Prevalence of frailty and its association with clinical outcomes in myeloproliferative neoplasms: a population-based study

Clinical implications of frailty in myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), are unknown. In this population-based study, all incident cases of MPN from the Ontario cancer registry between 2004 and 2019 (N = 10 336; ET = 5108; PV = 3843; MF = 1385) and their matched controls (for age, sex, residence, and income) in a 1:4 ratio were included. Baseline frailty measured using the Johns Hopkins Adjusted Clinical Groups frailty indicator and McIsaac frailty index (mFI), categorized as fit, prefrail, or frail if mFI <0.10, 0.11 to 0.20, >0.20), was significantly higher in ET, PV, and MF compared with matched controls (standardized mean difference of 0.27, 0.27, and 0.28). Over 23%, 20%, and 34% of patients with ET, PV, and MF were frail or prefrail despite a younger age (<65 years) or minimal comorbidities. In Cox proportional regression, frailty was independently associated with worse overall survival (OS) after adjusting for age, sex, and comorbidities compared with mFI-fit patients. The hazard ratios (95% confidence interval) for OS for mFI-prefrail and mFI-frail patients were: 1.6 (1.3-1.9) and 3.6 (2.9-4.4) in ET, 1.3 (1.1-1.5) and 2.7 (2.1-3.4) in PV, and 1.2 (1.0-1.5) and 2.0 (1.5-2.7) in MF. Patients with MPN have a substantially higher prevalence of frailty compared with matched controls, which is associated with reduced OS, independent of age or comorbidities.