Preclinical activity of the antibody-drug conjugate denintuzumab mafodotin (SGN-CD19A) against pediatric acute lymphoblastic leukemia xenografts.

BACKGROUND: Denintuzumab mafodotin (SGN-CD19A) is a CD19-targeting antibody-drug conjugate, comprising a monoclonal antibody conjugated to the potent cytotoxin monomethyl auristatin F. Since denintuzumab mafodotin has previously shown activity against B-cell malignancies in early-stage clinical trials, it was of interest to test it against the Pediatric Preclinical Testing Program preclinical models of CD19+ pediatric acute lymphoblastic leukemia (ALL). PROCEDURES: Denintuzumab mafodotin was evaluated against eight B-cell lineage ALL patient-derived xenografts (PDXs), representing B-cell precursor ALL, Ph-like ALL, and mixed-lineage leukemia rearranged infant ALL. Denintuzumab mafodotin was administered weekly for 3 weeks at 3 mg/kg. It was also tested in combination with an induction-type chemotherapy regimen of vincristine, dexamethasone, and l-asparaginase (VXL) against three PDXs. The relationship between cell surface and gene expression of CD19 and drug activity was also assessed. RESULTS: Denintuzumab mafodotin significantly delayed the progression of seven of eight PDXs tested and achieved objective responses in five of eight. There was no apparent subtype specificity of denintuzumab mafodotin activity. No correlations were observed between CD19 mRNA or cell surface expression and denintuzumab mafodotin activity, perhaps due to small sample size, and denintuzumab mafodotin treatment did not select for reduced CD19 expression. Combining denintuzumab mafodotin with VXL achieved therapeutic enhancement compared to either treatment alone. CONCLUSIONS: Denintuzumab mafodotin showed single-agent activity against selected B-lineage ALL PDXs, although leukemia growth was evident in most models at 28 days from treatment initiation. This level of activity for denintuzumab mafodotin is consistent with that observed in adults with ALL.

Risk-adapted therapy for young children with medulloblastoma (SJYC07): therapeutic and molecular outcomes from a multicentre, phase 2 trial.

