EPCT-01. Pediatric Brain Tumor Consortium (PBTC)-055: A phase I study of trametinib and hydroxychloroquine (HCQ) for BRAF-fusion or Neurofibromatosis type-1 (NF1)-associated pediatric gliomas

INTRODUCTION: Autophagy is a highly conserved process by which intracellular components are degraded and recycled promoting cell survival. Preclinically, autophagy has been implicated as a resistance mechanism in BRAF-mutant glioma cells treated with MAPK-pathway inhibitors. HCQ, an oral autophagy inhibitor, has been evaluated preclinically and clinically to overcome resistance. METHODS: PBTC-055 (NCT04201457) is a phase I/II trial of HCQ combined with trametinib (BRAF-fusion or NF1-associated gliomas) or trametinib and dabrafenib (BRAFV600E gliomas) in patients < 30 years with progressive glioma. Prior treatment with RAF and/or MEK inhibitor with sub-optimal response (no response or response followed by progression on therapy) was required. Here, we present phase I data combining trametinib with HCQ utilizing a rolling-6 design. HCQ was administered at escalating dose levels (8, 15, or 20 mg/kg/day divided BID) in combination with standard pediatric trametinib dosing. All patients received prior MEK inhibitor therapy; 5/18 (28%) exhibited no response and 13/18 (72%) progressed on active therapy. RESULTS: Eighteen eligible/evaluable subjects were enrolled. Median age was 9.6 years (2.5-20.4 years); 10 were male. There were 2 dose-limiting toxicities (both grade 3 rash one each at DL1 and DL3). The highest dose level of HCQ (20 mg/kg/day divided BID) was declared the RP2D. Grade 3 adverse events possibly related to therapy included skin infection, rash, cardiac ejection fraction decrease, weight loss, and anorexia. There were no grade 4 or 5 attributable toxicities. Preliminarily, combination pharmacokinetic assessment revealed similar metabolism of trametinib to that reported as a single agent; HCQ demonstrated more rapid clearance compared to adults. Pharmacodynamic assessments are ongoing. CONCLUSIONS: The combination of trametinib and HCQ is safe with a RP2D of HCQ of 20 mg/kg/day divided BID. Currently, subjects are enrolling on the phase II portion evaluating the efficacy of this novel combination.

MBCL-16. EFFICACY OF CARBOPLATIN GIVEN CONCOMITANTLY WITH RADIATION AND ISOTRETINOIN AS A PRO-APOPTOTIC AGENT IN MAINTENANCE THERAPY IN HIGH-RISK MEDULLOBLASTOMA: A REPORT FROM THE CHILDREN’S ONCOLOGY GROUP

BACKGROUND

Metastasis, residual disease, and diffuse anaplasia are high-risk features in medulloblastoma.

METHODS

This was a randomized phase 3 study. Patients age 3–21 years with high-risk medulloblastoma received (+/-) daily carboplatin with 36Gy craniospinal radiation and weekly Vincristine followed by six cycles of maintenance chemotherapy with Cisplatin, Cyclophosphamide and Vincristine (+/) 12 cycles of isotretinoin during and following maintenance. The primary endpoint was event-free survival, with exact log-rank test to compare arms. Retrospective molecular analysis included DNA methylation and exome sequencing.

RESULTS

Of 294 medulloblastoma patients enrolled, 261 were eligible by central review of radiology and pathology, median age 8.6 years (range 3.3–21.2), 70% male, 189 (72%) with metastatic disease, 58 (22%) with diffuse anaplasia, 14 (5%) with >1.5cm2 residual disease. The 5-year EFS and OS for all subjects was 63%+4 and 73%+3, respectively. Isotretinoin randomization was closed due to futility. 5-year EFS was 66 + 5 with carboplatin versus 59 + 5 without (p=0.11), with effect exclusively observed in Group 3 subtype: 73%+8 with carboplatin versus 54%+9 without (p<0.05). Overall survival differed by molecular subgroup (p=0.006): WNT 100%, SHH 54%+11, Group 3 74%+6, Group 4 77%+5 at 5 years. MYC amplification or isochromosome 17 were unfavorable in Group 3 (p=0.029). Chromosome 11 loss or chromosome 17 gain were favorable in group 4 (p<0.001). No survival difference was observed with TP53 mutation in SHH subtype in this high-risk cohort.

CONCLUSIONS

Therapy intensification with carboplatin improved survival for high-risk group 3 medulloblastoma. These findings further support an integrated clinical and molecular risk stratification for medulloblastoma.

MBCL-15. IMPACT OF MOLECULAR SUBGROUPS ON OUTCOMES FOLLOWING RADIATION TREATMENT RANDOMIZATIONS FOR AVERAGE RISK MEDULLOBLASTOMA: A PLANNED ANALYSIS OF CHILDREN’S ONCOLOGY GROUP (COG) ACNS0331

The COG conducted a randomized trial for average-risk medulloblastoma (AR-MB). Patients age 3–21 years were randomized to a radiation boost to the whole posterior fossa (PFRT) or an involved field volume (IFRT) after receiving CSI. Patients age 3–7 years were also randomized to standard dose CSI (23.4Gy, SDCSI) or low dose CSI (18Gy, LDCSI). 464 evaluable patients were available to compare PFRT vs. IFRT and 226 for SDCSI vs. LDCSI. 380 cases had sufficient tissue for DNA methylation-based molecular classification: 362 confirmed medulloblastoma; 6 non-medulloblastoma; 12 inconclusive. Molecular subgrouping confirmed the following representation amongst the evaluable cohort: 156 Group 4 (43.1%), 76 Group 3 (21.0%), 66 SHH (18.2%), 64 WNT (17.7%). Five-year event-free survival (EFS) estimates were 82.5±2.7% and 80.5±2.7% for IFRT and PFRT, respectively (p=0.44). Five-year EFS estimates were 71.4±4.4% and 82.9±3.7% for LDCSI and SDCSI, respectively (p=0.028). EFS distributions differed significantly by subgroup (p<0.0001). Group 3 had the worst outcome, while WNT had the best outcome. There was a significant difference in EFS by RT group among SHH patients; SHH patients receiving IFRT arm had better EFS compared to PFRT (p=0.018). There was a significant difference in EFS distributions by CSI group in Group 4 patients; young Group 4 patients treated with SDCSI had better EFS compared to LDCSI (p=0.047). As previously reported, IFRT is noninferior to PFRT in all patients with AR-MB but LDCSI is worse than SDCSI in younger children. Significant differences in outcome by study randomization and molecular subgroup are observed.

Advanced ADC Histogram, Perfusion, and Permeability Metrics Show an Association with Survival and Pseudoprogression in Newly Diagnosed Diffuse Intrinsic Pontine Glioma: A Report from the Pediatric Brain Tumor Consortium

BACKGROUND AND PURPOSE

Diffuse intrinsic pontine glioma is a lethal childhood brain cancer with dismal prognosis and MR imaging is the primary methodology used for diagnosis and monitoring. Our aim was to determine whether advanced diffusion, perfusion, and permeability MR imaging metrics predict survival and pseudoprogression in children with newly diagnosed diffuse intrinsic pontine glioma.

MATERIALS AND METHODS

A clinical trial using the poly (adenosine diphosphate ribose) polymerase (PARP) inhibitor veliparib concurrently with radiation therapy, followed by maintenance therapy with veliparib + temozolomide, in children with diffuse intrinsic pontine glioma was conducted by the Pediatric Brain Tumor Consortium. Standard MR imaging, DWI, dynamic contrast-enhanced perfusion, and DSC perfusion were performed at baseline and approximately every 2 months throughout treatment. ADC histogram metrics of T2-weighted FLAIR and enhancing tumor volume, dynamic contrast-enhanced permeability metrics for enhancing tumors, and tumor relative CBV from DSC perfusion MR imaging were calculated. Baseline values, post-radiation therapy changes, and longitudinal trends for all metrics were evaluated for associations with survival and pseudoprogression.

