Prognostic impact of 'multi-hit' <i>versus</i> 'single-hit' <i>TP53</i> alteration in patients with acute myeloid leukemia: results from the Consortium on Myeloid Malignancies and Neoplastic Diseases.

While there is clear evidence to suggest poorer outcome associated with multi-hit (MH) TP53 mutation (TP53MT) compared to a single-hit (SH) mutation in lower-risk myelodysplastic syndrome (MDS), data are conflicting in both higher-risk MDS and acute myeloid leukemia (AML). We conducted an in-depth analysis utilizing data from ten US academic institutions to study differences in molecular characteristics and outcomes of SH (N=139) versus MH (N=243) TP53MT AML. Complex cytogenetics were more common in MH than in SH TP53MT AML (P<0.001); whereas ASXL1 (P<0.001), RAS (P<0.001), splicing factor (P=0.003), IDH1/2 (P=0.001), FLT3 ITD (P<0.001) and NPM1 (P=0.005) mutations clustered significantly with SH TP53MT AML. Survival after excluding patients who received best supportive care alone was dismal but not significantly different between patients with SH or MH disease (event-free survival: 3.0 vs. 2.20 months, respectively, P=0.22; overall survival: 8.50 vs. 7.53 months, respectively, P=0.13). In multivariable analysis, IDH1 mutation and allogeneic hematopoietic stem cell transplantation as a time-dependent covariate were associated with superior event-free survival (hazard ratio [HR]=0.44, 95% confidence interval [95% CI]: 0.19-1.01, P=0.05 and HR=0.34, 95% CI: 0.18-0.62, P<0.001) and overall survival (HR=0.24, 95% CI: 0.08-0.71, P=0.01 and HR=0.28, 95% CI: 0.16-0.47, P<0.001). Complex cytogenetics (HR=1.56, 95% CI: 1.01-2.40, P=0.04) retained an unfavorable significance for overall survival. Our analysis suggests that MH TP53MT is less relevant in independently predicting outcomes in patients with AML than in those with MDS.