BACKGROUND: Young children with medulloblastoma have a poor overall survival compared with older children, due to use of radiation-sparing therapy in young children. Radiotherapy is omitted or reduced in these young patients to spare them from debilitating long-term side-effects. We aimed to estimate event-free survival and define the molecular characteristics associated with progression-free survival in young patients with medulloblastoma using a risk-stratified treatment strategy designed to defer, reduce, or delay radiation exposure. METHODS: In this multicentre, phase 2 trial, we enrolled children younger than 3 years with newly diagnosed medulloblastoma at six centres in the USA and Australia. Children aged 3-5 years with newly diagnosed, non-metastatic medulloblastoma without any high-risk features were also eligible. Eligible patients were required to start therapy within 31 days from definitive surgery, had a Lansky performance score of at least 30, and did not receive previous radiotherapy or chemotherapy. Patients were stratified postoperatively by clinical and histological criteria into low-risk, intermediate-risk, and high-risk treatment groups. All patients received identical induction chemotherapy (methotrexate, vincristine, cisplatin, and cyclophosphamide), with high-risk patients also receiving an additional five doses of vinblastine. Induction was followed by risk-adapted consolidation therapy: low-risk patients received cyclophosphamide (1500 mg/m2 on day 1), etoposide (100 mg/m2 on days 1 and 2), and carboplatin (area under the curve 5 mg/mL per min on day 2) for two 4-week cycles; intermediate-risk patients received focal radiation therapy (54 Gy with a clinical target volume of 5 mm over 6 weeks) to the tumour bed; and high-risk patients received chemotherapy with targeted intravenous topotecan (area under the curve 120-160 ng-h/mL intravenously on days 1-5) and cyclophosphamide (600 mg/m2 intravenously on days 1-5). After consolidation, all patients received maintenance chemotherapy with cyclophosphamide, topotecan, and erlotinib. The coprimary endpoints were event-free survival and patterns of methylation profiling associated with progression-free survival. Outcome and safety analyses were per protocol (all patients who received at least one dose of induction chemotherapy); biological analyses included all patients with tissue available for methylation profiling. This trial is registered with ClinicalTrials.gov, number NCT00602667, and was closed to accrual on April 19, 2017. FINDINGS: Between Nov 27, 2007, and April 19, 2017, we enrolled 81 patients with histologically confirmed medulloblastoma. Accrual to the low-risk group was suspended after an interim analysis on Dec 2, 2015, when the 1-year event-free survival was estimated to be below the stopping rule boundary. After a median follow-up of 5·5 years (IQR 2·7-7·3), 5-year event-free survival was 31·3% (95% CI 19·3-43·3) for the whole cohort, 55·3% (95% CI 33·3-77·3) in the low-risk cohort (n=23) versus 24·6% (3·6-45·6) in the intermediate-risk cohort (n=32; hazard ratio 2·50, 95% CI 1·19-5·27; p=0·016) and 16·7% (3·4-30·0) in the high-risk cohort (n=26; 3·55, 1·66-7·59; p=0·0011; overall p=0·0021). 5-year progression-free survival by methylation subgroup was 51·1% (95% CI 34·6-67·6) in the sonic hedgehog (SHH) subgroup (n=42), 8·3% (95% CI 0·0-24·0%) in the group 3 subgroup (n=24), and 13·3% (95% CI 0·0-37·6%) in the group 4 subgroup (n=10). Within the SHH subgroup, two distinct methylation subtypes were identified and named iSHH-I and iSHH-II. 5-year progression-free survival was 27·8% (95% CI 9·0-46·6; n=21) for iSHH-I and 75·4% (55·0-95·8; n=21) for iSHH-II. The most common adverse events were grade 3-4 febrile neutropenia (48 patients [59%]), neutropenia (21 [26%]), infection with neutropenia (20 [25%]), leucopenia (15 [19%]), vomiting (15 [19%]), and anorexia (13 [16%]). No treatment-related deaths occurred. INTERPRETATION: The risk-adapted approach did not improve event-free survival in young children with medulloblastoma. However, the methylation subgroup analyses showed that the SHH subgroup had improved progression-free survival compared with the group 3 subgroup. Moreover, within the SHH subgroup, the iSHH-II subtype had improved progression-free survival in the absence of radiation, intraventricular chemotherapy, or high-dose chemotherapy compared with the iSHH-I subtype. These findings support the development of a molecularly driven, risk-adapted, treatment approach in future trials in young children with medulloblastoma. FUNDING: American Lebanese Syrian Associated Charities, St Jude Children's Research Hospital, NCI Cancer Center, Alexander and Margaret Stewart Trust, Sontag Foundation, and American Association for Cancer Research.

Venetoclax responses of pediatric ALL xenografts reveal sensitivity of MLL-rearranged leukemia.

The clinical success of the BCL-2-selective BH3-mimetic venetoclax in patients with poor prognosis chronic lymphocytic leukemia (CLL) highlights the potential of targeting the BCL-2-regulated apoptotic pathway in previously untreatable lymphoid malignancies. By selectively inhibiting BCL-2, venetoclax circumvents the dose-limiting, BCL-XL-mediated thrombocytopenia of its less selective predecessor navitoclax, while enhancing efficacy in CLL. We have previously reported the potent sensitivity of many high-risk childhood acute lymphoblastic leukemia (ALL) xenografts to navitoclax. Given the superior tolerability of venetoclax, here we have investigated its efficacy in childhood ALL. We demonstrate that in contrast to the clear dependence of CLL on BCL-2 alone, effective antileukemic activity in the majority of ALL xenografts requires concurrent inhibition of both BCL-2 and BCL-XL We identify BCL-XL expression as a key predictor of poor response to venetoclax and demonstrate that concurrent inhibition of both BCL-2 and BCL-XL results in synergistic killing in the majority of ALL xenografts. A notable exception is mixed lineage leukemia-rearranged infant ALL, where venetoclax largely recapitulates the activity of navitoclax, identifying this subgroup of patients as potential candidates for clinical trials of venetoclax in childhood ALL. Conversely, our findings provide a clear basis for progressing navitoclax into trials ahead of venetoclax in other subgroups.

A phase II trial evaluating the feasibility of adding bevacizumab to standard osteosarcoma therapy.

