Real-World Dosing Patterns of Ruxolitinib Among Patients with Myelofibrosis: A US Community Oncology Practice

Presenter: Senxi Du, Student, Keck School of Medicine of University of Southern California

Co-Authors: Theresa Amoloja, Incyte Corporation, Wilmington, DE; Eileen Peng, Regional Cancer Care Associates, East Brunswick, NJ; Marisa Keck, Regional Cancer Care Associates, East Brunswick, NJ; Ellen Ronnen, Regional Cancer Care Associates, East Brunswick, NJ

Background: Myelofibrosis is a heterogeneous myeloproliferative neoplasm in which risk categorization informs prognosis and treatment.¹ Ruxolitinib is indicated for the treatment of patients with intermediate- or high-risk myelofibrosis; starting doses are determined by baseline platelet counts,² including: 20 mg twice daily for >200 × 10⁹/L; 15 mg twice daily for 100-200 × 10⁹/L; and 5 mg twice daily for 50-<100 × 10⁹/L (dose for <50 × 10⁹/L not established).^3,4

Objective: To describe the clinical characteristics and real-world dosing patterns of ruxolitinib among patients with myelofibrosis at a community practice.

Methods: This was a retrospective chart review of adults with confirmed intermediate- or high-risk myelofibrosis who received ruxolitinib between January 1, 2015, and June 20, 2019, at a single community hematology/oncology practice, excluding patients who participated in any myelofibrosis-related clinical trial.

Results: Data from 12 eligible patients were included. The median age was 69 years (range, 56-85 years) at myelofibrosis diagnosis (male, 67%; primary myelofibrosis, 50%). According to the Dynamic International Prognostic Scoring System, at diagnosis, 3 patients had high-risk myelofibrosis, 4 intermediate-2 risk, and 5 intermediate-1 risk; 8 patients had JAK2 mutation, 2 patients had no JAK2 mutation, and 2 patients had other unspecified mutations. At ruxolitinib initiation, the platelet counts were >200 × 10⁹/L (N = 8), 100-200 × 10⁹/L (N = 1), and 50 × 10⁹/L (N = 3). Starting doses varied: 20 mg twice daily (N = 3), 20 mg once daily (N = 1), 15 mg twice daily (N = 2), 10 mg twice daily (N = 2), 5 mg twice daily (N = 3), and 5 mg once daily (N = 1). In all, 7 patients continued ruxolitinib therapy through the study period, with a median duration of 37 months; 4 patients continued the same ruxolitinib dose from initiation until the last visit (5 mg twice daily, N = 2; 20 mg twice daily, N = 1) or ruxolitinib discontinuation (20 mg once daily, N = 1); 3 patients had dose increases, and 5 had decreases. The median time to first dose increase was 0.5 months, and to first dose decrease was 3.5 months. Two patients had dose interruptions (at 3 months and 38 months), and both patients reinitiated ruxolitinib therapy within 1 month. Five patients discontinued ruxolitinib after a median of 8 months for the following reasons: adverse event (initiated at 5 mg twice daily despite having platelets <50 × 10⁹/L), undergoing transplant, patient preference, severe chronic anemia after several dose adjustments, and lack of efficacy (initiated at 20 mg once daily instead of the recommended twice daily).

Conclusion: In a small number of patients with myelofibrosis who were managed at a community practice, a variety of ruxolitinib doses were given, including doses not validated by clinical trials (eg, once-daily doses^5,6).

1. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Myeloproliferative Neoplasms. Version 1.2020. May 21, 2020. www.nccn.org/professionals/physician_gls/pdf/mpn.pdf. Accessed September 2020.
2. Jakafi (ruxolitinib) tablets, for oral use [prescribing information]. Incyte Corporation; 2020.
3. Devos T, Selleslag D, Zachée P, Benghiat FS. Recommendations on the use of ruxolitinib for the treatment of myelofibrosis. Hematology. 2018;23:194-200.
4. Verstovsek S. Tips on using ruxolitinib in everyday practice as therapy for myelofibrosis. Leuk Lymphoma. 2014;55:5-6.
5. Verstovsek S, Kantarjian H, Mesa RA, et al. Safety and efficacy of INCB018424, a JAK1 and JAK2 inhibitor, in myelofibrosis. . 2010;363:1117-1127.
6. Talpaz M, Paquette R, Afrin L, et al. Interim analysis of safety and efficacy of ruxolitinib in patients with myelofibrosis and low platelet counts. J Hematol Oncol. 2013;6:81.