Paclitaxel for the treatment of progressive or recurrent childhood brain tumors: a pediatric oncology phase II study

Circulating Biomarkers for Monitoring Chemotherapy-Induced Cardiotoxicity in Children

Most commonly diagnosed cancer pathologies in the pediatric population comprise leukemias and cancers of the nervous system. The percentage of cancer survivors increased from approximatively 50% to 80% thanks to improvements in medical treatments and the introduction of new chemotherapies. However, as a consequence, heart disease has become the main cause of death in the children due to the cardiotoxicity induced by chemotherapy treatments. The use of different cardiovascular biomarkers, complementing data obtained from electrocardiogram, echocardiography cardiac imaging, and evaluation of clinical symptoms, is considered a routine in clinical diagnosis, prognosis, risk stratification, and differential diagnosis. Cardiac troponin and natriuretic peptides are the best-validated biomarkers broadly accepted in clinical practice for the diagnosis of acute coronary syndrome and heart failure, although many other biomarkers are used and several potential markers are currently under study and possibly will play a more prominent role in the future. Several studies have shown how the measurement of cardiac troponin (cTn) can be used for the early detection of heart damage in oncological patients treated with potentially cardiotoxic chemotherapeutic drugs. The advent of high sensitive methods (hs-cTnI or hs-cTnT) further improved the effectiveness of risk stratification and monitoring during treatment cycles.

Phase II Trial of Dabrafenib Plus Trametinib in Relapsed/Refractory BRAF V600-Mutant Pediatric High-Grade Glioma

PURPOSE

BRAF V600 mutation is detected in 5%-10% of pediatric high-grade gliomas (pHGGs), and effective treatments are limited. In previous trials, dabrafenib as monotherapy or in combination with trametinib demonstrated activity in children and adults with relapsed/refractory BRAF V600-mutant HGG.

METHODS

This phase II study evaluated dabrafenib plus trametinib in patients with relapsed/refractory BRAF V600-mutant pHGG. The primary objective was overall response rate (ORR) by independent review by Response Assessment in Neuro-Oncology criteria. Secondary objectives included ORR by investigator determination, duration of response (DOR), progression-free survival, overall survival (OS), and safety.

RESULTS

A total of 41 pediatric patients with previously treated BRAF V600-mutant HGG were enrolled. At primary analysis, median follow-up was 25.1 months, and 51% of patients remained on treatment. Sixteen of 20 discontinuations were due to progressive disease in this relapsed/refractory pHGG population. Independently assessed ORR was 56% (95% CI, 40 to 72). Median DOR was 22.2 months (95% CI, 7.6 months to not reached [NR]). Fourteen deaths were reported. Median OS was 32.8 months (95% CI, 19.2 months to NR). The most common all-cause adverse events (AEs) were pyrexia (51%), headache (34%), and dry skin (32%). Two patients (5%) had AEs (both rash) leading to discontinuation.

CONCLUSION

In relapsed/refractory BRAF V600-mutant pHGG, dabrafenib plus trametinib improved ORR versus previous trials of chemotherapy in molecularly unselected patients with pHGG and was associated with durable responses and encouraging survival. These findings suggest that dabrafenib plus trametinib is a promising targeted therapy option for children and adolescents with relapsed/refractory BRAF V600-mutant HGG.

Pediatric Chemotherapy Drugs Associated With Cardiotoxicity

Pediatric cancers are a common cause of childhood morbidity. As a result, chemotherapeutic regimens have been designed to target childhood cancers. These medications are necessary to treat pediatric cancers, however, oncology management options are accompanied by multiple negative and potentially fatal adverse effects. Although anthracyclines are the most commonly used chemotherapeutic agents associated with cardiotoxicity, we also explore other chemotherapeutic drugs used in children that can potentially affect the heart. Genetic variations resulting in single nucleotide polymorphism (SNP) have the propensity to modify the cardiotoxic effects of the chemotherapy drugs. The clinical presentation of the cardiac effects can vary from arrhythmias and heart failure to completely asymptomatic. A range of imaging studies and laboratory investigations can protect the heart from severe outcomes. The physiology of the heart and the effect of drugs in children vary vividly from adults; therefore, it is crucial to study the cardiotoxic effect of chemotherapy drugs in the pediatric population. This review highlights the potential contributing factors for cardiotoxicity in the pediatric population and discusses the identification and management options.

Inhibiting microcephaly genes as alternative to microtubule targeting agents to treat brain tumors

Medulloblastoma (MB) and gliomas are the most frequent high-grade brain tumors (HGBT) in children and adulthood, respectively. The general treatment for these tumors consists in surgery, followed by radiotherapy and chemotherapy. Despite the improvement in patient survival, these therapies are only partially effective, and many patients still die. In the last decades, microtubules have emerged as interesting molecular targets for HGBT, as various microtubule targeting agents (MTAs) have been developed and tested pre-clinically and clinically with encouraging results. Nevertheless, these treatments produce relevant side effects since they target microtubules in normal as well as in cancerous cells. A possible strategy to overcome this toxicity could be to target proteins that control microtubule dynamics but are required by HGBT cells much more than in normal cell types. The genes mutated in primary hereditary microcephaly (MCPH) are ubiquitously expressed in proliferating cells, but under normal conditions are selectively required during brain development, in neural progenitors. There is evidence that MB and glioma cells share molecular profiles with progenitors of cerebellar granules and of cortical radial glia cells, in which MCPH gene functions are fundamental. Moreover, several studies indicate that MCPH genes are required for HGBT expansion. Among the 25 known MCPH genes, we focus this review on KNL1, ASPM, CENPE, CITK and KIF14, which have been found to control microtubule stability during cell division. We summarize the current knowledge about the molecular basis of their interaction with microtubules. Moreover, we will discuss data that suggest these genes are promising candidates as HGBT-specific targets.

A Rare Case of Metastatic Primary Peritoneal Ependymoma: A Case Report and Literature Review

Background

Primary peritoneal ependymoma is an exceedingly rare tumour with only four cases reported in the literature. It typically follows an indolent disease course. We describe a rare case of metastatic primary peritoneal ependymoma which was treated with chemotherapy and radiotherapy resulting in prolonged survival to date for 10 years. Case Presentation. The patient was a 23-year-old female on presentation. She presented with right upper quadrant pain associated with an abdominal mass. Computed tomography demonstrated a large mass displacing the liver. Debulking surgery was done revealing a tumour arising from the peritoneum as well as multiple metastatic pleural and peritoneal nodules. Pathology was consistent with primary peritoneal ependymoma. The patient was then treated with multiple lines of chemotherapy containing etoposide as the backbone. She also received palliative radiotherapy to the thoracic metastases with good and durable response.