Increased vascular endothelial growth factor (VEGF) expression in osteosarcoma correlates with a poor outcome. We conducted a phase II trial to evaluate the feasibility and efficacy of combining bevacizumab, a monoclonal antibody against VEGF, with methotrexate, doxorubicin and cisplatin (MAP) in patients with localized osteosarcoma. Eligible patients received two courses of MAP chemotherapy before definitive surgery at week 10. Bevacizumab (15 mg/kg) was administered 3 days before starting chemotherapy then on day 1 of weeks 3 and 5 of chemotherapy. After surgery, patients received MAP for a total of 29 weeks; bevacizumab was added every 2 or 3 weeks on day 1 of chemotherapy at least 5 weeks after surgery. Group sequential monitoring rules were used to monitor for unacceptable bevacizumab-related targeted toxicity (grade 4 hypertension, proteinuria or bleeding, grade 3 or 4 thrombosis/embolism, and grade 2-4 major wound complications). Thirty-one patients (median age 12.8 years) with localized osteosarcoma were enrolled. No unacceptable targeted toxicities were observed except for wound complications (9 minor and 6 major), which occurred in 15 patients; none required removal of prosthetic hardware or amputation. The estimated 4-year event-free survival (EFS) rate and overall survival rate were 57.5 ± 10.0% and 83.4 ± 7.8%, respectively. Eight (28%) of 29 evaluable patients had good histologic response (<5% viable tumor) to preoperative chemotherapy. The addition of bevacizumab to MAP for localized osteosarcoma is feasible but frequent wound complications are encountered. The observed histologic response and EFS do not support further evaluation of bevacizumab in osteosarcoma.

Cognitive outcomes among survivors of focal low-grade brainstem tumors diagnosed in childhood.

Pediatric focal low-grade brainstem tumors are associated with excellent prognosis. Surgical resection and conformal radiation therapy are front-line treatment options; radiation therapy (RT) serves as an excellent treatment for disease progression. Given high survival rates and limited research regarding functional outcomes, the current study examined neurocognitive outcomes in a group of low-grade brainstem glioma survivors. Forty-three survivors of focal low-grade brainstem gliomas underwent neurocognitive assessment (58 % male; median = 6.9 years at diagnosis; median = 14.9 years at latest assessment). Treatment included combinations of surgery, chemotherapy, and RT with 70 % ultimately receiving RT. Neurocognitive outcomes were evaluated through retrospective chart review. Intellectual and academic performance were significantly different from normative expectations (full scale IQ = 86.5 ± 16.8; reading comprehension = 91.3 ± 16.4; math reasoning = 88.2 ± 18.9; reference group = 100 ± 15). Further, the percentage performing below average exceeded the expected 16 % in the normative sample (full scale IQ = 43 %; reading comprehension = 37 %; math reasoning = 50 %). Mean parent ratings did not reflect concerns regarding internalizing and externalizing behaviors or executive functioning (internalizing = 54.9 ± 12.7; externalizing = 51.6 ± 14.6, global executive composite = 57.1 ± 16.0; reference group = 50 ± 10); however, the proportion with clinically elevated scores was higher than the expected 16 % (internalizing = 42 %; externalizing = 26 %; global executive composite = 38 %). Mean performance fell below average for visual-motor coordination (81.8 ± 13.2) and parent ratings of adaptive functioning (73.4 ± 24.2), with 65 and 62 % falling outside the average range, respectively. There were no significant differences between those receiving and not receiving RT. Multiple cognitive domains were significantly different from normative expectations. Despite focal disease and treatment targeting subcortical brain regions, neurocognitive risks exist that may impact treatment planning and caregiver education.

Patients with retinoblastoma and chromosome 13q deletions have increased chemotherapy-related toxicities.

BACKGROUND: A total of 5-10% of patients with retinoblastoma (RB) harbor deletion of the long arm (q) chromosome 13 (13q-). The treatment-related toxicities in this population have not been described. METHODS: Sixty-eight RB patients on a single institutional protocol (RET5) from 2005 to 2010 were reviewed. Genetic screening identified 11 patients (seven female) with 13q-. Patients with early (Reese-Ellsworth [R-E] group I-III) disease (6/23 with 13q-) received eight courses of vincristine/carboplatin (VC). Patients with advanced (R-E group IV-V) bilateral disease (2/27 with 13q-) received two courses of vincristine/topotecan (VT) followed by nine courses of alternating VT/VC. Patients undergoing upfront enucleation received histopathology-based chemotherapy: intermediate risk (2/8 with 13q-) or high risk (1/10 with 13q-). Dose reductions were mandated for >7 day delay in two consecutive courses following hematologic toxicity. Grades 3 and 4 hematologic, infectious, and gastrointestinal toxicities were compared between RET5 patients with and without 13q-. RESULTS: Demographics were similar between groups. When present, prolonged neutropenia (median 7 days, range 0-14 days) delayed chemotherapy and resulted in more frequent dose reductions among 13q- patients (5/11) than non-13q- patients (4/57) (P < 0.01). GI toxicity was similar between groups (5/11 13q- vs. 13/57 non-13q-; P = 0.14), but halted chemotherapy in one 13q- patient. Infectious complications and disease outcomes were similar between groups. At follow-up, all patients are alive (median 6.1 years, range 7.6 months-9.5 years). CONCLUSIONS: 13q- RB patients had a higher incidence of neutropenia requiring chemotherapy dose reductions, but did not have increased treatment failure.

