Mesenchymal Transition and PDGFRA Amplification/Mutation Are Key Distinct Oncogenic Events in Pediatric Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine glioma (DIPG) is one of the most frequent malignant pediatric brain tumor and its prognosis is universaly fatal. No significant improvement has been made in last thirty years over the standard treatment with radiotherapy. To address the paucity of understanding of DIPGs, we have carried out integrated molecular profiling of a large series of samples obtained with stereotactic biopsy at diagnosis. While chromosomal imbalances did not distinguish DIPG and supratentorial tumors on CGHarrays, gene expression profiling revealed clear differences between them, with brainstem gliomas resembling midline/thalamic tumours, indicating a closely-related origin. Two distinct subgroups of DIPG were identified. The first subgroup displayed mesenchymal and pro-angiogenic characteristics, with stem cell markers enrichment consistent with the possibility to grow tumor stem cells from these biopsies. The other subgroup displayed oligodendroglial features, and appeared largely driven by PDGFRA, in particular through amplification and/or novel missense mutations in the extracellular domain. Patients in this later group had a significantly worse outcome with an hazard ratio for early deaths, ie before 10 months, 8 fold greater that the ones in the other subgroup (p = 0.041, Cox regression model). The worse outcome of patients with the oligodendroglial type of tumors was confirmed on a series of 55 paraffin-embedded biopsy samples at diagnosis (median OS of 7.73 versus 12.37 months, p = 0.045, log-rank test). Two distinct transcriptional subclasses of DIPG with specific genomic alterations can be defined at diagnosis by oligodendroglial differentiation or mesenchymal transition, respectively. Classifying these tumors by signal transduction pathway activation and by mutation in pathway member genes may be particularily valuable for the development of targeted therapies

Bayesian survival analysis in clinical trials:what methods are used in practice?

Background Bayesian statistics are an appealing alternative to the traditional frequentist approach to designing, analysing, and reporting of clinical trials, especially in rare diseases. Time-to-event endpoints are widely used in many medical fields. There are additional complexities to designing Bayesian survival trials which arise from the need to specify a model for the survival distribution. The objective of this article was to critically review the use and reporting of Bayesian methods in survival trials. Methods A systematic review of clinical trials using Bayesian survival analyses was performed through PubMed and Web of Science databases. This was complemented by a full text search of the online repositories of pre-selected journals. Cost-effectiveness, dose-finding studies, meta-analyses, and methodological papers using clinical trials were excluded. Results In total, 28 articles met the inclusion criteria, 25 were original reports of clinical trials and 3 were re-analyses of a clinical trial. Most trials were in oncology (n = 25), were randomised controlled (n = 21) phase III trials (n = 13), and half considered a rare disease (n = 13). Bayesian approaches were used for monitoring in 14 trials and for the final analysis only in 14 trials. In the latter case, Bayesian survival analyses were used for the primary analysis in four cases, for the secondary analysis in seven cases, and for the trial re-analysis in three cases. Overall, 12 articles reported fitting Bayesian regression models (semi-parametric, n = 3; parametric, n = 9). Prior distributions were often incompletely reported: 20 articles did not define the prior distribution used for the parameter of interest. Over half of the trials used only non-informative priors for monitoring and the final analysis (n = 12) when it was specified. Indeed, no articles fitting Bayesian regression models placed informative priors on the parameter of interest. The prior for the treatment effect was based on historical data in only four trials. Decision rules were pre-defined in eight cases when trials used Bayesian monitoring, and in only one case when trials adopted a Bayesian approach to the final analysis. Conclusion Few trials implemented a Bayesian survival analysis and few incorporated external data into priors. There is scope to improve the quality of reporting of Bayesian methods in survival trials. Extension of the Consolidated Standards of Reporting Trials statement for reporting Bayesian clinical trials is recommended

PDCT-01. BIOLOGICAL MEDICINE FOR DIFFUSE INTRINSIC PONTINE GLIOMAS ERADICATION (BIOMEDE): RESULTS OF THE THREE-ARM BIOMARKER-DRIVEN RANDOMIZED TRIAL IN THE FIRST 230 PATIENTS FROM EUROPE AND AUSTRALIA

