Methotrexate causes persistent deficits in memory and executive function in a juvenile animal model.

Methotrexate is a dihydrofolate reductase inhibitor widely employed in curative treatment for children with acute lymphoblastic leukemia (ALL). However, methotrexate administration is also associated with persistent cognitive deficits among long-term childhood cancer survivors. Animal models of methotrexate-induced cognitive deficits have primarily utilized adult animals. The purpose of present study is to investigate the neurotoxicity of methotrexate in juvenile rats and its relevant mechanisms. The doses and schedule of systemic and intrathecal methotrexate, given from post-natal age 3-7 weeks, were chosen to model the effects of repeated methotrexate dosing on the developing brains of young children with ALL. This methotrexate regimen had no visible acute toxicity and no effect on growth. At 15 weeks of age (8 weeks after the last methotrexate dose) both spatial pattern memory and visual recognition memory were impaired. In addition, methotrexate-treated animals demonstrated impaired performance in the set-shifting assay, indicating decreased cognitive flexibility. Histopathological analysis demonstrated decreased cell proliferation in methotrexate-treated animals compared to controls, as well as changes in length and thickness of the corpus callosum. Moreover, methotrexate suppressed microglia activation and RANTES production. In conclusion, our study demonstrated that a clinically relevant regimen of systemic and intrathecal methotrexate induces persistent deficits in spatial pattern memory, visual recognition memory and executive function, lasting at least 8 weeks after the last injection. The mechanisms behind methotrexate-induced deficits are likely multifactorial and may relate to suppression of neurogenesis, alterations in neuroinflammation and microglial activation, and structural changes in the corpus callosum.

Management of chemotherapy-induced febrile neutropenia in pediatric oncology patients: A North American survey of pediatric hematology/oncology and pediatric infectious disease physicians.

BACKGROUND: Chemotherapy-induced febrile neutropenia (FN) is traditionally managed with hospital admission for parenteral antibiotics until neutropenia resolves. Recent studies have explored risk stratification and the safety of managing "low-risk" patients as outpatients. Few studies have directly assessed pediatric provider preferences for managing FN. PROCEDURE: We conducted a survey of practicing US and Canadian pediatric hematology/oncology (PHO) and pediatric infectious disease (PID) physicians to assess their FN management preferences using case scenarios with varying risk profiles. RESULTS: Twenty-one percent (n = 186) of PHO and 32% (n = 123) of PID physicians completed the survey. Overall, both groups of providers agreed regarding which patients with FN could be managed outpatient. For a child with acute lymphoblastic leukemia receiving maintenance chemotherapy with an absolute neutrophil count (ANC) of 400 cells/µl, 35% (n = 66) of PHO and 49% (n = 60) of PID physicians would consider outpatient management (P = 0.02). Of those physicians selecting inpatient management, 41% (n = 49) of PHO and 52% (n = 33) of PID physicians would be willing to discharge the patient without an increase in ANC, if afebrile with a negative blood culture (P = 0.16). For a similar patient with an ANC of 100 cells/µl, only 23% (n = 35) of PHO and 42% (n = 39) of PID physicians would consider discharge without an increase in ANC (P = 0.002). CONCLUSIONS: Despite the lack of established guidelines for low-risk pediatric FN, a significant proportion of North American physicians report willingness to modify traditional management. This reinforces the need for evidence-based low-risk criteria and outpatient management guidelines to optimize consistency of care for these patients.

Pharmacogenetic Predictors of Treatment-Related Toxicity Among Children With Acute Lymphoblastic Leukemia.

PURPOSE OF REVIEW: The aim of this review is to summarize the most recent and most robust pharmacogenetic predictors of treatment-related toxicity (TRT) in childhood acute lymphoblastic leukemia (ALL). RECENT FINDINGS: Multiple studies have examined the toxicities of the primary chemotherapeutic agents used to treat childhood ALL in relation to host genetic factors. However, few results have been replicated independently, largely due to cohort differences in ancestry, chemotherapy treatment protocols, and definitions of toxicities. To date, there is only one widely accepted clinical guideline for dose modification based on gene status: thiopurine dosing based on TPMT genotype. Based on recent data, it is likely that this guideline will be modified to incorporate other gene variants, such as NUDT15. We highlight genetic variants that have been consistently associated with TRT across treatment groups, as well as those that best illustrate the underlying pathophysiology of TRT. In the coming decade, we expect that survivorship care will routinely specify screening recommendations based on genetics. Furthermore, clinical trials testing protective interventions may modify inclusion criteria based on genetically determined risk of specific TRTs.