Conclusion

We reported a rare case of metastatic primary peritoneal ependymoma. Etoposide containing the chemotherapy regimen is effective in the treatment of peritoneal ependymoma. Radiotherapy is also effective for palliation of local symptoms with durable response.

Endothelial cell malignancies in infants, children and adolescents: Treatment results of three Cooperative Weichteilsarkom Studiengruppe (CWS) trials and one registry

BACKGROUND

Endothelial cell malignancies are extremely rare in childhood. New identification of genetic abnormalities (WWTR1:CAMTA1 translocation) helps to recognize potential therapeutic targets. Little is known about treatment and outcome of these patients.

METHODS

Clinical course, treatment, and outcome in patients with endothelial cell malignancies treated within the Cooperative Weichteilsarkom Studiengruppe (CWS) trials CWS-91, -96, -2002P, and the Soft-Tissue Sarcoma Registry (SoTiSaR) were analyzed (1991-2019).

RESULTS

Patients had angiosarcoma (AS) (n = 12), malignant epithelioid hemangioendothelioma (EHE) (n = 16), and kaposiform hemangioendothelioma (KHE) (n = 13). The median age was 5.39 years (range, 0.8-17.34); 33 patients had localized disease (LD), and 8 patients had metastatic disease. Therapy consisted of chemotherapy (CHT) (AS n = 8, EHE n = 9, KHE n = 5), interferon or new agent therapy (EHE n = 5, 2 KHE n = 2), microscopically or macroscopically complete resection (AS n = 3, EHE n = 6, KHE n = 3), and radiotherapy (AS n = 6, EHE n = 2, KHE n = 1). Two patients (KHE) had watch-and-wait strategy resulting in stable disease. Complete remission (CR) was achieved in AS (10/12; 83%), EHE (10/16; 63%), and KHE (5/13; 38%). The five-year EFS and OS for patients with AS was 64% (± 29 CI 95%) and 80% (± 25, CI 95%), with EHE 62% (± 24, CI 95%) and 78% (± 23, CI 95%), with KHE 33% (± 34, CI 95%) and 92% (± 15, CI 95%), respectively. Complete resection was a significant prognostic factor for AS, LD for EHE.

CONCLUSIONS

Endothelial cell malignancies in childhood have a fair outcome with multimodal treatment. New treatment options are needed for metastic disease.

A phase 1/2 dose-finding, safety, and activity study of cabazitaxel in pediatric patients with refractory solid tumors including tumors of the central nervous system

BACKGROUND

This phase 1/2 study (NCT01751308) evaluated cabazitaxel in pediatric patients. Phase 1 determined the maximum tolerated dose (MTD) in patients with recurrent/refractory solid tumors, including central nervous system (CNS) tumors. Phase 2 evaluated activity in pediatric recurrent high-grade glioma (HGG) or diffuse intrinsic pontine glioma (DIPG).

PROCEDURE

In phase 1, a 3 + 3 dose-escalation study design was followed. Cabazitaxel was administered at a starting dose of 20 mg/m² . Dose-limiting toxicities (DLTs) during cycle 1 were assessed to determine the MTD. Tumor response and cabazitaxel pharmacokinetics were also assessed. In phase 2, patients received cabazitaxel at the MTD determined in phase 1. Tumor responses were assessed every 9 weeks (modified Response Assessment in Neuro-oncology criteria). Progression-free survival and cabazitaxel pharmacokinetics were evaluated, and overall survival was estimated.

RESULTS

In phase 1, 23 patients were treated, including 19 with CNS tumors. One patient had a partial response; five had stable disease for >3 cycles. Common adverse events included fatigue, diarrhea, nausea and vomiting, febrile neutropenia, and hypersensitivity reactions. Two of three DLTs (febrile neutropenia) occurred with a dose of 35 mg/m² ; the MTD was 30 mg/m² . Slightly higher cabazitaxel clearance was observed compared with adult trials. In phase 2, 16 patients (eight HGG and eight DIPG) were enrolled; 11 were evaluable for response and five withdrew (three due to anaphylaxis). All 11 patients progressed within four cycles. No responses were observed; the study was stopped due to futility.

CONCLUSIONS

The safety profile of cabazitaxel was consistent with previous studies. The MTD (30 mg/m² ) was higher than the adult MTD. Cabazitaxel did not demonstrate activity in recurrent/refractory HGG or DIPG.

Medulloblastoma in children and adolescents: a systematic review of contemporary phase I and II clinical trials and biology update

Survival rates for patients with medulloblastoma have improved in the last decades but for those who relapse outcome is dismal and new approaches are needed. Emerging drugs have been tested in the last two decades within the context of phase I/II trials. In parallel, advances in genetic profiling have permitted to identify key molecular alterations for which new strategies are being developed. We performed a systematic review focused on the design and outcome of early-phase trials evaluating new agents in patients with relapsed medulloblastoma. PubMed, clinicaltrials.gov, and references from selected studies were screened to identify phase I/II studies with reported results between 2000 and 2015 including patients with medulloblastoma aged <18 years. A total of 718 studies were reviewed and 78 satisfied eligibility criteria. Of those, 69% were phase I; 31% phase II. Half evaluated conventional chemotherapeutics and 35% targeted agents. Overall, 662 patients with medulloblastoma/primitive neuroectodermal tumors were included. The study designs and the response assessments were heterogeneous, limiting the comparisons among trials and the correct identification of active drugs. Median (range) objective response rate (ORR) for patients with medulloblastoma in phase I/II studies was 0% (0-100) and 6.5% (0-50), respectively. Temozolomide containing regimens had a median ORR of 16.5% (0-100). Smoothened inhibitors trials had a median ORR of 8% (3-8). Novel drugs have shown limited activity against relapsed medulloblastoma. Temozolomide might serve as backbone for new combinations. Novel and more homogenous trial designs might facilitate the development of new drugs.

Inhibitory effect of sustained perivascular delivery of paclitaxel on neointimal hyperplasia in the jugular vein after open cutdown central venous catheter placement in rats

PURPOSE

Inhibitory effect of paclitaxel on neointimal hyperplasia after open cutdown has not been elucidated.

METHODS

For the control group (n = 16), silicone 2.7-Fr catheters were placed via the right external jugular vein with the cutdown method. For the treatment group (n = 16), a mixture of 0.65 mg of paclitaxel and 1 mL of fibrin glue was infiltrated around the exposed vein after cutdown. After scheduled intervals (1, 2, 4, and 8 weeks), the vein segment was harvested and morphometric analysis was performed on cross-sections.

