Analysis of Predictive Factors for Early Response to Ruxolitinib in 320 Patients with Myelofibrosis From the Polish Adult Leukemia Group (PALG) Registry

In this real-life study, we investigated the predictors of response to ruxolitinib therapy in 320 Polish myelofibrosis (MF) patients. Leukocytosis < 25 G/L, reticulin fibrosis MF 1, shorter time from MF diagnosis to ruxolitinib start, and platelets >150 G/L correlated with better response to ruxolitinib. Establishing predictive factors for ruxolitinib response helps identify patients with a low likelihood of responding. Introduction: Ruxolitinib is widely used in myelofibrosis (MF). However, some patients do not optimally respond and require more efficacious treatment. Our analysis aimed to establish predictors of ruxolitinib response. Patients and Methods: We designed a multicenter, retrospective analysis of the efficacy of ruxolitinib treatment in patients with MF in 15 Polish hematology centers. As responses to ruxolitinib occur within the first 6 months, we used this point to evaluate the efficacy of treatment. Symptoms response was defined as >50% reduction of the MF constitutional symptoms assessed by Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF TSS). Spleen response was defined as >50% reduction of the difference between the spleen's baseline length and the upper limit norm measured by ultrasonography. Results: 320 MF patients were enrolled. At 6 months of therapy, the spleen response was detected in 140 (50%) patients, and symptoms response in 241 patients (76%). Multivariable analysis identified leukocytosis < 25 G/L (OR 2.06, 95%CI: 1.12-3.88, P = .0200), and reticulin fibrosis MF 1 (OR 2.22, 95%CI: 1.11-4.46, P = .0249) contributed to better spleen response. The time interval between MF diagnosis and ruxolitinib administration shorter than 3 months, and platelets >150 G/L (OR 1.69, 95% CI 1.01-2.83, P = .0466) influenced symptoms response. Conclusion: Establishing predictive factors for ruxolitinib response is particularly important given the potential for new therapies in MF. In patients with a low likelihood of responding to ruxolitinib, using other JAK inhibitors or adding a drug with a different mechanism of action to ruxolitinib may be of clinical benefit.