Patient characteristics

Between January 2012 and July 2022, 1054 patients were assessed, and 1034 received at least one dose of induction CT at 15 university hospitals; of them, 49% were women, the median age at diagnosis was 55 years (range 18–70). Other characteristics are described in Table 1. Patients above 60 years (from now considered the older cohort) presented a less proliferative disease (lower WBC, BM blasts, and LDH), and higher creatinine and bilirubin levels. Cytogenetic characterization was available in 95% of patients (n = 979); in the remaining 55 patients, metaphases were not optimal. According to the ELN-22 cytogenetic classification, 115 (12%) patients were favorable-risk, 657 (67%) intermediate-risk, and 207 (21%) cases had an adverse karyotype. Of the latter, 127 had a complex karyotype (CK), monosomal karyotype (MK) or both. Core binding factor (CBF) AML was two times more frequent in younger patients (14% vs. 7% for young and older groups, respectively, p < 0.001). NGS was performed in 296 patients, and the most frequently mutated genes were FLT3 (34%), NPM1 (34%), and DNMT3A (33%), followed by TET2 (16%), NRAS (14%), IDH2 (13%), and IDH1 (13%) (supplementary Fig. 1). TP53 alterations (deleted or mutated; TP53alt) were observed in 9% of cases analyzed. Patients above 60 years predominantly presented mutations in dysplasia-related genes and epigenetic regulators. Thus, the proportion of patients with either DNMT3A, TET2 or ASXL1, mutation (DTA) was 65% (71/109) in older adults vs. 42% (78/186) in younger patients (p < 0.001), and splicing mutations appeared in 22% of patients above 60 years of age in contrast to 11% of younger patients (p = 0.009). Further distribution of patients is depicted in the consort diagram (Fig. 1). According to the ELN-22 cytogenetic and molecular risk classification, 328 patients (32%) were considered favorable, while 405 (39%) were intermediate, and 301 (29%) adverse-risk with similar distribution in both age groups (p = 0.3).

Table 1 Patient characteristics in the overall cohort and in each age group (younger and older patients).Fig. 1: Consort diagram of the AML-12 protocol.

Each level represents a treatment cycle. Colors refer to ELN-22 risk category (blue: favorable, yellow: intermediate and red: adverse), and within them patients are distributed according to different genetic categories and age groups (n ≤ 60 | n > 60 years). Smaller squares between cycles show n of patients who discontinued protocol and their causes. CETLAM-fav includes ELN-22 favorable genetic categories plus NPM1mut/FLT3low. AlloHCT allogeneic stem cell transplant, CR1 first complete remission, CEBPAbi CEBPAbzip.

Induction therapy

CR was achieved in 792 (77%) of the 1034 patients. In 708 (89%) of the patients that achieved remission, only one course of induction CT was needed. A total of 124 (12%) patients were refractory, and 112 (11%) died due to complications during induction. Patients up to the age of 60 years presented a higher CR1 rate than those above that age (79% vs. 73%, respectively; p = 0.03) due to a higher induction death rate in the older cohort (8% in the young vs. 15% in the older cohort; p < 0.001). CR1 rates also differed according to genetics (Fig. 2 and supplementary Fig. 2) and ranged between 100% (17/17) in patients with biallelic CEBPA (CEBPAbi) mutation to 56% (74/132) and 33% (7/21) in patients with CK/MK/TP53alt and MECOM rearrangements (MECOMr), respectively.

Fig. 2: Induction results according to genetics in the overall AML-12 protocol (n = 1034).

Each bar shows the percentage of patients within a genetic category (legend on the left) who achieved complete remission (green), refractory disease (yellow) or induction death (red).

Post-remission therapy

Ninety-five percent of patients who achieved CR1 (751 out of 792) proceeded to Cons-1. The consort diagram illustrates the causes of protocol discontinuation before this point.

