Relapse Prevention with Tyrosine Kinase Inhibitors after Allogeneic Transplantation for Philadelphia Chromosome-Positive Acute Lymphoblast Leukemia: A Systematic Review

Abstract

Relapse after stem cell transplantation for Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) remains a significant challenge. In this systematic review, we compare survival outcomes of second-generation tyrosine kinase inhibitors (TKIs) nilotinib and dasatinib with first-generation TKI imatinib when these agents are used after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in Ph+ ALL. In addition, we review the literature on TKI use to prevent relapse in patients who proceed to allo-HSCT beyond first complete response (>CR1). We performed database searches (inception to January 2018) using PubMed, Cochrane Library, and Embase. After exclusions, 17 articles were included in this analysis. Imatinib was used post-transplant either prophylactically or preemptively in 12 studies, 7 prospective studies and 5 retrospective studies. Overall survival (OS) for most prospective studies at 1.5 to 3 and 5 years ranged between 62% to 92% and 74.5% to 86.7%. Disease-free survival at 1.5 to 5 years was 60.4% to 92%. Additionally, imatinib failed to show survival benefit in patients who were >CR1 at the time of allo-HSCT. The cumulative OS for most retrospective studies using imatinib at 1 to 2 and 3 to 5 years was 42% to 100% and 33% to 40% respectively. Event-free survival at 1 to 2 and 3 to 5 years was 33.3% to 67% and 20% to 31% respectively. Dasatinib was used as maintenance treatment in 3 retrospective studies (n = 34). The OS for patients with Ph+ ALL using dasatinib as maintenance regimen after allo-HSCT at 1.4 to 3 years was 87% to 100% and disease-free survival at 1.4 to 3 years was 89% to 100%. Ninety-three percent of patients with minimal residual disease (MRD) positive status after allo-HSCT became MRD negative. Three prospective studies used nilotinib. In 2 studies where investigators studied patients with advanced chronic myeloid leukemia and Ph+ ALL, the cumulative OS and event-free survival at 7.5 months to 2 years were 69% to 84% and 56% to 84%, respectively. In the third study (n = 5) in patients with Ph+ ALL, nilotinib use resulted in OS at 5 years of 60%. Our review showed that use of TKIs (all generations) after allo-HSCT for patients in CR1 improved OS when given as a prophylactic or preemptive regimen. Limited data suggest that second-generation TKIs (ie, dasatinib) have a better OS, especially in patients with MRD-positive status. Imatinib did not improve OS in patients who were >CR1 at the time of allo-HSCT; for this population, no data were available with newer generation TKIs. The evaluation of survival benefit with newer generation TKIs and their efficacy in patients in >CR1 needs further study in large randomized clinical trials.

Keywords: Acute lymphoblastic leukemia; Philadelphia chromosome; Relapse; Tyrosine kinase inhibitors.