A retrospective analysis of the impact of treatments and blood counts on survival and the risk of vascular events during the course of polycythaemia vera

Achievements and future outlook for JAK inhibitors in polycythaemia vera

INTRODUCTION

Polycythemia vera (PV) is driven by mutations in JAK2 kinase and subsequent JAK/STAT activation, presentation can range from an asymptomatic state to micro or macrovascular events. Characteristic aquagenic pruritus and fatigue can have a substantial impact on quality of life. Over time, a minority will transform into more aggressive conditions such as post-PV myelofibrosis or acute myeloid leukemia. The JAK1 and 2 inhibitor Ruxolitinib has been approved for the treatment of PV after the failure of first-line therapies. Other JAK inhibitors have not been extensively tested in PV.

AREAS COVERED

In this article, we describe how PV is diagnosed and conventional treatments before moving to cover the status of JAK inhibitors as a therapeutic option for this disease and other novel therapies following a literature review.

EXPERT OPINION

Ruxolitinib when used for PV delivers control of blood counts and reduces disease-related symptoms. Recent data have also suggested that treatment with Ruxolitinib can improve event-free survival and may be associated with disease modification. Adverse effects of Ruxolitinib such as the increased risk of infection and squamous cell skin cancers, most likely to be linked to immunosuppression and prior lines of therapies, require careful consideration.

Low-risk polycythemia vera treated with phlebotomies: clinical characteristics, hematologic control and complications in 453 patients from the Spanish Registry of Polycythemia Vera

Hematological control, incidence of complications, and need for cytoreduction were studied in 453 patients with low-risk polycythemia vera (PV) treated with phlebotomies alone. Median hematocrit value decreased from 54% at diagnosis to 45% at 12 months, and adequate hematocrit control over time (< 45%) was observed in 36%, 44%, and 32% of the patients at 6, 12, and 24 months, respectively. More than 5 phlebotomies per year in the maintenance phase were required in 19% of patients. Worsening thrombocytosis, age > 60 years, and microvascular symptoms constituted the main indications for starting cytoreduction. Median duration without initiating cytoreduction was significantly longer in patients younger than 50 years (< 0.0001). The incidence rate of thrombosis under phlebotomies alone was 0.8% per year and the estimated probability of thrombosis at 10 years was 8.5%. The probability of arterial thrombosis was significantly higher in patients with arterial hypertension whereas there was a trend to higher risk of venous thrombosis in cases with high JAK2V617F allele burden. Rates of major bleeding and second primary neoplasm were low. With a median follow-up of 9 years, survival probability at 10 years was 97%, whereas the probability of myelofibrosis at 10 and 20 years was 7% and 20%, respectively. Progression to acute myeloid leukemia was documented in 3 cases (1%). Current management of low-risk PV patients is associated with low rate of thrombosis and long survival. New treatment strategies are needed for improving hematological control and, in the long term, reducing progression to myelofibrosis.

Patterns of Hydroxyurea Prescription and Use in Routine Clinical Management of Polycythemia Vera: A Multicenter Chart Review Study

Objective:

This study aimed to evaluate real-life data on patterns of hydroxyurea prescription/use in polycythemia vera (PV).

Materials and Methods:

This retrospective chart review study included PV patients who had received hydroxyurea therapy for at least 2 months after PV diagnosis. Data were collected from 10 representative academic medical centers.

Results:

Of 657 patients, 50.9% were in the high-risk group (age ≥60 years and/or history of thromboembolic event). The median duration of hydroxyurea therapy was 43.40 months for all patients; 70.2% of the patients had ongoing hydroxyurea therapy at last follow-up. Hydroxyurea was discontinued in 22.4% of the patients; the most common reason was death (38.5%). The predicted time until hydroxyurea discontinuation was 187.8 months (standard error: ±21.7) for all patients. This duration was shorter in females (140.3±37.7 vs. 187.8±29.7) (p=0.08). This trend was also observed in surviving patients aged ≥50 years at hydroxyurea initiation (122.2±12.4 vs. 187.8±30.7, p=0.03). Among the patients who were still on hydroxyurea therapy, 40.3% had a hematocrit concentration of ≥45% at their last follow-up visit, and the rate of patients with at least one elevated blood cell count was 67.8%.