Death during Cons-1 occurred in 4 patients ( < 1%) and 718 (96%) patients remained in remission afterwards, whereas an early leukemia relapse was observed in 3% (7/282), 5% (13/289), and 5% (9/180) of favorable, intermediate, and adverse ELN-22 genetic risk patients respectively (p = 0.6) without significant differences among the two age groups. The outcome of patients in remission according to their ELN-22 genetic risk will be discussed next. Of note, given that our group considers NPM1mut/FLT3low patients as favorable-risk (thus not transplanted in CR1 but only in the case of a molecular relapse or in CR2), the outcome of NPM1mut/FLT3low cases will be described among the favorable category (from now CETLAM-fav) and not in the intermediate group, in all others, the ELN-22 classification was retrospectively applied.

Patients with favorable genetics

Two additional HDAC courses were feasible in 261 (68%) of the 383 initially diagnosed CETLAM-fav patients, 74% of the younger (187/252) and 57% (74/131) of the older adults (p < 0.001), and in 80% and 69% of the young and older patients in CR1 (p = 0.03).

Causes for protocol discontinuation during consolidations are described in the consort diagram. Among them, 18 patients in CR1 were bridged directly to alloHCT due to MRD positivity (n = 12), sustained aplasia (n = 3), or protocol deviation (n = 3). By the end of Cons-3, 218 (88%) of 249 patients with data available remained MRD negative and continued close monitoring [24].

Per protocol, in patients with MRD persistence after Cons-3, the intention was alloHCT in CR1. MRD positive status at this point was infrequent (n = 31, 12%), and alloHCT was performed in 17 (55%) of them.

Patients with intermediate and adverse genetics with indication of alloHCT in CR1

One-hundred seventy (49%) of the 350 initially diagnosed intermediate-risk AML and 66% of the patients in CR1 from this group completed the protocol from diagnosis to alloHCT in CR1. This procedure was performed in 71% (119/167) and 57% (51/89) of the patients in remission in the younger and older cohorts, respectively (p = 0.02). Forty-nine (21%) of 229 intermediate-risk patients in CR1 following Cons-1 did not reach alloHCT in CR1. This was mainly attributed to early leukemia relapse (41%; n = 20) or because they were considered unfit for the procedure due to CT toxicities (33%, n = 16). The latter was more frequent in the older adult cohort (n = 13) than in younger patients (n = 3).

Concerning the adverse category, 123 patients received an alloHCT in CR1. This represented 41% of the patients initially considered adverse-risk according to ELN-22 genetics and 64% of these patients in remission. When stratified by age, alloHCT in CR1 was achieved in 85 (47%) of 180 younger and 38 (31%) of 121 older adult adverse-risk patients (p = 0.006); if restricted to patients in CR1, this represented 72% (85/118) and 51% (38/75) of the young and older adults (p = 0.003). Different genetic subsets had an impact on the transplant feasibility: alloHCT was performed in CR1 in 3 (14%) of 21 MECOM-AML patients, 41 (31%) of 132 CK/MK/TP53alt cases, and 79 (53%) of 148 patients with other adverse genomic lesions (p < 0.001). Forty-six (27%) of the 170 adverse genetics patients in CR1 following Cons-1 were not transplanted in CR1; in 48% of these cases (n = 22), the reason was an early relapse, most of which happened in patients with CK/MK/TP53alt AML (50%, n = 11). Toxicities during CT precluded alloHCT in 10 cases, 7 of them older adults. Finally, 5 adverse-risk patients died during the Cons phase, and all but one belonged to the CK/MK/TP53alt category.

Time-dependent outcomes

After a median follow-up of 45 months (95%CI 40-50), the median OS of the whole cohort was 33 months, and the 4-year (4-yr) OS, cumulative incidence of relapse (CIR), and EFS were 46 ± 2%, 37 ± 3%, and 38 ± 2% respectively. Among each age group, 4-yr OS was 53 ± 2% vs 33 ± 3% for patients ≤ or > 60 years (p < 0.001, Fig. 3). Survival curves for other age subgroups are available in supplementary Fig. 3.

