Incidence of blast-phase disease in myelofibrosis, according to anemia severity

Anemia affects almost all patients during the natural progression of myelofibrosis (MF) and is a key factor linked with increased risk of blast-phase (BP) transformation. Around 30–45% of patients who receive ruxolitinib treatment for MF develop Grade 3–4 anemia; however, data surrounding BP progression in patients treated with ruxolitinib are limited.¹

Palandri et al.¹ published a study in Cancer reporting on the incidence of BP according to anemia severity in a large real-world cohort of patients diagnosed with primary and secondary MF, treated with ruxolitinib. We summarize the key points below.

Study design¹

• Retrospective study
• Patients with MF (N = 886) were administered ruxolitinib outside of clinical trials
• Data was collected between 2013 and 2022

Key findings¹

• Median ruxolitinib duration was 2.4 years
• Median follow-up duration was 3.1 years
• At ruxolitinib initiation, 67.4% of patients had anemia
  • 10.2% were red blood cell (RBC) transfusion-dependent
  • 11.1% had an RBC transfusion requirement
• In total, 13.2% of patients experienced BP evolution
• The global BP incidence rate ratio (IRR) was 3.74 per 100 patient-years
• The IRR of BP in patients with no anemia was 2.34 per 100 patient-years vs 4.22 (p = 0.02), 4.89 (p = 0.009), and 4.93 (p = 0.006) per 100 patient-years in patients with Grade 1, Grade 2 and Grade 3–4 anemia, respectively
• The IRR of BP per 100 patient-years was higher in patients who were RBC transfusion-dependent than patients with an RBC transfusion requirement or patients who were RBC transfusion independent (5.03 vs 4.48 vs 3.52 per 100 patient-years, respectively)
• A univariate regression model identified that patients with either a platelet count <100×10⁹/L or anemia had a higher probability of BP evolution (p = 0.006 and p = 0.33, respectively)
• Patients with no anemia had the highest 5-year PFS rate, while patients with Grade 3–4 anemia had the lowest (Figure 1)

Figure 1. 5-year progression-free survival rates according to grade of anemia in patients with MF*

PFS, progression-free survival.
*Adapted from Palandri, et al.¹

• During the first 6 months, 9.2% of patients who had no anemia at the start of therapy developed Grade 3–4 anemia during treatment with ruxolitinib