RESULTS

Fifty children were evaluable for survival analyses. Higher baseline relative CBV was associated with shorter progression-free survival (P = .02, Q = 0.089) and overall survival (P = .006, Q = 0.055). Associations of higher baseline mean transfer constant from the blood plasma into the extravascular extracellular space with shorter progression-free survival (P = .03, Q = 0.105) and overall survival (P = .03, Q = 0.102) trended toward significance. An increase in relative CBV with time was associated with shorter progression-free survival (P < .001, Q < 0.001) and overall survival (P = .004, Q = 0.043). Associations of longitudinal mean extravascular extracellular volume fraction with progression-free survival (P = .03, Q = 0.104) and overall survival (P = .03, Q = 0.105) and maximum transfer constant from the blood plasma into the extravascular extracellular space with progression-free survival (P = .03, Q = 0.102) trended toward significance. Greater increases with time were associated with worse outcomes. True radiologic progression showed greater post-radiation therapy decreases in mode_ADC_FLAIR compared with pseudoprogression (means, -268.15 versus -26.11, P = .01.) CONCLUSIONS: ADC histogram, perfusion, and permeability MR imaging metrics in diffuse intrinsic pontine glioma are useful in predicting survival and pseudoprogression.

MRI Features of Histologically Diagnosed Supratentorial Primitive Neuroectodermal Tumors and Pineoblastomas in Correlation with Molecular Diagnoses and Outcomes: A Report from the Children's Oncology Group ACNS0332 Trial

BACKGROUND AND PURPOSE

Supratentorial primitive neuroectodermal tumors and pineoblastomas have traditionally been grouped together for treatment purposes. Molecular profiling of these tumors has revealed a number of distinct entities and has led to the term "CNS-primitive neuroectodermal tumors" being removed from the 2016 World Health Organization classification. The purpose of this study was to describe the MR imaging findings of histologically diagnosed primitive neuroectodermal tumors and pineoblastomas and correlate them with molecular diagnoses and outcomes.

MATERIALS AND METHODS

Histologically diagnosed primitive neuroectodermal tumors and pineoblastomas were enrolled in this Children's Oncology Group Phase III trial, and molecular classification was retrospectively completed using DNA methylation profiling. MR imaging features were systematically studied and correlated with molecular diagnoses and survival.

RESULTS

Of the 85 patients enrolled, 56 met the inclusion criteria, in whom 28 tumors were in pineal and 28 in nonpineal locations. Methylation profiling revealed a variety of diagnoses, including pineoblastomas (n = 27), high-grade gliomas (n = 17), embryonal tumors (n = 7), atypical teratoid/rhabdoid tumors (n = 3), and ependymomas (n = 2). Thus, 39% overall and 71% of nonpineal tumor diagnoses were discrepant with histopathology. Tumor location, size, margins, and edema were predictors of embryonal-versus-nonembryonal tumors. Larger size and ill-defined margins correlated with poor event-free survival, while metastatic disease by MR imaging did not.

CONCLUSIONS

In nonpineal locations, only a minority of histologically diagnosed primitive neuroectodermal tumors are embryonal tumors; therefore, high-grade glioma or ependymoma should be high on the radiographic differential. An understanding of molecularly defined tumor entities and their relative frequencies and locations will help the radiologist make more accurate predictions of the tumor types.

Extensive Molecular and Clinical Heterogeneity in Patients With Histologically Diagnosed CNS-PNET Treated as a Single Entity: A Report From the Children's Oncology Group Randomized ACNS0332 Trial

PURPOSE

Children with histologically diagnosed high-risk medulloblastoma, supratentorial primitive neuroectodermal tumor of the CNS (CNS-PNET), and pineoblastoma (PBL) have had poor survival despite intensive treatment. We included these patients in this Children's Oncology Group trial. Molecular profiling later revealed tumor heterogeneity that was not detectable at protocol inception. Enrollment of patients with CNS-PNET/PBL was subsequently discontinued, and outcomes for this part of the study are reported here.

PATIENTS AND METHODS

In this phase III, four-arm prospective trial, consenting children age 3-22 years with newly diagnosed CNS-PNET were randomly assigned (1:1) to receive carboplatin during radiation and/or adjuvant isotretinoin after standard intensive therapy. Primary outcome measure was event-free survival (EFS) in the intent-to-treat population. Molecular tumor classification was retrospectively completed using DNA methylation profiling.

RESULTS

Eighty-five participants with institutionally diagnosed CNS-PNETs/PBLs were enrolled. Of 60 patients with sufficient tissue, 31 were nonpineal in location, of which 22 (71%) represented tumors that were not intended for trial inclusion, including 18 high-grade gliomas (HGGs), two atypical teratoid rhabdoid tumors, and two ependymomas. Outcomes across tumor types were strikingly different. Patients with supratentorial embryonal tumors/PBLs exhibited 5-year EFS and overall survival of 62.8% (95% CI, 43.4% to 82.2%) and 78.5% (95% CI, 62.2% to 94.8%), respectively, whereas patients with molecularly classified HGG had EFS and overall survival of 5.6% (95% CI, 0% to 13.0%) and 12.0% (95% CI, 0% to 24.7%), respectively. Neither carboplatin, nor isotretinoin significantly altered outcomes for all patients. Survival for patients with HGG was similar to that of historic studies that avoid craniospinal irradiation and intensive chemotherapy.

CONCLUSION

For patients with CNS-PNET/PBL, prognosis is considerably better than previously assumed when molecularly confirmed HGGs are removed. Identification of molecular HGGs may spare affected children from unhelpful intensive treatment. This trial highlights the challenges of a histology-based diagnosis for pediatric brain tumors and indicates that molecular profiling should become a standard component of initial diagnosis.

Neurologic impairments from pediatric low-grade glioma by tumor location and timing of diagnosis

BACKGROUND

The neurologic outcomes of low-grade gliomas (LGGs) according to tumor location and duration of presenting symptoms remain poorly characterized in children.

PROCEDURE

We retrospectively reviewed neurologic impairments in 246 pediatric patients with LGGs (88 with optic pathway and midline tumors, 56 with posterior fossa tumors, 52 with cerebral hemisphere tumors, 35 with brainstem tumors, and 15 with spinal cord tumors) who were treated at St. Jude Children's Research Hospital between 1995 and 2005. We compared neurologic impairments (defined by Common Terminology Criteria for Adverse Events, version 4.03) by tumor location and prediagnosis symptom interval (PSI) (≥ 3 months or < 3 months) at first and last patient visits.

RESULTS

The median age of diagnosis was 7.1 years; median PSI was 2.1 months; and median time to last follow-up was 11.6 years. LGGs in the cerebral hemispheres resulted in significantly fewer neurologic impairments, compared with that of other locations at baseline (P < 0.001) and at last follow-up (P < 0.001). In all patients, PSIs greater than 3 months resulted in a significantly higher incidence of ataxia and dysmetria at last follow-up (42%, P = 0.003). Greater PSI was also significantly associated with worsening lower extremity motor weakness from cerebral hemisphere tumors; dysmetria from optic pathway and midline tumors; eye and visual dysfunction from posterior fossa tumors; and ear and vestibular disturbances from brainstem tumors (P ≤ 0.05).

CONCLUSION

Neurologic impairment in pediatric LGGs varies by tumor location, and PSIs greater than 3 months affect some functionally important neurologic outcomes.

Abstract 1617: Analysis of single mouse tumor response results from the Pediatric Preclinical Testing Program (PPTP)

Traditional approaches to evaluating antitumor agents using human tumor xenograft models have usually used 8-10 mice in control and treatment groups against a limited panel of tumor models. However, with increasing evidence of molecular/genetic subsets of tumors within a histotype, there is a need to establish panels of tumors that accurately reflect such heterogeneity. The consequences of evaluating agents in a large number of models is that it is highly resource consuming. An alternative approach is to use fewer animals per tumor line, allowing a greater number of models to be evaluated that capture greater molecular/genetic heterogeneity of the cancer type.