Fig. 3: Survival outcomes of the AML-12 overall cohort.

Overall survival (OS) and event-free survival (EFS) are shown on the left and middle figures, respectively. In these, the overall cohort outcome is shown in black, younger patients in red and older patients in blue. The right figure shows cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) of the older (blue) and younger (red) patients.

Overall, patients ≤60 years had a lower relapse incidence; 4-yr CIR 34 ± 2% vs. 43 ± 3% for the young and older cohorts, respectively (p = 0.017), and older patients presented higher 4-yr non-leukemic death (NLD): 12 ± 2% vs 18 ± 3% in young and older adults, respectively (p = 0.024, Fig. 3).

Survival outcomes of each genetic subset and in the two age groups appear in Table 2. When stratified according to ELN-2022 classification, OS and EFS for each risk group was 68 ± 3% and 56 ± 3% in favorable patients, 41 ± 3% and 35 ± 3% for intermediate and 28 ± 3% and 24 ± 3% for the adverse-risk group, albeit with clear differences among younger and older patients (Fig. 4 and supplementary Fig. 4).

Table 2 Survival outcomes according to each genetic subset in both age groups.Fig. 4: Outcomes according to ELN-22 risk classification (above) and ICSA genetic groups (below).

For the latter the favorable group includes ELN-22 favorable-risk genetics and NPM1mut/FLT3low, the very adverse group refers to CK/MK/TP53alt/MECOMr and the intermediate group contains all other patients.

Of note, in the series reported here, the three genetic groups showing the best clinical discrimination were favorable (as in CETLAM-fav, which included favorable genetics according to ELN-2022 plus patients with NPM1mut/FLT3low), adverse (with either CK/MK/TP53alt/MECOMr), and intermediate including the remaining patients. OS and EFS in these categories at 4-years were 70 ± 3% and 57 ± 3%; 15 ± 3% and 11 ± 3%; and 38 ± 3% and 32 ± 2%, respectively, (p < 0.001 for both OS and EFS, Fig. 4).

Median OS was not reached in patients with RUNX1::RUNX1T1 or CEBPAbi, regardless of age (supplementary Fig. 5). Lower OS was observed in older adults with CBFB::MYH11 (4-yr OS 66 ± 8% vs 43 ± 13% for young and older, respectively; p = 0.016) due to the high toxic death rate in the older group (7 [50%] of 14 cases) compared to younger patients (4 [9%] out of 44 patients; p < 0.001), whereas no differences in relapse rates were found (4-yr CIR 33% vs 26% in the same groups respectively, p = 0.5). In NPM1mut/FLT3low patients, survival was high in both age groups and matched or even surpassed that of NPM1mut/FLT3wt patients. Patients older than 60 years with CETLAM-fav genetics had a remarkable 4-yr OS of 59 ± 5%, in contrast to the poor outcome of this age group in the presence of intermediate and adverse genetics (4-yr OS 23 ± 4% and 10 ± 3%, median OS of 16 and 9 months, respectively; p < 0.001). Older adults had worse survival in the presence of KMT2A rearrangements (median OS of 98 months in younger vs. 8 months in older patients p = 0.033) and in those with dysplasia-related mutations (median OS not reached vs 17 months, respectively, p = 0.009, Table 2). Finally, the survival of adverse-risk patients with either CK/MK/TP53alt/MECOMr was dismal for both age groups: 4-yr OS 18 ± 5% in younger vs 10 ± 4% in older adults (p = 0.2, median OS of 9 months for both groups). Further outcomes regarding EFS are shown in supplementary Fig. 5.

MRD

MRD data were available in 629 (88%) of 718 patients in CR1 following Cons-1. MRDneg status was achieved in 459 evaluable patients (73%), with no differences in rates of MRDneg in each age group (MRDneg in 314 (75%) patients ≤60 yrs and 145 (69%) in >60 years, p = 0.15). In the landmark analysis, MRDneg status was associated with improved OS compared to MRDpos patients (4-yr OS 64 ± 3% vs. 53 ± 4% in MRDneg and MRDpos; p = 0.015). MRDneg patients also presented with higher EFS (4-yr EFS 55 ± 3% vs. 48 ± 4%, p = 0.039) and lower CIR (4-yr CIR 32 ± 2% vs. 40 ± 2% for the same groups respectively, p = 0.029; supplementary Fig. 6).