RESULTS

Proliferation of smooth muscle cell (SMC) was strongly suppressed in the treatment group, and the ratio of neointima to vein wall was significantly reduced in the treatment group (8 weeks; 0.63 ± 0.08 vs. 0.2 ± 0.08, P < 0.05). Luminal patency was significantly more preserved in the treatment group, and the luminal area was significantly wider in the paclitaxel-treated group compared to the control group (8 weeks; 1.91 ± 0.43 mm² vs. 5.1 ± 0.43 mm², P < 0.05). Mean SMC counts measured at 1 and 2 weeks after cutdown were significantly lower in the treatment group (2 weeks; 115 ± 22 vs. 62 ± 22). Paclitaxel was undetectable in systemic circulation (<10 ng/mL).

CONCLUSION

Sustained perivascular delivery of paclitaxel with fibrin glue was effective in inhibiting neointimal hyperplasia in rat jugular vein after open cutdown.

Phase I and Phase II Objective Response Rates are Correlated in Pediatric Cancer Trials: An Argument for Better Clinical Trial Efficiency

Although many phase I trials report tumor response, formal analysis of efficacy is deferred to phase II. We reviewed paired phase I and II pediatric oncology trials to ascertain the relationship between phase I and II objective response rate (OR%). Single-agent phase I trials were paired with corresponding phase II trials (comparable study drug, dosing schedule, and population). Phase I trials without efficacy data or a matching phase II trial were excluded. OR% was tabulated for all trials, and phase II authors' subjective conclusions regarding efficacy were documented; 35 pairs of trials were analyzed. The correlation between phase I and II OR% was 0.93. Between phase II studies with a "positive" conclusion versus a "negative" one, there was a statistically significant difference in mean phase I OR% (32.0% vs. 4.5%, P<0.001). Thirteen phase II studies were undertaken despite phase I OR% of 0%; only 1 had a "positive" conclusion, and none exceeded OR% of 15%. OR% are highly correlated between phase I and II pediatric oncology trials. Although not a formal measure of drug efficacy, phase I OR% may provide an estimate of phase II response, inform phase II study design, and should be given greater consideration.

Childhood medulloblastoma

Medulloblastoma accounts for 15-20% of childhood nervous system tumours. The risk of dying was reduced by 30% in the last twenty years. Patients are divided in risk strata according to post-surgical disease, dissemination, histology and some molecular features such as WNT subgroup and MYC status. Sixty to 70% of patients older than 3 years are assigned to the average-risk group. High-risk patients include those with disseminated and/or residual disease, large cell and/or anaplastic histotypes, MYC genes amplification. Current and currently planned clinical trials will: (1) evaluate the feasibility of reducing both the dose of craniospinal irradiation and the volume of the posterior fossa radiotherapy (RT) for those patients at low biologic risk, commonly identified as those having a medulloblastoma of the WNT subgroup; (2) determine whether intensification of chemotherapy (CT) or irradiation can improve outcome in patients with high-risk disease; (3) find target therapies allowing tailored therapies especially for relapsing patients and those with higher biological risk.

Identifying novel therapeutic agents using xenograft models of pediatric cancer

In the USA, the overall cure rate for all childhood cancers is seventy percent, and in many patients that ultimately fail curative therapy, initial responses to current multimodality treatments (surgery, radiation therapy and chemotherapy) is good, with overall 5-year event-free survival approaching 80 %. However, current approaches to curative therapy result in significant morbidity and long-term sequelae, including cardiac dysfunction and cognitive impairment. Furthermore, dose-intensive chemotherapy with conventional agents has not significantly improved outcomes for patients that present with advanced or metastatic disease. Classical cytotoxic agents remain the backbone for curative therapy of both hematologic and solid tumors of childhood. While 'molecularly' targeted agents have shown some clinical activity, responses are often modest and of short duration; hence, there is a need to identify new classes of cytotoxic agent that are effective in patients at relapse and that have reduced or different toxicity profiles to normal tissues. Here we review the pediatric preclinical testing program experience of testing novel agents, and the value and limitations of preclinical xenograft models and genetically engineered mouse models for developing novel agents for treatment of childhood cancer.

Survival After Relapse of Medulloblastoma

Survival after recurrence of medulloblastoma has not been reported in an unselected cohort of patients in the contemporary era. We reviewed 55 patients diagnosed with medulloblastoma between 2000 and 2010, and treated at Seattle Children's Hospital to evaluate patterns of relapse treatment and survival. Fourteen of 47 patients (30%) over the age of 3 experienced recurrent or progressive medulloblastoma after standard therapy. The median time from diagnosis to recurrence was 18.0 months (range, 3.6 to 62.6 mo), and site of recurrence was metastatic in 86%. The median survival after relapse was 10.3 months (range, 1.3 to 80.5 mo); 3-year survival after relapse was 18%. There were trend associations between longer survival and having received additional chemotherapy (median survival 12.8 vs. 1.3 mo, P=0.16) and radiation therapy (15.4 vs. 5.9 mo, P=0.20). Isolated local relapse was significantly associated with shorter survival (1.3 vs. 12.8 mo, P=0.009). Recurrence of medulloblastoma is more likely to be metastatic than reported in previous eras. Within the limits of our small sample, our data suggest a potential survival benefit from retreatment with cytotoxic chemotherapy and radiation even in heavily pretreated patients. This report serves as a baseline against which to evaluate novel therapy combinations.

Initial testing (stage 1) of the anti-microtubule agents cabazitaxel and docetaxel, by the pediatric preclinical testing program

BACKGROUND

Although microtubule-destabilizing agents (principally vincristine) are in common use in pediatric oncology, the microtubule-stabilizing taxanes are uncommonly used to treat childhood cancers. Cabazitaxel has been reported to have activity superior to that of docetaxel in preclinical models of multidrug-resistant adult cancers, and it was active in patients who had progressed on or after docetaxel. The PPTP conducted a comparison of these two agents against the PPTP in vitro panel and against a limited panel of solid tumor xenografts.

PROCEDURES

Cabazitaxel and docetaxel were tested against the PPTP in vitro cell line panel at concentrations from 0.01 to 0.1 μM and in vivo against a subset of the PPTP solid tumor xenograft models at a dose of 10 or 7.5 mg/kg on an every 4 days × 3 I.V. schedule.

RESULTS

In vitro, both cabazitaxel and docetaxel had similar potency (median rIC50 0.47 nM and 0.88 nM, respectively) and a similar activity profile, with Ewing sarcoma cells being significantly more sensitive to both agents. In vitro sensitivity to docetaxel inversely correlated with mRNA expression for ABCB1, but the correlation with ABCB1 expression was weaker for cabazitaxel. In vivo cabazitaxel demonstrated significantly greater activity than docetaxel in five of 12 tumor models, inducing regressions in six models compared with three models for docetaxel.

CONCLUSIONS

Cabazitaxel demonstrated superior activity compared to docetaxel. The lower cabazitaxel systemic exposure tolerated in humans compared to mice needs to be considered when extrapolating these results to the clinical setting.