Initial Testing of NSC 750854, a Novel Purine Analog, Against Pediatric Tumor Models by the Pediatric Preclinical Testing Program.

BACKGROUND: NSC 750854 is a purine analog with an antitumor activity profile distinctive from that of other anticancer purines. It has shown significant activity against adult cancer preclinical models. PROCEDURE: NSC 750854 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations from 1.0 nM to 10 µM and against the PPTP in vivo xenograft panels administered intraperitoneally at a dose of 5 mg/kg daily for 5 days repeated at day 15. RESULTS: The median relative IC50 (rIC50 ) value for the PPTP cell lines was 32 nM (range from 11 to 124 nM), with consistent cytotoxicity across all cell lines. Acute lymphoblastic leukemia (ALL) cell lines were more sensitive to NSC 750854 than non-ALL cell lines. NSC 750854 induced significant differences in EFS distribution compared to control in 31 of 35 (89%) solid tumor xenografts. It induced tumor growth inhibition meeting criteria for intermediate or high event free survival (EFS) T/C activity in 17 of 32 (53%) evaluable solid tumor xenografts (most consistently in the rhabdomyosarcoma panel). Objective responses were observed in 15 of 37 (41%) solid tumor xenografts and in all eight leukemia models with complete response (CR) or maintained complete response (MCR) in seven of eight leukemia models. CONCLUSIONS: NSC 750854 has a unique spectrum of antitumor activity compared with other agents tested by the PPTP as it induces regression in tumor models with limited sensitivity to most agents tested to date. Given the promising level of activity observed for NSC 750854 against PPTP preclinical models, further exploration of its mechanism of action is warranted.

Subsequent malignant neoplasms in pediatric patients initially diagnosed with neuroblastoma.

BACKGROUND: Most prior studies evaluating subsequent malignant neoplasms (SMNs) in patients with neuroblastoma are restricted to long-term survivors and/or their treatment exposures. This study investigates SMNs in patients diagnosed with neuroblastoma at our institution. METHODS: Records of 646 patients treated for neuroblastoma at St Jude Children's Research Hospital between 1961 and 2005 were reviewed. Data from patients with SMNs were analyzed and the 20- and 30-year cumulative incidence of SMNs and standardized incidence ratio were calculated. RESULTS: Twenty-one patients had a SMN. The 20- and 30-year cumulative incidences of a SMN were 2.6%±0.7% and 4.6%±1.1%, respectively. The standardized incidence ratio was 8.3 (95% confidence interval, 5.0-13.0). Five patients developed a SMN within 5 years from diagnosis. The median latency for the development of acute myeloid leukemia/myelodysplastic syndrome (n=4), sarcomas (n=7), and carcinomas (n=5) were 3.6, 9, and 24.2 years, respectively. Nine patients died from their SMN, including all with acute myeloid leukemia/myelodysplastic syndrome. CONCLUSIONS: Patients with neuroblastoma have an increased risk of secondary neoplasia. Modification of risk-adapted therapies will likely alter the affected patient population and the incidence of SMNs. Future studies are necessary to link SMNs to treatment exposures and to evaluate the risk of SMNs beyond 30 years from diagnosis.

Initial testing (stage 1) of glembatumumab vedotin (CDX-011) by the pediatric preclinical testing program.