We analyzed 67 agents evaluated by the PPTP to determine whether a single mouse, chosen by a random number generating routine in Excel, predicted the median response for groups of mice (solid tumors n = 10; acute lymphoblastic leukemias n = 8). Agents evaluated included standard cytotoxic agents, tyrosine kinase inhibitors, receptor-binding antibodies, and anti-angiogenic agents. Data were analyzed to determine predictive value for 79 xenograft models, and to identify classes of antitumor agent where predictive value of single mouse experiments was poor.

The individual tumor response was compared to the group median response using response criteria developed in the PPTP. A total of 2106 comparisons were made. The single tumor response accurately predicted the group median response in 1684 comparisons (79.34%). Models had a range for accurate prediction (0.583 - 0.918). Allowing for mis-prediction of + or - one response category, the overall prediction rate increased to 95.63%. Single tumor results accurately predicted objective response rates (ORR) determined by group response, in 66 of 67 studies. There was a single study where single mouse data incorrectly predicted an agent as ‘active’ (&gt;20% ORR).

For most tumor models the single mouse appears to give results similar to groups of 8-10 mice. Importantly, even allowing for slight inaccuracy (± 1 response category), the single mouse experiment identified all active agents, and in the worse case over-predicted activity in one tumor histotype. The advantage of the single mouse experimental design is that it allows for inclusion of models that encompass greater molecular heterogeneity, thus recapitulating the clinical heterogeneity more accurately. Potentially, this design also reduces the numbers of mice used for experimentation. However, to generate these patient derived xenograft models, particularly solid tumors at diagnosis and relapse will require national and international coordination through organizations such as the Children's Oncology Group.

Citation Format: Brendan Murphy, Han Yin, John M. Maris, Anders E. Kolb, Richard Gorlick, Patrick C. Reynolds, Min Kang, Stephen T. Keir, Raushan Kurmasheva, Igor Dvorchik, Jianrong Wu, Catherine Billups, Malcolm A. Smith, Peter J. Houghton. Analysis of single mouse tumor response results from the Pediatric Preclinical Testing Program (PPTP). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1617. doi:10.1158/1538-7445.AM2015-1617

Delayed diagnosis of childhood low-grade glioma: causes, consequences, and potential solutions

PURPOSE

Diagnosis of childhood brain tumors is delayed more than diagnosis of other pediatric cancers. However, the contribution of the most common pediatric brain tumors, lowgrade gliomas (LGG), to this delay has never been investigated.

METHODS

We retrospectively reviewed cases of childhood LGG diagnosed from January 1995 through December 2005 at our institution. The pre-diagnosis symptom interval (PSI) was conservatively calculated, and its association with race, sex, age, tumor site, tumor grade, and outcome measures (survival, disease progression, shunt use, seizures, extent of resection) was analyzed. Cases of neurofibromatosis type 1 were reported separately.

RESULTS

The 258 children had a median follow-up of 11.1 years, and 226 (88 %) remained alive. Greater pre-diagnosis symptom interval (PSI) was significantly associated with grade I (vs. grade II) tumors (p = 0.03) and age >10 years at diagnosis (p = 0.03). Half of the 16 spinal tumors had a PSI > 6 months. PSI was significantly associated with progression (p = 0.02) in grade I tumors (n = 195) and in grade I tumors outside the posterior fossa (n = 134, p = 0.03). Among children with grade I tumors, median PSI was longer in those who had seizures (10.3 months) than in those who did not (2.5 months) (p = 0.09).

CONCLUSIONS

Delayed diagnosis of childhood LGG allows tumor progression. To reduce time to diagnosis, medical curricula should emphasize inclusion of LGG in the differential diagnosis of CNS neoplasm.

Abstract 3969: Pediatric preclinical testing program (PPTP) evaluation of BMN 673, an inhibitor of poly-adp ribose polymerase (PARP), with temozolomide (TMZ)

Introduction: BMN 673 is a potent and selective inhibitor of PARP1/2. Inhibitors of PARP such as BMN 673 show clinical activity against cancers lacking homologous repair through mutations in BRCA1 and 2. PARP inhibitors are of particular interest for Ewing sarcoma (ES) given reports of ES cell lines being preferentially sensitive to PARP inhibitors. However, BMN 673 and other PARP inhibitors have shown limited single agent activity against Ewing sarcoma xenografts.

Methods: BMN 673 (10 nM) was evaluated in combination with TMZ and topotecan against the 23 cell lines of the PPTP in vitro panel using 96 hour exposure. For in vivo combination studies, two dose levels of BMN 673 (0.25 & 0.1 mg/kg BID x 5 days) given with TMZ [12 & 30 mg/kg/day x 5 days, respectively] were evaluated against ES xenografts. The combination regimen using the lower dose (LD) of TMZ and higher dose of BMN 673 was studied against other histotypes. Standard PPTP measures of in vivo antitumor activity were employed to assess response.

Results: BMN 673 markedly potentiated TMZ activity in vitro, with the TMZ rIC50 reduced by a median of 10-fold for PPTP cell lines, with ES cell lines showing a median 50-fold reduction. BMN 673 potentiated topotecan to a lesser degree (median 2.8-fold reduction in rIC50), with no differential sensitivity by histotype.

In vivo, 10 ES xenografts showed little or no response to 5 days of treatment with single agent TMZ (30 mg/kg) or BMN 673 (0.25 mg/kg BID), but 8 of 10 showed complete responses (CR) or maintained CR (MCR) to BMN 673 and TMZ (LD), and 5 of 10 showed CR or MCR to BMN 673 and higher-dose TMZ. The 10 ES xenografts could be separated into 2 groups based on duration of response to the combinations, with 5 showing delayed growth or brief objective responses (median time to event ≤ 30 days), and with the other 5 showing prolonged time to regrowth (median &gt; 77 days). Among 5 neuroblastoma xenografts, all showed significant treatment effects to BMN 673 plus TMZ(LD), with 1 achieving CR. Among 4 osteosarcoma xenografts, each showed significant tumor growth delay, but no objective responses were noted. Among 3 glioblastoma xenografts, 2 of 3 achieved maintained CRs (MCR) to the BMN 673 plus TMZ(LD) combination. Excessive toxicity was observed for ALL xenografts in NOD-SCID mice treated with the combination.

Conclusions: While BMN 673 shows limited single agent activity against PPTP solid tumor and ALL models with responses limited to models also highly sensitive to cisplatin, the BMN 673 plus TMZ(LD) combination shows dramatic activity for a subset of Ewing sarcoma xenografts and for selected additional models. Based on these results a pediatric phase 1 trial of BMN 673 plus TMZ with a phase 2 expansion for Ewing sarcoma is proceeding. Efforts are ongoing to relate genomic alterations identified through exome sequencing to responsiveness of ES xenografts to BMN 673 plus TMZ. (Supported by NO1-CM-42216)

Citation Format: Malcolm Smith, Min Kang, Patrick Reynolds, Richard Gorlick, Anders Kolb, John Maris, Richard Lock, Hernan Carol, Stephen Keir, Catherine Billups, Raushan Kurmasheva, Peter Houghton. Pediatric preclinical testing program (PPTP) evaluation of BMN 673, an inhibitor of poly-adp ribose polymerase (PARP), with temozolomide (TMZ). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3969. doi:10.1158/1538-7445.AM2014-3969

Cell and molecular determinants of in vivo efficacy of the BH3 mimetic ABT-263 against pediatric acute lymphoblastic leukemia xenografts

PURPOSE

Predictive biomarkers are required to identify patients who may benefit from the use of BH3 mimetics such as ABT-263. This study investigated the efficacy of ABT-263 against a panel of patient-derived pediatric acute lymphoblastic leukemia (ALL) xenografts and utilized cell and molecular approaches to identify biomarkers that predict in vivo ABT-263 sensitivity.