Initial testing (stage 1) of the tubulin binding agent nanoparticle albumin-bound (nab) paclitaxel (Abraxane(®)) by the Pediatric Preclinical Testing Program (PPTP)

BACKGROUND

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel, Abraxane(®)) is FDA approved for the treatment of several adult cancers. Antimitotic agents are essential components for curative therapy of pediatric solid tumors, although taxanes have shown limited activity. Because of the novel formulation, nab-paclitaxel was evaluated against a limited series of Pediatric Preclinical Testing Program (PPTP) solid tumors.

PROCEDURES

Nab-paclitaxel was tested against a limited subset of PPTP solid tumor xenograft models at a dose of 50 mg/kg using a q4d × 3 schedule intravenously.

RESULTS

Nab-paclitaxel was well tolerated in vivo, producing maximum weight loss of approximately 10% with recovery to baseline weight in the week following the third dose. All 20 xenograft models tested were considered evaluable for efficacy. Nab-paclitaxel induced statistically significant differences in event-free survival (EFS) distribution compared to control in 19 of 20 (95%) of the solid tumors. Objective responses were observed in 12 of 20 (60%) solid tumor xenografts. Complete responses (CR) or maintained CR were observed in 5 of 8 Ewing sarcoma models and 6 of 8 rhabdomyosarcomas. There were no objective regressions in either neuroblastoma (n = 2) or osteosarcoma (n = 2) xenograft panels. At the dose tested, systemic exposures of nab-paclitaxel in mice were somewhat greater than those tolerated in humans.

CONCLUSIONS

The high level of activity observed against the rhabdomyosarcoma and Ewing sarcoma PPTP preclinical models makes nab-paclitaxel an interesting agent to consider for pediatric evaluation.

Initial testing (stage 1) of BAL101553, a novel tubulin binding agent, by the pediatric preclinical testing program

BAL101553 is a highly water soluble prodrug of BAL27862 that arrests tumor cell proliferation and induces cell death in cancer cells through disruption of the microtubule network. In vitro BAL27862 demonstrated potent activity, with the median relative IC50 (rIC50 ) of 13.8 nM (range 5.4-25.2 nM). The in vitro activity of BAL27862 against the PPTP cell lines is distinctive from that previously described for vincristine. BAL101553 induced significant differences in EFS distribution compared to control in 16 of 30 (53%) solid tumor xenografts and in two of four (67%) of the evaluable ALL xenografts. No objective responses were observed.

Diffuse intrinsic pontine gliomas: treatments and controversies

Diffuse intrinsic pontine gliomas (DIPGs) are a fairly common pediatric brain tumor, and children with these tumors have a dismal prognosis. They generally are diagnosed within the first decade of life, and due to their location within the pons, these tumors are not surgically resectable. The median survival for children with DIPGs is less than 1 year, in spite of decades of clinical trial development of unique approaches to radiation therapy and chemotherapy. Novel therapies are under investigation for these deadly tumors. As clinicians and researchers make a concerted effort to obtain tumor tissue, the molecular signals of these tumors are being investigated in an attempt to uncover targetable therapies for DIPGs. In addition, direct application of chemotherapies into the tumor (convection-enhanced delivery) is being investigated as a novel delivery system for treatment of DIPGs. Overall, DIPGs require creative thinking and a disciplined approach for development of a therapy that can improve the prognosis for these unfortunate children.

Preclinical profile of cabazitaxel

First-generation taxanes have changed the treatment paradigm for a wide variety of cancers, but innate or acquired resistance frequently limits their use. Cabazitaxel is a novel second-generation taxane developed to overcome such resistance. In vitro, cabazitaxel showed similar antiproliferative activity to docetaxel in taxane-sensitive cell lines and markedly greater activity in cell lines resistant to taxanes. In vivo, cabazitaxel demonstrated excellent antitumor activity in a broad spectrum of docetaxel-sensitive tumor xenografts, including a castration-resistant prostate tumor xenograft, HID28, where cabazitaxel exhibited greater efficacy than docetaxel. Importantly, cabazitaxel was also active against tumors with innate or acquired resistance to docetaxel, suggesting therapeutic potential for patients progressing following taxane treatment and those with docetaxel-refractory tumors. In patients with tumors of the central nervous system (CNS), and in patients with pediatric tumors, therapeutic success with first-generation taxanes has been limited. Cabazitaxel demonstrated greater antitumor activity than docetaxel in xenograft models of CNS disease and pediatric tumors, suggesting potential clinical utility in these special patient populations. Based on therapeutic synergism observed in an in vivo tumor model, cabazitaxel is also being investigated clinically in combination with cisplatin. Nonclinical evaluation of the safety of cabazitaxel in a range of animal species showed largely reversible changes in the bone marrow, lymphoid system, gastrointestinal tract, and male reproductive system. Preclinical safety signals of cabazitaxel were consistent with the previously reported safety profiles of paclitaxel and docetaxel. Clinical observations with cabazitaxel were consistent with preclinical results, and cabazitaxel is indicated, in combination with prednisone, for the treatment of patients with hormone-refractory metastatic prostate cancer previously treated with docetaxel. In conclusion, the demonstrated activity of cabazitaxel in tumors with innate or acquired resistance to docetaxel, CNS tumors, and pediatric tumors made this agent a candidate for further clinical evaluation in a broader range of patient populations compared with first-generation taxanes.

Nab-paclitaxel is an active drug in preclinical model of pediatric solid tumors

PURPOSE

To investigate the antitumor effect of nab-paclitaxel, an albumin-stabilized nanoparticle formulation of paclitaxel, on pediatric solid tumor models.

EXPERIMENTAL DESIGN

A panel of three rhabdomyosarcoma, one osteosarcoma and seven neuroblastoma cell lines were exposed to increasing concentrations of nab-paclitaxel in vitro. Cell viability was evaluated using the Alamar Blue Assay. Antitumor effect was further assessed in vivo in NOD/SCID xenograft and metastatic neuroblastoma mouse models. Tumor sections were analyzed by immunohistochemistry for cleaved caspase-3 and phospho-histone H3. Plasma and intratumoral paclitaxel concentrations were measured by liquid chromatography-mass spectrometry. Ratio of intratumoral and plasma concentration was compared between nab-paclitaxel and paclitaxel treatment groups.

