Data on Veterans Suggest Ruxolitinib Led to Significant PMF Survival Gains

A new study of mortality among veterans with primary myelofibrosis (PMF) suggests that the approval of ruxolitinib (Jakafi) has coincided with a significant improvement in patient survival rates.

The report was published in BMC Cancer.

The myeloproliferative neoplasm myelofibrosis can arise de novo or it can transform from polycythemia vera or essential thrombocythemia. People with primary myelofibrosis have a median overall survival (OS) of 2.3 to 11.3 years, explained the study authors. The wide range of OS time frames is because a host of factors—age, constitutional symptoms, hemoglobin levels, and white blood cell count—can affect an individual’s risk level. Those factors are used to calculate patients’ International Prognostic Scoring System (IPSS) risk score.

Patients with intermediate- or high-risk myelofibrosis are eligible to take ruxolitinib, a Janus kinase 1/2inhibitor first approved by the FDA in 2011. In phase 3 trials and a postmarketing trial, the therapy led to improved OS.

The study investigators wanted to see whether introducing the therapy led to a significant change in survival patterns in people with PMF. They decided to analyze data from the Veterans Health Administration (VHA) to see whether they could identify shifts in survival from the era before the approval of ruxolitinib and the period after the drug’s introduction.

The investigators used a pair of 3-year data sets for their comparison. The preruxolitinib data set spanned 2007 to 2010 and included 193 patients. The postruxolitinib data set covered 2015 to 2018 and included 974 patients. Patients were included in the latter cohort regardless of whether they were taking ruxolitinib. The investigators compared patient risk factors and outcomes.

These 2 cohorts varied in terms of their level of IPSS risk factors. In the preruxolitinib cohort, 80 of 193 patients had at least 2 risk factors. In the postruxolitinib cohort, just 197 of 974 patients had at least 2 risk factors. Of the latter cohort, 83 (8.5%) patients took ruxolitinib.

However, the survival impact was significant. The median OS in the preruxolitinib group was 1.7 years and was not reached in the postruxolitinib cohort. Likewise, the overall mortality rates were 79.8% vs 47.3%, respectively, resulting in a 53% lower risk of death. When the investigators stratified patients based on the presence of at least 2 IPSS risk factors, they found a similar mortality advantage in the postruxolitinib era.

Those data suggest ruxolitinib is making a difference in patient outcomes, but the authors said they also raise the question of why only 8.5% of the later cohort was prescribed the drug. One potential reason they proposed is that many patients were given hydroxyurea. They added that some patients might not have met VHA criteria for the therapy.

Still, the study authors said the survival data are compelling and likely due not just to new treatments like ruxolitinib, but also to better diagnostic techniques. They said future research should compare contemporary cohorts treated with and without ruxolitinib.

“[G]iven that only a small portion of patients in the postruxolitinib group received ruxolitinib in this study, future analyses should examine mortality differences in patients who received ruxolitinib compared with those who did not, using data from real-world clinical practice,” they concluded.

Reference

Tashi T, Yu J, Pandya S, Dieyi C, Scherber R, Parasuraman S. Trends in overall mortality among US veterans with primary myelofibrosis. BMC Cancer. Published online January 14, 2023. doi:10.1186/s12885-022-10495-6