Background: Non-CML myeloproliferative neoplasms (MPNs) include essential thrombocythemia (ET), polycythemia vera (PV), myelofibrosis (MF) and MPN not otherwise specified (MPN-NOS), and are characterized by activation of JAK2 signaling and abnormal blood cell production. Reported median overall survival (OS) for MF ranges from a few (Cervantes et al. J Clin Oncol epub 2012;42:0240) to several years (Hultcrantz et al. J Clin Oncol epub 2012;42:1925). ET and PV median OS is reported to be a decade or more, although recent findings based on the Swedish cancer registry indicate that PV and ET patients may experience shorter survival than previously understood (Hultcrantz et al. J Clin Oncol epub 2012;42:1925; Barbui et al. 2011;29:3179–3184). Survival of MPN-NOS patients is not well characterized in the literature. MPN patients experience multiple comorbidities that can increase the risk of disability and death. However, survival rates of MPN patients from a nationally representative US population have not been recently described. MPN is more prevalent in the elderly; therefore, Medicare enrollees are a highly relevant source for US-based survival estimates in these diseases.
Objective: To compare survival rates of MPN patients (ET, PV, MF and MPN-NOS) with matched non-MPN/non-cancer controls.
Methods: In this retrospective study, data were taken from the Survey, Epidemiology, and End Results (SEER)-Medicare linked database in the US. SEER-Medicare combines clinical information from the SEER cancer registry with medical and pharmacy claims for Medicare enrollees. Codes for reporting MPN cases to SEER have been available since 2001. In our study, Medicare enrollees with a new SEER MPN diagnosis between Jan 1, 2001 and Dec 31, 2007 were selected and evaluated for survival. Patients were classified into MPN subtypes as indicated by their SEER registry diagnosis. First MPN diagnosis was required to occur at or before Medicare enrollment to allow for continuous follow-up. Non-MPN/non-cancer control groups were selected from Medicare for each MPN subtype and matched to cases 5:1 based on year of birth, gender, race, geographic location, and reason for Medicare eligibility. Survival for both case and matching controls was determined starting from the case diagnosis date. Survival was estimated using the Kaplan-Meier method.
Results: A total of 4,274 MPN patients (n = 1217 ET, 1625 PV, 522 MF and 910 MPN-NOS) were identified for inclusion and assigned matching controls.
Conclusions: Survival in MF and MPN-NOS patients was worse than that of patients with ET or PV and significantly worse than matched controls. Contrary to the commonly held thought that PV and ET patients experience near-normal life expectancy, survival of patients with ET or PV was substantially inferior to matched controls. These findings have implications for the clinical management of MPN patients and underscore the need for effective therapies in all MPN subtypes.
