Characteristics and Outcome of Patients with Acute Myeloid Leukemia (AML) Refractory to One Cycle of High Dose Cytarabine-Based Induction Chemotherapy.
Authors: Ravandi Farhad , Cortes Jorge , Faderl Stefan , O'Brien Susan , Garcia-Manero Guillermo , Verstovsek Srdan , de Lima Marcos , Pierce Sherry , Brandt Mark , Borthakur Gautam , Ferrajoli Alessandra , Wierda William G. , Koller Charles A , Kantarjian Hagop M. 
Published: October 2019

Abstract
Abstract 1038
Poster Board I-60

Background:
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.

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

Methods:
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.

Results:
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).

Conclusions:
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.

Disclosures:
No relevant conflicts of interest to declare.