Stacey L. Berg

Paclitaxel in doxorubicin-refractory or mitoxantrone-refractory breast cancer: a phase I/II trial of 96-hour infusion.

PURPOSE A phase I study of paclitaxel infused over 96-hours was performed to determine toxicity, maximum-tolerated dose (MTD), and pharmacokinetics in patients with incurable lymphomas and solid tumors. A phase II study was performed at the MTD of paclitaxel in patients with doxorubicin/mitoxantrone-refractory metastatic breast cancer. PATIENTS AND METHODS In the phase I study, paclitaxel dose levels ranged from 120 to 160 mg/m2, administered on a 21-day cycle. Patients with metastatic breast cancer who had either no response or a partial response (PR) to doxorubicin or mitoxantrone and had measurable disease were eligible for the phase I and II studies. Expression of the multidrug resistance (mdr-1) gene was determined in tumor biopsies by mRNA quantitative polymerase chain reaction. RESULTS Twelve patients received a total of 73 cycles of paclitaxel on the phase I study. Dose-limiting mucositis and/or grade IV granulocytopenia was reached at 160 mg/m2, and 140 mg/m2 was selected as the phase II dose. Thirty-six consecutive patients with metastatic breast cancer were treated, of whom three were not assessable. The median age was 49 years, with disease in the liver and/or lung in 76%. Patients received a median of two prior regimens for metastatic disease, and 73% had no response to prior doxorubicin or mitoxantrone. Of 33 patients treated with paclitaxel, 16 patients (48%) achieved a PR and five (15%) achieved a minor response (MR). With a median potential follow-up duration of 60 weeks, the median progression-free and overall survival durations were 27 and 43 weeks, respectively. No correlation was found between extent of prior treatment or prior response to doxorubicin/mitoxantrone, and response to paclitaxel. Paclitaxel pharmacokinetics showed a correlation between both granulocyte and mucosal toxicity, and serum steady-state concentrations (Css) more than 0.07 mumol/L. Patients with liver metastases had significantly decreased paclitaxel clearance and higher paclitaxel Css. Levels of mdr-1 were uniformly low in all tumor biopsies studied. CONCLUSION The recommended phase II dose of paclitaxel is 140 mg/m2 in patients without liver metastases and 105 mg/m2 in patients with liver metastases. Ninety-six-hour infusions of paclitaxel were effective and well tolerated in patients with doxorubicin/mitoxantrone-refractory breast cancer. Prolonged infusion schedules may be more effective than shorter schedules and deserve further study.

Phase II Study of Nelarabine (compound 506U78) in Children and Young Adults With Refractory T-Cell Malignancies: A Report From the Children’s Oncology Group

PURPOSE Nelarabine (compound 506U78), a water soluble prodrug of 9-b-d-arabinofuranosylguanine, is converted to ara-GTP in T lymphoblasts. We sought to define the response rate of nelarabine in children and young adults with refractory or recurrent T-cell disease. PATIENTS AND METHODS We performed a phase II study with patients stratified as follows: stratum 1: > or = 25% bone marrow blasts in first relapse; stratum 2: > or = 25% bone marrow blasts in > or = second relapse; stratum 3: positive CSF; stratum 4: extramedullary (non-CNS) relapse. The initial nelarabine dose was 1.2 g/m2 daily for 5 consecutive days every 3 weeks. There were two dose de-escalations due to neurotoxicity on this or other studies. The final dose was 650 mg/m2/d for strata 1 and two patients and 400 mg/m2/d for strata 3 and four patients. RESULTS We enrolled 121 patients (106 assessable for response) at the final dose levels. Complete plus partial response rates at the final dose levels were: 55% in stratum 1; 27% in stratum 2; 33% in stratum 3; and 14% in stratum 4. There were 31 episodes of > or = grade 3 neurologic adverse events in 27 patients (18% of patients). CONCLUSION Nelarabine is active as a single agent in recurrent T-cell leukemia, with a response rate more than 50% in first bone marrow relapse. The most significant adverse events associated with nelarabine administration are neurologic. Further studies are planned to determine whether the addition of nelarabine to front-line therapy for T-cell leukemia in children will improve survival.

