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Hi, my name is Michael Grunwald. I'm a leukemia specialist at Levine Cancer Institute in Charlotte, North Carolina. I'm here at the American Society of Hematology annual meeting. Today I'm here to present my poster examining the treatment patterns and blood counts among patients with polycythemia vera, treated with hydroxyurea in the United States. An analysis from the REVEAL study.
Polycythemia vera, or PV, is associated with erythrocytosis with or without thrombocytosis and or leukocytosis. Increased risk of thrombosis and symptoms including fatigue, early satiety, and abdominal discomfort. Hydroxyurea is a common cytoreductive strategy used to control blood counts and splenomegaly in patients with PV at high risk of thrombosis. Although blood counts in many patients with PV are effectively controlled with hydroxyurea, a proportion of patients fail to achieve controlled blood counts.
The European Leukemia Net, or ELN, has defined response criteria for blood count control as well as hydroxyurea resistance and intolerance in patients with PV. The REVEAL observational study is being conducted to describe contemporary demographics, burden of disease, clinical management, patient reported outcomes, and healthcare resource utilization among patients with PV in the United States.
The objective of our analysis is to describe hydroxyurea treatment patterns, blood count control, and hydroxyurea intolerance among patients enrolled in reveal. Eligible patients for reveal are greater than or equal to 18 years of age with a polycythemia vera diagnosis who are actively managed by a physician. Patients with high risk PV were defined as being greater than or equal to 60 years of age, and/or having a history of thrombosis. Patients who had ever been treated with or were currently receiving hydroxyurea were included in this analysis. Blood counts in hydroxyurea intolerances were examined relative to European Leukemia Net, ELN, definitions, in respective of hydroxyurea dose. Criteria used to assess complete hematologic response was also based on ELN criteria. Hematocrit less than 45% without phlebotomy, and platelet count less than or equal to 400, and white blood cell count less than or equal to 10.
Polycythemia vera history was available up to six months prior to enrollment. Hydroxyurea treatment patterns were assessed by evaluating dose modifications and discontinuations. Toxicities were assessed following initiation of hydroxyurea. Now to our results. In total, 2,510 patients were enrolled in reveal. Of these, 1,432 ever received hydroxyurea, and 1,390 received hydroxyurea for greater than or equal to three months. Median age was 67 years, and median duration of disease prior to enrollment was four years. 54.2% of patients were male, 89.1% were white, and 77.3% were high risk. Patient demographics were balanced across all cohorts. Approximately 84% of patients who received hydroxyurea were considered high risk. Median exposure to hydroxyurea for all patients who received the drug was 35.7 months. The majority of patients, 72.5% of patients, received between 500-1,000 milligrams per day of hydroxyurea. Only 6.5% ever received a dose of 2 grams or greater, the dose threshold outlined by ELN criteria.
The two most common hydroxyurea doses were 500 milligrams daily and 1,000 milligrams daily. This was similar in patients who received hydroxyurea for greater than or equal to three months. These patients spent a median of 28.5 months at their maximum daily hydroxyurea dose. Approximately one third of patients who received hydroxyurea for greater than or equal to three months had greater than or equal to one hydroxyurea dose adjustment. 14.6% had both dose increases and decreases, and 16.6% interrupted treatment with hydroxyurea. The majority of patients who received hydroxyurea for three months or longer continued hydroxyurea treatment at data cut off. The highest frequency of hydroxyurea dose adjustments occurred in patients with less than one year of hydroxyurea exposure at the time of enrollment. The frequency of dose changes was similar among other patients, meaning the patients with greater than one year of treatment with hydroxyurea.
Adverse events were the most common reason for permanent hydroxyurea discontinuation, interruption, and dose decreases. Lack of efficacy was the most common reason for dose increases. Among the 1,106 evaluable patients, 57.1% had greater than or equal to one hematocrit value above 45% after receiving hydroxyurea for three months or longer. The median of the maximum hematocrit value after being on hydroxyurea for three months was 48.3% among those who reported a value above 45%. Compared with a median of 42% among those who did not have hematocrit values above 45%. 32.9% of patients continued to undergo phlebotomy after three months of hydroxyurea. Of 414 evaluable patients who received a phlebotomy after three months of hydroxyurea, 82.9% continued to have a HCT greater than 45%.
Of 973 patients who had spleen palpation performed at enrollment, 181, or 18.6%, treated with hydroxyurea had a palpable spleen. At enrollment, patients who received phlebotomies within the previous three months consistently showed elevated hematocrit and white blood cell values regardless of the duration of hydroxyurea exposure. Hydroxyurea related non-hematologic toxicities including leg ulcers were observed in 7.4% of patients during hydroxyurea treatment. A proportion of patients who achieved hematocrit control with hydroxyurea experienced cytopenias. In conclusion, in reveal, hydroxyurea is a commonly used therapy for polycythemia vera, but over half of patients, 57% of patients treated with hydroxyurea for three months or longer continued to have hematocrit above 45%.
Despite patients being on hydroxyurea for a median of 36.6 months, only 6.5% of patients ever received hydroxyurea doses of 2 grams or greater daily. Lack of efficacy and adverse events were the most common reason for permanent discontinuation of hydroxyurea. Patients who underwent phlebotomy within three months prior to enrollment were more likely to have persistently elevated hematocrit and white blood cell counts, indicating that the need for phlebotomy may be a sign of more proliferative disease. This analysis further emphasizes the need for active management of PV with appropriate hydroxyurea dose titration to maintain blood count control while monitoring for signs or symptoms of hydroxyurea intolerance.
Thank you for watching my presentation today.