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 ³ 450 x 10/L), recently renamed MDS/MPN with ring sideroblasts and thrombocytosis. Management of RARS-T is extrapolated from MDS and MPN treatment options namely for alleviating symptoms of anemia and, occasionally, for thrombocytosis. Individual case reports have suggested that 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 of lenalidomide in non-del 5q lower risk MDS, 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 hematological improvement (HI) responses among different treatment options.

METHODS:

This is a retrospective, single-center study. Patients with RARS-T were identified from the MDS Database at Moffitt Cancer Center. Samples for somatic mutation testing were obtained at time of referral. Descriptive statistics were used to describe baseline characteristics and response rates to treatment. 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 mean age was 67 years (38-80), 15 pts were male (45.5%), and majority were Caucasians (n=27, 82%). According to international prognostic scoring system (IPSS), 24 patients (73%) were low risk and 9 pts (27%) were int-1 risk. By revised IPSS, 11 pts (33%), 18 (55%), 3 (9%), and 1 (3%) were very low, low, intermediate, and high risk, respectively. The mean WBC was 7.7 (2.8-25.7), the mean Hemoglobin was 9.9 g/dl (7.3-12.4), and the mean platelet count was 682 (372-1644). Among 20 pts who had Next generation sequencing for somatic mutations at time of referral, 19 pts (95%) had SF3B1 mutation and 4 pts (20%) had JAK-2 V617 F mutation.

The median OS was 90 mo (95% CI 47-134). For pts with JAK-2 V617F mutations, the median OS was 110 mo versus 74 mo for those with wild type (p=0.24). The rate of AML transformation was 3% (one patient 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 patients 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 outcomes, with long overall survival and a low rate of AML transformation. Rates of hematological improvement with the use of azacitidine were lower than expected. Lenalidomide is an effective treatment option and should be considered when treating patients with RARS-T.

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