EXPERIMENTAL DESIGN

The in vivo efficacy of ABT-263 was tested against a panel of 31 patient-derived ALL xenografts composed of MLL-, BCP-, and T-ALL subtypes. Basal gene expression profiles of ALL xenografts were analyzed and confirmed by quantitative RT-PCR, protein expression and BH3 profiling. An in vitro coculture assay with immortalized human mesenchymal cells was utilized to build a predictive model of in vivo ABT-263 sensitivity.

RESULTS

ABT-263 demonstrated impressive activity against pediatric ALL xenografts, with 19 of 31 achieving objective responses. Among BCL2 family members, in vivo ABT-263 sensitivity correlated best with low MCL1 mRNA expression levels. BH3 profiling revealed that resistance to ABT-263 correlated with mitochondrial priming by NOXA peptide, suggesting a functional role for MCL1 protein. Using an in vitro coculture assay, a predictive model of in vivo ABT-263 sensitivity was built. Testing this model against 11 xenografts predicted in vivo ABT-263 responses with high sensitivity (50%) and specificity (100%).

CONCLUSION

These results highlight the in vivo efficacy of ABT-263 against a broad range of pediatric ALL subtypes and shows that a combination of in vitro functional assays can be used to predict its in vivo efficacy.

Cumulative cisplatin dose is not associated with event-free or overall survival in children with newly diagnosed average-risk medulloblastoma treated with cisplatin based adjuvant chemotherapy: report from the Children's Oncology Group

BACKGROUND

Survival rates for children with medulloblastoma have risen over the past decade, in part due to the addition of cisplatin-containing adjuvant chemotherapy. Total dose of cisplatin required for optimal treatment is unknown. The purpose of this study was to evaluate the survival outcomes based on cumulative cisplatin doses (CCD) in children with newly diagnosed average-risk medulloblastoma.

PROCEDURE

CCD data were reviewed for 363 patients in a prospective study evaluating patients between 3 and 21 years with a newly diagnosed average-risk medulloblastoma and treated with craniospinal radiation and post-radiation cisplatin based adjuvant chemotherapy.

RESULTS

Eight-year event-free survival (EFS) and overall survival (OS) estimates were 78.2 ± 2.6% and 83.9 ± 2.4%, respectively. Only 73 patients received the protocol specified CCD of 600 mg/m(2), primarily due to mandated cisplatin toxicity-related dose reductions. The median CCD given to those without relapse or death on treatment was 487.5 mg/m(2). CCD, as a time-dependent covariate, was not associated with EFS (P = 0.54) or OS (P = 0.11). The 343 patients who completed chemotherapy failure-free were categorized into four groups according to CCD (n = 10; 75-150 mg/m(2)), (n = 26; 151-300 mg/m(2)), (n = 113; 301-450 mg/m(2)), and (n = 194; 451-600 mg/m(2)). There were no statistically significant differences in distributions of EFS (P = 0.53) or OS (P = 0.49) among these four groups.

CONCLUSION

CCD is not associated with EFS or OS suggesting that lower doses of cisplatin may be incorporated into future medulloblastoma trials, thereby limiting its toxicity profile without affecting survival. If ototoxicity is encountered, more stringent cisplatin dose modification/cessation rules seem warranted.

Abstract C206: Pediatric Preclinical Testing Program (PPTP) evaluation of BMN 673, an inhibitor of Poly-ADP Ribose Polymerase (PARP), alone and with Temozolomide (TMZ)

Introduction: BMN 673 is a potent and selective inhibitor of PARP1/2. Inhibitors of PARP such as BMN 673 show clinical activity against cancers lacking homologous repair through mutations in BRCA1 and 2. For Ewing sarcoma (ES), the EWS/FLI1 chimeric transcription factor increases PARP expression, and PARP appears to facilitate EWS/FLI1 function. Two reports have indicated that ES cell lines are more sensitive to PARP inhibitors than most other cell lines.

Methods: BMN 673 was evaluated as a single agent and in combination with TMZ against the 23 cell lines of the PPTP in vitro panel using 96 hour exposure. In single-agent studies, daily oral BMN 673 administration was tested against the PPTP solid tumor xenografts (SCID mice) and acute lymphoblastic leukemia (ALL; NOD-SCID mice) panels using a dose of 0.16 mg/kg BID x 5 and 0.33 mg/kg QD on weekends for up to 28 days. In combination studies, two dose levels of BMN 673 (0.25 & 0.1 mg/kg BID x 5 days) given with TMZ (12 & 30 mg/kg/day x 5 days, respectively) were evaluated against ES xenografts. Standard PPTP measures of in vivo antitumor activity were employed to assess response.

Results: The median relative IC50 (rIC50) for BMN 673 against the PPTP cell lines was 28 nM, with a range from 4 nM to &gt;1000 nM. There was a trend for lower rIC50 values for the ES cell line panel. In combination with a fixed concentration of BMN 673 (10 nM), the TMZ rIC50 was markedly reduced for some PPTP cell lines, with ES cell lines showing up to a 60-fold reduction. In vivo, BMN 673 was well tolerated with only a 1.9% toxicity rate in the treated groups. BMN 673 induced significant improvements in event-free survival (EFS) distribution compared to control in 18 of 35 (51%) of the evaluable solid tumor xenografts, but in 0 of 8 ALL models. Only 2 of 34 (6%) evaluable solid tumor xenografts and no ALL models showed EFS T/C values &gt; 2. Complete responses (CR) were observed for a Wilms tumor and a medulloblastoma model.

BMN 673 in combination with TMZ induced CRs that were maintained through week 12 for 2 of 4 ES xenografts (TMZ dosed at either 12 or 30 mg/kg/day). Among an additional 6 ES xenografts that have recently initiated testing, 3 have ongoing CRs to the combination at Weeks 4 to 5. None of the ES xenografts responded to 5 days of treatment with single agent TMZ (30 mg/kg) or BMN 673 (0.5 mg/kg/day).

Conclusions: Single agent BMN 673 shows limited activity against the PPTP solid tumor and ALL models, with no single agent activity against ES xenografts in vivo, despite ES cell lines demonstrating differential sensitivity in vitro. BMN 673 as a single agent induced CRs in 2 of 43 models, both of which are also highly responsive to cisplatin. Dramatic activity for the BMN 673 plus TMZ combination was observed for 5 of 10 ES models, with maintained CRs noted in vivo at TMZ doses as low as 12 mg/kg. Based on these results a pediatric phase 1 trial of BMN 673 plus TMZ is planned. (Supported by NO1-CM-42216)

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C206.

Citation Format: Malcolm Smith, Min Kang, Patrick Reynolds, Richard Gorlick, Anders Kolb, John Maris, Richard Lock, Hernan Carol, Stephen Keir, Catherine Billups, Raushan Kurmasheva, Peter Houghton. Pediatric Preclinical Testing Program (PPTP) evaluation of BMN 673, an inhibitor of Poly-ADP Ribose Polymerase (PARP), alone and with Temozolomide (TMZ). [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C206.

Abstract 2758: Pediatric preclinical testing program (PPTP) stage 1 evaluation of MLN0128, a potent TOR kinase inhibitor

Introduction: The PI3K-TORC1 pathway links extracellular (growth factors) and intracellular (nutrient sensing) to cell cycle progression and proliferation. This pathway is dysregulated in many adult cancers, but less is known regarding childhood malignancies. MLN0128 is a novel orally-available small molecule inhibitor of both the TORC1 and TORC2 complexes, key components of the PI3K/mTOR signaling pathway.

Methods: MLN0128 was evaluated against the 23 cell lines of the PPTP in vitro panel using 96 hour exposure at concentrations from 0.1 nM to 1.0 μM. MLN0128 was tested against the PPTP solid tumor xenografts (SCID mice) and acute lymphoblastic leukemia (ALL; NOD-SCID mice) panels using a dose of 1 mg/kg administered by the P.O. route daily for 21 days.

