Therapy-associated leukemic transformation in myeloproliferative neoplasms - What do we know?

Myeloproliferative Neoplasms (MPNs) are a group of progressive diseases that share a common pathogenesis, clinical and laboratory features, as well as a spontaneous risk of secondary AML. Certain MPN therapies have been associated with an increased risk of leukemic conversion, with robust data highlighting the highest rates with 32P, chlorambucil, and pipobroman. Herein, we review risk factors for leukemic transformation, including therapy-related MPN-BP, with a focus on the debate surrounding the potential leukemogenicity of hydroxyurea. Lastly, we discuss emerging studies on the association between ruxolitinib and high grade B-cell lymphomas. We conclude that statistical associations have not implicated hydroxyurea monotherapy as leukemogenic. However, it is difficult to definitely disprove an association, as large prospective, controlled studies with decades of follow-up would be needed to draw conclusions. Overall, the concept of therapy-related neoplasms remains important to the field, and mandates judicious selection and sequencing of therapies for MPN patients.