Real-World Dosing Patterns of Ruxolitinib in Patients with Polycythemia Vera Who Are Resistant to or Intolerant of Hydroxyurea

Background

Polycythemia vera (PV) is a myeloproliferative neoplasm affecting >100,000 people in the United States annually. Patients (pts) with PV are at risk for thromboembolic events (TEs), premature death, and high symptom burden. Hydroxyurea (HU) is recommended for high-risk pts with PV; however, up to 40% of pts become resistant and/or intolerant to the drug (Demuynck T, et al. Ann Hematol. 2019;98:1421-1426). Ruxolitinib (RUX), a Janus kinase (JAK) 1/JAK2 inhibitor, is currently the only FDA-approved treatment option for pts with PV who are resistant to or intolerant of HU. We conducted a retrospective chart review to characterize the reasons pts were switched from HU to RUX and to describe the real-world dosing patterns of RUX in pts with PV.

Methods

This retrospective medical chart review was conducted at US community hematology/oncology practices in the Cardinal Health Oncology Provider Extended Network. Eligible pts were ≥18 y old, initiated RUX therapy during the index period (January 1, 2015, to December 31, 2016), were previously treated with HU for ≥3 mo, and were seen at least twice during the 6 mo following RUX initiation. Data were collected for the 12 mo prior to RUX initiation (including near the time of HU discontinuation), near the time of RUX initiation (index), and up to the last provider visit. Pt and clinical characteristics were collected, including blood counts, symptoms, TEs, cardiovascular disease risk factors, phlebotomy, and HU and RUX treatment patterns. Target enrollment was 250 pts; interim results are presented here.

Results

Providers identified 99 pts for inclusion; mean (SD) age was 64 (9.9) y, 56% were male, and 68% had high-risk PV (ie, age ≥60 y and/or history of TE). All pts had been tested for the JAK2V617F mutation, and 99% were positive. At the time of HU discontinuation, 28% of pts had reached an HU dose of ≥2 g/d; median (range) HU treatment duration was 9.7 (3.6-182.4) mo. Causes of HU discontinuation were resistance (63%), intolerance (17%), resistance and intolerance (11%), and other reasons (9%; Table). The most frequent reasons for HU discontinuation due to resistance were hematocrit (Hct) ≥45% (79%), symptoms (45%), leukocytosis (32%), thrombocytosis (31%), and splenomegaly (22%). The most frequent intolerance signs and symptoms were nausea (43%), stomatitis (25%), fever (18%), and skin ulcers (14%).

With respect to the RUX starting dose, 44 pts (44%) initiated RUX at the US package insert-recommended dose of 10 mg twice daily (BID); median (range) treatment duration for these pts was 26.4 (3.2-52.0) mo (Table). During the first 6 mo of RUX treatment, dose modification was noted in 19 pts (43%) who initiated at 10 mg BID (dose increase, n=13 [30%]; dose decrease, n=5 [11%]; dose interruption, n=1 [2%]). The most common reasons for dose increase were continued need for phlebotomy (39%) and symptoms (39%). Five pts required a dose reduction; the most common reason was low hemoglobin levels (n=3). Overall, pts starting at 10 mg BID had more dose modifications in the first 6 mo of RUX treatment (43%), with fewer dose modifications needed after 6 mo (25%). Hct control (Hct <45%) at initiation and after 6 mo of RUX treatment was 14% and 75%, respectively. At the time of the last visit, 48% of pts were still taking RUX. The majority of pts (65%) who discontinued RUX had no dosing changes from the time of initiation to discontinuation.

Conclusions

In this interim analysis of real-world data pertaining to pts with PV who discontinued HU and were subsequently treated with RUX, the most common resistance events leading to HU discontinuation were Hct ≥45%, uncontrolled symptoms, leukocytosis, thrombocytosis, and splenomegaly. Discontinuations due to intolerance were most commonly attributed to nausea, stomatitis, fever, and skin ulcers. Of pts who were switched from HU to RUX, the duration of HU treatment was shorter and the proportion of pts treated with HU doses of ≥2 g/d was higher than has been reported for all pts discontinuing HU, irrespective of their next line of therapy (Grunwald MR, et al. ASH Annual Meeting 2017. Poster 1633). Less than half of pts initiated RUX at the recommended dose of 10 mg BID; 41% of pts dosed in accordance with the recommended starting dose experienced dosing modifications (primarily dose increases); however, the majority of pts who discontinued RUX had no dosing modifications during their treatment. Results from the entire cohort of 250 pts will be presented.

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