Results: In vitro the median relative IC50 value for the PPTP cell lines was 19 nM, with a range from 2 nM to 102 nM. There was a trend for lower median rIC50 values for the rhabdomyosarcoma and Ewing sarcoma cell line panels (8 nM and 5 nM, respectively). The median rIC50 value for the ALL cell lines (68 nM) was significantly greater than that for the non-ALL cell lines.

In vivo MLN0128 was well tolerated, with only a 1.4% toxicity rate in the treated groups, compared to a 0.3% toxicity rate in control animals. All 38 tested xenograft models were considered evaluable for efficacy. MLN0128 induced significant differences in EFS distribution compared to control in 24 of 31 (77%) of the evaluable solid tumor xenografts, but did not induce significant differences in EFS distribution in any of the 7 evaluable ALL xenografts. MLN0128 induced tumor growth inhibition meeting criteria for intermediate EFS T/C activity (EFS T/C &gt; 2) in 6 of 30 (20%) evaluable solid tumor xenografts. Intermediate activity for the EFS T/C metric occurred in the rhabdoid tumor panel (2 of 3) and in single xenografts in four other panels. Objective responses were not observed for the solid tumor or for the ALL xenograft panels. Pharmacodynamic studies to determine TOR inhibition are planned.

Conclusions: The activity observed for MLN0128 against the PPTP preclinical models is similar to that previously reported by the PPTP for another TOR kinase inhibitor (Houghton PJ, et al. Pediatr Blood Cancer. 58:191-9, 2012). When combined with PPTP results reported for PI3K and AKT inhibitors (Reynolds CP, et al. Pediatr Blood Cancer. 2012. Epub 2012/09/25 and Gorlick R, et al. Pediatr Blood Cancer. 59:518-24, 2012), the available data suggest that kinase inhibitors targeting the PI3K pathway produce limited single agent activity for the tumor types represented by the PPTP models. (Supported by award NO1-CM-42216 from the NCI).

Citation Format: Peter Houghton, Min H. Kang, Patrick Reynolds, Richard Lock, Hernan Carol, Richard Gorlick, Anders Kolb, John Maris, Stephen Keir, Catherine Billups, Raushan Kurmasheva, Malcolm Smith. Pediatric preclinical testing program (PPTP) stage 1 evaluation of MLN0128, a potent TOR kinase inhibitor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2758. doi:10.1158/1538-7445.AM2013-2758

Abstract LB-354: Pediatric Preclinical Testing Program (PPTP) stage 1 evaluation of the XPO1/CRM1 inhibitor KPT-330

Introduction: KPT-330 is an oral Selective Inhibitor of Nuclear Export (SINE) that binds covalently to XPO1 at Cys528 resulting in its irreversible inactivation. The nuclear export of over 200 proteins with specific nuclear export sequences (NES) is mediated via XPO1. Amongst the client proteins are many tumor suppressor and growth regulatory proteins (e.g., FOXO, IκB, pRb, p53, p73, p21, and p27).

Methods: KPT-330 was tested against the PPTP's in vitro cell line panel at concentrations ranging from 1.0 nM to 10.0 μM using the PPTP's standard 96 hour exposure period. It was tested against the PPTP solid tumor xenografts using a dose of 10 mg/kg administered by the oral route thrice weekly (M-W-F) for 4 weeks with a total treatment/observation period of 6 weeks.

Results: The median relative IC50 (rIC50) value for the PPTP cell lines was 125 nM, with a range from 13 nM to greater than 10 μM. There were no significant differences in rIC50 values by histotype, although there was a trend for greater sensitivity for the Ewing sarcoma cell lines (median rIC50 = 57 nM) and lesser sensitvity for the neuroblastoma cell lines (median rIC50 = 235 nM). Most cell lines showed Relative I/O% values between -75% and -100%, consistent with a prominent cytotoxic effect for KPT-330.

KPT-330 was well tolerated in vivo. It induced significant differences in EFS distribution compared to control in 29 of 37 (78%) solid tumor xenografts and in 5 of 8 (63%) ALL xenografts. For those xenografts with a significant difference in EFS distribution between treated and control groups, an EFS T/C value of greater than 2.0 indicates a substantial agent effect in slowing tumor growth. KPT-330 induced this level of effect in 11 of 32 (34%) solid tumor xenografts, most frequently for the Wilms tumor (2 of 3) and the Ewing sarcoma (4 of 5) panels. Objective responses were observed in 3 of 38 (4%) solid tumor xenografts, including a maintained complete response (MCR) for a Wilms tumor xenograft, a CR for a medulloblastoma xenograft, and a CR for a slow-growing ependymoma xenograft. For the ALL panel, 2 of 8 (25%) xenografts achieved either CR (ALL-8, T-cell ALL) or MCR (ALL-19, B-precursor ALL).

Conclusions: KPT-330 shows potent in vitro activity against many PPTP cell lines, consistent with the activation of multiple tumor suppressor proteins across diverse tumor genotypes. KPT-330 shows tumor regressing activity against selected PPTP solid tumor and ALL xenografts, and shows tumor growth inhibition for a larger number of models. Defining the relationship between KPT-330 systemic exposure in mice and humans will be important in assessing the clinical relevance of the PPTP in vivo results. Planned PD testing may identify biomarkers associated with response of pediatric preclinical models to KPT-330. KPT-330 is in phase 1 clinical trials in adults with advanced solid or hematological malignancies (NCT01607905 and NCT01607892). (Supported by NCI NO1-CM-42216)

Citation Format: Peter Houghton, Min Kang, Patrick Reynolds, Richard Gorlick, Anders Kolb, John Maris, Stephen Keir, Hernan Carol, Richard Lock, Catherine Billups, Raushan Kurmasheva, Yosef Landesman, Sharon Shacham, Michael Kauffman, Malcolm A. Smith. Pediatric Preclinical Testing Program (PPTP) stage 1 evaluation of the XPO1/CRM1 inhibitor KPT-330. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-354. doi:10.1158/1538-7445.AM2013-LB-354

Establishment and characterization of the first pediatric adrenocortical carcinoma xenograft model identifies topotecan as a potential chemotherapeutic agent

PURPOSE

Pediatric adrenocortical carcinoma (ACC) is a rare and highly aggressive malignancy. Conventional chemotherapeutic agents have shown limited utility and are largely ineffective in treating children with advanced ACC. The lack of cell lines and animal models of pediatric ACC has hampered the development of new therapies. Here we report the establishment of the first pediatric ACC xenograft model and the characterization of its sensitivity to selected chemotherapeutic agents.

EXPERIMENTAL DESIGN

A tumor from an 11-year-old boy with previously untreated ACC was established as a subcutaneous xenograft in immunocompromised CB17 scid(-/-) mice. The patient harbored a germline TP53 G245C mutation, and the primary tumor showed loss of heterozygosity with retention of the mutated TP53 allele. Histopathology, DNA fingerprinting, gene expression profiling, and biochemical analyses of the xenograft were conducted and compared with the primary tumor and normal adrenal cortex. The second endpoint was to assess the preliminary antitumor activity of selected chemotherapeutic agents.

RESULTS

The xenograft maintained the histopathologic and molecular features of the primary tumor. Screening the xenograft for drug responsiveness showed that cisplatin had a potent antitumor effect. However, etoposide, doxorubicin, and a panel of other common cancer drugs had little or no antitumor activity, with the exception of topotecan, which was found to significantly inhibit tumor growth. Consistent with these preclinical findings, topotecan as a single agent in a child with relapsed ACC resulted in disease stabilization.

CONCLUSION

Our study established a novel TP53-associated pediatric ACC xenograft and identified topotecan as a potentially effective agent for treating children with this disease.