Phase I Study of the Proteasome Inhibitor Bortezomib in Pediatric Patients With Refractory Solid Tumors: A Children's Oncology Group Study (ADVL0015)

PURPOSE To determine the maximum-tolerated dose, dose-limiting toxicity (DLT), and pharmacodynamics of the proteasome inhibitor bortezomib (formerly PS-341) in children with recurrent or refractory solid tumors. PATIENTS AND METHODS An intravenous bolus of bortezomib was administered twice weekly for 2 consecutive weeks at either 1.2 or 1.6 mg/m2/dose followed by a 1-week rest. The pharmacodynamics of bortezomib were evaluated by measurement of whole blood 20S proteasome activity. RESULTS Fifteen patients, 11 assessable, were enrolled between November 2001 and February 2003. Dose-limiting thrombocytopenia, which prevented administration of a complete course (four doses in 2 weeks) of therapy, occurred in two of five assessable children enrolled at the 1.6 mg/m2 dose level. There were no other DLTs. Inhibition of 20S proteasome activity seemed to be dose dependent. The average inhibition 1 hour after drug administration on day 1 was 67.2% +/- 7.6% at the 1.2 mg/m2/dose and 76.5% +/- 3.3% at the 1.6 mg/m2/dose. There were no objective antitumor responses. CONCLUSION Bortezomib is well tolerated in children with recurrent or refractory solid tumors. The recommended phase II dose of bortezomib for children with solid tumors is 1.2 mg/m2/dose, administered as an intravenous bolus twice weekly for 2 weeks followed by a 1-week break.

MDM2 inhibition sensitizes neuroblastoma to chemotherapy-induced apoptotic cell death

Novel therapeutic approaches are urgently needed for high-stage neuroblastoma, a major therapeutic challenge in pediatric oncology. The majority of neuroblastoma tumors are p53 wild type with intact downstream p53 signaling pathways. We hypothesize that stabilization of p53 would sensitize this aggressive tumor to genotoxic chemotherapy via inhibition of MDM2, the primary negative upstream regulator of p53. We used pharmacologic inhibition of the MDM2-p53 interaction with the small-molecule inhibitor Nutlin and studied the subsequent response to chemotherapy in neuroblastoma cell lines. We did 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and terminal deoxynucleotidyl transferase assays to measure proliferation and apoptosis in several cell lines (IMR32, MYCN3, and JF) treated with combinations of cisplatin, etoposide, and Nutlin. We found consistent and robust decreases in proliferation and increases in apoptosis with the addition of Nutlin 3a to etoposide or cisplatin in all cell lines tested and no response to the inactive Nutlin 3b enantiomer. We also show a rapid and robust accumulation of p53 protein by Western blot in these cells within 1 to 2 hours of treatment. We conclude that MDM2 inhibition dramatically enhances the activity of genotoxic drugs in neuroblastoma and should be considered as an adjuvant to chemotherapy for this aggressive pediatric cancer and for possibly other p53 wild-type solid tumors. [Mol Cancer Ther 2006;5(9):2358–65]

Diagnostic Yield of Clinical Tumor and Germline Whole-Exome Sequencing for Children With Solid Tumors.

Importance Whole-exome sequencing (WES) has the potential to reveal tumor and germline mutations of clinical relevance, but the diagnostic yield for pediatric patients with solid tumors is unknown. Objective To characterize the diagnostic yield of combined tumor and germline WES for children with solid tumors. Design Unselected children with newly diagnosed and previously untreated central nervous system (CNS) and non-CNS solid tumors were prospectively enrolled in the BASIC3 study at a large academic childrens hospital during a 23-month period from August 2012 through June 2014. Blood and tumor samples underwent WES in a certified clinical laboratory with genetic results categorized on the basis of perceived clinical relevance and entered in the electronic health record. Main Outcomes and Measures Clinical categorization of somatic mutations; frequencies of deleterious germline mutations related to patient phenotype and incidental medically-actionable mutations. Results Of the first 150 participants (80 boys and 70 girls, mean age, 7.4 years), tumor samples adequate for WES were available from 121 patients (81%). Somatic mutations of established clinical utility (category I) were reported in 4 (3%) of 121 patients, with mutations of potential utility (category II) detected in an additional 29 (24%) of 121 patients. CTNNB1 was the gene most frequently mutated, with recurrent mutations in KIT, TSC2, and MAPK pathway genes (BRAF, KRAS, and NRAS) also identified. Mutations in consensus cancer genes (category III) were found in an additional 24 (20%) of 121 tumors. Fewer than half of somatic mutations identified were in genes known to be recurrently mutated in the tumor type tested. Diagnostic germline findings related to patient phenotype were discovered in 15 (10%) of 150 cases: 13 pathogenic or likely pathogenic dominant mutations in adult and pediatric cancer susceptibility genes (including 2 each in TP53, VHL, and BRCA1), 1 recessive liver disorder with hepatocellular carcinoma (TJP2), and 1 renal diagnosis (CLCN5). Incidental findings were reported in 8 (5%) of 150 patients. Most patients harbored germline uncertain variants in cancer genes (98%), pharmacogenetic variants (89%), and recessive carrier mutations (85%). Conclusions and Relevance Tumor and germline WES revealed mutations in a broad spectrum of genes previously implicated in both adult and pediatric cancers. Combined reporting of tumor and germline WES identified diagnostic and/or potentially actionable findings in nearly 40% of newly diagnosed pediatric patients with solid tumors.