Conclusion:

Hydroxyurea prescription patterns and treatment aims are frequently not in accordance with the guideline recommendations. Its discontinuation rate is higher in females.

Leukocytosis and thrombosis in essential thrombocythemia and polycythemia vera: a systematic review and meta-analysis

In the last years, a growing amount of evidence has been produced regarding the role of leukocytosis as a risk factor for thrombosis in patients with myeloproliferative neoplasms, predominantly in polycythemia vera (PV) and essential thrombocythemia (ET). Results from epidemiologic studies on this issue, however, are inconclusive. We conducted a systematic review and meta-analysis of articles published in the last 12 years addressing the issue, according to a predefined protocol. Forty-one articles analyzing >30 000 patients met our inclusion criteria and were deemed of acceptable methodologic quality. In addition to data on thrombosis, data were collected on bleeding, hematologic evolution, secondary cancer, and death. The relative risk (RR) of thrombosis in the presence of leukocytosis was 1.59 (95% CI, 1.40-1.80), mainly accounted for by ET (RR, 1.65; 95% CI, 1.43-1.91) and arterial thrombosis (RR, 1.45; 95% CI, 1.13-1.86) subgroups; the effect was not significant in venous thrombosis alone. Sensitivity analyses considering recurrent events as well as white blood cell estimates adjusted or unadjusted for confounding factors confirmed the primary results. In addition, the pooled RR of studies that tested white blood cell counts in time-dependent models suggested a causative effect of leukocytes in the mechanism that triggers thrombosis. The effect of leukocytosis on bleeding (RR, 1.87; 95% CI, 1.26-2.77) and death (RR, 1.89; 95% CI, 1.59-2.23) was confirmed, whereas conclusions on hematologic evolutions and solid tumors were uncertain. To confirm the accuracy of these results, an investigation on individual patient data in a large collective archive of homogeneous patients is warranted.

Perspectives on interferon-alpha in the treatment of polycythemia vera and related myeloproliferative neoplasms: minimal residual disease and cure?

The first clinical trials of the safety and efficacy of interferon-alpha2 (IFN-alpha2) were performed about 30 years ago. Since then, several single-arm studies have convincingly demonstrated that IFN-alpha2 is a highly potent anti-cancer agent in several cancer types but unfortunately not being explored sufficiently due to a high toxicity profile when using non-pegylated IFN-alpha2 or high dosages or due to competitive drugs, that for clinicians at first glance might look more attractive. Within the hematological malignancies, IFN-alpha2 has only recently been revived in patients with the Philadelphia-negative myeloproliferative neoplasms-essential thrombocytosis, polycythemia vera, and myelofibrosis (MPNs)-and in patients with chronic myelogenous leukemia (CML) in combination with tyrosine kinase inhibitors. In this review, we tell the IFN story in MPNs from the very beginning in the 1980s up to 2018 and describe the perspectives for IFN-alpha2 treatment of MPNs in the future. The mechanisms of actions are discussed and the impact of chronic inflammation as the driving force for clonal expansion and disease progression in MPNs is discussed in the context of combination therapies with potent anti-inflammatory agents, such as the JAK1-2 inhibitors (licensed only ruxolitinib) and statins as well. Interferon-alpha2 being the cornerstone treatment in MPNs and having the potential of inducing minimal residual disease (MRD) with normalization of the bone marrow and low-JAK2V617F allele burden, we believe that combination therapy with ruxolitinib may be even more efficacious and hopefully revert disease progression in many more patients to enter the path towards MRD. In patients with advanced and transforming disease towards leukemic transformation or having transformed to acute myeloid leukemia, "triple therapy" is proposed as a novel treatment modality to be tested in clinical trials combining IFN-alpha2, DNA-hypomethylator, and ruxolitinib. The rationale for this "triple therapy" is given, including the fact that even in AML, IFN-alpha2 as monotherapy may revert disease progression. We envisage a new and bright future with many more patients with MPNs obtaining MRD on the above therapies. From this stage-and even before-vaccination strategies may open a new horizon with cure being the goal for some patients.