Incidence and Prognostic Impact of Gene Mutations in Older Patients with AML Treated in the ALFA-9801 Study.

Introduction: The impact of gene mutations, i.e. poor-prognosis FLT3 internal tandem duplications (ITDs) and good-prognosis NPM1 or CEBPA mutations, has been welldocumented in several recent reports dealing with younger patients with acute myeloid leukemia (AML). As these mutations were associated with cytogenetically normal (CN) AML, most of these reports focused on CN-AML patients. Both FLT3-ITD and NPM1 mutations were also associated with higher WBC. The objective of the present study was to evaluate the incidence, correlations, and prognostic value of these mutations in older patients with the disease.

Methods: The French ALFA group has screened a total of 583 patients, including 333 younger patients (15–50 years) treated in the ALFA-9802 trial and 250 older patients (50–70 years) treated in the ALFA-9801 trial. The older ALFA-9801 trial included 468 patients with previously untreated de novo AML and studied the role of idarubicin (IDA) as compared to high-dose daunorubicin (DNR) as well as interleukine-2 as a maintenance therapy (C. Pautas et al. ASH 2007, abstract #162). Comparison between the 250 patients tested for mutations in that trial and the 218 patients not tested showed no differences in age, sex ratio, FAB classification, bone marrow blasts percentage, randomization arm, and performance status at entry in the study. There was, however, a higher rate of patients with intermediate cytogenetics (p=.01) or increased WBC (p=.01) in the former subgroup.

Results: Median age of the 250 patients tested was 60 years. Cytogenetics was studied in 232 patients (12 favorable, 174 intermediate, 46 unfavorable). One hundred twenty-two patients (49%) had CN-AML. CR rate was 67.5% and estimated 4-year OS was 26% (95% CI, 20–33). Incidences of FLT3-ITD, NPM1, and CEBPA mutations were 37/250 (15%), 64/249 (26%), and 20/249 (8%), respectively. These incidences were very similar than in the younger ALFA-9802 population [50/329 (15%), 76/321 (24%), and 24/316 (8%), respectively]. In these older AML patients, the correlation between increased WBC and FLT3-ITD (p<.001) or NPM1 mutation (p<.001) was still observed. Conversely, NPM1 mutations only (p<.001), but not FLT3-ITDs (p=.10) or CEBPA mutations (p=.99), were significantly associated with CN-AML. In the whole group of 249 patients with either normal or abnormal karyotype tested for all mutations, 46 were NPM1+/FLT3-ITDwt, 19 FLT3-ITD+/NPM1wt, 18 FLT3-ITD+/NPM1+, and 166 NPM1wt/FLT3-ITDwt. CR rate was 87%, 84%, 56%, and 75% and median OS was 20.5, 18.6, 6.0, and 14.6 months, respectively. In the 20 CEBPA+ patients, CR rate was 80% and median OS was 22.8 months. In the group of 122 CN-AML patients tested for all mutations, 36 were NPM1+/FLT3-ITDwt, 8 FLT3-ITD+/NPM1wt, 15 FLT3-ITD+/NPM1+, and 63 NPM1wt/FLT3- ITDwt. CR rate was 92%, 87.5%, 60%, and 78% and median OS was 20.5, 16.9, 7.0, and 16.8 months, respectively. In the 10 CEBPA+ patients, CR rate was 80% and median OS was not reached. In multivariate analysis including age, WBC, cytogenetics (favorable versus others), and gene mutational status (NPM1+ or CEBPA+ if FLT3-ITDwt versus others), a pejorative effect of age (p=.02) and WBC (p<.001), but a protective effect of mutational status (HR= 0.66, p=.05) and favorable cytogenetics (HR=0.43, p=.06) was observed in the whole patient population. Nevertheless, estimated 4-year OS was only 37% (95% CI, 23–50) in patients with a favorable mutational status. In those with CNAML and a favorable mutational status, estimated 4-year OS reached only 40% (95% CI, 23–56). In this subgroup of patients with CN-AML, WBC was the only significant prognostic factor identified in multivariate analysis (p<.001).

Conclusion: This study conducted in a large cohort of patients aged 50 to 70 years and prospectively treated in the same trial showed that gene mutational status still affect the outcome of older patients with AML. Mutation incidences are in the same range than in younger patients. Nevertheless, their impact on OS appeared to be less marked than in younger patients, probably due to the worse general outcome observed in these older patients.