BACKGROUND: Glembatumumab vedotin is an antibody-auristatin conjugate that targets cells expressing the transmembrane glycoprotein NMB (GPNMB, also known as osteoactivin). It has entered clinical evaluation for adult cancers that express GPNMB, including melanoma and breast cancer. PROCEDURES: Glembatumumab vedotin was administered intravenously at a dose of 2.5 mg/kg using a weekly × 3 schedule, and its antitumor activity was evaluated against selected Pediatric Preclinical Testing Program (PPTP) solid tumor xenografts using standard PPTP response metrics. RESULTS: Among PPTP xenografts, GPNMB was primarily expressed on the osteosarcoma xenografts, all of which expressed GPNMB at the RNA level, although at varying levels. Protein expression assessed by immunohistochemistry (IHC) showed variation across the osteosarcoma xenografts with one model showing no tumor cell expression. Glembatumumab vedotin induced statistically significant differences (P < 0.05) in event-free survival (EFS) distribution compared to control in each of the six osteosarcoma models studied. Three of six osteosarcoma xenografts demonstrated a maintained complete response (MCR). Two other xenografts showed progressive disease with growth delay, while the final xenograft showed progressive disease with no growth delay. Two of the osteosarcoma xenografts with MCRs showed the highest GPNMB expression at the RNA level. Conversely, the xenograft with the lowest GPNMB mRNA expression had the poorest response to glembatumumab vedotin. Two rhabdomyosarcoma xenografts that did not express GPNMB showed limited responses to glembatumumab vedotin. CONCLUSIONS: Glembatumumab vedotin yielded high-level activity against three of six osteosarcoma xenografts, with evidence for response being related to GPNMB expression levels.

Initial testing (stage 1) of the Polo-like kinase inhibitor volasertib (BI 6727), by the Pediatric Preclinical Testing Program.

BACKGROUND: Volasertib (BI 6727) is a potent inhibitor of Polo-like kinase 1 (Plk1), that is overexpressed in several childhood cancers and cell lines. Because of its novel mechanism of action, volasertib was evaluated through the PPTP. PROCEDURES: Volasertib was tested against the PPTP in vitro cell line panel at concentrations from 0.1 nM to 1.0 µM and against the PPTP in vivo xenograft panels administered IV at a dose of 30 mg/kg (solid tumors) or 15 mg/kg (ALL models) using a q7dx3 schedule. RESULTS: In vitro volasertib demonstrated cytotoxic activity, with a median relative IC50 value of 14.1 nM, (range 6.0-135 nM). Volasertib induced significant differences in EFS in 19 of 32 (59%) of the evaluable solid tumor xenografts and in 2 of 4 (50%) of the evaluable ALL xenografts. Volasertib induced tumor growth inhibition meeting criteria for intermediate EFS T/C (>2) activity in 11 of 30 (37%) evaluable solid tumor xenografts, including neuroblastoma (4 of 6) and glioblastoma (2 of 3) panels, and 2 of 4 ALL models. Objective responses (CR's) were observed for 4 of 32 solid tumor (two neuroblastoma, one glioblastoma, and one rhabdomyosarcoma) and one of four ALL xenografts. CONCLUSIONS: Volasertib shows potent in vitro activity against the PPTP cell lines with no histotype selectivity. In vivo, volasertib induced regressions in several xenograft models. However, pharmacokinetic data suggest that mice tolerate higher systemic exposure to volasertib than humans, suggesting that the current results may over-estimate potential clinical efficacy against the childhood cancers studied.

Pathologic risk-based adjuvant chemotherapy for unilateral retinoblastoma following enucleation.

BACKGROUND: There are no standardized diagnostic or treatment guidelines for patients with advanced unilateral retinoblastoma. MATERIALS AND METHODS: Patients with advanced unilateral retinoblastoma were prospectively treated after enucleation using a risk-based protocol. Patients were assigned to low risk (LR), intermediate risk (IR), or high risk (HR) based on pathology. LR patients underwent observation. IR patients received 4 courses of chemotherapy with vincristine, doxorubicin, and cyclophosphamide (VDC). In the HR group, patients received 3 courses of VDC alternating with 3 courses of vincristine, carboplatin, and etoposide (VCE) and irradiation when indicated. RESULTS: Fifty patients with advanced unilateral retinoblastoma were treated (LR, n=36; IR, n=7; HR, n=7). All eyes were Reese-Ellsworth group V. All bone scans (n=81), lumbar punctures (n=16), and bone marrow aspirates (n=16) were negative. Chemotherapy was well tolerated. Grades 3/4 hematologic toxicities were seen in all patients; grades 3/4 nonhematologic toxicities were seen in half the patients. Only one patient in the HR group received radiation therapy. All patients were alive at the time of analysis with no signs of disease recurrence. Median follow-up was 3.4 years (range, 0.8 to 6.4 y). CONCLUSIONS: Patients with nonmetastatic unilateral retinoblastoma undergoing primary enucleation can be cured with a graduated intensity approach based on pathology.

