Real-World Survival Among Patients with Intermediate- to High-Risk Myelofibrosis in the United States: Impact of Ruxolitinib Approval

Background

The myeloproliferative neoplasm myelofibrosis (MF) is associated with reduced overall survival (OS) compared with the general population (Hultcrantz M, et al. J Clin Oncol. 2012;30[24]:2995-3001; Price GL, et al. PLoS One. 2014;9[3]:e90299). The Janus kinase 1 and 2 inhibitor ruxolitinib (RUX) was approved by the US Food and Drug Administration in November 2011 for the treatment of adult patients with intermediate- or high-risk MF based on data from the phase 3 COMFORT trials, which showed significantly improved OS in patients who received RUX (Verstovsek S, et al. J Hematol Oncol. 2017;10:156). Understanding the clinical benefit of RUX in real-world practice requires an understanding of changes in patient outcomes for those exposed to RUX compared with those never exposed to RUX, both before and after approval. The aim of this analysis was to assess the OS of patients newly diagnosed with intermediate- to high-risk MF before RUX approval, and for those who were RUX-unexposed vs -exposed in the post-RUX approval time frame.

Study Design and Methods

All data from the Medicare Fee-for-Service claims database (Parts A/B/D) from January 2010 to December 2017 were used to identify patients who were ≥65 years old (intermediate-1 or higher risk MF due to age) with ≥1 inpatient claim or ≥2 outpatient claims with a documented MF diagnosis. The index date was the date of the first qualifying MF claim; ≥12 months of pre-index continuous medical and pharmacy enrollment was required. Patients with evidence of an MF diagnosis ≤12 months before the index date were excluded. Patients with a diagnosis of myelodysplastic syndrome, hematologic malignancies (leukemias, multiple myeloma, and lymphomas), or solid tumors either ≤12 months before, on, or any time after index were also excluded in a stepwise manner. The study sample was classified into 3 groups: patients diagnosed with MF pre-RUX approval (index year 2010–2011; no post-index exposure to RUX); those diagnosed with MF post-RUX approval and unexposed to RUX (index year 2012–2017); and those diagnosed with MF post-RUX approval and exposed to RUX (index year 2012–2017). One-year survival rate and risk of mortality were estimated using Kaplan-Meier and Cox proportional hazards regression analyses, adjusting for baseline demographic and clinical characteristics. OS was measured from the index date until death or end of follow-up. Patients without a death date were censored at disenrollment or the end of the study period, whichever occurred first.

Results

Among eligible patients with an MF diagnosis (N=1677), median age was 78 years, 39.8% were male, and 84.1% were white. The analysis included 278 patients diagnosed pre-RUX approval (all RUX-unexposed) and 1399 diagnosed post-RUX approval (RUX-unexposed, n=1127; RUX-exposed, n=272). Median follow-up for the pre- and post-RUX approval groups was 12.5 and 11.3 mo (RUX-unexposed, 10.2 mo; RUX-exposed, 14.0 mo), respectively. In the pre-RUX approval group, 119 (42.8%) patients had a valid death date compared with 436 (31.2%) in the post-RUX approval group (RUX unexposed, n=382 [33.9%]; RUX exposed, n=54 [19.9%]). The 1-year survival rate (95% CI) was 55.6% (49.4%–61.3%) for the pre-RUX approval group, 72.5% (69.5%–75.2%) for the post-RUX approval RUX-unexposed group, and 82.3% (76.7%–86.7%) for the post-RUX approval RUX-exposed group (Figure). The risk of mortality was lowest among RUX-exposed patients (adjusted hazard ratio [HR], 0.36; 95% CI, 0.26–0.50; P<0.0001 vs the pre-RUX approval group). Patients in the post-RUX approval group who had never been exposed to RUX also had a lower risk of mortality, although less pronounced than RUX-exposed patients, compared with the pre-RUX approval group (adjusted HR, 0.67; 95% CI, 0.56–0.80; P<0.0001).

Conclusions

In this real-world study of US patients diagnosed with intermediate- or high-risk MF, 1-year OS was improved in patients diagnosed after RUX approval compared with before RUX approval. Notably, in the post-RUX approval time frame, 1-year OS was greater for those who received RUX than for those who did not receive RUX. These findings complement the survival benefit results demonstrated in the COMFORT studies using real-world data.