Faculty Bibliography

L-asparaginase (L-ASNase) has been an essential component of multiagent chemotherapy for acute lymphoblastic leukemia in childhood for over 3 decades. There are currently 2 Food and Drug Administration (FDA)-approved formulations of L-ASNase derived from Escherichia coli and 1 non-FDA approved formulation derived from Erwinia chrysanthemi. Modifications in L-ASNase have included pegylation, which decreases drug immunogenicity and increases the half-life, allowing less frequent administration. Although L-ASNase is well-tolerated in most patients and causes little myelosuppression, significant toxicities occur in up to 30% of patients. Hypersensitivity is the most common toxicity of L-ASNase therapy and limits the further use of the drug. Other significant toxicities relate to a reduction in protein synthesis and include pancreatitis, thrombosis, central nervous system complications, and liver dysfunction. The spectrum of common toxicities and the efficacy of different formulations of L-ASNase are presented in this review

BACKGROUND: Current event-free survival (EFS) rates for children with newly diagnosed acute myeloid leukemia (AML) approach 50-60%. We hypothesize that further improvements in survival are unlikely to be achieved with traditional approaches such as dose intensive chemotherapy or hematopoietic stem cell transplants, since these therapies have been rigorously explored in clinical trials. This report highlights efforts to assess the response rates and survival outcomes after first or greater relapse in children with AML. PROCEDURE: We performed a retrospective cohort review of pediatric patients with relapsed and refractory AML (rAML) previously treated at TACL institutions between the years of 1995 and 2004. Data regarding disease characteristics at diagnosis and relapse, treatment response, and survival was collected on 99 patients and 164 medullary relapses or treatment failures. RESULTS: The complete response (CR) rate following the second therapeutic attempt was 56 +/- 5%. CR rates following a third treatment attempt was 25 +/- 8% while 17 +/- 7% achieved CR following the fourth through sixth treatments. The 5-year disease-free survival in patients achieving CR following a second therapeutic attempt was 43 +/- 7%. The 5-year EFS and overall survival (OS) rates for all patients receiving a second treatment attempt was 24 +/- 5% and 29 +/- 5%, respectively. CONCLUSIONS: This CR rate following a second therapeutic attempt and OS rate in patients with rAML is consistent with the literature. There are limited published data of CR rates for subsequent relapses. Our data can serve as a historical benchmark to compare outcomes of future therapeutic trials in rAML against traditional chemotherapy regimens.

BACKGROUND: Outcomes remain poor for children after relapse of acute lymphoblastic leukemia (ALL), especially after early marrow relapse. Bortezomib is a proteasome inhibitor with in vitro synergy with corticosteroids and clinical activity in human lymphoid malignancies. PROCEDURE: This is a Phase I study of escalating doses bortezomib administered days 1, 4, 8, and 11, added to 4-drug induction chemotherapy with vincristine, dexamethasone, pegylated L-asparaginase, and doxorubicin (VXLD) in children with relapsed ALL. RESULTS: Ten patients were enrolled, five in first marrow relapse, and five in second relapse. Four patients were enrolled at dose level 1 (bortezomib 1 mg/m(2)). One patient was not evaluable for toxicity because of omitted dexamethasone doses. No dose-limiting toxicity (DLT) was observed. Six patients were enrolled at dose level 2 (bortezomib 1.3 mg/m(2)). One patient had dose-limiting hypophosphatemia and rhabdomyolysis after 1 dose of bortezomib, and died from a diffuse zygomyces infection on day 17. Five additional patients were enrolled with no subsequent DLTs. As planned, no further dose escalation was pursued. The regimen had predictable toxicity related to the chemotherapy drugs. Two patients had mild peripheral neuropathy (grades 1 and 2). Six of nine evaluable patients (67%) achieved a complete response (CR), and one had a bone marrow CR with persistent central nervous system leukemia. CONCLUSIONS: The combination of bortezomib (1.3 mg/m(2)) with VXLD is active with acceptable toxicity in pretreated pediatric patients with relapsed ALL. We are expanding the 1.3 mg/m(2) cohort for a phase II estimate of response. Study registered at ClinicalTrials.gov (http://clinicaltrials.gov/ct2/show/NCT00440726).

One of the challenges of incorporating molecularly targeted drugs into multi-agent chemotherapy (backbone) regimens is defining dose-limiting toxicities (DLTs) of the targeted agent against the background of toxicities of the backbone regimen. An international panel of 22 pediatric acute lymphocytic leukemia (ALL) experts addressed this issue (www.ALLNA.org). Two major questions surrounding DLT assessment were explored: (1) how toxicities can be best defined, assessed, and attributed; and (2) how effective dosing of new agents incorporated into multi-agent ALL clinical trials can be safely established in the face of disease- and therapy-related systemic toxicities. The consensus DLT definition incorporates tolerance of resolving Grade 3 and some resolving Grade 4 toxicities with stringent safety monitoring. This functional DLT definition is being tested in two Children's Oncology Group (COG) ALL clinical trials.