Activating FLT3 mutations including internal tandem duplications (FLT3-ITD) and tyrosine-kinase domain mutation (FLT3-TKD) occur in approximately one third of patients with acute myeloid leukemia (AML) and are particularly associated with a poor outcome in case of FLT3-ITD. Sunitinib is a multitargeted FLT3 inhibitor approved for the treatment of advanced/metastatic renal cancer and metastatic/unresectable malignant GIST after failure of imatinib. Sunitinib has been evaluated in refractory AML as single agent treatment resulting in transient blast count reduction and in several cases of partial response in AML with activating FLT3 mutations.
To evaluate the feasibility of a standard induction and consolidation therapy in combination with orally administered sunitinib in elderly AML patients with activating FLT3 mutations.
Patients aged 60 years or higher with AML with activating FLT3 mutations (FLT3-ITD, FLT3-TKD) and fit enough for intensive chemotherapy were eligible. Induction therapy included cytarabine 100 mg/m2 per continuous infusion on days 1–7 and daunorubicin 60 mg/m2 i.v. on days 1–3 (DA). A second course was allowed in responding patients, who did not achieve a complete remission (CR). In patients achieving a CR after induction therapy three consolidation cycles were intended (cytarabine 1 g/m2 i.v. bid, on days 1,3,5). A 3+3 dose escalation/de-escalation scheme was used to define the dose and scheduling of sunitinib. The first cohort of three patients received oral sunitinib continuously starting from day 1 in a dose of 25 mg/day (level 1). Dose escalation to level 2 with sunitinib 37.5 mg/day continuously or dose de-escalation to level −1 with 25 mg day 1 to 7 had been defined in the protocol. After definition of the maximally tolerated dose (MTD) an extension of the cohort at that dose was intended.
A total of twenty-two patients were enrolled between January 2009 and March 2011. The median age was 70 years (range 60–78), 13 were female. The type of AML was de novo in 16 pts., s-AMLin one patient and t-AML in 4 pts. Fifteen patients had a FLT3-ITD (68%) and 7 a FLT3-TKD (32%) mutation. A NPM1 mutation was present in 11 patients (50%), 15 patients exhibited a normal karyotype, 3 an intermediate-2 risk karyotype according to ELN guidelines and 2 a complex karyotype and 2 had no evaluable metaphases. In the first cohort 5 patients were treated and two experienced dose-limiting toxicity (DLT), i) prolonged hematological recovery beyond day 35 in a patient achieving a CR and ii) a hand-foot-syndrome grade III. Four of the 5 patients achieved a CR. According to the protocol the following patients received treatment at dose level −1 with sunitinib 25mg days 1 to 7. In this cohort only one DLT occurred, again prolonged hematological recovery. Thus the MTD was defined at dose level −1. Response to induction therapy in all patients was CR in 13 pts. (59%), partial remission in 1 pt. (4.5%), refractory disease in 5 pts. (23%), death in 3 pts. (13.5%). CR rate in AML with FLT3-ITD was 53% (8/15) and 71% (5/7) in those with FLT3-TKD. All 13 patients achieving CR received repetitive cycles of high-dose cytarabine consolidation therapy and 7 proceeded to single agent sunitinib maintenance therapy (median 11 months, range 1–24 months). In these patients relapse occurred in 10, one patient died due to severe colitis during consolidation therapy and two patients are in sustained CR. Two patients not achieving a CR after induction therapy underwent allogeneic stem cell transplantation form matched unrelated donors. Twelve of the 22 patients died leading to a median survival of 18.8 months and a 2 year survival of 36% (95%-CI, 19–70%). Median relapse-free survival was 11 months.
Combination of intensive induction and consolidation therapy with oral sunitinib in AML with activating FLT3 mutations is feasible with 25 mg sunitinib given during intensive therapy on days 1 to 7 and continuously during maintenance.
Fiedler:Novartis: Consultancy, Research Funding; Pfizer Inc.: Consultancy, Research Funding.
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Asterisk with author names denotes non-ASH members.