Do all patients with polycythemia vera or essential thrombocythemia need cytoreduction?

Polycythemia vera (PV) and essential thrombocythemia (ET) are Philadelphia chromosome–negative chronic myeloproliferative neoplasms (MPNs), characterized by expansion of normal blood counts, bleeding, thrombosis, and the potential for transformation to myelofibrosis (MF) or acute myeloid leukemia (AML). The primary goals of treatment for MPNs are to reduce the risk of thrombosis, alleviate systemic symptom burden (eg, fatigue, pruritus, microvascular symptoms, and symptomatic splenomegaly), and to prevent transformation to MF/ AML. Preventing transformation is clearly important, but not expected with current therapies. Currently, cytoreduction is advised based on vascular risk assessments, which include age and thrombosis history, as well as molecular profile in ET. Traditionally, cytoreduction has been advised only in patients with high vascular risk. Recently, a large prospective study evaluated the safety and efficacy of cytoreduction in patients with ET with less-than-high-risk vascular profiles. A larger question in the MPN field is whether cytoreduction is advisable for all patients with ET and PV, regardless of risk. This article reviews existing data on cytoreduction, evaluating hydroxyurea, interferons, and ruxolitinib in ET and PV. This review evaluates whether evidence supports a more liberal strategy of cytoreduction for all patients with ET and PV.