Lenalidomide Is Effective Treatment Option For Patients With Refractory Anemia With Ring Sideroblasts And Thrombocytosis

CONTEXT AND OBJECTIVE: Refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) is a provisional entity included in the MDS/MPN overlap syndromes with features of refractory anemia with ring sideroblasts (RARS) and thrombocytosis (platelet count uf0b3 450 x 10/L). Individual case reports suggested lenalidomide may be effective in treating RARS-T. In non-del 5q, low-risk MDS, 25% of patients (pts) became red blood cell transfusion independent (RBC-TI). In the phase II study, 35% of pts with RARS treated with lenalidomide achieved RBC-TI. The primary objective of this study is to evaluate a series of pts with RARS-T and compare HI responses among different treatment options. METHODS: This is a retrospective, single-center study. Utilizing the MDS Database at Moffitt Cancer Center, we identified pts with RARS-T. The primary endpoint was HI using international working group criteria (IWG) 2006. The median overall survival (OS) was calculated from time of diagnosis.RESULTS: We identified 33 pts with RARS-T. The median OS was 90mo (95% CI 47-134). The rate of AML transformation was 3% (one pt only). Among the 33 pts, 8 pts had no treatment (observation only), 22 pts (67%) received erythroid stimulating agent (ESA) prior to any active therapy, 2 pts received lenalidomide with no prior ESA, and 1 pt ruxolitinib with no prior ESA. Twelve pts (36%) received lenalidomide (7 as first line active therapy after ESA and 2 without prior ESA exposure) and 13 pts (33%) received azacitidine (6 as first line active therapy after ESA).The HI rate for ESA was 36% (12/22) with a median duration of ESA treatment of 33mo. The HI rate for lenalidomide was 50% (6/12) with a median duration of lenalidomide treatment of 10.3mo. Among the 9 pts who received lenalidomide as first line active therapy (2 pts without prior ESA exposure) HI rate was 56%. The HI rate for azacitidine was 15% (2/13) with a median duration of azacitidine treatment of 6.3mo.CONCLUSIONS: Pts with RARS-T had favorable outcome with long overall survival and low rate of AML transformation while azacitidine HI were lower than expected. Lenalidomide is an effective treatment option for RARS-T.