RESULTS

Nab-paclitaxel displayed significant cytotoxicity against most pediatric solid tumor cell lines in vitro in a dose-dependent manner. In vivo, nab-paclitaxel showed antitumor activity in both rhabdomyosarcoma (RH4 and RD) and neuroblastoma [SK-N-BE(2) and CHLA-20] xenograft models. In the SK-N-BE(2) metastatic model, nab-paclitaxel treatment significantly extended animal survival compared with control (P < 0.01). Nab-paclitaxel treatment induced tumor cell-cycle arrest and apoptosis in vivo. In the RH4 model, increased local relapse-free intervals were observed with nab-paclitaxel treatment (37.7 ± 3.2 days) comparing with paclitaxel (13.6 ± 2.07 days). Local relapsed tumors following paclitaxel treatment proved to be paclitaxel-resistant and remained responsive to nab-paclitaxel. Mechanistically, a higher tumor/plasma paclitaxel drug ratio in favor of nab-paclitaxel was observed.

CONCLUSIONS

Nab-paclitaxel showed significant antitumor activity against all pediatric solid tumors associated with an enhanced drug intratumor delivery. Furthermore, testing of nab-paclitaxel in pediatric solid-tumor patient population is under development.

Can taxanes provide benefit in patients with CNS tumors and in pediatric patients with tumors? An update on the preclinical development of cabazitaxel

PURPOSE

While first-generation taxanes are valuable treatment options for many solid tumors, they are limited by an inability to cross the blood-brain barrier (BBB) and by limited efficacy in pediatric patients. Following promising preclinical data for the next-generation taxane cabazitaxel, including activity in tumor models fully sensitive, poorly sensitive or insensitive to docetaxel, and its ability to cross the BBB, further preclinical studies of cabazitaxel relevant to these two clinical indications were performed.

METHODS

Cabazitaxel brain distribution was assessed in mice, rats and dogs. Cabazitaxel antitumor activity was assessed in mice bearing intracranial human glioblastoma (SF295; U251) xenografts, and subcutaneous cell line-derived human pediatric sarcoma (rhabdomyosarcoma RH-30; Ewing's sarcoma TC-71 and SK-ES-1) or patient-derived pediatric sarcoma (osteosarcoma DM77 and DM113; Ewing's sarcoma DM101) xenografts. The activity of cabazitaxel-cisplatin combination was evaluated in BALB/C mice bearing the syngeneic murine colon adenocarcinoma, C51.

RESULTS

Cabazitaxel penetrated rapidly in the brain, with a similar brain-blood radioactivity exposure relationship across different animal species. In intracranial human glioblastoma models, cabazitaxel demonstrated superior activity to docetaxel both at early (before BBB disruption) and at advanced stages, consistent with enhanced brain penetration. Compared with similar dose levels of docetaxel, cabazitaxel induced significantly greater tumor growth inhibition across six pediatric tumor models and more tumor regressions in five of the six models. Therapeutic synergism was observed between cisplatin and cabazitaxel, regardless of administration sequence.

CONCLUSIONS

These preclinical data suggest that cabazitaxel could be an effective therapy in CNS and pediatric tumors, supporting ongoing clinical evaluation in these indications.

Progress from clinical trials and emerging non-conventional therapies for the treatment of Medulloblastomas

Medulloblastomas are highly aggressive tumors of the cerebellum with an embryonal origin. Despite current treatment modalities which include a combination of surgery, chemotherapy and/or radiation, challenges still exist to effectively treat some patients, especially those within the younger age group. In an effort to find improved therapies, ongoing research led by world-wide teams have explored non-conventional therapeutic strategies, as well as examined the efficacy of several drugs in clinical trials among patients with Medulloblastomas. We outline in this article, recent advances on the efficacy and toxicity of numerous therapeutic agents including those that are DNA damaging agents, microtubules binding compounds, and those that are inhibitors of Topoisomerase and of the Notch and Hedgehog signaling pathway, which were assessed in recent Phase I and II clinical trials. Among these clinical trials, it is unfortunate that the outcomes were dismal with the majority of the patients with Medulloblastomas still succumbing to relapse after conventional therapies. Furthermore, it is yet to be established clearly the clinical efficacy of non-conventional therapies such as immunotherapy and gene therapy. Moreover, there is growing interest in proton therapy as a potential replacement for photon therapy, while high dose chemotherapy and autologous stem cell rescue may improve therapeutic efficacies. However, further research is needed to resolve the inherent toxicity from these novel therapeutic methods. In conclusion, novel therapies based on a better understanding of the biology of Medulloblastomas are pivotal in improving non-conventional therapies in the treatment of this deadly disease.

Paclitaxel-based chemotherapy for aggressive kaposiform hemangioendothelioma of the temporomastoid region: Case report and review of the literature

BACKGROUND

Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor of infancy and childhood. This tumor results in poor prognosis, and therefore, development of a more effective treatment is needed.

METHODS AND RESULTS

We describe an 11-year-old boy presenting with left facial palsy caused by aggressive KHE of the left temporomastoid region. He was treated with paclitaxel-based chemotherapy, because of the difficulty with complete surgical resection for anatomic factor, multiple lung metastases on diagnosis, and no response to conventional treatments. This treatment reduced the volume of primary tumor and lung metastatic lesions, but the efficacy was transitory.

CONCLUSIONS

Paclitaxel-based chemotherapy for aggressive KHE may be effective, therefore the multimodality therapy including paclitaxel of aggressive KHE, particularly in the head and neck, needs to be investigated in further studies.

Childhood medulloblastoma

Among all the childhood central nervous system tumours, medulloblastoma and other neuroectodermal tumours account for 16-25% of cases. The causative factors of medulloblastoma/PNET have not been well established. It is more frequent in boys than in girl and in children than in adults. There was a significant improvement of survival for children diagnosed in 2000-2002 compared to those diagnosed in 1995-1999. The risk of dying was reduced by 30%. Patients are generally divided into risk-stratified schemes on the basis of age, the extent of residual disease, and dissemination. Sixty to 70% of patients older than 3 years are assigned to the average-risk group. High-risk patients include those in the disseminated category, and in North American trials those that have less than a gross or near-total resection, which is arbitrarily defined as 1.5 cm(2) of post-operative residual disease. Current and currently planned clinical trials will:define molecular and biological markers that improve outcome prediction in patients with medulloblastoma and which can be incorporated for front-line stratification of newly defined risk subgroups.

Phase II trial of ixabepilone administered daily for five days in children and young adults with refractory solid tumors: a report from the children's oncology group

PURPOSE

Ixabepilone is a microtubule-stabilizing agent with activity in adult solid tumors and in pediatric tumor xenograft models that are resistant to paclitaxel. The maximum tolerated dose on the daily-for-5-days i.v. schedule was 6 mg/m(2)/dose in adults and 8 mg/m(2)/dose in children, and the primary dose-limiting toxicity (DLT) was neutropenia. This study aimed to determine the response rate to ixabepilone in six solid tumor strata in children and young adults.

