Fractionated gemtuzumab ozogamicin and standard dose cytarabine produced prolonged second remissions in patients over the age of 55 years with acute myeloid leukemia in late first relapse.

Gemtuzumab ozogamicin (fGO), a humanized anti-CD33 monoclonal antibody linked to calicheamicin in combination with intensive chemotherapy gives high response rates in adult acute myeloid leukemia (AML) patients in relapse. However, reduced intensity chemotherapy in combination with fractionated GO has not been tested in aged relapsing patients. Patients from our institution with CD33+ AML aged 55 years or more in first late relapse (≥ 6 months) were proposed participation in a GO compassionate use program. Induction therapy consisted in fractionated GO (fGO; 3 mg/m², days 1, 4, 7) with standard-dose cytarabine (200 mg/m² /day, 7 days). Patients were consolidated with two courses of GO and intermediate dose cytarabine. Twenty-four patients (median age 68 years) received fGO with cytarabine. Median follow-up was 42 months. The response rate was 75%, including complete remission (CR) in 16 patients and CR with incomplete platelet recovery (CRp) in two patients. Two-year overall survival (OS) was 51% (95% CI: 28-69) and 2 years relapse-free survival (RFS) was 51% (95%CI: 25-72). Duration of second CR (CR2) was longer than first CR (CR1) in 9 out of 18 patients. Minimal residual disease (MRD) was negative in evaluable patients in CR2, particularly in NPM1 mutated cases. Toxicity was in line with that of the same fractionated single agent GO schedule. Fractionated GO with low intensity chemotherapy produced high response rates and prolonged CR2 in aged AML patients in first late relapse.

Outcome of older patients with acute myeloid leukemia in first relapse.

To provide data for future drug evaluation, we analyzed the outcome of 393 patients aged 50 years or older (median, 64 years) with AML in first relapse after treatment in recent ALFA trials. Salvage options were retrospectively classified as follows: best supportive care (BSC), low-dose cytarabine (LDAC), gemtuzumab ozogamicin (GO), intensive chemotherapy (ICT), or ICT combined with GO. Second complete remission (CR2) rate was 31% and median post-relapse survival was 6.8 months (0, 17, 42.5, 53, and 80% and 3.2, 5.6, 8.9, 9, and 19.8 months in BSC, LDAC, GO, ICT, and ICT + GO subsets, respectively). Age, performance status, WBC, CR1 duration, and favorable AML karyotype, but not other cytogenetic or molecular features, influenced post-relapse outcome. Multivariate adjustment and propensity score matching showed that intensive salvage (ICT/ICT+GO/GO versus LDAC/BSC) was associated with longer post-relapse survival, at least in patients with CR1 duration ≥12 months (P = 0.001 and 0.0005, respectively). Of interest, GO appeared to be as effective as standard ICT, and ICT + GO combination more effective than standard ICT. In conclusion, older patients with CR1 duration ≥12 months appeared to benefit from intensive salvage and results observed with GO-containing salvage suggest that GO combination studies should be actively pursued in this setting.