New Cytogenetic Abnormalities Are Frequent in AML and MDS Relapsing after Allogeneic Hematopoietic Cell Transplantation (HCT).

There are limited data regarding the incidence or prognostic value of cytogenetic abnormalities in pts with leukemic relapse after allogeneic hematopoietic cell transplantation (HCT). Between 2002 and 2005, 70 consecutive pts with high risk AML or MDS were transplanted with a reduced intensity preparative regimen of fludarabine 30 mg/m²/day IV (150 mg/m² total), alemtuzumab SC 20 mg/day IV (100 mg total) D-7 to D-3, and melphalan 140 mg/m² IV D-2, with tacrolimus given for post-transplantation immunosuppression. Twenty-five pts relapsed or progressed; 21 had AML, 3 had MDS and 1 had mast cell leukemia.

Twenty-two pts had cytogenetic analysis available prior to HCT and at relapse. Cytogenetic abnormalities were present in 12/22 (55%) pts prior to HCT. The median OS was 184 days (95% CI: 81 – 300) after relapse. Four pts with cytogenetic abnormalities prior to HCT reverted to a normal karyotype at relapse. Ten pts had no changes in their cytogenetics from HCT to relapse; they either remained normal or retained the same abnormality. Eight pts developed a new clonal abnormality at relapse, and had a median OS of 106 days (95% CI: 30 – 322). There was a non-significant trend toward inferior OS among pts with new abnormalities compared to the other groups (HR = 1.74, 95% CI 0.69 – 4.44, P = 0.24). The higher than previously reported rate of clonal evolution (8/22, 36%) may be due to the high prevalence of refractory disease at HCT in this cohort, more refined cytogenetic analysis, or regimen related factors (e.g. reduced intensity conditioning). The same clonal abnormality with or without new changes occurred in 7/22 pts. Thus, minimal residual disease monitoring in the subset of pts harboring pre-HCT karyotypic derangements may be a viable strategy for early detection and intervention. Our data suggest that clonal evolution at relapse of AML and MDS after HCT is relatively frequent, and in this small series, a trend toward worse outcomes exists for pts who develop new cytogenetic abnormalities. Larger studies are warranted to more completely characterize the prognostic value of cytogenetics and karyotypic evolution at relapse after HCT.