Phase I Clinical Trial of Intrathecal Topotecan in Patients With Neoplastic Meningitis

PURPOSE A phase I trial of intrathecal (IT) topotecan was performed to determine the optimal dose, the dose-limiting toxic effects, and the incidence and severity of other toxic effects in patients 3 years and older with neoplastic meningitis. PATIENTS AND METHODS Twenty-three assessable patients received IT topotecan administered by means of either lumbar puncture or an indwelling ventricular access device (Ommaya reservoir). Intrapatient dose escalation from 0.025 mg to 0.2 mg was performed in the first cohort of patients. Subsequent cohorts of patients were treated at fixed dose levels of 0.2 mg, 0.4 mg, or 0.7 mg. Serial samples of CSF for pharmacokinetic studies were obtained in a subset of patients with Ommaya reservoirs. RESULTS Arachnoiditis, characterized by fever, nausea, vomiting, headache, and back pain, was the dose-limiting toxic effect in two of four patients enrolled at the 0.7 mg dose level. The maximum-tolerated dose (MTD) was 0.4 mg. Six of the 23 assessable patients had evidence of benefit manifested as prolonged disease stabilization or response. CONCLUSION The MTD and recommended phase II dose of IT topotecan in patients who are 3 years or older is 0.4 mg. A phase II trial of IT topotecan in children with neoplastic meningitis is in progress.

Decision Making in Pediatric Oncology: Who Should Take the Lead? The Decisional Priority in Pediatric Oncology Model

Decision making in pediatric oncology can look different to the ethicist and the clinician. Popular ethical theories argue that clinicians should not make decisions for patients, but rather provide information so that patients can make their own decisions. However, this theory does not always reflect clinical reality. We present a new model of decision making that reconciles this apparent discrepancy. We first distinguish decisional priority from decisional authority. The person (parent, child, or clinician) who first identifies a preferred choice exercises decisional priority. In contrast, decisional authority is a nondelegable parental right and duty, in which a mature child may join. This distinction enables us to analyze decisional priority without diminishing parental authority. This model analyzes decisions according to two continuous underlying characteristics. One dominant characteristic is the likelihood of cure. Because cure, when possible, is the ultimate goal, the clinician is in a better position to assume decisional priority when a child probably can be cured. The second characteristic is whether there is more than one reasonable treatment option. The interaction of these two complex continual results in distinctive types of decisional situations. This model explains why clinicians sometimes justifiably assume decisional priority when there is one best medical choice. It also suggests that clinicians should particularly encourage parents (and children, when appropriate) to assume decisional priority when there are two or more clinically reasonable choices. In this circumstance, the family, with its deeper understanding of the childs nature and preferences, is better positioned to take the lead.

Effect of R-verapamil on the pharmacokinetics of paclitaxel in women with breast cancer.

