Faculty Bibliography

Several recent studies have indicated that an increased concentration of plasma homocysteine is an independent risk factor for the premature development of vascular disease. These important findings emphasize the need for careful selection of an appropriate analytical approach to diagnose and treat individuals who may be at risk. We compared the results obtained from the measurement of plasma total homocysteine (free + protein-bound fractions) by high-performance liquid chromatography (HPLC) with the measurement of plasma free homocystine (free fraction) by conventional ion-exchange chromatography in 10 patients with inherited defects of homocysteine metabolism and 13 obligate heterozygote individuals. This study can be used to formulate recommendations on the appropriate use of these assays in different clinical circumstances. Our results show that the concentration of total plasma homocysteine must exceed 60 mumol/L before plasma free homocystine becomes detectable by conventional ion-exchange chromatography. Similarly, assessment of the urinary excretion of homocysteine in these patients indicates that it may not become consistently detectable by conventional ion-exchange chromatography or HPLC until plasma total homocysteine exceeds 150 mumol/L. On this basis, while most patients with classical homocystinuria would be detected by analysis of plasma using conventional ion-exchange chromatography or by measurement of of the urinary homocysteine excretion, occasional patients would be missed. When monitoring patients receiving treatment for classical homocystinuria, in whom metabolic control is good, and when investigating individuals with a suspected inherited defect of cobalamin or folate metabolism, a method which measures plasma total homocysteine should be used. The identification of moderate hyperhomocysteinaemia of undefined cause investigated in relation to a history of early vacsular disease can only be identified by this approach.

Thirty-three children ranging from 2 weeks to 12 years of age were selected for allopurinol loading, 16 on the basis of an increased urinary ourotate excretion detected by routine organic acid analysis (group A), and 17 for clinical reasons suggesting a urea cycle defect (group B). The allopurinol load test proved positive in 13 of 16 patients from group A, mean peak orotate 64.0 mumol/mmol creatinine (upper limit of reference range, 13.2) and 11 of 17 patients from group B, mean peak orotate 41.0 mumol/mmol creatinine (upper limit of reference range, 13.2). Thorough investigation of these patients including urinary and plasma amino acid analysis and, in 17 cases, liver biopsy for histology and measurement of ornithine carbamyltransferase (OCT) and carbamyl-phosphate synthetase (CPS) activity failed to identify any evidence of a urea cycle disorder. However, muscle biopsies performed in 11 patients showed some evidence of mitochondrial disease in four cases, two defined on the basis of reduced respiratory chain enzyme activity and two on the basis of mtDNA abnormalities. These findings indicate that an increased excretion of orotate in sick children may not be uncommon and that a positive allopurinol load test result may not indicate a specific inherited urea cycle defect. In addition, these results raise the interesting possibility that defective ureagenesis may be a feature of mitochondrial disease in some individuals.

The binding of the lipophilic nutrients, retinal, vitamin D2, and retinyl palmitate by beta-lactoglobulin was measured by analysis of changes in the fluorescence of the tryptophanyl residue of beta-lactoglobulin or the retinyl moiety. The fluorescence intensity of the tryptophanyl residue was quenched by retinoid or vitamin D binding but was enhanced by palmitate binding. The analysis of competitive binding experiments with palmitate indicated that retinal and palmitate did not compete for the same site; however, vitamin D2, which binds with a stoichiometry of 2, appeared to displace palmitate at higher concentrations. Also, the retinoids and vitamin D2 were bound more tightly than was palmitate. The results are consistent with the model in which the retinoids and vitamin D2 bind in the calyx formed by the beta-barrel; palmitate and a second molecule of vitamin D2 bind in a surface pocket near the dimer contact region. Retinyl palmitate, which has both moieties, appeared to bind at both sites.

