Abstract: The survival rate for children with acute lymphoblastic leukemia (ALL) has dra­matically improved over the last 50 years. However, for those in the adolescent and young adult (AYA) age-group of 15–30 years with ALL, there has not been the same degree of improvement. Historically, pediatric and adult providers have utilized different treatment approaches based on clinical trials. However, studies that have compared the outcome of AYA patients with ALL treated on pediatric or adult clinical trials have generally shown substantially better outcomes for this patient population treated with the pediatric trials. Additionally, hematopoietic stem cell transplantation has been considered as part of intensified therapy for AYA patients with ALL. Herein, we review the outcomes with chemotherapy alone and with hematopoietic stem cell transplantation, and explore the challenges faced in determining the ideal therapy for the AYA population of patients.


Keywords: adolescent young adult oncology, leukemia, hematopoietic stem cell transplantation 


INTRODUCTION

Acute lymphoblastic leukemia (ALL) is a multifaceted disease in its biological pathogenesis, with variety of populations affected and numerous epidemiological factors.1 The treatment regimens are typically intense and involve many chemothera­peutic agents that carry a multitude of toxicity risks. However, the improvement in the prognosis for children diagnosed with ALL has been one of the great success stories for the 20th and early 21st centuries for cancer care. While only 30% of chil­dren diagnosed with ALL survived in 1970, more than 85% survive today, with some populations of patients having a .95% survival at 5 years. Unfortunately, the same cannot be said for young adults between 15 and 30 years of age with ALL, which, for the purposes of this review, we will consider to be the adolescent and young adult (AYA) population. For the patients in this age-group, the prognosis has been less promising and can vary from 35% to 75% disease-free survival at 5 years, depending on the leukemic subtype and therapy utilized.2–4 Efforts to improve the prognosis for this group of patients have been challenging, and controversy between pediatric and adult oncologists regarding the optimal treatment has contributed to a lack of clarity over a standard approach to care. This includes a discrepancy among some providers regarding the utilization of hematopoietic stem cell transplantation (HSCT). Here, we review many of the issues that need to be considered in determining the ideal treatment course for AYAs with ALL.

BACKGROUND

ALL develops as a result of deregulation in various pathways in the cell cycle that serve to control cell survival and prolif­eration.1,5 ALL in particular is characterized by an uncontrol­lable proliferation of malignant cells with an arrest of normal lymphoid progenitor cell development.6 As a result, normal bone marrow cells are replaced by malignant lymphoblasts, thereby inhibiting homeostatic hematogenous and immune functions.7,8 In ALL, examination of the bone marrow will most likely reveal a hypercellular and homogenous popula­tion of blasts.

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