Retrospective analysis of prognostic factors associated with response and overall survival in patients with RAEB-t MDS treated with decitabine.

Abstract

6598 Background: Response to decitabine, a hypomethylating agent for treatment of MDS of all FAB subtypes and Intermediate-1, Intermediate-2 and High-risk IPSS groups, was assessed using IWG 2000 criteria. The revised WHO definition of AML is ≥20% blasts instead of ≥30% blasts, so IWG updated its response criteria in 2006. The current analysis updates response data using IWG 2006 criteria. Methods: A retrospective analysis was conducted of a pooled subset of patients with MDS from two decitabine trials: 3-day dosing (phase III) or 5-day dosing (phase II). Patients with baseline marrow blasts ≥20% receiving decitabine (RAEB-t group) were compared with patients with baseline marrow blasts <20% (MDS group). Comparisons were made of baseline characteristics (Fisher’s exact test and t test); overall response rates (ORR) (Fisher’s exact test); and overall survival (OS) (log-rank test; significance p<.05). Results: The RAEB-t group (n=26) had a significantly shorter time from MDS diagnosis (7.3 vs 18.3mo), higher IPSS risk (76.9% vs 15.9% of patients), and lower median baseline platelet count (62.3 vs 112.7 x103/mL) vs the MDS group (n=157), yet the two groups still had similar OIR, PR, mCR, HI, stable disease, and disease progression. Adverse events were similar between groups. Conclusions: Based on this retrospective analysis, decitabine yielded a similar response rate in RAEB-t patients as in other MDS patients, except for a lower CR rate, consistent with the higher proportion of IPSS high-risk. Moreover, the RAEB-t patients did not progress to AML (≥30% blasts) more rapidly than the MDS population. As such, clinical responses in the RAEB-t group are encouraging. RAEB-t (n=26) n (%) MDS (n=157) n (%) P* ORR (CR+mCR+PR) 4 (15.4) 44 (28.0) 0.2311 OIR (CR+mCR+PR+HI) 9 (34.6) 67 (42.7) 0.5223 CR 0 25 (15.9) 0.0278 mCR 2 (7.7) 14 (8.9) 1.0000 PR 2 (7.7) 5 (3.2) 0.2602 HI 5 (19.2) 23 (14.7) 0.5589 Stable disease 8 (30.8) 43 (27.4) 0.8137 Progressive disease 4 (15.4) 27 (17.2) 1.0000 Abbreviations: CR, complete response; HI, hematologic improvement; mCR, marrow complete response; OIR, overall improvement rate; PR, partial response. *Fisher’s exact test.