Characteristics and Outcome of Patients with Acute Myeloid Leukemia (AML) Refractory to One Cycle of High Dose Cytarabine-Based Induction Chemotherapy.

Outcome of patients (pts) with AML refractory to initial induction is assumed to be poor but the available data is limited. Furthermore, pts refractory to standard dose cytarabine-based regimens may be salvaged with high dose ara-C (HiDaC, defined as daily ara-C dose ≥ 1 g/m²). Information on the outcome of pts refractory to initial HiDaC - based induction is more limited.

To better characterize predictors of poor response to HiDaC-based induction and to evaluate the outcome of pts refractory to such induction regimens.

We identified pts treated with induction regimens containing HiDaC at the University of Texas – M D Anderson Cancer Center who did not achieve a compete remission (CR) after one cycle of induction. We examined their pre-treatment characteristics and compared them with similar pts achieving a CR. We also examined their response to salvage chemotherapy and outcome.

Among 1179 pts treated with HiDaC-based induction therapy from 1995 to 2009, 285 were primary refractory to one course of induction. Their median age was 59 (range, 18 - 85). Median pretreatment WBC was 9.0 × 10⁹/L (range, 0.3 – 394 × 10⁹/L). Cytogenetics included-5/-7/complex 101 (35%), diploid 85 (30%), other intermediate 98 (34%), favorable 1 (<1%). 165 (58%) pts had antecedent hematological disorder. Induction regimens used included HiDaC with anthracyclines (n=181, 64%), HiDaC with non-anthracycline chemotherapy (fludarabine, clofarabine, topotecan, and troxacitabine) (n=104, 36%) Pts with primary refractory disease were older (Median age 59 vs. 56; p=000004), more likely to have chromosome 5/7 or complex cytogenetic abnormalities (P=0.0001), more likely to have AHD (p=0.0001), and had a higher presentation WBC (P=0.036), but not a higher incidence of FLT3 mutations (p=0.85) than those achieving CR. Primary refractory disease was not more likely with non-anthracycline containing regimens than those with anthracyclines (p=0.58). Salvage chemotherapy included combination chemotherapy in 111 (39%)(non-ara-C regimen in 40, containing ara-C in 71), single agent chemotherapy in 64 (22%), allogeneic stem cell transplant in 22 (8%) and none in 88 (31%). Forty-three (15%) pts responded to salvage including 35 CR and 8 CRp. 114 (58%) pts were resistant and 35 (18%) died; 5 (3%) were lost to follow-up. With a median follow-up of 115 weeks (range 8 – 347 weeks) in pts responding to salvage, 21 pts (7%) were alive and in CR, for at least 6 months including 14 who underwent an allogeneic stem cell transplant (median overall survival for these 21 pts, 30 months; range, 13 to 87 months).

Outcome of pts with disease refractory to HiDaC-based induction is poor. Alternative strategies are needed in these pts who are likely to be resistant to standard chemotherapy.

No relevant conflicts of interest to declare.