PURPOSE To study the effect of the multidrug-resistance reversal agent R-verapamil on the pharmacokinetic behavior of paclitaxel. METHODS Six women with breast cancer who received paclitaxel as a 3-hour infusion with and without R-verapamil were monitored with frequent plasma sampling up to 24 hours postinfusion. Paclitaxel concentrations were measured using a reverse-phase high-pressure liquid chromatography assay. RESULTS Concomitant administration of R-verapamil resulted in a decrease in mean (+/- SD) paclitaxel clearance from 179 +/- 67 mL/min/m2 to 90 +/- 34 mL/min/m2 (P < .03) and in a twofold increase in paclitaxel exposure (area under the curve [AUC]). The mean end-infusion paclitaxel concentration was also twofold higher: 5.1 +/- 1.8 mumol/L versus 11.3 +/- 4.1 mumol/L (P < .03). CONCLUSION The alteration in paclitaxel pharmacokinetics when paclitaxel and R-verapamil are coadministered complicates the interpretation of response and toxicity data from clinical trials of this drug combination.

Poly(ADP-ribose) polymerase inhibitor ABT-888 potentiates the cytotoxic activity of temozolomide in leukemia cells: influence of mismatch repair status and O6-methylguanine-DNA methyltransferase activity

The poly(ADP-ribose) polymerase (PARP) inhibitor ABT-888 potentiates the antitumor activity of temozolomide (TMZ). TMZ resistance results from increased O6-methylguanine-DNA methyltransferase (MGMT) activity and from mismatch repair (MMR) system mutations. We evaluated the relative importance of MGMT activity, MMR deficiency, nonhomologous end joining (NHEJ), and PARP activity in ABT-888 potentiation of TMZ. MMR-proficient and MMR-deficient leukemia cells with varying MGMT activity, as well as primary leukemia samples, were used to determine TMZ IC50 alone and with ABT-888. ABT-888 effectively inhibited PARP activity and enhanced TMZ growth inhibition in most leukemia cells. ABT-888 potentiation was most effective in MMR-deficient cells with low MGMT activity [potentiation factor (PF) = 21]. ABT-888 also potentiated TMZ activity in MMR-deficient cells with elevated MGMT activity. Unexpectedly, ABT-888 also enhanced TMZ activity in MMR-proficient cells (PF = 3–7). ABT-888 potentiation was unrelated to NHEJ activity. ABT-888 potentiated TMZ (PF = 2–5) in two of four acute myeloid leukemia patient samples but showed little potentiation in primary acute lymphoblastic leukemia. In conclusion, although ABT-888 potentiation of TMZ was most pronounced in MMR-deficient cells with low MGMT activity, neither MMR proficiency nor MGMT overexpression completely abrogated ABT-888 potentiation of TMZ. [Mol Cancer Ther 2009;8(8):2232–42]

Plasma and Cerebrospinal Fluid Pharmacokinetics of Imatinib after Administration to Nonhuman Primates

Purpose: Imatinib mesylate (Gleevec, Glivec, STI571, imatinib) is a potent tyrosine kinase inhibitor approved for the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. The role of imatinib in the treatment of malignant gliomas and other solid tumors is being evaluated. We used a nonhuman primate model that is highly predictive of the cerebrospinal fluid penetration of drugs in humans to study the pharmacokinetics of imatinib in plasma and cerebrospinal fluid (CSF) after i.v. and p.o. administration. Experimental Design: Imatinib, 15 mg/kg i.v. over 30 min (n = 3) or 30 mg/kg p.o. (n = 3), was administered to nonhuman primates. Imatinib was measured in serial samples of plasma and CSF using high-pressure liquid chromatography with UV absorbance or mass spectroscopic detection. Pharmacokinetic parameters were estimated using model-independent methods. Results: Peak plasma imatinib concentrations ranged from 6.4 to 9.5 μm after i.v. dosing and 0.8 to 2.8 μm after p.o. dosing. The mean ±SD area under the plasma concentration versus time curve was 2480 ±1340 μm·min and 1191 ±146 μm·min after i.v. and p.o. dosing, respectively. The terminal half-life was 529 ±167 min after i.v. dosing and 266 ±88 min after p.o. dosing. After i.v. dosing the steady state volume of distribution was 5.9 ±2.8 liter/kg, and the total body clearance was 12 ±5 ml/min/kg. The mean peak CSF concentration was 0.25 ±0.07 μm after i.v. dosing and 0.07 ±0.04 μm after p.o. dosing. The mean CSF:plasma area under the plasma concentration versus time curve ratio for all of the animals was 5% ±2%. Conclusions: There is limited penetration of imatinib into the CSF of nonhuman primates after i.v. and p.o. administration.