PF674 OUTCOME OF PATIENTS WITH MYELOFIBROSIS AFTER RUXOLITINIB DISCONTINUATION: ROLE OF DISEASE STATUS AND TREATMENT STRATEGIES IN 218 PATIENTS
Authors: F. Palandri, M. Breccia, M. Bonifacio, N. Polverelli, E.M. Elli, G. Benevolo, M. Tiribelli, E. Abruzzese, A. Iurlo, F. Heidel, M. Bergamaschi, A. Tieghi, M. Crugnola, F. Cavazzini, G. Binotto, A. Isidori, N. Sgherza, C. Bosi, B. Martino, R. Latagliata, G. Auteri, L. Scaffidi, D. Griguolo, M. Trawinska, D. Cattaneo, L. Catani, M. Krampera, U. Vitolo, R.M. Lemoli, A. Cuneo, G. Semenzato, R. Foà, F. Di Raimondo, D. Bartoletti, M. Cavo, G.A. Palumbo, N. Vianelli
Journal: HemaSphere (2019)

Background: After discontinuation of Ruxolitinib (RUX), the outcome of patients (pts) with myelofibrosis (MF) has been reported to be poor. Aims: Here, we investigated the impact of baseline features, responses, and type of salvage therapy on survival in 218 pts who received and discontinued RUX in routine clinical practice. Methods: A clinical database was created in 20 European Hematology Centers including retrospective data of 521 MF pts treated with RUX from Jan 2011 to October 2018. Spleen/symptoms response to RUX were evaluated according to the 2013 IWG‐MRT/ELN criteria. Overall (OS) was estimated from the date of RUX discontinuation to the date of death or last contact (log‐rank test). Comparisons of continuous or categorical variables between groups were carried out by Wilcoxon‐Mann‐Whitney rank‐sum test or χ2, respectively. Risk factors for RUX discontinuation and prognostic factors for survival were identified using Cox proportional hazards model. Results: After a median follow‐up from RUX start of 37 months, 268 out of 521 (51.2%) pts stopped RUX, with a discontinuation rate of 19.6 per 100 patient‐years. Intermediate‐2/High DIPSS risk score, platelet count &lt;100 x10 9 /l, Charlson Comorbidity Index ≥2 and unfavorable karyotype were significantly associated with a higher probability of drug interruption. Fifty pts (18.7%) died while taking RUX; median survival time of the remaining 218 pts after RUX stop was 13.2 months. Causes of RUX discontinuation in the 218 pts were: lack (22.9%) / loss (11.9%) of response, progression to blast phase (23.4%), toxicity (28.9%; specifically anemia [10.5%], thrombocytopenia [6.9%], infections [9.2%], other adverse events [2.3%]), second solid neoplasia (4.6%), and thrombosis (3.2%). 11 pts (5.1%) stopped RUX while in response and underwent allogeneic stem cell transplantation (alloSCT). Compared to the 256 pts still on treatment at last contact, the 218 pts who discontinued RUX had started the therapy with a significantly more advanced disease in terms of higher DIPSS risk score, larger splenomegaly, and deeper cytopenias. Previous response to RUX did not influence OS. OS was significantly influenced by disease status (chronic vs blast phase) but not by reason of discontinuation (resistance vs intolerance) ( Fig. 1a ). A total of 167 pts discontinued RUX in chronic phase (CP) and had a median survival after discontinuation of 27.5 mos. In this cohort, hemoglobin&lt;10 g/dl (p = 0.01) and a circulating blasts ≥1% (p = 0.01) at the time of RUX withdrawal correlated with worse survival. 111 CP pts (66.5%) received a salvage therapy that included JAK2 ‐inhibitors and/or other investigational agents in 31 cases and only conventional medical therapies in 54; 26 pts underwent alloSCT after conventional therapies. Pts treated with novel agents had a significantly better OS ( Fig. 1b ). 51 (23.4%) pts discontinued RUX in BP, and 28 (54.9%) received salvage treatments including hydroxyurea (n. 14), hypometylating agents (n. 7), chemotherapy (n. 6), alloSCT (n. 5). Median survival time was significantly higher for pts who received therapy after RUX (7.9 mos vs 2.2 in untreated pts, p = 0.005). Summary/Conclusion: A greater burden of disease at RUX start is significantly associated with higher discontinuation rate. After RUX stop, outcome is mostly influenced by disease phase and type of salvage therapies, with CP pts treated with novel agents having the best outcome. Earlier RUX therapy and innovative salvage strategies may improve outcome of MF pts. image