Is routine pelvic surveillance imaging necessary in patients with Wilms tumor?

BACKGROUND: It is unclear whether routine pelvic imaging is needed in patients with Wilms tumor. Thus, the primary objective of the current study was to examine the role of routine pelvic computed tomography (CT) in a cohort of pediatric patients with Wilms tumor. METHODS: With institutional review board approval, the authors retrospectively identified 110 patients who had Wilms tumor diagnosed between January 1999 and December 2009 with surveillance imaging that continued through March 2011. The authors estimated overall survival (OS), event-free survival (EFS), and dosimetry from dose length product (DLP) conversion to the effective dose (ED) for every CT in a subgroup of 80 patients who had CT studies obtained using contemporary scanners (2002-2011). Metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters were placed within organs of anthropomorphic phantoms to directly calculate the truncal ED. ED(DLP) was correlated with ED(MOSFET) to calculate potential pelvic dose savings. RESULTS: Eighty patients underwent 605 CT examinations that contained DLP information, including 352 CT scans of the chest, abdomen, and pelvis; 123 CT scans of the chest and abdomen; 102 CT scans of the chest only; 18 CT scans of the abdomen and pelvis; 9 CT scans of the abdomen only; and 1 CT that was limited to the pelvis. The respective 5-year OS and EFS estimates were 92.8% ± 3% and 2.6% ± 4.3%. Sixteen of 110 patients (15%) developed a relapse a median of 11.3 months (range, 5.0 months to 7.3 years) after diagnosis, and 4 patients died of disease recurrence. Three patients developed pelvic relapses, all 3 of which were symptomatic. The estimated ED savings from sex-neutral CT surveillance performed at a 120-kilovolt peak without pelvic imaging was calculated as 30.5% for the average patient aged 1 year, 30.4% for the average patient aged 5 years, 39.4% for the average patient aged 10 years, and 44.9% for the average patient aged 15 years. CONCLUSIONS: Omitting pelvic CT from the routine, off-therapy follow-up of patients with Wilms tumor saved an average 30% to 45% of the ED without compromising disease detection.

Survival of pediatric patients after relapsed osteosarcoma: the St. Jude Children's Research Hospital experience.

BACKGROUND: Chemotherapy has improved the outcome of patients with newly diagnosed osteosarcoma, but its role in relapsed disease is unclear. METHODS: We reviewed the records of all patients who were treated for relapsed high-grade osteosarcoma at our institution between 1970 and 2004. Postrelapse event-free survival (PREFS) and postrelapse survival (PRS) were estimated, and outcome comparisons were made using an exact log-rank test. RESULTS: The 10-year PREFS and PRS of the 110 patients were 11.8% ± 3.5% and 17.0% ± 4.3%, respectively. Metastasis at initial diagnosis (14%), and relapse in lung only (75%) were not significantly associated with PREFS or PRS. Time from initial diagnosis to first relapse (RL1) ≥18 months (43%), surgery at RL1 (76%), and ability to achieve second complete remission (CR2, 56%) were favorably associated with PREFS and PRS (P ≤ 0.0002). In patients without CR2, chemotherapy at RL1 was favorably associated with PREFS (P = 0.01) but not with PRS. In patients with lung relapse only, unilateral relapse and number of nodules ( ≤ 3) were associated with better PREFS and PRS (P ≤ 0.0005); no patients with bilateral relapse survived 10 years. The median PREFS after treatment with cisplatin, doxorubicin, methotrexate, and ifosfamide was 3.5 months (95% confidence interval, 2.1-5.2), and the median PRS was 8.2 months (95% confidence interval, 5.2-15.1). CONCLUSIONS: Late relapse, surgical resection, and unilateral involvement (in lung relapse only) favorably impact outcome after relapse. Surgery is essential for survival; chemotherapy may slow disease progression in patients without CR2. These data are useful for designing clinical trials that evaluate novel agents.

Intensity modulated radiation therapy provides excellent local control in high-risk abdominal neuroblastoma.

