What Is the Role of HSCT in Philadelphia-Chromosome-Positive and Philadelphia-Chromosome-Like ALL in the Tyrosine Kinase Inhibitor Era?

Kim Vettenranta,Jochen Buechner,Veronika Dobsinska,Peter Svec,Kirk R Schultz,Gabriella Kertész

doi:10.3389/fped.2021.807002

Abstract

Previously, the outcome of paediatric Philadelphia-chromosome–positive (Ph+) ALL treated with conventional chemotherapy alone was poor, necessitating the use of haematopoietic stem cell transplantation (HSCT) for the best outcomes. The recent addition of tyrosine kinase inhibitors (TKIs) alongside the chemotherapy regimens for Ph+ ALL has markedly improved outcomes, replacing the need for HSCT for lower risk patients. An additional poor prognosis group of Philadelphia-chromosome–like (Ph-like) ALL has also been identified. This group also can be targeted by TKIs in combination with chemotherapy, but the role of HSCT in this population is not clear. The impact of novel targeted immunotherapies (chimeric antigen receptor T cells and bispecific or drug-conjugated antibodies) has improved the outcome of patients, in combination with chemotherapy, and made the role of HSCT as the optimal curative therapy for Ph+ ALL and Ph-like ALL less clear. The prognosis of patients with Ph+ ALL and persistent minimal residual disease (MRD) at the end of consolidation despite TKI therapy or with additional genetic risk factors remains inferior when HSCT is not used. For such high-risk patients, HSCT using total-body-irradiation–containing conditioning is currently recommended. This review aims to provide an update on the current and future role of HSCT for Ph+ ALL and addresses key questions related to the management of these patients, including the role of HSCT in first complete remission, MRD evaluation and related actions post HSCT, TKI usage post HSCT, and the putative role of HSCT in Ph-like ALL.

Highlights

Philadelphia-chromosome–positive (Ph+) acute lymphoblastic leukaemia (ALL) and, more recently, Philadelphiachromosome–like (Ph-like; known as BCR-ABL–like) ALL have been identified to be associated with poor prognosis when patients receive standard chemotherapy regimens [1,2,3]
With the advent of tyrosine kinase inhibitors (TKI) (Figure 1), the prognosis for paediatric patients with Ph+ ALL treated with TKIs added to the chemotherapy backbones began to approach that of non-Ph+ ALL patients [4,5,6,7,8]
We summarize the current role of haematopoietic stem cell transplantation (HSCT) in Ph+/Ph-like ALL

Summary

Introduction

Philadelphia-chromosome–positive (Ph+) acute lymphoblastic leukaemia (ALL) and, more recently, Philadelphiachromosome–like (Ph-like; known as BCR-ABL–like) ALL have been identified to be associated with poor prognosis when patients receive standard chemotherapy regimens [1,2,3]. Ph+ ALL is found in fewer than 5% of paediatric patients with ALL but in more than 20% of adults with ALL, with the incidence in adolescents falling in between. Subgroups of Ph+ patients (e.g., those with IKZF mutations) with a substantially less favourable prognosis have been identified [6, 9]. The role of HSCT in Ph-like ALL is less clear. We summarize the current role of HSCT in Ph+/Ph-like ALL

Objectives

Findings

Conclusion