EXPERIMENTAL DESIGN

We conducted a phase II trial of ixabepilone (8 mg/m(2)/dose for 5 days every 21 days) using a two-stage design in taxane-naïve children and young adults with treatment-refractory, measurable rhabdomyosarcoma, Ewing sarcoma family tumors, osteosarcoma, synovial sarcoma, or malignant peripheral nerve sheath tumor, neuroblastoma, and Wilms tumor.

RESULTS

Sixty-one eligible patients (36 male) were enrolled. Median (range) age was 13 years (range, 3-36). Fifty-nine patients were fully evaluable for toxicity and response. DLTs, most commonly myelosuppression, occurred in 11 patients (15% incidence in 3-18 years old and 33% in 19-36 years old; P = 0.2) during cycle 1. The median (range) number of cycles was 2 (range, 1-38). No partial or complete responses (response evaluation criteria in solid tumors) were observed. Seven patients received >or=3 cycles, and two had prolonged stable disease (Wilms' tumor, 38 cycles; synovial sarcoma, 8 cycles).

CONCLUSIONS

Ixabepilone at 8 mg/m(2)/dose daily for 5 days was tolerable in children and adolescents, but did not show evidence of clinical activity in the childhood solid tumors studied.

Salvage chemotherapy for metastatic and recurrent ependymoma of childhood

INTRODUCTION

Chemotherapy has limited role in the up-front management of ependymoma. At the time of recurrence, the role of chemotherapy is also ill defined and the choice of chemotherapeutic agents is often arbitrary, based on anecdotal data and personal experience.

METHODS

The purpose of this review is to describe and critically analyze the published literature on chemotherapy in patients with recurrent and metastatic ependymoma.

DISCUSSION

The disappointing response rate with single agents (12.9%) and combinations (17.4%) emphasizes the need to re-evaluate the current chemotherapeutic approach of intracranial ependymoma, and biological studies are needed to identify targets that may be considered for clinical trials.

Phase I study of paclitaxel with standard dose ifosfamide in children with refractory solid tumors: a Pediatric Oncology Group study (POG 9376)

PURPOSE

A dose-escalation Phase I study of taxol (paclitaxel) administered in combination with standard dose ifosfamide was conducted in children with relapsed or refractory solid tumors. Primary objectives were to estimate the maximum tolerated dose (MTD) and to describe the dose-limiting toxicities (DLTs).

PATIENTS AND METHODS

Paclitaxel was administered as a 6-hr continuous infusion (hr 0-6), followed by intravenous ifosfamide (2 g/m(2)/day x 3 days) over 1 hr at hours 6-7, 24-25, and 48-49. Patients at dose level 1 received 250 mg/m(2) paclitaxel. Subsequent dose escalation proceeded using a standard 3 x 3 Phase I design.

RESULTS

Fifteen patients received a combined 46 courses of therapy. The median age was 14.5 years (range, 2-19 years), and diagnoses included sarcoma (7), neuroblastoma (3), and other (5). Three patients received paclitaxel at 250 mg/m(2) (10 courses), six at 325 mg/m(2) (19 courses), three at 425 mg/m(2) (8 courses), and three at 550 mg/m(2) (9 courses). DLTs occurred in 2/3 patients at 550 mg/m(2) paclitaxel during cycle 1, including grade 3 hypotension and grade 4 anaphylaxis in 1 patient each. Common non-dose-limiting toxicities included bone marrow suppression and peripheral neuropathy. Response was evaluable in 14 patients and included mixed response (3), stable disease (5), and progressive disease (6).

CONCLUSION

Paclitaxel hypersensitivity reactions were dose limiting when the drug was administered as a 6-hr infusion. The MTD and recommended Phase II dose of paclitaxel administered as a 6-hr continuous intravenous infusion followed by standard dose intravenous ifosfamide is 425 mg/m(2) paclitaxel.

Dose intensive melphalan and cyclophosphamide with autologous hematopoietic stem cells for recurrent medulloblastoma or germinoma

PURPOSE

To determine the response, toxicity, and survival for children with progressive or recurrent medulloblastoma and germinoma using a single myeloablative course of chemotherapy supported by autologous hematopoietic stem cells.

PATIENTS AND METHODS

Subjects were in second remission or had minimal residual disease at the time of study entry. The conditioning regimen consisted of cyclophosphamide 6,000 mg/m(2) plus melphalan 180 mg/m(2).

RESULTS

Twenty-nine evaluable pediatric patients were accrued. The most frequent major toxicities were myelosuppression, infections, and stomatitis, but no toxic deaths were recorded. Best responses were: CR = 6, CCR = 13, PR = 6, SD = 2, and PD = 2. There were 6 medulloblastoma and 3 germinoma survivors with a median follow-up of 7.5 years (range = 2.8-10). Two germinoma survivors received radiotherapy after autografting for presumptive progressive disease.

CONCLUSION

Myeloablative chemotherapy consisting of cyclophosphamide and melphalan was tolerable in the relapsed brain tumor setting with 19/29 cases achieving CR or CCR status and 9/29 becoming long-term survivors.

Convection enhanced delivery for treating brain tumors and selected neurological disorders: symposium review

In 2003 the Cleveland Clinic Brain Tumor Institute sponsored a symposium to mark the progress being made in what was then a new approach to treating brain tumors - convection enhanced delivery (CED) [Vogelbaum MA (2005) J NeuroOncol 73(1):57-69]. A second symposium was held in February, 2006, to review new accomplishments and identify promising avenues of research in this evolving but still novel therapy. Among the general subjects covered by a host of international experts in their respective fields were advances in CED technology, new clinical applications of the technology, advances in CED-related imaging procedures, reviews of current or proposed trials, new drugs and the status of projects moving from lab to clinical practice. Specific subjects included the design of new catheters, the development of mathematic models for planning, novel therapeutics for CED treatment of stroke, spinal cord degenerative disease and epilepsy, liposome-based agents administered via CED, ultra-sound driven CED, monitoring the in vivo effects of intratumoral paclitaxel and other topics. Each speaker's presentation has been abstracted along with relevant references.

Ependymomas

Optimal management of ependymomas includes surgical resection and evaluation of the extent of central nervous system involvement using cerebrospinal fluid cytology and craniospinal contrast-enhanced MRI. In instances of measurable residual disease, reoperation should be considered because survival of patients with ependymomas is significantly improved by performance of a complete resection. In patients not considered for further surgery and with residual disease, limited-field radiotherapy is usually administered. The role of craniospinal irradiation in patients with local disease and no evidence of metastasis is controversial because most tumor recurrences are local and at the site of the primary tumor. No clear role for adjuvant chemotherapy has been demonstrated. When used, chemotherapy for ependymomas has been administered primarily to children aged younger than 3 years as adjuvant therapy and to patients with recurrent disease who are not considered surgical candidates as salvage therapy. Recurrent ependymomas are managed by reoperation of tumors that are surgically accessible, by radiotherapy if not previously administered, and by salvage chemotherapy. The role of stereotactic radiotherapy administered as radiosurgery or brachytherapy is unclear because all reports are anecdotal. Because salvage chemotherapy is not curative, no standard therapy exists, and a variety of chemotherapy agents and drug schedules have been investigated.

