Follow-up Analysis of a Randomized Comparison of Prolonged Myelosuppressive Maintenance Therapy Versus Intensive Consolidation Therapy as Postremission Therapy in AML.

We previously showed that a prolonged myelosuppressive maintenance chemotherapy was superior to S-HAM as a postremission therapy in patients > 16 years of age with AML after a TAD-HAM double induction therapy and TAD consolidation chemotherapy with regard to relapse-free survival (RFS) and borderline significance of the overall survival (OS) in responding patients (Buchner et al., JCO 2003, 21:4496-4504). Here we present long-term follow-up data with a median follow-up of 7.9 years from diagnosis and 7.1 years from the date of complete remission.

Eight hundred thirty-two patients (median age, 54 years; range, 16 to 82 years) with de novo AML were upfront randomized in the AMLCG1992 study of the German AML Co-operative Group to receive 6-thioguanine, cytarabine, and daunorubicin (TAD) plus cytarabine and mitoxantrone (HAM; cytarabine 3 g/m² [age < 60 years] or 1 g/m² [age ≥ 60 years] x 6 (HAM in patients ≥ 60 years only in case of blast persistence on day 16 of therapy) induction, TAD consolidation, and monthly maintenance with cycles of cytarabine combined with either daunorubicin (course 1), 6-thioguanine (course 2), cyclophosphamide (course 3), and again 6-thioguanine (course 4), and restarting with course 1 for 3 years, or to receive TAD-HAM-TAD and one course of intensive consolidation with sequential HAM (S-HAM) with cytarabine 1 g/m² (age < 60 years) or 0.5 g/m² (age ≥ 60 years) x 8 instead of maintenance.

A total of 576 patients (69.2%) achieved a complete remission (CR) those were 294 of 429 (68.5%) patients randomized to receive maintenance and 282 of 403 (70.0%) patients randomized to receive intensive consolidation S-HAM (p=n.s.). 190 patients received maintenance therapy as intended and 135 patients received an intensive consolidation therapy as intended. This prolonged follow-up analysis verified the superior relapse-free survival in all patients in the maintenance arm (10-year RFS 30.0 ± 5.6 versus 19.9 ± 6.1 %, p = 0.015). Stratified by age, the 10-year RFS was superior in younger patients < 60 years (36.9 ± 7.1 versus 25.2 ± 8.0 %, p = 0.038) and borderline significant in elderly patients (17.2 ± 4.5 versus 6.8 ± 6.2 %, p = 0.075). A subgroup analysis of known risk groups (lactate dehydrogenase (LDH) level < 700U/l versus ≥ 700U/l at diagnosis, cytogenetic risk profile, bone marrow blasts on day 16 after the start of the induction therapy) revealed a superior RFS in the subgroup of patients with LDH level > 700 U/l at diagnosis (33.5 ± 12.3 versus 18.2 ± 9.5 %, p = 0.043). This superior RFS also translated into a superior 10-year relapse-free interval (RFI) of all responding patients in the maintenance arm (35.7 ± 6.3 versus 27.6 ± 5.9 %, p = 0.015) with borderline significance in younger patients (42.9 ± 7.4 versus 35.0 ± 7.4 %, p = 0.053) and a significant difference in elderly patients (20.6 ± 10.0 versus 8.4 ± 7.5 %, p = 0.043). In this updated analysis, there was a trend, but no significant difference in the OS (maintenance arm: 10-year OS 24.3 ± 4.8, intensive consolidation arm: 19.7 ± 4.7 %, p = 0.148), and we verified a trend for a better OS in responding patients for the maintenance arm (10-year OS in responding patients 33.6 ± 7.5 versus 28.5 ± 6.2 %, p = 0.093). The event-free survival (EFS) also showed a trend towards better EFS in the maintenance arm (10-year EFS 20.7 ± 4.2 versus 14.8 ± 4.1 %, p = 0.082) which was significant in elderly patients (10-year EFS 10.5 ± 5.5 versus 3.9 ± 3.7 %, p = 0.044). Discussion: This updated analysis with a long-term follow-up of median 7.9 years from diagnosis and 7.1 years from CR verified the superior RFS and the trend for enhanced OS in responding patients. These results suggest the superiority of a prolonged monthly myelosuppressive maintenance therapy as compared to intensive consolidation S-HAM after TAD-HAM induction and TAD consolidation.

No relevant conflicts of interest to declare.