of tx was assessed. Recommended dose (REC) as per US FDA label of RUX was determined via baseline platelet count; atypical dose (ATY) was defined as non-REC RUX. The Kaplan-Meier method was used to estimate median overall survival (OS) from start of RUX tx. Descriptive statistics are used in this report. Results: A total of 183 pts (USA: 105, UK: 78) were included in the analysis. Mean age at diagnosis was 63 years, 69% were male, and 82% were White. Most pts had primary MF (84%), Int-2-risk disease (51%), and JAK2 V617F driver mutation (67%). RUX was first-line MF tx in 100 pts (55%). Of 140 pts with baseline platelet counts, 46% started on REC RUX, and 54% started ATY RUX. Of pts who initiated ATY RUX, those with platelet count below 200 ×109/L were more likely to receive a higher dose; those with a platelet count above 200 ×109/L, were more likely to receive a lower dose. The median time from diagnosis to RUX initiation overall was 1.3 months (mos); this was shorter in pts initiated on REC RUX and longer in pts initiated on ATY RUX (Table). The median duration of tx (DoT) was higher for pts who initia