Taxanes in paediatric oncology: And now?

Taxanes are a group of anticancer agents that target microtubules, promote their assembly, and stabilize them. The resulting effects are mitotic blockage and induction of apoptosis, whose mechanism of initiation remains to be fully determined. Among adults, taxanes are one of the most powerful and most commonly used anticancer drugs. They show a wide range of activity in malignancies such as breast, ovarian, and lung cancers. In paediatric oncology, pre-clinical and clinical data are quite limited. Six phase I studies, two phase II, and rare case reports have been published. This review will focus on the paediatric pre-clinical and clinical findings with taxanes. Based on data from the literature, we will try to explain the results and foresee the possible use of taxanes in paediatric oncology. Indeed, three main advances have been made regarding taxanes: (1) Increased efficacy when used in multidrug-based chemotherapy regimen. (2) New administration schedules based on anti-angiogenic properties when given at daily very low doses. (3) Development of new taxanes with decreased recognition by Pgp, the product of the MDR1 gene. Thus, although the initial experience with taxanes in paediatric oncology has been disappointing, it may be too early to leave out taxanes and we should further investigate their use among children with cancer.

Efficacy of vincristine and etoposide with escalating cyclophosphamide in poor-prognosis pediatric brain tumors

The objective of this study was to assess the efficacy of the VETOPEC regimen, a regimen of vincristine and etoposide with escalating doses of cyclophosphamide (CPA), in pediatric patients with high-risk brain tumors. Three consecutive studies by the Australia and New Zealand Children's Cancer Study Group--VETOPEC I, Baby Brain 91, and VETOPEC II--have used a specific chemotherapy regimen of vincristine (VCR), etoposide (VP-16) and escalating CPA in patients with relapsed, refractory, or high-risk solid tumors. Patients in the VETOPEC II cohort were treated with very high dose CPA with peripheral blood stem cell (PBSC) rescue. We analyzed the subset of patients with high-risk brain tumors treated with these intensive VETOPEC-based protocols to assess the response, toxicity, and survival. We also assessed whether the use of very high dose chemotherapy with stem cell rescue improved the response rate or affected toxicity. Seventy-one brain tumor patients were treated with VETOPEC-based protocols. Of the 54 patients evaluable for tumor response, 17 had a complete response (CR) and 20 a partial response (PR) to treatment, which yielded an overall response rate of 69%. The CR + PR was 83% (19/23) for medulloblastomas, 56% (5/9) for primitive neuroectodermal tumors, 55% (6/11) for grade 3 and 4 astrocytomas, and 80% (6/8) for ependymomas. At a median follow-up of 36 months, overall survival for the entire cohort of 71 patients was 32%, with event-free survival of 13%. There were no toxic deaths within the PBSC-supported VETOPEC II cohort, despite higher CPA doses, compared with 7% among the non-PBSC patients. This regimen produces high response rates in a variety of very poor prognosis pediatric brain tumors. The maximum tolerated dose of CPA was not reached. Higher escalation in doses of CPA did not deliver a further improvement in response. With PBSC rescue in the VETOPEC II study, hematologic toxicity was no longer a limiting factor. The response rates observed support further development of this chemotherapy regimen.

In vivo evaluation of ixabepilone (BMS247550), a novel epothilone B derivative, against pediatric cancer models

PURPOSE

Vinca alkaloids, agents that cause depolymerization of microtubules, are highly active in treatment of many pediatric cancers. In contrast, taxanes, agents that stabilize microtubules, are far less effective against the same cancer types. The purpose of the current study was to evaluate the antitumor activity of ixabepilone, an epothilone B derivative representing a new class of microtubule-stabilizing antimitotic agent in a wide variety of pediatric solid tumor models.

EXPERIMENTAL DESIGN

Ixabepilone was administered i.v. every 4 days for three doses to scid mice bearing s.c. human rhabdomyosarcoma (three lines), neuroblastoma (four), Wilms' tumors (six), osteosarcoma (four), or brain tumors (seven). Tumor diameters were measured weekly, and tumor growth or regressions were determined. Pharmacokinetic studies were done following a single administration of drug at the maximum tolerated dose (MTD) level (10 mg/kg).

RESULTS

At the MTD (10 mg/kg), ixabepilone induced objective responses (all tumors in a group achieved > or = 50% volume regression) in three of three rhabdomyosarcoma lines, three of five neuroblastomas, six of seven Wilms' tumor models, two of six osteosarcoma, and four of eight brain tumor models. However, the dose-response curve was steep with only 2 of 19 tumors models regressing (> or = 50%) at 4.4 mg/kg. In comparison, paclitaxel administered at the MTD on the same schedule failed to induce objective regressions of three tumor lines that were highly sensitive to treatment with ixabepilone. Pharmacokinetics following single i.v. administration of ixabepilone at its MTD (10 mg/kg) were biexponential with C(max) of 12.5 micromol/L, elimination half-life of 19.2 hours, and total area under the curve of 5.8 micromol/L-h. The achieved drug exposure of ixabepilone at this efficacious MTD dose level in mice is similar to those achieved in patients given the recommended phase II dose of 40 mg/m2 by either 1- or 3-hour infusion every 3 weeks, a regimen that has shown significant anticancer activity in phase II clinical trials in adult patients.

CONCLUSIONS

Administered at doses ranging from 66% to 100% of its MTD in mice, the epothilone B derivative ixabepilone shows broad spectrum activity against a panel of pediatric tumor xenograft models. Pharmacokinetic analysis indicates that the systemic ixabepilone exposure achieved in mice at its MTD is similar to that achieved in patients at the recommended phase II dose of 40 mg/m2 administered every 3 weeks. Importantly, the present results showed a clear distinction in sensitivity of pediatric solid tumors to this epothilone derivative compared with paclitaxel.

Intracavitary chemotherapy (paclitaxel/carboplatin liquid crystalline cubic phases) for recurrent glioblastoma -- clinical observations

Human malignant brain tumors have a poor prognosis in spite of surgery and radiation therapy. Cubic phases consist of curved biocontinuous lipid bilayers, separating two congruent networks of water channels. Used as a host for cytotoxic drugs, the gel-like matrix can easily be applied to the walls of a surgical resection cavity. For human glioblastoma recurrences, the feasibility, safety, and short-term effects of a surgical intracavitary application of paclitaxel and carboplatin encapsulated by liquid crystalline cubic phases are examined in a pilot study. A total of 12 patients with a recurrence of a glioblastoma multiforme underwent re-resection and received an intracavitary application of paclitaxel and carboplatin cubic phases in different dosages. Six of the patients received more than 15 mg paclitaxel and suffered from moderate to severe brain edema, while the remaining patients received only a total of 15 mg paclitaxel. In the latter group, brain edema was markedly reduced and dealt medically. Intracavitary chemotherapy in recurrent glioblastoma using cubic phases is feasible and safe, yet the clinical benefit remains to be examined in a clinical phase II study.

