Real-World Treatment Patterns and Blood Count Control in Patients with Polycythemia Vera Who Switched from Hydroxyurea to Ruxolitinib

Introduction: Polycythemia vera (PV) is a myeloproliferative neoplasm that typically presents with elevated hemoglobin and/or hematocrit (Hct) levels. Current National Comprehensive Cancer Network guidelines recommend maintaining Hct <45% with phlebotomy or cytoreductive treatment, such as hydroxyurea (HU), in all patients. This analysis describes treatment patterns, blood count control, and use of phlebotomy in patients with PV who switched from HU to ruxolitinib at community practices in the United States.

Methods: This retrospective study included adults with a new PV diagnosis and ≥2 postdiagnosis visits during the study period of January 2014 to May 2023 in the Integra Precision Q electronic health record database. Patients who switched from HU to ruxolitinib, either as line of treatment (LOT) 1 to LOT2 or from LOT2 to LOT3, were characterized in this analysis. Elevated blood counts were defined as Hct ≥45%, white blood cell (WBC) count ≥11×10⁹/L, or platelet (PLT) count >400, aligning with European LeukemiaNet response criteria and findings from the CYTO-PV study. Treatment duration and time between treatments were based on date of prescription refills.

Results: Of 10,112 patients who met eligibility criteria in the full study, 443 patients switched from HU to ruxolitinib (LOT2: n=317; LOT3: n=126) and were included in this analysis; 47/443 (10.6%) received ruxolitinib as combination therapy, either in combination with HU (46/47; 97.9%) or with pegylated-interferon (1/47; 2.1%). Mean (SD) age at HU initiation was 68.6 (10.4) years (79.7% ≥60 years); 49% were female, and 62% were White. Mean (SD) time from PV diagnosis to HU initiation was 9.3 (14.9) months and from PV diagnosis to ruxolitinib initiation was 31.0 (23.8) months (LOT2: 27.5 [23.6]; LOT3: 39.8 [22.0]).

Median (IQR) duration of HU treatment was 9.7 (3.6–27.5) months as LOT1 and 9.2 (3.9–25.0) months as LOT2. Mean (SD) time between end date of HU and start date of ruxolitinib was 4.3 (11.3) months for LOT1 to LOT2 and 3.1 (7.4) months for LOT2 to LOT3. Median (IQR) duration of ruxolitinib treatment was 10.5 (4.1–28.7) months for LOT2 and 12.2 (5.0–29.4) months for LOT3. Median (IQR) time from ruxolitinib initiation to the end of the study period was 20.4 (9.1–39.5) months. At that time, 170 (38.4%) patients continued on ruxolitinib (LOT2: 37.2%; LOT3: 41.3%).

Of the patients who switched to ruxolitinib, 178 had Hct data available at all 4 time points, of which 74 (41.6%) had elevated Hct (ie, ≥45%) following HU treatment and before ruxolitinib initiation; elevated Hct was observed in 40/178 (22.5%), 32/178 (18.0%), and 26/178 (14.6%) patients at 3, 6, and 12 months from ruxolitinib initiation, respectively. Of 192 patients with available WBC data, 105 (54.7%) had elevated WBC (ie, ≥11×10⁹/L) following HU and before ruxolitinib; elevated WBC was seen in 78/192 (40.6%), 89/192 (46.4%), and 88/192 (45.8%) at 3, 6, and 12 months from ruxolitinib initiation. Additionally, of 200 patients with available PLT data, 85 (42.5%) had elevated PLT (ie, >400) following HU and before ruxolitinib treatment; elevated PLT was seen in 92/200 (46.0%), 93/200 (46.5%), and 85/200 (42.5%) at 3, 6, and 12 months from ruxolitinib initiation. The differences in percentages of patients meeting treatment goals for Hct control compared with WBC and PLT may reflect current treatment guidelines in PV.

Among patients who initiated ruxolitinib as LOT2, mean (SD) phlebotomies per patient per year (PPPY) were 7.2 (9.5) during HU treatment (start date through end date HU) vs 3.8 (3.3) during ruxolitinib treatment (start date through end date ruxolitinib). Among patients who initiated ruxolitinib as LOT3, mean (SD) phlebotomies PPPY were 5.0 (4.2) during HU treatment vs 3.6 (5.3) during ruxolitinib treatment.

Conclusions: Patients switching from HU to ruxolitinib treatment had improved Hct and WBC count control. Additionally, frequency of phlebotomy was numerically lower during ruxolitinib treatment vs during HU treatment. Taken together, these data suggest clinical benefits for patients switching to ruxolitinib following inadequate disease control with HU treatment.