Normal Life Expectancy for Polycythemia Vera Patients Is Possible

Introduction: Polycythemia vera (PV), a chronic myeloproliferative neoplasm, is characterized by shortened overall survival (OS) due to potentially fatal thrombosis, progression to myelofibrosis (MF), and acute leukemia. Treatment with aspirin, attentive phlebotomy (PHL) and cytoreductive agents can prevent thrombosis; but it is unknown whether available treatments can achieve a normal life-span for PV patients (pts). Our objective was to assess the extent by which PV alters OS of pts receiving available treatment at our center and in the community.

Methods: We obtained demographics and survival data of adult PV pts from our Weill Cornell Medicine (WCM) Research Database Repository (PV-WCM) diagnosed from 1974-2020 as previously described (Abu-Zeinah et al. Leukemia 2021); and from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program, 2001-2017. PV-WCM thrombosis and MF progression data were available. WCM institutional review board approval and SEER data use agreement were in place. OS of PV pts was estimated using Kaplan-Meier (KM) analysis. Propensity Score Matching was used to identify a subgroup of SEER pts (PV-SEER) with similar age, sex, and race demographics to PV-WCM for comparison of OS. Cox proportional hazards was used for multivariable analysis (MVA) of survival. Actuarial survival of the US population matched by age, sex, race, and year-of-birth was obtained from US Census. Observed OS was compared to actuarial OS using one-sided log-rank test.

Results: We identified 470 PV-WCM and 16,492 PV pts from SEER. The median OS of the PV-WCM cohort and the SEER population was 26.6 and 12.8 years, respectively, but the groups differed by age and sex (Fig 1A). PV-WCM and matched PV-SEER, however, were well balanced by age, sex, and race (standardized mean difference <0.1). The median OS of PV-WCM was 10.8 years longer than PV-SEER (p<0.001, Fig 1B). MVA confirmed 65% lower mortality in the PV-WCM group relative to the PV-SEER population (p<0.001, Fig 1C). PV-SEER OS was shorter than actuarial OS of the US population (mortality HR 2.47, p<0.001), whereas PV-WCM OS was not significantly different than expected (mortality HR 1.15, p=0.136). Excess late mortality was observed in PV-WCM after 17 years, potentially due to increased incidence of MF progression, affecting almost 50% of PV pts after 25 years (Fig 1D).

Discussion: These data point to the success of attentive management with aspirin, targeted PHL, and cytoreductive therapy at a specialty center in reducing the mortality of PV, owing in part, to ELN and NCCN treatment recommendations for preventing fatal thrombosis. Although excess thrombosis was not eliminated in PV-WCM pts, the incidence rate was low after the first two years (Fig 1D). In contrast, the incidence of MF progression increased, potentially contributing to excess late mortality. Current PV risk stratification and treatment recommendations neither predict nor aim to mitigate progression to MF, and do not satisfy the needs of younger, low-risk pts who are often symptomatic and harbor a lifetime threat of progression (Fig 1E). The recent Low-PV study showed that low-risk pts may also benefit from cytoreductive therapy with an agent such as interferon-alpha (rIFNα) over PHL alone (Barbui et al. Lancet Hematol 2021). PV-WCM pts treated with rIFNα (n=137), previously shown to have improved MF-free survival and OS (Abu-Zeinah et al. Leukemia 2021), had an OS similar to the matched US population (p=0.33, Fig 1F); whereas pts not treated with rIFNα had modestly shortened OS (HR 1.26, p=0.03). Because PV progression is among the leading causes of late morbidity and mortality, and available therapy can mitigate this, it may be time to reconsider and improve upon PV risk stratification and treatment.

Conclusion: This large population-based and single center study shows that although PV survival remains shortened, normal life expectancy for PV pts is possible with available care. The discrepancy between survival in the community and at a specialized center highlights the need for greater community outreach, health equity, and education regarding treatment standards for PV. Hopefully, this study motivates development of new PV risk stratification and treatment recommendations that focus not only on hematologic control and thrombosis prevention, but also on preventing MF progression, improving OS, and restoring normal life expectancy.

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