Elevated expression of the neurotrophin-3 (NT-3) receptor TrkC by childhood medulloblastomas is associated with favorable clinical outcome. Here, we provide evidence that TrkC is more than simply a passive marker of prognosis. We demonstrate that: (a) medulloblastomas undergo apoptosis in vitro when grown in the presence of NT-3; (b) overexpression of TrkC inhibits the growth of intracerebral xenografts of a medulloblastoma cell line in nude mice; and (c) trkC expression by individual tumor cells is highly correlated with apoptosis within primary medulloblastoma biopsy specimens. TrkC-mediated NT-3 signaling promotes apoptosis by activating multiple parallel signaling pathways and by inducing immediate-early gene expression of both c-jun and c-fos. Considered collectively, these results support the conclusion that the biological actions of TrkC activation affect medulloblastoma outcome by inhibiting tumor growth through the promotion of apoptosis

PURPOSE: From 1986 to 1992, 'eight-drugs-in-one-day' (8-in-1) chemotherapy both before and after radiation therapy (XRT) (54 Gy tumor/36 Gy neuraxis) was compared with vincristine, lomustine (CCNU), and prednisone (VCP) after XRT in children with untreated, high-stage medulloblastoma (MB). PATIENTS AND METHODS: Two hundred three eligible patients with an institutional diagnosis of MB were stratified by local invasion and metastatic stage (Chang T/M) and randomized to therapy. Median time at risk from study entry was 7.0 years. RESULTS: Survival and progression-free survival (PFS) +/- SE at 7 years were 55%+/-5% and 54%+/-5%, respectively. VCP was superior to 8-in-1 chemotherapy, with 5-year PFS rates of 63%+/-5% versus 45%+/-5%, respectively (P = .006). Upon central neuropathology review, 188 patients were confirmed as having MB and were the subjects for analyses of prognostic factors. Children aged 1.5 to younger than 3 years had inferior 5-year estimates of PFS, compared with children 3 years old or older (P = .0014; 32%+/-10% v 58%+/-4%, respectively). For MB patients 3 years of age or older, the prognostic effect of tumor spread (MO v M1 v M2+) on PFS was powerful (P = .0006); 5-year PFS rates were 70%+/-5%, 57%+/-10%, and 40%+/-8%, respectively. PFS distributions at 5 years for patients with M0 tumors with less than 1.5 cm2 of residual tumor, versus > or = 1.5 cm2 of residual tumor by scan, were significantly different (P = .023; 78%+/-6% v 54%+/-11%, respectively). CONCLUSION: VCP plus XRT is a superior adjuvant combination compared with 8-in-1 chemotherapy plus XRT. For patients with M0 tumors, residual tumor bulk (not extent of resection) is a predictor for PFS. Patients with M0 tumors, > or = 3 years with < or = 1.5 cm2 residual tumor, had a 78%+/-6% 5-year PFS rate. Children younger than 3 years old who received a reduced XRT dosage had the lowest survival rate

PURPOSE: This study was undertaken to evaluate the response of recurrent brain tumors to intravenous etoposide and to evaluate the efficacy of mannitol in augmenting etoposide's tumoricidal effect. PATIENTS AND METHODS: Ninety-nine children between one and 21 years of age with recurrent brain tumors were randomly assigned to treatment with intravenous etoposide 150 mg/M2, with or without mannitol 15 gm/M2, daily for five days every three weeks for one year or until disease progression or death. Computerized tomographic (CT) or magnetic resonance image (MRI) scans, obtained after three cycles of therapy, were compared with pre-therapy scans. Scans were centrally reviewed. RESULTS: Of 87 evaluable patients, 12 (13.8%) were determined to have had an objective response by the institutional radiologist. On central review, 7/66 (10.6%) responses were documented. Responses in centrally reviewed patients were observed in 2/12 (16.7%) low grade astrocytomas, 4/26 (15.4%) medulloblastoma or primitive neuroectodermal tumors (PNET), 1/13 (7.7%) high grade astrocytomas and 0/15 (0%) brain stem gliomas. Survival at one year was 53% (SE 12%) for low grade astrocytomas, 38% (SE 7%) for medulloblastoma or PNET, 28% (SE 10%) for high grade astrocytomas and 9% (SE 5%) for brain stem gliomas. An effect of mannitol was not observed. CONCLUSION: Intravenous etoposide has a low level of activity in the treatment of recurrent low grade astrocytomas and medulloblastoma or PNET. The efficacy of this agent was not enhanced by the coincident intravenous administration of mannitol

