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Biomedical subjects

K E Warren

Publications and source records attributed to K E Warren.

9 recordsLinked to original sources
PubMed2001

Comparison of one-, two-, and three-dimensional measurements of childhood brain tumors.

BACKGROUND: End points for assessing drug activity in brain tumors are determined by measuring the change in tumor size by magnetic resonance imaging (MRI) relative to a pretreatment or best-response scan. Traditionally, two-dimensional (2D) tumor measurements have been used, but one-dimensional (1D) measurements have recently been proposed as an alternative. Because software to estimate three-dimensional (3D) tumor volume from digitized MRI images is available, we compared all three methods of tumor measurement for childhood brain tumors and clinical outcome. METHODS: Tumor size from 130 MRI scans from 32 patients (32 baseline and 98 follow-up scans, for a total of 130 scans; median, three scans per patient; range, two to 18 scans) was measured by each method. Tumor-response category (partial response, minor response, stable disease, or progressive disease) was determined from the percentage change in tumor size between the baseline or best-response scan and follow-up scans. Time to clinical progression was independently determined by chart review. All statistical tests were two-sided. RESULTS: Concordances between 1D and 2D, 1D and 3D, and 2D and 3D were 83% (95% confidence interval [CI] = 67% to 99%), 61% (95% CI = 47% to 75%), and 66% (95% CI = 52% to 80%), respectively, on follow-up scans. Concordances for 1D and 3D and for 2D and 3D were statistically significantly lower than the concordance for 1D and 2D (P< .001 and P = .003, respectively). Concordance among 1D, 2D, and 3D methods in detecting partial response was high; there was less concordance in classifying tumors in the minor response and progressive-disease categories. Median times to progression measured by the 1D, 2D, and 3D methods were 154, 105, and 112 days, respectively, compared with 114 days based on neurologic symptoms and signs (P = .09 for overall comparison). CONCLUSIONS: Detection of partial responses was not influenced by the measurement method, but estimating time to disease progression may be method dependent for childhood brain tumors.

Brain Neoplasms↗
PubMed2001

Phase I trial of lobradimil (RMP-7) and carboplatin in children with brain tumors.

PURPOSE: To determine the maximum tolerated dose (MTD), the incidence and severity of toxicities, and the pharmacokinetics of lobradimil administered intravenously over 10 min in combination with carboplatin in children with refractory brain tumors. METHODS: A group of 25 children with primary brain tumors received carboplatin and lobradimil on two consecutive days every 28 days. The 10-min lobradimil infusion began 5 min before the end of the carboplatin infusion. Four lobradimil dose levels (100, 300, 450 and 600 ng/kg ideal body weight, IBW) were studied in cohorts of 4 to 13 patients. Carboplatin was adaptively dosed based on the glomerular filtration rate to achieve a target plasma area under the concentration-time curve (AUC) of 7.0 mg min/ml per course (5.0 mg min/ml for patients who had previously received craniospinal radiation or myeloablative chemotherapy). RESULTS: Lobradimil toxicity was immediate, tolerable and rapidly reversible. The most frequent toxicities were hypotension, flushing, headache and gastrointestinal complaints. One patient on the 600 ng/kg dose level had a seizure during the lobradimil infusion. The incidence and severity of lobradimil toxicities were not dose-related and the lobradimil dose was not escalated beyond the 600 ng/kg IBW dose level. Two patients had partial responses and ten patients had stable disease. Myelosuppression (thrombocytopenia more prominent than neutropenia) was the primary toxicity attributed to carboplatin. Lobradimil pharmacokinetics were characterized by rapid clearance from the plasma compartment and substantial interpatient variability. CONCLUSIONS: The combination of carboplatin and lobradimil is safe and tolerable. An MTD for lobradimil was not defined because toxicity was not dose-related. The recommended pediatric phase II dose of lobradimil is 600 ng/kg IBW.

Adolescent↗
PubMed2000

Effect of P-glycoprotein modulation with cyclosporin A on cerebrospinal fluid penetration of doxorubicin in non-human primates.

PURPOSE: P-glycoprotein (Pgp) is a transmembrane drug efflux pump that is expressed in multidrug-resistant cancer cells and in a variety of normal tissues, including brain capillary endothelial cells which comprise the blood-brain barrier. We studied the effects of the Pgp inhibitor, cyclosporin A (CsA), on the cerebrospinal fluid (CSF) penetration of the Pgp substrate, doxorubicin, in non-human primates. METHODS: The animals received doxorubicin alone (2.0 mg/kg i.v. over 60 min) or doxorubicin (1 mg/kg i.v. over 60 min) and CsA (loading dose 4.0 mg/kg i.v. over 2 h, followed by continuous infusion of 12 mg/kg per day over 48 h). Plasma and CSF were collected over 48 h and the doxorubicin concentration was measured by reverse-phase high-pressure liquid chromatography (HPLC) with fluorescence detection (detection limit 5 nM). A two-compartment model was fitted to the plasma concentration-time data. RESULTS: Pgp was demonstrated to be present in the epithelium of the choroid plexus by immunohistochemical methods, indicating that CSF drug penetration could be used as a surrogate for blood-brain barrier penetration. Steady state whole blood CsA concentrations, which were measured with a fluorescence-polarization immunoassay (TDX) that detects both CsA and its metabolites, ranged from 551-1315 microg/l at 24 h. The clearance of doxorubicin in four animals was reduced by 34%, 38%, 45% and 49% when given with CsA. The doxorubicin concentration in the CSF was <5 nM in all animals, both after doxorubicin alone and doxorubicin with CsA. CONCLUSIONS: The Pgp inhibitor, CsA, at a concentration that alters systemic clearance of doxorubicin, does not appear to significantly increase the CSF penetration of doxorubicin.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Effect of fluconazole on the pharmacokinetics of doxorubicin in nonhuman primates.

