A Population-Based Study on Survival of 652 Higher Risks Myelofibrosis Patients Treated with Ruxolitinib in Italy

Introduction

Myelofibrosis (MF) is a severe disease, and patients in the higher prognostic risk categories have a median overall survival (OS) ranging between 2 and 4 years after diagnosis. Ruxolitinib (RUX) is the first approved drug for MF, with an impact on OS reported in different studies, such as a post-hoc analysis of the registration trials (Verstovsek et al, 2017) and in the real-world setting (Guglielmelli et al, 2022).

In Italy, RUX is available since October 2014 for intermediate-2 (INT-2) and high risk (HR) patients and since January 2018 also for intermediate-1 MF cases. High-cost drugs are delivered and monitored by each regional health authority. In this study, we analyzed the outcome of INT-2 and HR MF patients treated with RUX in three Italian regions, accounting for a population of almost 20 million people.

Methods

This is a population-based retrospective cohort study based on healthcare utilization databases of Lombardy, Tuscany, and Lazio regions, including data on hospital admissions, drug prescriptions, outpatient's health services and demographics.

The study cohort included all beneficiaries of the Regional Health Service who started RUX between October 2014 and December 2017 (to include only INT-2 and HR MF patients) and followed up until 31st July 2021 (minimum observation period of the study: 3.5 years). The Multisource Comorbidity Score (MCS) was calculated to assess concurrent medical conditions (Corrao et al, 2017).

The primary outcome of the study was OS, defined as the time between RUX start and death for any cause or censoring due to migration, end of data availability or stem cell transplant (SCT). OS was estimated by the Kaplan-Meier method and 95% confidence interval (95%CI) was calculated. The secondary outcome was identification of risk factors associated with mortality via a multivariable Cox regression model evaluating the following variables: gender, age, year of RUX start and initial dose, SCT (included as time-dependent variable) and MCS score (low, intermediate, high). Data were analyzed separately for each region and subsequently pooled together by using fixed-effects meta-analyses.

The incidence of adverse events (AEs) and secondary malignancies (included blast phase, BP, or post MF-myelodysplastic syndromes, MDS) that required hospital admission and occurring during follow-up was assessed and expressed as incidence rate (IR) x100 person-years (p-y). Infections, bleedings, and major thrombotic events were considered if they occurred within 90 days from the last RUX prescription and before evolution into BP/MDS.

Results

During the study period, 652 MF patients were started on RUX. Mean age at first administration was 68.7 years. In details, 317 (48.6%) subjects were younger than 70 years and 69 (10.6%) 80 years or older. Males represented 56% of the total cohort. Region of residence was Lombardy in 290 (44.5%), Lazio in 215 (33%) and Tuscany in 147 (22.5%) of the cases. The MCS was intermediate in 58.3% of the subjects. SCT was performed in 71 (10.9%) patients. RUX initial dose was 5 mg BID in 32% of cases and at least 20 mg BID in 25.6% of the whole cohort.

At a median study follow-up of 39.8 months, overall, 364 (55.8%) deaths occurred. Median OS was 47.7 months (95%CI: 38.7-52.2), as reported in Figure 1. The 1-, 3- and 6-years OS rates were 85%, 63% and 34%, respectively. Factors independently associated with mortality were male gender, older age classes, high MCS score and less than 20 mg BID as RUX initial dose (Table 1).

The most frequent AEs were infections (IR: 11 x100 p-y), bleeding events (3.9 x100 p-y) and thrombosis (1.5 x100 p-y). Secondary solid tumors had an IR of 5.6 x100 p-y, while the latter was 1.1 x100 p-y for lymphoproliferative disorders. Evolution into BP/MDS was reported in 103 (15.8%) patients of the cohort, with an IR of 5.5 x100 p-y.

Conclusions

Our study provides RUX treatment outcomes in an unselected real-world population-based cohort of 652 patients with higher risks MF, in residents of three Italian regions accounting for 20 million inhabitants.

In this study on 652 INT-2 and HR MF patients observed for a minimum follow-up period of 3.5 years, RUX demonstrates to have a robust effect on survival, underpinning its use at appropriate doses in the management of these patients.

MF progression rate into BP/MDS after RUX start seems not to be modified with respect to pre-RUX historical data (Mora et al, 2023).