Initial testing (stage 1) of the cyclin dependent kinase inhibitor SCH 727965 (dinaciclib) by the pediatric preclinical testing program

BACKGROUND

SCH 727965 is a novel drug in clinical development that potently and selectively inhibits CDK1, CDK2, CDK5, and CDK9. The activity of SCH 727965 was evaluated against the PPTP's in vitro and in vivo panels.

PROCEDURES

SCH 727965 was tested against the PPTP in vitro panel using 96 hours exposure at concentrations ranging from 0.1 nM to 1.0 µM. It was tested against the PPTP in vivo panels at a dose of 40 mg/kg administered intraperitoneally twice weekly for 2 weeks and repeated at Day 21 with a total observation period of 6 weeks.

RESULTS

The median IC(50) value for the cell lines was 7.5 nM, with less than fourfold range between the minimum (3.4 nM) and maximum (11.2 nM) IC(50) values. SCH 727965 demonstrated an activity pattern consistent with cytotoxicity for most of the cell lines. Forty-three xenograft models were studied and SCH 727965 induced significant delays in event free survival distribution compared to control in 23 of 36 (64%) evaluable solid tumor xenografts and in 3 of 7 ALL xenografts. SCH 727965 did not induce objective responses in the solid tumor panels and the best response observed was stable disease for one osteosarcoma xenograft. In the leukemia panel, there were two objective responses with a complete response observed in a single xenograft.

CONCLUSIONS

SCH 727965 shows an interesting pattern of activity suggesting its potential applicability against selected childhood cancers, particularly leukemias.

Improving the histopathologic diagnosis of pediatric malignancies in a low-resource setting by combining focused training and telepathology strategies

BACKGROUND

Accurate diagnosis is critical for optimal management of pediatric cancer. Pathologists with experience in pediatric oncology are in short supply in the developing world. Telepathology is increasingly used for consultations but its overall contribution to diagnostic accuracy is unknown.

PROCEDURE

We developed a strategy to provide a focused training in pediatric cancer and telepathology support to pathologists in the developing world. After the training period, we compared trainee's diagnoses with those of an experienced pathologist. We next compared the effectiveness of static versus dynamic telepathology review in 127 cases. Results were compared by Fisher's exact test.

RESULTS

The diagnoses of the trainee and the expert pathologist differed in only 6.5% of cases (95% CI, 1.2-20.0%). The overall concordance between the telepathology and original diagnoses was 90.6% (115/127; 95% CI, 84.1-94.6%).

CONCLUSIONS

Brief, focused training in pediatric cancer histopathology can improve diagnostic accuracy. Dynamic and static telepathology analyses are equally effective for diagnostic review.

Stanford V chemotherapy and involved field radiotherapy for children and adolescents with unfavorable risk Hodgkin lymphoma: Results of a multi-institutional prospective clinical trial

9502

Background: To evaluate the efficacy of 12 weeks of Stanford V chemotherapy (prednisone, vinblastine, doxorubicine, nitrogen mustard, etoposide, vincristine, and bleomycin) without routine growth factor support plus response-adapted low-dose, involved-field radiotherapy (IFRT) in children and adolescents with unfavorable risk Hodgkin lymphoma (HL). Methods: Multi-institutional (St. Jude Children’s Research Hospital, Stanford University, Children’s Hospital Boston, Massachusetts General Hospital and Maine Children’s Hospital) clinical trial. One hundred forty-one patients with clinical stages IIB (n=43), IIIB (n=19), IVA (n=27), and IVB (n=52) HL were treated with 12 weeks of Stanford V chemotherapy and low dose IFRT between June 2002 and May 2011. Involved nodal sites in complete remission (CR, defined as > 75% shrinkage of the original tumor and PET negative) after 8 weeks of Stanford V received 15 Gy IFRT; those sites that achieved only partial response received 25.5 Gy IFRT after completion of all 12 weeks of chemotherapy. Results: With a median follow-up of 4.6 years, the 3-year overall and event-free survival (EFS) are 97% (SE=2%) and 79% (SE=4%) respectively. There was no significant difference in EFS by stage (IIB vs. IIIB vs. IV; P=0.84). Ten patients developed progessive disease and 18 relapsed, while 5 have died (1 after relapse in an accident and 4 of refractory disease). Most common toxicities were grade 3 hematologic with 234 episodes of neutropenia in 101 patients (72%) and 85 episodes of anemia in 52 patients (37%); Fever and neutropenia occurred 13 times in 12 patients (9%). Conclusions: Risk-adapted, combined-modality therapy using 12 weeks of Stanford V chemotherapy plus IFRT is well tolerated in this population with manageable acute toxicities. Overall survival is comparable to other more intense chemotherapy regimens. Future high-risk front line therapies may consider a Stanford V backbone with targeted intensification and further tailoring of radiation therapy.

Abstract LB-317: Pediatric Preclinical Testing Program (PPTP) evaluation of volasertib (BI 6727), a Polo-like kinase (PLK) inhibitor

Background: Volasertib is a first in class, selective and potent cell cycle kinase inhibitor that induces mitotic arrest and apoptosis by targeting PLK. Genomic screens have identified PLK1 as a potential therapeutic target for several pediatric cancers, including rhabdomyosarcoma and neuroblastoma. Methods: Volasertib (provided by Boehringer Ingelheim) was tested in vitro at concentrations from 0.1 nM to 1.0 µM. Volasertib was tested against the PPTP solid tumor xenografts using a dose of 30 mg/kg administered intravenously weekly x 3. For the ALL panel (using NOD-SCID mice), the MTD was 15 mg/kg, and this dose was used for efficacy testing. The total planned treatment period was 3 weeks with an additional 3 weeks observation. Two measures of antitumor activity were primarily used: 1) an objective response measure modeled after the clinical setting; and 2) a time to event (4-fold increase in tumor volume) measure based on the median event-free survival (EFS) of treated (T) and control (C) animals for each xenograft. Intermediate activity requires EFS T/C &gt; 2, with high activity additionally requiring regression at the end of the observation period. Results: The median relative IC50 (rIC50) value for the PPTP cell lines was 14.1 nM, with a range from 6.0 nM to 135 nM. The median rIC50 values were lowest for the ALL cell line panel compared to the remaining cell lines (11.9 versus 16.0 nM, respectively), but this difference was not significant, and overall there were no differences in rIC50 by histotype. Against the PPTP in vivo panels volasertib induced significant differences in EFS distribution compared to control in 19 of 32 (59%) evaluable solid tumor xenografts and in 2 of 4 (50%) evaluable ALL xenografts. Volasertib induced tumor growth inhibition meeting criteria for intermediate EFS T/C activity in 11 of 30 (37%) evaluable solid tumor xenografts. Intermediate activity for the EFS T/C metric was most consistently observed in the neuroblastoma (4 of 6) and glioblastoma (2 of 3) panels. For the ALL panel, 2 of 4 (50%) xenografts met criteria for intermediate activity. Objective responses were observed for 4 of 32 solid tumor and 1 of 4 ALL xenografts. Two of 6 neuroblastoma xenografts demonstrated CRs, as did 1 of 3 glioblastoma and 1 of 5 rhabdomyosarcoma xenografts evaluable for this response measure. Conclusions: Volasertib showed low nanomolar in vitro potency against the PPTP cell lines with no histotype selectivity. Volasertib induced regressions in 5 of 36 evaluable PPTP xenografts with the neuroblastoma panel showing the most consistent pattern of responsiveness to volasertib. Given available pharmacokinetic data showing that mice tolerate higher systemic exposure to volasertib than humans, it is unlikely that the PPTP in vivo results are under-estimating the potential clinical activity of volasertib against the childhood cancer types evaluated here. (Supported by NCI NO1CM42216)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-317. doi:1538-7445.AM2012-LB-317

Initial testing (stage 1) of the mTOR kinase inhibitor AZD8055 by the pediatric preclinical testing program

BACKGROUND

AZD8055 is a small molecule ATP-competitive inhibitor of the serine/threonine kinase mTOR that regulates cap-dependent translation through the mTORC1 complex and Akt activation through the mTORC2 complex. Procedures AZD8055 was tested against the PPTP in vitro panel at concentrations ranging from 1.0 nM to 10 µM and against the PPTP in vivo panels at a dose of 20 mg/kg administered orally daily x 7 for 4 weeks.