Local chemotherapy of F98 rat glioblastoma with paclitaxel and carboplatin embedded in liquid crystalline cubic phases

Implanted drug carrier systems for retarded chemotherapy against gliomas are mainly based upon polymers containing nitrosoureas. The authors have developed an intracavitary carrier system of biodegradable liquid crystalline cubic phases encapsulating carboplatin and paclitaxel and studied it for release kinetics, antitumor activity, and survival prolongation. A total of 61 Fisher rats with F98 tumors were divided into six treatment groups at day 12 post-inoculation, receiving either no treatment, surgery with partial tumor resection, or partial resection with implantation of cubic phases containing either paclitaxel and carboplatin, paclitaxel alone, carboplatin alone, or no drug. Animals were killed for tumor size analysis at day 21 post-inoculation (n=28) or were included in survival studies (n=33). Additional 12 animals received a paclitaxel/carboplatin application and were killed at different time intervals (6 h, 24 h, 48 h, 5 d, 7 d, 10 d post-agent application) for in vivo diffusion studies. Animals from the paclitaxel/carboplatin group showed a significantly smaller tumor (mean 3.25 mm2+/-SD 1.79 mm2) than animals from the control group (15.30+/-5.86 mm2; P=0.0031), animals having received the empty matrix (11.62+/-6.66 mm2; P=0.0241), and animals after tumor resection without implantation (20.87+/-3.56 mm2; P<or=0.0001). There was no significant difference in survival. Carboplatin was found in brain tissue at 6 h, paclitaxel was found at up to 48 h after implantation at 3 mm distance. Biodegradable crystalline cubic phases embedding cytotoxic drugs as paclitaxel and carboplatin might play an important role in local glioblastoma treatment.

Second-line chemotherapy with the association of liposomal daunorubicin, carboplatin and etoposide in children with recurrent malignant brain tumors

Progressive or recurrent high-grade gliomas are characterized by a very poor prognosis, and the relevance of second-line chemotherapy is still unassessed. Although it has been reported that liposomal anthracyclines and carboplatin show some activity in these patients, their association has never been investigated. We have treated six children with recurrent high-grade glioma after surgery, radiotherapy and chemotherapy, and one child with progressive teratoid/rhabdoid tumor with the combination of liposomal daunorubicin and carboplatin plus etoposide. Five out of seven children showed a major response and the 29 month progression-free survival was 38%. The above regimen was feasible and children showed only little and transient hematological toxicity. In our opinion, these results justify further investigation of the above combination chemotherapy for recurrent or progressive malignant brain tumors in children.

Reversal of P-glycoprotein-mediated paclitaxel resistance by new synthetic isoprenoids in human bladder cancer cell line

We isolated a paclitaxel-resistant cell line (KK47/TX30) from a human bladder cancer cell line (KK47/WT) in order to investigate the mechanism of and reversal agents for paclitaxel resistance. KK47/TX30 cells exhibited 700-fold resistance to paclitaxel and cross-resistance to vinca alkaloids and topoisomerase II inhibitors. Tubulin polymerization assay showed no significant difference in the ratio of polymerized alpha- and beta-tubulin between KK47/WT and KK47/TX30 cells. Western blot analysis demonstrated overexpression of P-glycoprotein (P-gp) and lung resistance-related protein (LRP) in KK47/TX30 cells. Drug accumulation and efflux studies showed that the decreased paclitaxel accumulation in KK47/TX30 cells was due to enhanced paclitaxel efflux. Cell survival assay revealed that verapamil and cepharanthine, conventional P-gp modulators, could completely overcome paclitaxel resistance. To investigate whether new synthetic isoprenoids could overcome paclitaxel resistance, we synthesized 31 isoprenoids based on the structure of N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine (SDB), which could reverse multidrug resistance (MDR), as shown previously. Among those examined, trans-N,N'-bis(3,4-dimethoxybenzyl)-N-solanesyl-1,2-diaminocyclohexane (N-5228) could completely reverse paclitaxel resistance in KK47/TX30 cells. N-5228 inhibited photoaffinity labeling of P-gp by [(3)H]azidopine, suggesting that N-5228 could bind to P-gp directly and could be a substrate of P-gp. Next, we investigated structural features of these 31 isoprenoids in order to determine the structural requirements for the reversal of P-gp-mediated paclitaxel resistance, suggesting that the following structural features are important for overcoming paclitaxel resistance: (1) a basic structure of 8 to 10 isoprene units, (2) a cyclohexane ring or benzene ring within the framework, (3) two cationic sites in close proximity to each other, and (4) a benzyl group with 3,4-dimethoxy functionalities, which have moderate electron-donating ability. These findings may provide valuable information for the development of P-gp-mediated MDR-reversing agents.

Primitive neuroectodermal tumors/medulloblastoma

The therapy for medulloblastoma/primitive neuroectodermal tumors of the central nervous system is surgery, followed by combination chemo-radiotherapy. The radiation field is the entire craniospinal axis, which is only avoided when treating infants. The treatment is, therefore, lengthy and toxic. Less aggressive therapy is given to patients who clinically appear to have less evidence of disease. Intensive basic research has begun to identify genetic factors of the disease, but these remain far from clinical application.

Carboplatin before and during radiation therapy for the treatment of malignant brain stem tumours: a study by the Société Française d'Oncologie Pédiatrique

Childhood malignant brain stem tumours have a very poor prognosis with a median survival of 9 months despite radiotherapy. No chemotherapy has improved survival. However, carboplatin has been reported to have activity in glial tumours as well as antitumour synergy with radiation. Our aims were to test the response rate of these tumours to carboplatin alone and to evaluate the efficacy on survival of carboplatin alone followed by concurrent carboplatin and radiotherapy. Patients younger than 16 years with typical clinical and radiological presentation of infiltrating brain stem tumour, as well as histologically-documented cases in the atypical forms, were eligible. Two courses of carboplatin (1050 mg/m2 over 3 days) were administered initially. This treatment was followed by a chemoradiotherapy phase including five weekly carboplatin courses (200 mg/m2) and conventional radiotherapy. 38 eligible patients were included. No tumour response was observed after the initial phase. This schedule of first-line carboplatin followed by concurrent carboplatin and radiotherapy did not improve survival.