BACKGROUND: Locoregional failure is a significant concern in patients with high-risk abdominal neuroblastoma (NB) receiving radiotherapy. Locoregional control outcomes were studied in children with NB receiving intensity modulated radiotherapy (IMRT). PROCEDURE: Twenty children (11 females, 9 males) with NB (median age at diagnosis 3.4 years) receiving IMRT were analyzed for locoregional failure, outcomes, and toxicities. IMRT doses were 23.4 Gy (n = 12), 30 Gy (n = 1), 30.6 Gy (n = 5), and 36.0 Gy (n = 2) based on extent of resection. Five patients had tumors with MYCN amplification, and 19 had metastatic disease. All patients were treated consistently using reproducible immobilization techniques; physiological motion was assessed by 4D-CT, and target localization by cone-beam computed tomography. ICRU 62 volumetric conventions were employed based on institutional data for pediatric target volume and organ motion. RESULTS: No patient developed primary site infield or locoregional failure at a median follow-up of 2.2 years. Distant failure (median time to distant failure 1.6 years) occurred in the brain, lungs, or skeletal sites in eight patients, five of whom died. The 2-year event-free survival was 58.5 ± 13.3% and cumulative incidence of local and distant failures was 0% and 41.5 ± 11.9%, respectively. Asymptomatic loose stool during RT occurred in nearly all patients, but required no intervention. CONCLUSIONS: IMRT is feasible, safe in the short term, and yields excellent locoregional control. Despite subtotal resection in some cases, locoregional control appeared to be increased by conformal radiotherapy with ICRU 62-compliant volumes. Dose escalation beyond 30.6 Gy may be unnecessary with improved target volume coverage.

Initial testing (stage 1) of the phosphatidylinositol 3' kinase inhibitor, SAR245408 (XL147) by the pediatric preclinical testing program.

BACKGROUND: Activation of the PI3 kinase pathway occurs frequently in many adult cancers and is implicated in tumor cell proliferation, survival, and resistance to chemotherapy and radiotherapy. However, less is known regarding the relevance of this pathway in pediatric cancers. Here we have evaluated SAR245408, a novel small molecule PI3K inhibitor, against childhood cancer cell lines and xenografts. PROCEDURES: SAR245408 was tested against the PPTP in vitro cell line panel at concentrations from 10 to 100 µM and against the PPTP in vivo xenograft panels at a dose of 100 mg/kg administered orally daily × 14. RESULTS: In vitro SAR245408 demonstrated cytotoxic activity, with a median relative IC50 value of 10.9 µM (range 2.7-24.5 µM). SAR245408 was well tolerated in vivo, and all 44 tested xenograft models were evaluable for efficacy. SAR245408 induced significant differences in EFS distribution compared to control in 29 of 37 (79%) of solid tumor xenografts and in two of seven (29%) ALL xenografts. SAR245408 induced tumor growth inhibition meeting criteria for intermediate EFS T/C activity (EFS T/C > 2) in 4 of 37 (11%) solid tumor xenografts. Intermediate EFS T/C activity was also observed for two of seven (29%) evaluable ALL xenografts. Objective responses were not observed for solid tumor or for ALL xenografts. CONCLUSIONS: Under the conditions evaluated in this study, SAR245408 achieved modest single-agent activity against most PPTP preclinical models. Further exploration of SAR245408 in combination with standard agents or with other signaling inhibitors could be considered.

Initial testing of the MDM2 inhibitor RG7112 by the Pediatric Preclinical Testing Program.

BACKGROUND: RG7112 is a selective inhibitor of p53-MDM2 binding that frees p53 from negative control, activating the p53 pathway in cancer cells leading to cell cycle arrest and apoptosis. RG7112 was selected for evaluation by the Pediatric Preclinical Testing Program (PPTP) due to the relatively low incidence of p53 mutations in pediatric cancers compared with adult malignancies. PROCEDURES: RG7112 and its inactive enantiomer RG7112i were evaluated against the 23 cell lines of the PPTP in vitro panel using 96 hours exposure (1 nM to 10 µM). It was tested against the PPTP in vivo panel focusing on p53 wild-type (WT) xenografts at a dose of 100 mg/kg daily for 14 days followed by 4 weeks of observation. Response outcomes were related to MDM2 and p53 expression datasets (http://pptp.nchresearch.org/data.html). RESULTS: RG7112 demonstrated cytotoxic activity with a lower median IC(50) for p53 WT versus p53 mutant cell lines (approximately 0.4 µM vs. >10 µM, respectively). RG7112 induced tumor growth inhibition meeting criteria for intermediate activity (EFS T/C > 2) in 10 of 26 (38%) solid tumor xenografts. Objective responses included medulloblastoma, alveolar rhabdomyosarcoma, Wilms, rhabdoid and Ewing sarcoma xenografts. For the ALL panel, there was one partial response, five complete responses and one maintained complete response. The ALL xenografts expressed the highest levels of p53 among the PPTP panels. CONCLUSIONS: RG7112 induced tumor regressions in solid tumors from different histotype panels, and exhibited consistent high-level activity against ALL xenografts. This high level of activity supports prioritization of RG7112 for further evaluation.

