OBJECTIVETo assess the incidence and risk factors for evolution of acquired aplastic anemia (AA) into myelodysplastic syndrome/acute myeloid leukemia (MDS/AML).

METHODA total of 1003 AA patients hospitalized in our institute hospital between January 1991 and December 2009 enrolled into this study. The incidence and risk factors for AA developing MDS/AML by the Kaplan-Meier method and Cox proportional hazards models, respectively.

RESULTSThe median follow-up was 62 (2 - 423) months and the projected 5-year survival rate was (78.0 +/- 1.0)%. Twenty-seven patients evolved to MDS/AML, of whom 11, 6 and 10 were from NSAA, SAA and VSAA subgroups, respectively. The estimated cumulative incidence of MDS/AML transformation for these 1003 patients after diagnosis was (4.5 +/- 1.0)% at 10 year. The incidence of MDS/AML transformation in VSAA subgroup [(12.8 +/- 3.5)%] was significantly higher than in NSAA subgroup [(4.1 +/- 1.9)%] (P < 0.001) and SAA subgroup [(3.5 +/- 1.4)% ] (P = 0.008), but no difference between the latter two subgroups (P = 0.616). Age [RR = 3.527 (95% CI: 1.598 - 7.784), P = 0.002], severity of disease [RR = 5.122 (95% CI: 2.214 - 11.853), P < 0.001], the duration (days) of rhuG-CSF therapy [RR = 10.782 (95% CI: 4.600 - 25.269), P < 0.001] and exposure to ray, chemicals or drugs [RR = 3.401 (95% CI: 1.535 - 7.534), P = 0.003] were risk factors for the transformation in both univariate and multivariate analyses.

CONCLUSIONLong-term follow-up is essential to assess the incidence and risk factors for evolutions of acquired AA into MDS/AML, and to administer salvage therapy for transformation in time during follow-up.