OBJECTIVETo evaluate the clinical characteristics and risk factors of clonal evolution after immunosuppressive therapy (IST) in children with severe/very severe aplastic anemia (SAA/VSAA).

METHODSThe clinical data of 231 children with newly-diagnosed SAA/VSAA who received IST were retrospectively studied. The incidence and risk factors of clonal evolution after IST were analyzed.

RESULTSThe 5-year overall survival rate of the 231 patients was 82.7%. Except for 18 cases of early deaths, 213 patients were evaluated for IST efficacy. Among the 231 patients, cytogenetic abnormalities for at least two chromosome metaphase were detectable in 14 (7.4%) patients, and PNH clones were detectable in either peripheral red blood cells or neutrophils for 95 patients. Among the 213 patients evaluated for IST efficacy, 15 patients experienced clonal evolution after IST. Five patients had PNH and trisomy 8 which were defined as favorable progressions, and ten patients experienced monosomy 7 and MDS/AML as unfavorable progressions. The 5-year accumulative incidence of favorable and unfavorable progression were (2.2±2.2)% and (4.8±3.3)%, respectively. Until the last follow-up, 100% (5/5) of patients with favorable progressions and 50% (5/10) of patients with unfavorable progressions survived. WBC>3.5×10/L, CD3T cell percentage>80%, dosage of antithymocyte globulin >3.0 mg/(kg·d) and no response to IST were related to unfavorable progressions by univariate analysis. Cox multivariate analysis revealed that an increased CD3T cell percentage (>80%) and no response to IST were independent risk factors for unfavorable progressions.

CONCLUSIONSThe children with SAA/VSAA who have an increased CD3T cell percentage at diagnosis or have no response to IST are in high risks of unfavorable progressions.