Antifungal prophylaxis in cancer patients who are undergoing chemotherapy is associated with prolonged neutropenia. We measured the effect of fluconazole on doxorubicin pharmacokinetics in nonhuman primates to determine if neutropenia is related to a pharmacokinetic interaction that delays the clearance of the chemotherapeutic agent. Fluconazole pretreatment had no effect on doxorubicin pharmacokinetics.

Animals↗
PubMed2000

Proton magnetic resonance spectroscopic imaging in children with recurrent primary brain tumors.

PURPOSE: Proton magnetic resonance spectroscopic imaging ((1)H-MRSI) is a noninvasive technique for spatial characterization of biochemical markers in tissues. We measured the relative tumor concentrations of these biochemical markers in children with recurrent brain tumors and evaluated their potential prognostic significance. PATIENTS AND METHODS: (1)H-MRSI was performed on 27 children with recurrent primary brain tumors referred to our institution for investigational drug trials. Diagnoses included high-grade glioma (n = 10), brainstem glioma (n = 7), medulloblastoma/peripheral neuroectodermal tumor (n = 6), ependymoma (n = 3), and pineal germinoma (n = 1). (1)H-MRSI was performed on 1. 5-T magnetic resonance imagers before treatment. The concentrations of choline (Cho) and N-acetyl-aspartate (NAA) in the tumor and normal brain were quantified using a multislice multivoxel method, and the maximum Cho:NAA ratio was determined for each patient's tumor. RESULTS: The maximum Cho:NAA ratio ranged from 1.1 to 13.2 (median, 4.5); the Cho:NAA ratio in areas of normal-appearing brain tissue was less than 1.0. The maximum Cho:NAA ratio for each histologic subtype varied considerably; approximately equal numbers of patients within each tumor type had maximum Cho:NAA ratios above and below the median. Patients with a maximum Cho:NAA ratio greater than 4.5 had a median survival of 22 weeks, and all 13 patients died by 63 weeks. Patients with a Cho:NAA ratio less than or equal to 4.5 had a projected survival of more than 50% at 63 weeks. The difference was statistically significant (P =.0067, log-rank test). CONCLUSION: The maximum tumor Cho:NAA ratio seems to be predictive of outcome in children with recurrent primary brain tumors and should be evaluated as a prognostic indicator in newly diagnosed childhood brain tumors.

Adolescent↗
PubMed2000

Modulation of clinical drug resistance in a B cell lymphoma patient by the protein kinase inhibitor 7-hydroxystaurosporine: presentation of a novel therapeutic paradigm.

Emerging evidence suggests that apoptosis is an important mechanism of tumor cell death from antineoplastic therapy. 7-hydroxystaurosporine (UCN-01) is a novel protein kinase inhibitor that increases chemotherapy-induced apoptosis in vitro and is in early phases of clinical development. In this report, we present a 68-year-old patient with chemotherapy-resistant lymphoma treated with UCN-01 and chemotherapy. He had a stage IV plasmacytoid lymphoma that failed to enter remission with high-dose EPOCH II (etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin) chemotherapy. Due to disease progression and transformation to large cell lymphoma in the liver and bone marrow, he received UCN-01. Four weeks later, he received "standard-dose" EPOCH because of progression, developed severe neutropenia for 9 days, and expired from Candida sepsis on day 23. At autopsy, there was no histological evidence of residual lymphoma, although PCR for immunoglobulin gene rearrangement analysis revealed a faint clonal band in two of six nodes but none in the liver. Significantly, no B cells were detected by immunohistochemistry in lymph nodes, and a polyclonal ladder pattern associated with the presence of normal B cells was not seen in the immunoglobulin gene rearrangement PCR assay. Profound peripheral lymphopenia (50 cells/microliter) was also observed. Pharmacokinetics showed UCN-01 salivary concentrations, a surrogate for free drug concentrations, to be within an effective range in vitro (45 nmol/L) as a modulator of DNA-damaging agent cytotoxicity. In vitro, UCN-01 is synergistic with multiple cytotoxic agents and increases fludarabine-induced apoptosis in a human breast cell line. These results suggest that UCN-01 sensitized the lymphoma to the cytotoxic effects of EPOCH, possibly by modulating the "threshold" for apoptosis, and may illustrate a new paradigm for reversal of drug resistance.

Aged↗
PubMed1999

Renal medullary carcinoma in an adolescent with sickle cell trait.

We describe the complex presentation of a patient with renal medullary carcinoma, a newly described entity primarily affecting young patients with sickle cell trait. Renal medullary carcinoma is an aggressive, rapidly destructive tumor associated with a delayed diagnosis and a poor outcome. The most common presenting signs and symptoms include hematuria, abdominal or flank pain, and weight loss. Sickle cell trait as the sole cause of hematuria in young black patients is a diagnosis of exclusion. Hemoglobin electrophoresis, intravenous pyelography, and computed tomography scans should be the minimal studies performed in young black patients with hematuria.

Adolescent↗