RESULTS

In vitro the median relative IC(50) for AZD8055 against the PPTP cell lines was 24.7 nM. Relative I/O values >0% (consistent with a cytostatic effect) were observed in 8 cell lines and 15 cell lines showed Relative I/O values ranging from -4.7 to -92.2% (consistent with varying degrees of cytotoxic activity). In vivo AZD8055 induced significant differences in EFS distribution compared to controls in 23 of 36 (64%) evaluable solid tumor xenografts, and 1 of 6 evaluable ALL xenografts. Intermediate activity for the time to event activity measure (EFS T/C >2) was observed in 5 of 32 (16%) solid tumor xenografts evaluable. The best response was stable disease. PD2 (progressive disease with growth delay) was observed in 20 of 36 (55.6%) evaluable solid tumor xenografts. AZD8055 significantly inhibited 4E-BP1, S6, and Akt phosphorylation following day 1 and day 4 dosing, but suppression of mTORC1 or mTORC2 signaling did not predict tumor sensitivity.

CONCLUSIONS

AZD8055 demonstrated broad activity in vitro, but at the dose and schedule studied demonstrated limited activity in vivo against the PPTP solid tumor and ALL panels.

Initial testing (stage 1) of the IGF-1 receptor inhibitor BMS-754807 by the pediatric preclinical testing program

BACKGROUND

BMS-754807 is a small molecule ATP-competitive inhibitor of the type-1 insulin-like growth factor receptor currently in phase 1 clinical trials.

PROCEDURES

BMS-754807 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro panel at concentrations ranging from 1.0 nM to 10 µM and was tested against the PPTP in vivo panels at a dose of 25 mg/kg administered orally BID for 6 days, repeated for 6 weeks.

RESULTS

In vitro BMS-754807 showed a median EC(50) value of 0.62 µM against the PPTP cell lines. The median EC(50) for the four Ewing sarcoma cell lines was less than that for the remaining PPTP cell lines (0.19 µM vs. 0.78 µM, P = 0.0470). In vivo BMS-754807 induced significant differences in EFS distribution compared to controls in 18 of 32 evaluable solid tumor xenografts (56%) tested, but in none of the ALL xenografts studied. Criteria for intermediate activity for the time to event activity measure (EFS T/C > 2) were met in 7 of 27 solid tumor xenografts evaluable for this measure. The best response was PD2 (progressive disease with growth delay), which was observed in 18 of 32 solid tumor xenografts. PD2 responses were most commonly observed in the rhabdomyosarcoma, neuroblastoma, osteosarcoma, Ewing sarcoma, and Wilms tumor panels.

CONCLUSIONS

BMS-754807 activity in vitro is consistent with a specific IGF-1R effect that has half-maximal response in the 0.1 µM range and that is observed in a minority of the PPTP cell lines. In vivo intermediate activity was most commonly observed in the neuroblastoma and rhabdomyosarcoma panels.

Initial testing (stage 1) of the Akt inhibitor GSK690693 by the pediatric preclinical testing program

BACKGROUND

GSK690693 is a small molecule ATP-competitive inhibitor of the pro-survival kinase Akt. Since Akt regulates multiple downstream targets including transcription factors, glycogen synthase 3, the pro-apoptotic protein Bad, as well as MDM2 and mTORC1, it was tested against the in vitro and in vivo panels of the Pediatric Preclinical Testing Program (PPTP).

PROCEDURES

GSK690693 was tested in vitro at concentrations from 1 nM to 10 µM, and against the in vivo panel of xenografts at a dose of 30 mg/kg daily × 5 for 6 consecutive weeks. Three measures of in vivo antitumor activity were used: (1) an objective response measure modeled after the clinical setting; (2) a treated to control (T/C) tumor volume measure; and (3) a time to event measure based on the median event-free survival (EFS) of treated and control animals for each xenograft.

RESULTS

GSK690693 inhibited cell growth in vitro with IC(50) values between 6.5 nM and >10 µM. In vivo, GSK690693 significantly increased EFS in 11 of 34 (32%) solid tumor xenografts, most notably in all 6 osteosarcoma models, but not in any of the 8 ALL xenografts tested. No objective responses were observed and only one solid tumor met EFS T/C criteria for intermediate activity.

CONCLUSIONS

GSK690693 demonstrated broad activity in vitro, however our results against both the solid tumor and ALL PPTP in vivo panels demonstrate that, as single agent at the dose and schedule used, GSK690693 has only modest antitumor activity.

Initial testing (stage 1) of AZD6244 (ARRY-142886) by the Pediatric Preclinical Testing Program

BACKGROUND

AZD6244 (ARRY-142886) is a potent small molecule inhibitor of MEK1/2 that is in phase 2 clinical development.

PROCEDURES

AZD6244 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro panel (1 nM-10 microM). In vivo AZD6244 was tested at a dose of 100 mg/kg administered orally twice daily 5 days per week for 6 weeks. Subsequently, AZD6244 was evaluated against two juvenile pilocytic astrocytoma (JPA) xenografts using once and twice daily dosing schedules. Phosphorylation of ERK1/2 was used as a surrogate for in vivo inhibition of MEK1/2 was determined by immunoblotting.

RESULTS

At the highest concentration used in vitro (10 microM) AZD6244 only inhibited growth by 50% in 5 of the 23 cell lines. Against the in vivo tumor panels, AZD6244 induced significant differences in EFS distribution in 10 of 37 (27%) solid tumor models and 0 of 6 acute lymphoblastic leukemia (ALL) models. There were no objective responses. Pharmacodynamic studies indicated at this dose and schedule AZD6244 completely inhibited ERK1/2 phosphorylation. AZD6244 was evaluated against two JPA xenografts, BT-35 (wild-type BRAF) and BT-40 (mutant [V600E] BRAF). BT-40 xenografts were highly sensitive to AZD6244, whereas BT-35 xenografts progressed on AZD6244 treatment.

CONCLUSIONS

At the dose and schedule of administration used, AZD6244 as a single agent had limited in vitro and in vivo activity against the PPTP tumor panels despite inhibition of MEK1/2 activity. However, AZD6244 was highly active against BT-40 JPA xenografts that harbor constitutively activated BRAF, causing complete regressions.

Comparison of two methods for carboplatin dosing in children with retinoblastoma

BACKGROUND

Carboplatin is the most effective drug in retinoblastoma but systemic clearance is variable in young patients. While most regimens use a flat dose, individualized targeting may provide a more adjusted systemic exposure.

PATIENTS AND METHODS

We compared carboplatin doses between two groups of children with retinoblastoma that were treated using a flat dose of 560 mg/m(2) or a targeted AUC of 6.5 using a modified Calvert formula.

RESULTS

Ninety-eight patients with retinoblastoma received a total of 576 cycles of carboplatin (median 8 cycles). Fifty patients (51%) received a fixed dose per m(2), 32 (33%) received a dose based on AUC, 1 patient received fixed dose per kilogram, and in 15 patients a combination AUC and fixed doses was used. The median cumulative carboplatin dose (mg/m(2)) for patients who received eight cycles using fixed per m(2) dosing was 2151.8 (range, 1414.2-2852.0), compared to 1104.1 for nine patients who received eight cycles using Calvert dosing (range, 779.0-1992.7) (P < 0.001). For cycles given using AUC, the median percentage of the hypothetical fixed per m(2) dose was 70% (range, 48-134%). Younger patients had larger differences. Patients receiving carboplatin based on fixed per m(2) dosing were 3.0 times more likely to have a platelet transfusion (95% confidence interval, 1.3-7.3).

