Pegylated Interferon is an effective and well-tolerated cytroreductive agent in patients with myeloproliferative neoplasms aged over 60 years

ABSTRACT

Pegylated Interferon (PegIFN) is the recommended first-line cytoreductive therapy in patients aged <40 years with essential thrombocythaemia (ET) or polycythaemia vera (PV). However, its use in patients >60 years is often limited due to concerns about tolerability. In this study, we evaluate the efficacy and tolerability of PegIFN in patients >60 years at University College London Hospitals (UCLH). Using electronic medical records, we identified patients with ET, PV or myelofibrosis at UCLH who commenced treatment with PegIFN between 2010 and 2020 and were aged >60 years on starting therapy. Data were collected until April 2021 to allow a minimum of 1-year follow-up. Complete Haematological responses were defined as per standard European Leukaemia Net criteria. Adverse events (AE) were graded 1-5 according to Common Terminology Criteria for Adverse Events (CTCAE). Thrombosis risk was graded according to IPSET criteria for ET patients. Patients with PV were classed as high risk if they were aged >65 or had a previous history of thrombosis. Eighteen patients were included in the study. The median age was 75.1 years (range 63-91), 61% were female. Ten out of 18 (56%) had a diagnosis of ET, seven out of 18 (39%) of PV and 1/18 (6%) of post-ET myelofibrosis. Fifteen out of 18 (83%) were positive for JAK2 V617F, and two out of 18 (17%) were positive for CALR mutation. Ten out of 18 (56%) had significant cardiovascular co-morbidities at diagnosis. Five out of 18 (28%) had arterial or venous thromboembolic disease at diagnosis. Sixteen out of 18 (89%) were high-risk for thromboembolic events at diagnosis. Seventeen (94%) patients had PegIFN as a second-or thirdline agent. Of these, 15 out of 17 had received hydroxycarbamide (HU) as first-line therapy;two out of 17 had interferon alpha. PegIFN was started at a median age of 70 years (range 50-86) and continued for 5.7 years (range 2-13). Twelve out of 18 (67%) patients achieved complete remission (CR) on PegIFN monotherapy;1 out of 18 (6%) achieved CR on PegIFN and HU combination therapy, and the remaining 5 out of 18 (28%) achieved a partial remission (PR). The median time to CR was 5 months (range 1-40 months). Ten out of 18 (56%) had grade 1-2 AEs including skin rashes, cytopenia and fatigue. Three out of 18 (17%) developed a major thromboembolic event while on treatment (brachial artery embolism, transient ischaemic attack and a non-ST elevation myocardial infarction). Of these, two out of three failed to achieve a CR on PegIFN and required ongoing venesection. The third had suboptimal response due to dose escalation limited by grade 3 neutropenia. Thirteen patients (72%) remained on pegIFN at the end of the study period. Of those who discontinued, three out of five stopped due to cytopenias, one out of five died during the study period of Covid-19 infection and one out of five transformed to myelodysplastic syndrome. In this study, we present a group of patients who were at high risk for thrombosis due to their age and cardiovascular risk factors. The majority of AEs documented were grade 1-2, with only three out of 18 (17%) patients discontinuing due to AEs. The rate of CR 72% similar to that quoted in imminent studies including MPN-RC (Knudsen et al, 2018) and DALIAH trials (Mascarenhas et al, 2018), which recruited larger numbers of youngers ET and PV patients on PegIFN. Over 20% of MPN patients develop resistance or intolerance to HU (Sever et al, 2014);therefore, there is a need for alternative cytoreductive agents. Our study demonstrates PegIFN to be effective and well-tolerated for use in patients >60 years and is an excellent cytoreductive option in this cohort.