Safety and Efficacy of Busulphan Based on Dosing Patterns in the Real-World Management of Myeloproliferative Neoplasms.

Introduction: Myeloproliferative neoplasms (MPNs), such as polycythaemia vera (PV), essential thrombocythemia (ET) and myelofibrosis (MF), are primarily treated by managing blood counts to reduce the thrombotic risk using cytoreductive agents. Busulphan, an oral alkylating agent, has been historically used for MPN management due to its myelosuppressive effects, but concerns about its risk of leukaemic transformation have limited its use. Methods: This real-world retrospective study evaluated the safety and efficacy of busulphan in 115 MPN patients across 13 UK hospitals. Responses in patients with ET and PV only were assessed using European LeukemiaNet (ELN) criteria. Results: With a median age of 78 years, the overall response rate was 78.1%, with 29% of PV and 18% of ET patients achieving complete responses. Dosing regimens were similarly distributed between repeated single doses of busulphan (31%), courses of treatment lasting 1-4 weeks (30%) and continuous therapy for more than 4 weeks (35%). No cases of disease progression to acute leukaemia or myelofibrosis were recorded during the median follow-up of 23 months. Adverse events were infrequent, with fatigue and cytopaenia being the most common (4% each). Conclusion: Busulphan demonstrated a favourable safety profile and is a viable cytoreductive option, particularly for elderly patients who are intolerant to hydroxycarbamide. Trial Registration: The authors have confirmed clinical trial registration is not needed for this submission.