Sole Trisomy 8 in AML: Concomitant Molecular Markers, Stability of Genetic Patterns and Impact On Outcome.

Trisomy 8 belongs to the most frequent cytogenetic aberrations in AML and is classified to intermediate-risk karyotypes if not within favorable or complex karyotypes (Grimwade et al., Blood 2010). Some study groups showed pts with sole trisomy 8 (+8sole) respond poorly to cytarabine-based chemotherapies. In addition, there is dissent whether trisomy 8 is a primary event or a secondary hit in pathogenesis.

Evaluation of pts with +8sole with respect to related molecular markers, stability of cytogenetic and molecular aberrations and impact on outcome.

1,181 newly diagnosed adult AML pts with intermediate-risk karyotypes were distributed as follows: +8 (n=117), normal karyotype (NK) (n=801), other intermediate-risk abnormalities (n=263). In detail, 80/117 pts with trisomy 8 (68.4%) showed +8sole. All of these 80 pts were screened for the molecular markers: ASXL1, CEBPA, FLT3- ITD, FLT3- TKD, IDH1, MLL- PTD, NPM1, and RUNX1. WT1 was analyzed in 79 and IDH2 in 78 pts. For comparison we characterized 400 NK pts for all before mentioned molecular markers.

Comparing clinical features +8sole pts were older than NK (69.9 vs 63.6 years; p<0.001). No differences were seen for gender, Hb, WBC or PLT counts.

+8sole pts harbored more often ASXL1 mut than NK pts (47.5% (38/80) vs 15.0% (60/400); p<0.001) and also more frequently RUNX1 mut (36.3% (29/80) vs. 15.8% (63/400); p<0.001). In contrast, +8sole pts less frequently showed NPM1 mut (16.3% (13/80) vs 49.3% (197/400; p<0.001) or CEBPA mut (5.0% (4/80) vs 14.5% (58/400); p=0.018). All 4 cases with +8sole and CEBPA mut were monoallelic, whereas only 37.7% (23/58) of NK pts with CEBPA mut were monoallelic (p=0.031). Incidences for FLT3- ITD, FLT3- TKD, IDH1, IDH2, MLL- PTD, and WT1 did not differ between +8sole and NK.

We analyzed relapse samples of 12 pts: 10/12 (83.3%) showed +8sole and their individual molecular marker pattern identical to diagnosis. However, 2/12 did show progress: one with +8sole and NPM1 mut at diagnosis gained FLT3- ITD in relapse. Case 2 habored an ASXL1 mut in addition to +8sole at diagnosis but relapsed with ASXL1 mut and a complex karyotype (including +8). Thus, +8sole as well as the corresponding mutations are stable through course of disease. Furthermore, in 5 pts we analyzed samples from MDS phase preceding AML. Two pts were genetically stable with either ASXL 1mut or MLL- PTD, and +8sole in MDS as well as in s-AML. One patient showed +8sole and ASXL1 mut in MDS and gained RUNX1 mut in s-AML. Interestingly, 2 pts harbored an ASXL1 mut and a NK at diagnosis of MDS, but an ASXL1 mut and +8sole at diagnosis of s-AML. This leads to the hypothesis of ASXL1 mut being first hit, whereas +8sole is gained during course of disease. Comparing overall survival (OS) for all pts with available follow-up data and intensive treatment regimes there was a significantly worse outcome for pts with +8sole (n=38) compared to NK (n=300; 13.0 vs 35.7 mo; p=0.003). Furthermore, we evaluated the total cohort (n=338) for impact of molecular markers. Pts with ASXL1 mut, FLT3-ITD, MLL-PTD, and RUNX1 mut showed worse outcome than pts without the respective marker mutated (p<0.001; <0.001; 0.009; <0.001, respectively). In contrast, pts with NPM1 mut, NPM1 mut/no FLT3-ITD or biallelic CEBPA mut showed better OS (p=0.003; <0.001; 0.044). FLT3- TKD, IDH1, IDH2, WT1, and CEBPA had no impact on OS. Combing markers associated with poor prognosis (ASXL1, FLT3-ITD, MLL- PTD, RUNX1) we detected at least one of these in 75% (60/80) within +8sole but only in 46.3% (185/400) within NK (p<0.001). Therefore we evaluated pts with at least one of these poor prognostic markers (n=147) and found median OS of 12.4 vs 49.6 months for pts with none of these (n=191; p<0.001). For multivariable Cox regression analysis age, WBC count, karyotype, biallelic CEBPA, NPM1 and the combined group of poor prognostic molecular markers were included (all being significant in univariable analysis). Age, WBC count and the combined group of poor prognostic molecular markers were significant (p<0.001, <0.001, 0.026, respectively). +8sole did not show an independent impact on OS.

+8sole had poor outcome compared to NK. This is related to the concomitant presence of adverse molecular markers, particularly ASXL1, and RUNX1, or both. Thus, for risk stratification of pts with +8sole ASXL1 and RUNX1 mutation assessment should be considered.

Alpermann:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership. Eder:MLL Munich Leukemia Laboratory: Employment. Kohlmann:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Equity Ownership.