SOHO State of the Art Updates and Next Questions | Asparaginase-Understanding and Overcoming Toxicities in Adults with ALL

The adoption of pediatric-inspired regimens in young adults with newly diagnosed acute lymphoblastic leukemia (ALL) has significantly improved their survival outcomes. Pediatric-inspired regimens in ALL rely profoundly on delivering adequate dosing of non-myelosuppressive drugs of which asparaginase, a bacterial derived agent, is a key component. Asparaginase therapy is associated with a spectrum of unique toxicities that are observed more frequently in adult patients compared to children with ALL, and this observation has contributed to the reluctance of adult oncologists to administer the drug to their patients. Understanding the breadth of asparaginase toxicity and the associated risk factors may help in preventing severe manifestations and allow safer treatment for adults with ALL. In this review, we will discuss the different formulations of asparaginase and the appropriate dosing in adults with ALL. We will further discuss the frequency and risk factors for individual toxicities of asparaginase along with strategies for their prevention and management.

Asparaginase in the Treatment of Acute Lymphoblastic Leukemia in Adults: Current Evidence and Place in Therapy

Acute lymphoblastic leukemia (ALL) is a rare hematologic malignancy resulting in the production of abnormal lymphoid precursor cells. Occurring in B-cell and T-cell subtypes, ALL is more common in children, comprising nearly 30% of pediatric malignancies, but also constitutes 1% of adult cancer diagnoses. Outcomes are age-dependent, with five-year overall survival of greater than 90% in children and less than 20% in older adults. L-asparaginase, an enzyme not found in humans, depletes serum levels of L-asparagine. As leukemic cells are unable to synthesize this amino acid, its deprivation results in cell death. The success of asparaginase-containing regimens in the treatment of pediatric ALL, and poor outcomes with conventional cytotoxic regimens in adults, have led to trials of pediatric or pediatric-inspired regimens incorporating asparaginase in the adolescent and young adult (AYA) and adult populations. Initially purified from Escherichia coli, newer formulations of asparaginase have been developed to address short half-life, high immunogenic potential, and manufacturing difficulties. Unfamiliarity with asparaginase use and management of its unique toxicities may result in treatment-decisions that negatively impact outcomes. In this review, we address the current use of asparaginase in the treatment of ALL, with an emphasis on its role in the treatment of adults, key clinical trials, recognition and management of toxicities, and ongoing directions of study.

L-asparaginase mediated therapy in L-asparagine auxotrophic cancers: A review

Microbial L-asparaginase is the most effective first-line therapeutic used in the treatment protocols of paediatric and adult leukemia. Leukemic cell's auxotrophy for L-asparagine is exploited as a therapeutic strategy to mediate cell death through metabolic blockade of L-asparagine using L-asparaginase. Escherichia coli and Erwinia chrysanthemi serve as the major enzyme deriving sources accepted in clinical practise and the enzyme has bestowed improvements in patient outcomes over the last 40 years. However, an array of side effects generated by the native enzymes due to glutamine co-catalysis and short serum stays augmenting frequent dosages, intended a therapeutic switch towards the development of biobetter alternatives for the enzyme including the formulations resulting in sustained local depletion of L-asparagine. In addition, the treatment with L-asparaginase in few cancer types has proven to elicit drug-induced cytoprotective autophagy mechanisms and therefore warrants concern. Although the off-target glutamine hydrolysis has been viewed in contributing the drug-induced secondary responses in cells deficient with asparagine synthetase machinery, the beneficial role of glutaminase-asparaginase in proliferative regulation of asparagine prototrophic cells has been looked forward. The current review provides an overview on the enzyme's clinical applications in leukemia and possible therapeutic implications in other solid tumours, recent advancements in drug formulations, and discusses the aspects of two-sided roles of glutaminase-asparaginases and drug-induced cytoprotective autophagy mechanisms.

Health care utilisation and costs associated with different treatment protocols for newly diagnosed childhood acute lymphoblastic leukaemia: A population-based study in Ontario, Canada

BACKGROUND

Although different treatment protocols for childhood acute lymphoblastic leukaemia (ALL) all achieve high cure rates, their health care utilisation and costs have not been rigorously compared.

METHODS

Disease, treatment, and outcome data were chart abstracted for all children with ALL in Ontario, Canada, diagnosed 2002-2012. Linkage to population-based databases identified health care utilisation. Utilisation-associated costs were determined through validated algorithms. Chemotherapy-associated costs were calculated separately. Health care utilisation and costs were compared between patients receiving Children's Oncology Group (COG) versus Dana-Farber Cancer Institute (DFCI)-based treatment.

FINDINGS

Of 802 patients, 146 (18.2%) were treated on DFCI-based protocols. COG patients experienced significantly higher rates of emergency department (ED) visits (adjusted rate ratio [aRR]: 1.3, 95% confidence interval [CI]: 1.1-1.5; p = 0·01), whereas outpatient visit rates were 60% higher among DFCI patients (aRR: 1.6, 95% CI: 1.5-1.7, p < 0.0001). In adjusted analyses, DFCI-associated cost intensity was 70% higher (aRR: 1.7, 95% CI: 1.5-1.9; p < 0.0001), mainly attributable to outpatient visit costs. Total chemotherapy costs were higher among COG-treated patients ($39,400 ± $1100 versus $33,400 ± $2800; p = 0.02). Among PEG-ASNase-treated patients, total chemotherapy costs were highest among DFCI patients (median $54,200 ± $7400; p = 0.003 versus COG patients).

INTERPRETATION

COG and DFCI treatments were associated with higher ED visit rates and higher outpatient visit rates, respectively. Overall utilisation-associated costs were increased in DFCI-treated patients. Administration of some intravenous chemotherapy at home and decreases in PEG-ASNase cost would decrease health care utilisation and costs for all patients and mitigate differences between COG and DFCI protocols.

FUNDING

C¹⁷ Research Network.