Outcomes of alloHCT in CR1 for intermediate and adverse-risk patients

Among 293 non-favorable patients transplanted after consolidation as per protocol, 70% were ≤60 years old, and 30% were older adults (supplementary Table 2). Non-relapse mortality at 100 days, 6 months, and 1 year from transplant was 3%, 9%, and 14% in patients ≤ 60 years and 5%, 14%, and 15% in those >60 years (p = 0.3). There were no differences in outcome after alloHCT for intermediate risk-patients depending on age with a 4-yr OS from transplant of 58 ± 5% and 49 ± 8% in young and older groups, respectively (p = 0.1). Older adults with ELN2022 adverse genetics had a 4 yr OS from transplant of 34 ± 8%, compared to younger adults who presented 4-yr OS of 48 ± 6%, respectively (p = 0.06). In the most adverse subgroup (CK/MK/TP53alt/MECOMr), 4-yr OS from transplant was dismal regardless of age, in younger patients was 20 ± 8 (with identical 4-yr EFS) and older adults presented 4-yr OS and EFS of 18 ± 9%.

Prognostic factors and ICSA risk score

The variables that retained an independent prognostic impact in the multivariable analysis for OS were age ( ≤ 60 vs. >60 years), gender (female/male), ECOG (0–2, ≥3), WBC counts ( ≤ 20, 21-99, >99×109/L), increased creatinine ( > 1,2 mg/dL), bilirubin above average ( > 1.2 mg/dL), and genetic category (CETLAM-fav, CK/MK/TP53alt/MECOMr, other). Multicollinearity among these variables was minimal according to VIF values (range 1.05-2.11) hence they were integrated into a scoring system (ICSA: Intensive Chemotherapy Score for AML, Fig. 5). Each patient’s total score was calculated (range 0–9) and, based on their survival impact, six risk groups were defined: very low (0 points), low (1 points), intermediate-low (2 points), intermediate-high (3 points), high (4–5 points), and very high (6–9 points). The C-index for the model was 0.71, and the 4-yr OS for each risk category was 85 ± 6%, 70 ± 4%, 55 ± 4%, 36 ± 4%, 18 ± 4%, and 0%, respectively (p < 0.001). Regarding EFS, the score identified five groups since very-low and low categories had comparable outcomes. Of note, we confirmed that the score discriminated survival risk groups equally well for younger and older patients separately, and also that the ICSA risk groups correlated with induction results: very low risk patients had CR1 rates of 100% (46 out of 46 patients), that progressively decreased in each risk category. Similarly, the number of refractory patients and induction deaths ascended progressively as the patient risk increased (supplementary material).

Fig. 5: Multivariate cox-regression and ICSA score.

WBC white blood cells, CK complex karyotype, MK monosomal karyotype.

Finally, this model was validated using an external retrospective cohort of 581 AML patients treated intensively within a previous CETLAM protocol (AML-03, NCT01723657). Patient characteristics from this series are available in supplementary Table 3; limited molecular analyses were available, and patients were mostly risk-stratified by cytogenetics, NPM1, and FLT3 mutations. In the validation cohort, ICSA segregated patients in 5 risk groups both for OS (4-yr OS in each risk category of 75%, 67%, 37%, 32%, 21%, and 0%; p < 0.001) and for EFS (p < 0.001; Fig. 6) and the model yielded a C-index of 0.66.

Fig. 6: OS and EFS of the validation cohort according to the ICSA score.

The table shows for each ICSA risk group the distribution of patients, the OS and the c-index for both the model-building cohort (AML-12 protocol) and the validation cohort (AML-03 protocol).