International audienceAbstract BACKGROUND Diffuse intrinsic pontine glioma (DIPG) is one of the most devastating brain neoplasms. Despite 50 years of clinical trials, no improvement of survival has been observed and most children die within 2 years of diagnosis. Only radiotherapy transiently controls disease progression. METHODS/AIMS: BIOMEDE was conceived as a randomized multi-arm multi-stage program (drop-the-loser adaptive design). It started with an open-label phase-II trial comparing three drugs (everolimus, dasatinib, erlotinib) combined with irradiation, allocated according to the presence of their specific targets) with a planned sample size of 250 patients. A stereotactic biopsy was performed at diagnosis to centrally confirm the diagnosis of DIPG (presence of histone H3K27M mutation or loss of K27 trimethylation) and assess biomarkers/targets (PTEN-loss, EGFR-overexpression). Targeted therapies were started concomitantly with radiotherapy and were continued until disease progression. The main objective of the study was to compare the efficacy of randomized groups in terms of overall survival (OS). RESULTS At the 3rd interim analysis, based on 193 randomized patients among the 230 study patients, the IDMC concluded that the study was unlikely to meet its primary objective even if 250 patients were randomized. The median OS from the time of randomization was 10.9, 9.5 and 9 months for everolimus, dasatinib and erlotinib, respectively, which is comparable to historical controls. The median number of courses administered was 7, 5.5 and 6 respectively. Treatment was discontinued due to toxicity in 2%, 13%, and 15%, respectively. No biopsy-related death was reported and diagnostic yield was excellent, with only 5 non-informative biopsies. CONCLUSION BIOMEDE shows the feasibility of biologically-driven treatment in DIPG on a large international scale. Based on the better toxicity profile and the slightly better efficacy, although not statistically significant, the steering committee proposed that everolimus should be used as the control arm for the next step, BIOMEDE 2.0

Biological medicines for diffuse intrinsic pontine glioma (DIPG) eradication (BIOMEDE): Final results of an international randomized phase II platform trial comparing 3 targeted therapies in combination with radiotherapy from ITCC, SIOPE-Brain and ANZCHOG.

International audience10003 Background: DIPG is the most aggressive brain cancer in children and adolescents with a median survival of 9 months. Surgery is not possible due to the invasive nature of the disease in a critical area of the brain; only radiotherapy has shown a transient palliative effect on disease progression and no adjuvant therapy has proven to increase disease control. Methods: We launched a large randomized biomarker-driven platform trial to compare three targeted therapies (erlotinib, everolimus and dasatinib) in combination with 54 Gy radiotherapy, in newly diagnosed patients with DIPG (NCT02233049). A central pathological review was performed prior to study entry to confirm the diagnosis of DIPG with H3K27me3 loss (with or without H3K27M mutation) and assess biomarkers. The randomization was designed so that a drug could not be allocated if the corresponding biomarker was absent in the tumor (EGFR overexpression for erlotinib, mTOR activation for everolimus, no specific biomarker for dasatinib). Tumors underwent whole genome sequencing and RNAseq to evaluate prognostic and theranostic biomarkers. Primary endpoint was overall survival. Results: Among the 279 DIPG patients screened for the randomized trial between October 2014 and September 2019, 233 were enrolled in 45 centers in 7 countries; among the 46 screen failures, the diagnosis of DIPG could not be confirmed in 23 patients. No biopsy- or treatment-related death was reported. Serious adverse events > = 3 unrelated to disease progression were reported in 40% of patients, 34%, 36% and 46%, in the erlotinib, everolimus and dasatinib arms, respectively (p = 0.32). With a median follow-up of 5.3 years, median overall survival (OS) from the date of randomization was 9.0 (95% confidence interval, 7.4-14.4), 11.3 (10.3-13.4) and 9.4 (7.7-10.7) months for erlotinib, everolimus and dasatinib, respectively (p = 0.45). OS were not statistically different from those of a historical biopsy-proven cohort. The molecular profiling with copy number aberrations (CNA) had a strong impact on survival (log-rank test, p = 0.0001) as shown by the preliminary analysis of the first hundred patients identifying a group of tumors with very poor prognosis with a HR for death of 1.96 (1.07-3.64) characterized by TP53 mutations (p = 3.05e-11) associated with more CNA (p < 0.0001). Conclusions: This trial demonstrated the feasibility and safety of a large randomized trial for DIPG based on biomarker information from a stereotactic biopsy at diagnosis in an international multicenter setting and generated new tumor biological insights to further develop innovative therapies. Clinical trial information: NCT02233049