Incidence of blast phase in myelofibrosis patients according to anemia severity at ruxolitinib start and during therapy.

BACKGROUND: Anemia is frequently present in patients with myelofibrosis (MF), and it may be exacerbated by treatment with the JAK2-inhibitor ruxolitinib (RUX). Recently, a relevant blast phase (BP) incidence has been reported in anemic MF patients unexposed to RUX. METHODS: The authors investigated the incidence of BP in 886 RUX-treated MF patients, included in the "RUX-MF" retrospective study. RESULTS: The BP incidence rate ratio (IRR) was 3.74 per 100 patient-years (3.74 %p-y). At therapy start, Common Terminology Criteria for Adverse Events grade 3-4 anemia (hemoglobin [Hb] <8 g/dL) and severe sex/severity-adjusted anemia (Hb <8/<9 g/dL in women/men) were present in 22.5% and 25% patients, respectively. IRR of BP was 2.34 in patients with no baseline anemia and reached respectively 4.22, 4.89, and 4.93 %p-y in patients with grade 1, 2, and 3-4 anemia. Considering the sex/severity-adjusted Hb thresholds, IRR of BP was 2.85, 4.97, and 4.89 %p-y in patients with mild/no anemia, moderate, and severe anemia. Transfusion-dependent patients had the highest IRR (5.03 %p-y). Progression-free survival at 5 years was 70%, 52%, 43%, and 27% in patients with no, grade 1, 2, and 3-4 anemia, respectively (p < .001). At 6 months, 260 of 289 patients with no baseline anemia were receiving ruxolitinib, and 9.2% had developed a grade 3-4 anemia. By 6-month landmark analysis, BP-free survival was significantly worse in patients acquiring grade 3-4 anemia (69.3% vs. 88.1% at 5 years, p < .001). CONCLUSIONS: This study highlights that anemia correlates with an increased risk of evolution into BP, both when present at baseline and when acquired during RUX monotherapy. Innovative anemia therapies and disease-modifying agents are warranted in these patients.

Clinical outcomes of ruxolitinib treatment in 595 intermediate-1 risk patients with myelofibrosis: The RUX-MF Real-World Study.

BACKGROUND: Ruxolitinib (RUX) is a JAK1/2 inhibitor approved for the therapy of myelofibrosis (MF) based on clinical trials including only intermediate2-high risk (INT2/HIGH) patients. However, RUX is commonly used in intermediate-1 (INT1) patients, with scarce information on responses and outcome. METHODS: The authors investigated the benefit of RUX in 1055 MF patients, included in the "RUX-MF" retrospective study. RESULTS: At baseline (BL), 595 (56.2%) patients were at INT1-risk according to DIPSS (PMF) or MYSEC-PM (SMF). The spleen was palpable at <5 cm, between 5 and 10 cm, and >10 cm below costal margin in 5.9%, 47.4%, and 39.7% of patients, respectively; 300 (54.1%) were highly symptomatic (total symptom score ≥20). High-molecular-risk (HMR) mutations (IDH1/2, ASXL-1, SRSF2, EZH2, U2AF1Q157) were detected in 77/167 patients. A total of 101 (19.2%) patients had ≥1 cytopenia (Hb < 10 g/dL: n.36; PLT <100 x 109/L: n = 43; white blood cells <4 x 109/L: n = 40). After 6 months on RUX, IWG-MRT-defined spleen and symptoms response rates were 26.8% and 67.9%, respectively. In univariate analysis, predictors of SR at 6 months were no HMR mutations odds ratio [OR], 2.0, p = .05], no cytopenia (OR, 2.10; p = .01), and blasts <1% (OR, 1.91; p = .01). In multivariate analysis, absence of HMR maintained a significant association (OR, 2.1 [1.12-3.76]; p = .01). CONCLUSIONS: In INT1 patients, responses were more frequent and durable, whereas toxicity rates were lower compared to INT2/high-risk patients. Presence of HMR mutations, cytopenia, and peripheral blasts identified less-responsive INT1 patients, who may benefit for alternative therapeutic strategies.