CONCLUSIONS

Carboplatin administration needs to consider the changes in renal function occurring during the first months of life. The use of a targeted AUC provides the most accurate method; however, mg per kg of body weight dosing is a very reliable alternative method.

The insulin-like growth factor-1 receptor-targeting antibody, CP-751,871, suppresses tumor-derived VEGF and synergizes with rapamycin in models of childhood sarcoma

Signaling through the type 1 insulin-like growth factor receptor (IGF-1R) occurs in many human cancers, including childhood sarcomas. As a consequence, targeting the IGF-1R has become a focus for cancer drug development. We examined the antitumor activity of CP-751,871, a human antibody that blocks IGF-1R ligand binding, alone and in combination with rapamycin against sarcoma cell lines in vitro and xenograft models in vivo. In Ewing sarcoma (EWS) cell lines, CP751,871 inhibited growth poorly (<50%), but prevented rapamycin-induced hyperphosphorylation of AKT(Ser473) and induced greater than additive apoptosis. Rapamycin treatment also increased secretion of IGF-1 resulting in phosphorylation of IGF-1R (Tyr1131) that was blocked by CP751,871. In vivo CP-751,871, rapamycin, or the combination were evaluated against EWS, osteosarcoma, and rhabdomyosarcoma xenografts. CP751871 induced significant growth inhibition [EFS(T/C) >2] in four models. Rapamycin induced significant growth inhibition [EFS(T/C) >2] in nine models. Although neither agent given alone caused tumor regressions, in combination, these agents had greater than additive activity against 5 of 13 xenografts and induced complete remissions in one model each of rhabdomyosarcoma and EWS, and in three of four osteosarcoma models. CP751,871 caused complete IGF-1R down-regulation, suppression of AKT phosphorylation, and dramatically suppressed tumor-derived vascular endothelial growth factor (VEGF) in some sarcoma xenografts. Rapamycin treatment did not markedly suppress VEGF in tumors and synergized only in tumor lines where VEGF was dramatically inhibited by CP751,871. These data suggest a model in which blockade of IGF-1R suppresses tumor-derived VEGF to a level where rapamycin can effectively suppress the response in vascular endothelial cells.

Initial testing of aplidin by the pediatric pre-clinical testing program

Aplidin was tested in vitro at concentrations ranging from from 0.1 nM to 1.0 microM and in vivo at a dose of 0.6 mg/kg administered intraperitoneally on an every 4 days x 3-schedule that was repeated at day 21. In vitro, Aplidin was most active against acute lymphoblastic leukemia (ALL) cell lines. In vivo, Aplidin induced significant differences in EFS distribution in 12 of 28 (43%) solid tumor models and 2 of 6 evaluable ALL models. Aplidin showed potent in vitro activity and induced significant in vivo tumor growth inhibition in some xenografts, but did not induce tumor regressions.

Lack of correlation between the histologic and magnetic resonance imaging results of optic nerve involvement in eyes primarily enucleated for retinoblastoma

PURPOSE

To correlate the histologic and magnetic resonance imaging results of the optic nerve in eyes primarily enucleated for retinoblastoma.

DESIGN

Retrospective, clinicopathologic correlation.

PARTICIPANTS

Sixty-seven consecutive patients with retinoblastoma who underwent primary enucleation.

METHODS

The histologic results of 67 eyes from 67 patients with retinoblastoma who underwent primary enucleation between March 1997 and January 2008 were studied for evidence of optic nerve invasion. Two neuroradiologists independently reviewed available preoperative magnetic resonance imaging studies with special emphasis on nonenhanced T2-weighted and gadolinium-enhanced T1-weighted imaging for evidence of optic nerve invasion. A weighted kappa statistic was used to assess agreement between observers.

MAIN OUTCOME MEASURES

Correlation between neuroradiologists and histologic results.

RESULTS

Of the 67 eyes studied, 60 had preoperative magnetic resonance images, 58 of which were deemed appropriate for review by both neuroradiologists. Review of the histologic results showed optic nerve involvement in 62 (93%) of 67 eyes: 28 prelaminar (42%), 24 laminar (36%), and 10 postlaminar (15%). On review of the magnetic resonance scans, the first neuroradiologist identified optic nerve involvement in 57 (95%) of 60 eyes: 26 prelaminar (43%), 10 laminar (17%), and 11 postlaminar (18%). The second neuroradiologist identified optic nerve involvement in 46 (77%) of 60 eyes: 33 prelaminar (55%), 9 laminar (15%), and 4 postlaminar (7%). Moderate agreement existed between neuroradiologists (kappa, 0.55). Poor and fair agreement existed between each of the 2 neuroradiologists and histologic results, respectively (kappa, 0.29 and 0.17). Exophytic tumors showed the greatest disparity (kappa, -0.20 and -0.13) between magnetic resonance imaging and histologic results.

CONCLUSIONS

Limited correlation was found between magnetic resonance imaging and histologic results in assessing optic nerve invasion in eyes with retinoblastoma. Magnetic resonance imaging using routine imaging technologies, although useful in the evaluation of retinoblastoma, has limited usefulness in assessing the exact extent of optic nerve invasion; high-risk features of retinoblastoma such as postlaminar invasion remain best defined by histologic analysis. This study demonstrates that the interpretation of optic nerve involvement by a radiologist should not be the determining factor to defer enucleation in favor of neoadjuvant therapy.

p18Ink4c and p53 Act as tumor suppressors in cyclin D1-driven primitive neuroectodermal tumor

The retinoblastoma (RB) tumor suppressor pathway is likely important in primitive neuroectodermal tumors (PNET) of the brain. In fact, 10% to 15% of children born with RB mutations develop brain PNETs, commonly in the pineal gland. Cyclin D1, which in association with cyclin-dependent kinase (Cdk) 4 and Cdk6 phosphorylates and inactivates the RB protein, is expressed in 40% of sporadic medulloblastoma, a PNET of the cerebellum. To understand tumorigenic events cooperating with RB pathway disruption in brain PNET, we generated a transgenic mouse where cyclin D1 was expressed in pineal cells. Cyclin D1 enhanced pinealocyte proliferation, causing pineal gland enlargement. However, proliferation ceased beyond 2 weeks of age with reversal of Cdk4-mediated Rb phosphorylation despite continued expression of the transgene, and the pineal cells showed heterochromatin foci suggestive of a senescent-like state. In the absence of the p53 tumor suppressor, cell proliferation continued, resulting in pineal PNET that limited mouse survival to approximately 4 months. Interestingly, the Cdk inhibitor p18(Ink4c) was induced in the transgenic pineal glands independently of p53, and transgenic mice that lacked Ink4c developed invasive PNET, although at an older age than those lacking p53. Analogous to our mouse model, we found that children with heritable RB often had asymptomatic pineal gland enlargement that only rarely progressed to PNET. Our finding that the Cdk4 inhibitor p18(Ink4c) is a tumor suppressor in cyclin D1-driven PNET suggests that pharmacologic interventions to inhibit Cdk4 activity may be a useful chemoprevention or therapeutic strategy in cancer driven by primary RB pathway disruption.

Initial testing of VNP40101M (Cloretazine) by the pediatric preclinical testing program

VNP40101M is a novel alkylating agent that yields two reactive compounds (a chloroethylating species and methylisocyanate) and has demonstrated activity against a wide spectrum of tumor xenografts. VNP40101M was tested against an in vivo panel of five pediatric brain tumor xenografts at a dose of 18 mg/kg/day administered for 5 days. O-6-methylguanine-DNA methyltransferase (MGMT) levels of xenografts were assessed by Western blot analysis. Only one xenograft (GBM2), which lacked detectable MGMT expression, demonstrated an objective response to VNP40101M. VNP4010M antitumor activity was observed only in the absence of MGMT expression, with resistance to VNP4010M seen even with low MGMT expression.