Initial testing (stage 1) of ganetespib, an Hsp90 inhibitor, by the Pediatric Preclinical Testing Program.

Ganetespib, an Hsp90 inhibitor, was tested against the PPTP in vitro cell line panel and selected xenografts in vivo, including JAK2- and BRAF-mutated models. Ganetespib demonstrated potent in vitro cytotoxic activity (median rIC50 8.8 nM, range 4.4-27.1 nM). In vivo, ganetespib induced significant differences in EFS distribution for 4 of 11 xenografts. Intermediate activity (EFS T/C > 2) was noted only for the MV4;11 xenograft, and there were no objective responses. Administered as single agents, Hsp90 inhibitors examined by the PPTP have shown limited evidence for a therapeutic window against both solid tumor and leukemia pediatric preclinical models.

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

BACKGROUND: Antimitotic agents are essential components for curative therapy of pediatric acute leukemias and many solid tumors. Eribulin is a novel agent that differs from both Vinca alkaloids and taxanes in its mode of binding to tubulin polymers. PROCEDURES: Eribulin was tested against the PPTP in vitro cell line panel at concentrations from 0.1 nM to 1.0 µM and against the PPTP in vivo xenograft panels at a dose of 1 mg/kg (solid tumors) or 1.5 mg/kg (ALL models) using a q4dx3 schedule repeated at Day 21. RESULTS: In vitro eribulin demonstrated cytotoxic activity, with a median relative IC50 value of 0.27 nM, (range <0.1-14.8 nM). Eribulin was well tolerated in vivo, and all 43 xenograft models were considered evaluable for efficacy. Eribulin induced significant differences in event-free survival (EFS) distribution compared to control in 29 of 35 (83%) of the solid tumors and in 8 of 8 (100%) of the ALL xenografts. Objective responses were observed in 18 of 35 (51%) solid tumor xenografts. Complete responses (CR) or maintained CR were observed in panels of Wilms tumor, Ewing sarcoma, rhabdomyosarcoma, glioblastoma, and osteosarcoma xenografts. All eight ALL xenografts achieved CR or MCR. CONCLUSIONS: The high level of activity observed for eribulin against the PPTP preclinical models makes this an interesting agent to consider for pediatric evaluation. The activity pattern observed for eribulin in the solid tumor panels is equal or superior to that observed previously for vincristine.

Phase II study of alisertib as a single agent for treating recurrent or progressive atypical teratoid/rhabdoid tumor.

BACKGROUND: Recurrent atypical teratoid/rhabdoid tumor (AT/RT) is, most often, a fatal pediatric malignancy with limited curative options. METHODS: We conducted a phase II study of Aurora kinase A inhibitor alisertib in patients aged <22 years with recurrent AT/RT. Patients received alisertib once daily (80 mg/m2 as enteric-coated tablets or 60 mg/m2 as liquid formulation) on Days 1-7 of a 21-day cycle until progressive disease (PD) occurred. Alisertib plasma concentrations were measured in cycle 1 on Days 1 (single dose) and 7 (steady state) and analyzed with noncompartmental pharmacokinetics. Trial efficacy end point was ≥10 participants with stable disease (SD) or better at 12 weeks. RESULTS: SD (n = 8) and partial response (PR) (n = 1) were observed among 30 evaluable patients. Progression-free survival (PFS) was 30.0% ± 7.9% at 6 months and 13.3% ± 5.6% at 1 year. One-year overall survival (OS) was 36.7% ± 8.4%. Two patients continued treatment for >12 months. PFS did not differ by AT/RT molecular groups. Neutropenia was the most common adverse effect (n = 23/30, 77%). The 22 patients who received liquid formulation had a higher mean maximum concentration (Cmax) of 10.1 ± 3.0 µM and faster time to Cmax (Tmax = 1.2 ± 0.7 h) than those who received tablets (Cmax = 5.7 ± 2.4 µM, Tmax = 3.4 ± 1.4 h). CONCLUSIONS: Although the study did not meet predetermined efficacy end point, single-agent alisertib was well tolerated by children with recurrent AT/RT, and SD or PR was observed in approximately a third of the patients.