TO THE EDITOR:
In their recent publication entitled, “Relationship between additional mutations at diagnosis and treatment response in patients with essential thrombocythemia,”1 Mosnier et al1 examined the effect of somatic mutations on the response to first-line therapy with hydroxyurea or pegylated interferon. Although the study was well-planned and yielded interesting results, I assert that some of the study results, specifically as they apply to the cohort of patients with JAK2 V617F essential thrombocythemia (ET), may be misleading, because this treatment group was confounded by the inclusion of patients with polycythemia vera (PV). My assertion is supported by the patient hemoglobin levels, which reached a high of 17.2 g/dL in the pegylated interferon cohort, and 17.7 g/dL in the hydroxyurea cohort, far exceeding the World Health Organization 2016 ET diagnostic criteria.2 It is also supported by the JAK2 V617 variant allele frequency, which in some patients exceeded 50%, whereas the variant allele frequency in patients with ET is always <50%.3 Unfortunately, although not the authors’ fault, using the revised International Prognostic Score for Essential Thrombocythemia for risk stratification was also misleading because this risk assessment tool was derived from a data set in which patients with PV were also conflated with patients with ET.4 Indeed, despite unequivocal genetic evidence that ET and PV are different diseases,5,6 there have been several declarations based on disease phenotype alone that JAK2 V617F-positive ET and PV form a biological continuum,7,8 which have been widely accepted.9,10 As an aside, so too have the European Leukemia Network guidelines, which were subsequently repudiated by their developers as having no clinical relevance.11 We are now in the era of precision medicine and artificial intelligence, and it is time that the myeloproliferative neoplasm field embraces its responsibilities, lest current uncritical behavior become permanently embedded to the detriment of patients with myeloproliferative neoplasms.
Contribution: J.L.S. planned and wrote the manuscript.
Conflict-of-interest disclosure: The author declares no competing financial interests.
Correspondence: Jerry L. Spivak, 700 New Hampshire Ave, NW, Apt 1102, Washington, DC 20037; email: jlspivak@jhmi.edu.