The dose intensity of the PCV regimen can be doubled using peripheral blood stem cell (PBSC) support. This study sought to determine the feasibility of giving dose-intensive PCV concurrently with radiation therapy. Twelve patients, age 3.2-22.7 years, median 7.5 years, with newly diagnosed high grade gliomas were enrolled. Diagnoses included diffuse intrinsic brainstem gliomas (BSG) (n = 6), glioblastoma (n = 4), anaplastic astrocytoma (n = 2). PBSCs were harvested prior to chemotherapy with G-CSF priming. Chemotherapy consisted of CCNU 130 mg/m2 and vincristine 1.5 mg/m2 on day 0, and procarbazine 150 mg/m2 on days 1-7. PBSCs were reinfused on day 9 of each course. Four courses of chemotherapy were administered every 28 days or when blood counts recovered. The first course was administered the week prior to RT, the second course began on week 3 of RT and the third and fourth course were given after RT. Hematologic toxicity was mild and the majority of courses were given on schedule. Five of six patients with diffuse BSG showed clinical improvement and three showed a radiographic response; however, only one remains alive 12+ months from diagnosis. All four patients with non-brainstem large-volume tumors showed clinical deterioration and radiographic progression during or shortly after RT. MRI scans showed massive edema and enhancement. Median time to radiographic progression was five months. Median overall survival was 11 months. We conclude that dose-intensive, time-compressed PCV given concurrently with large-volume RT appears to result in unacceptable toxicity in patients with large residual tumors

Recent advances in neurosurgical techniques and diagnostic imaging capabilities have facilitated gross total resection and accurate staging of disease extent in a greater proportion of patients. The addition of chemotherapy to surgery and craniospinal radiation has improved the outcome of patients diagnosed with medulloblastoma. Long-term follow-up studies have documented the neuroendocrine and neuropsychological deficits seen in the survivors. This paper reviews key studies using all three modalities over the past two decades and presents on-going therapeutic strategies using a risk-adapted approach. Further areas of basic research and evolving data on studies in relapsed patients are also briefly discussed

The first section of this article focuses on epidemiology, cause, diagnosis, and treatment of brain tumors in children and adolescents. The second section addresses the long-term consequences of tumors and their treatment, and a special emphasis is paid to cognitive and psychological outcomes

PURPOSE: Medulloblastoma is the most common malignant brain tumor of childhood. After treatment with surgery and radiation therapy, approximately 60% of children with medulloblastoma are alive and free of progressive disease 5 years after diagnosis, but many have significant neurocognitive sequelae. This study was undertaken to determine the feasibility and efficacy of treating children with nondisseminated medulloblastoma with reduced-dose craniospinal radiotherapy plus adjuvant chemotherapy. PATIENTS AND METHODS: Over a 3-year period, 65 children between 3 and 10 years of age with nondisseminated medulloblastoma were treated with postoperative, reduced-dose craniospinal radiation therapy (23.4 Gy) and 55.8 Gy of local radiation therapy. Adjuvant vincristine chemotherapy was administered during radiotherapy, and lomustine, vincristine, and cisplatin chemotherapy was administered during and after radiation. RESULTS: Progression-free survival was 86% +/- 4% at 3 years and 79% +/- 7% at 5 years. Sites of relapse for the 14 patients who developed progressive disease included the local tumor site alone in two patients, local tumor site and disseminated disease in nine, and nonprimary sites in three. Brainstem involvement did not adversely affect outcome. Therapy was relatively well tolerated; however, the dose of cisplatin had to be modified in more than 50% of patients before the completion of treatment. One child died of pneumonitis and sepsis during treatment. CONCLUSION: These overall survival rates compare favorably to those obtained in studies using full-dose radiation therapy alone or radiation therapy plus chemotherapy. The results suggest that reduced-dose craniospinal radiation therapy and adjuvant chemotherapy during and after radiation is a feasible approach for children with nondisseminated medulloblastoma