Phlebotomy Requirements Are Lower In Polycythemia Vera Patients With Low Ferritin Stores.

e19537 Background: Polycythemia vera (PV) is a myeloid neoplasm of clonal red cell proliferation. Most PV patients are iron deficient at diagnosis, prior to the onset of therapeutic phlebotomy, the mainstay of treatment. More recent studies have also suggested that aberrant iron homeostasis contributes to persistently elevated hematocrit in iron deficient PV patients. In healthy individuals, iron deficiency leads to anemia such that the co-occurrence of polycythemia and iron deficiency in PV is pathological. The purpose of our study is to investigate whether iron deficiency, as defined by serum ferritin < 15 μg/L, at PV diagnosis can predict phlebotomy requirements in PV patients. Methods: 173 patients were diagnosed with PV between 2010 and 2019 at our institution. We analyze ferritin levels, phlebotomy frequency, and cytoreductive therapy in PV patients. Patients are stratified into a “high ferritin” (serum ferritin > 30 μg/L) or “low ferritin” (serum ferritin < 15 μg/L) groups and analyzed at 0-6 months and 4-6 years after diagnosis. 91% of PV patients were treated with phlebotomy and 70% with cytoreductive therapy. 23 and 13 patients had both a ferritin level and a record of the number of phlebotomies at 0-6 months or 4-6 years after diagnosis, respectively. Results: The average number of phlebotomies at 0-6 months after diagnosis was 3.1±1.7, with no statistically significant difference between the low and high ferritin groups. The average number of phlebotomies at 4-6 years after diagnosis was 2.9±2.5, with no statistically significant difference between the low and high ferritin groups (1.9 vs. 4.6 phlebotomies, respectively; p = 0.136). In patients with low ferritin at diagnosis, phlebotomy requirements decreased at 4-6 years relative to 0-6 months after diagnosis (1.9 vs. 3.1 phlebotomies; p = 0.009) while no difference occurred in the high ferritin group. In all PV patients, average serum ferritin increased with time from diagnosis (R = 0.81) and cannot be explained by cytoreductive therapy as there was no significant effect on average ferritin levels (137 vs. 60 μg/L; p = 0.295) or phlebotomy requirements (3.2 vs. 3.4; p = 0.803) at 4-6 years after PV diagnosis. Conclusions: Low ferritin levels at PV diagnosis decreased phlebotomy frequency at 4-6 years relative to 0-6 months after diagnosis. Additionally, cytoreductive therapy did not significantly affect phlebotomy requirements or ferritin levels at 4-6 years post-PV diagnosis. Further work is needed to assess the molecular pathways involved in iron-deficient erythrocytosis in PV.