Impact of Imatinib Dose Escalation in Chronic Myeloid Leukemia Patients in Chronic Phase with Sub-Optimal Response or Failure with Imatinib 400 Mg.
Authors: Pagnano Katia BB , Delamain Marcia T , Miranda Eliana C.M. , Duarte Vagner O , Alves Brunna Eulálio , De Souza Carmino Antonio , Lorand-Metze Irene 
Published: October 2019

Abstract
Abstract 3289
Poster Board III-1
Imatinib dose escalation has been used in sub-optimal response and therapeutic failure to imatinib in conventional doses. The aim of this study was to evaluate the efficacy of imatinib dose increase in CML patients in CP who did not achieve the best response to imatinib 400 mg QID.

Patients and methods:
All CML patients in CP treated in our institution with imatinib 400mg between March 2002 and December 2008 were evaluated. Imatinib was escalated to 600–800mg in cases with sub-optimal response or failure, according to Leukemia Net or IRIS Trial criteria. All survival curves were calculated from date of dose increase: overall survival (OS) until death or last follow-up, event free survival (EFS) until loss of complete hematological response (CHR) or major cytogenetic response (MCyR), progression to accelerated phase (AP) or blast crisis (BC) or death from any cause. Transformation free survival (TFS) was calculated from dose increase until progression to AP, BC or death.

Results:
137 patients in CP were treated with imatinib 400 mg. Dose was escalated in 55 (40%) patients due to loss or failure to achieve CRH (13 = 24%); progression to BC (2 = 3.5%); no CCR (11 = 20%); loss of RCC (5 = 9%); CCR without major molecular response (MMR) after 18 months of imatinib (24 = 43.5%). Males: 37, females 18 cases. Median age: 44 (16–74) years. Twenty-eight patients (49%) were treated with imatinib as first line therapy and 51% had used IFN previously. Median time between diagnosis and imatinib start was 4.5 (0–94) months. Responses: 94% achieved CHR; 58% CCR and 34% MMR. After dose increase, 31 (56%) responded: 58% of the patients with previous sub-optimal molecular response achieved MMR. Among those who benefited from dose increase, only 3 cases lost the response: one with hematological resistance and two with cytogenetic resistance (2 lost CCR and one CHR). Seven out of 16 patients who increased dose due to cytogenetic failure (loss of response, failure and sub-optimal response) achieved response: one had partial cytogenetic response (PCyR) and 6 CCR. Five patients with hematological failure presented response: CHR (2), CCR (1), PCyR (1) and MMR (1). Patients with BC (2 cases) did not respond to dose escalation. TFS was 89% and 67% in 2 and 5 years, respectively. EFS was 71% and 64% in 2 and 5 years respectively. When stratified by the type of failure, EFS was 100%, 49% and 34% in the group with molecular sub-optimal response with median time of 22 (4–41) months, cytogenetic 17 (1.2–42) and hematological failure 7.7 (0.2–57), respectively (P<0.03).

Conclusions:
imatinib dose escalation was successful in molecular sub-optimal response. However, the patients who do not achieve MMR might be candidates to second line treatment. Patients who did not achieve cytogenetic or hematological response did worse with imatinib dose escalation.

Disclosures:
No relevant conflicts of interest to declare.