Liliana Goumnerova

Prediction of central nervous system embryonal tumour outcome based on gene expression

Embryonal tumours of the central nervous system (CNS) represent a heterogeneous group of tumours about which little is known biologically, and whose diagnosis, on the basis of morphologic appearance alone, is controversial. Medulloblastomas, for example, are the most common malignant brain tumour of childhood, but their pathogenesis is unknown, their relationship to other embryonal CNS tumours is debated, and patients’ response to therapy is difficult to predict. We approached these problems by developing a classification system based on DNA microarray gene expression data derived from 99 patient samples. Here we demonstrate that medulloblastomas are molecularly distinct from other brain tumours including primitive neuroectodermal tumours (PNETs), atypical teratoid/rhabdoid tumours (AT/RTs) and malignant gliomas. Previously unrecognized evidence supporting the derivation of medulloblastomas from cerebellar granule cells through activation of the Sonic Hedgehog (SHH) pathway was also revealed. We show further that the clinical outcome of children with medulloblastomas is highly predictable on the basis of the gene expression profiles of their tumours at diagnosis.

Integrative Genomic Analysis of Medulloblastoma Identifies a Molecular Subgroup That Drives Poor Clinical Outcome

PURPOSE Medulloblastomas are heterogeneous tumors that collectively represent the most common malignant brain tumor in children. To understand the molecular characteristics underlying their heterogeneity and to identify whether such characteristics represent risk factors for patients with this disease, we performed an integrated genomic analysis of a large series of primary tumors. PATIENTS AND METHODS We profiled the mRNA transcriptome of 194 medulloblastomas and performed high-density single nucleotide polymorphism array and miRNA analysis on 115 and 98 of these, respectively. Non-negative matrix factorization-based clustering of mRNA expression data was used to identify molecular subgroups of medulloblastoma; DNA copy number, miRNA profiles, and clinical outcomes were analyzed for each. We additionally validated our findings in three previously published independent medulloblastoma data sets. RESULTS Identified are six molecular subgroups of medulloblastoma, each with a unique combination of numerical and structural chromosomal aberrations that globally influence mRNA and miRNA expression. We reveal the relative contribution of each subgroup to clinical outcome as a whole and show that a previously unidentified molecular subgroup, characterized genetically by c-MYC copy number gains and transcriptionally by enrichment of photoreceptor pathways and increased miR-183∼96∼182 expression, is associated with significantly lower rates of event-free and overall survivals. CONCLUSION Our results detail the complex genomic heterogeneity of medulloblastomas and identify a previously unrecognized molecular subgroup with poor clinical outcome for which more effective therapeutic strategies should be developed.

Intensive Multimodality Treatment for Children With Newly Diagnosed CNS Atypical Teratoid Rhabdoid Tumor

PURPOSE Atypical teratoid rhabdoid tumor (ATRT) of the CNS is a highly malignant neoplasm primarily affecting young children, with a historic median survival ranging from 6 to 11 months. Based on a previous pilot series, a prospective multi-institutional trial was conducted for patients with newly diagnosed CNS ATRT. PATIENTS AND METHODS Treatment was divided into five phases: preirradiation, chemoradiation, consolidation, maintenance, and continuation therapy. Intrathecal chemotherapy was administered, alternating intralumbar and intraventricular routes. Radiation therapy (RT) was prescribed, either focal (54 Gy) or craniospinal (36 Gy, plus primary boost), depending on age and extent of disease at diagnosis. RESULTS Between 2004 and 2006, 25 patients were enrolled; 20 were eligible for evaluation. Median age at diagnosis was 26 months (range, 2.4 months to 19.5 years). Gross total resection of the primary tumor was achieved in 11 patients. Fourteen patients had M0 disease at diagnosis, one patient had M2 disease, and five patients had M3 disease. Fifteen patients received radiation therapy: 11 focal and four craniospinal. Significant toxicities, in addition to the expected, included radiation recall (n = 2) and transverse myelitis (n = 1). There was one toxic death. Of the 12 patients who were assessable for chemotherapeutic response (pre-RT), the objective response rate was 58%. The objective response rate observed after RT was 38%. The 2-year progression-free and overall survival rates are 53% +/- 13% and 70% +/- 10%, respectively. Median overall survival has not yet been reached. CONCLUSION This intensive multimodality regimen has resulted in a significant improvement in time to progression and overall survival for patients with this previously poor-prognosis tumor.

Recurrent somatic mutations in ACVR1 in pediatric midline high-grade astrocytoma

Pediatric midline high-grade astrocytomas (mHGAs) are incurable with few treatment targets identified. Most tumors harbor mutations encoding p.Lys27Met in histone H3 variants. In 40 treatment-naive mHGAs, 39 analyzed by whole-exome sequencing, we find additional somatic mutations specific to tumor location. Gain-of-function mutations in ACVR1 occur in tumors of the pons in conjunction with histone H3.1 p.Lys27Met substitution, whereas FGFR1 mutations or fusions occur in thalamic tumors associated with histone H3.3 p.Lys27Met substitution. Hyperactivation of the bone morphogenetic protein (BMP)-ACVR1 developmental pathway in mHGAs harboring ACVR1 mutations led to increased levels of phosphorylated SMAD1, SMAD5 and SMAD8 and upregulation of BMP downstream early-response genes in tumor cells. Global DNA methylation profiles were significantly associated with the p.Lys27Met alteration, regardless of the mutant histone H3 variant and irrespective of tumor location, supporting the role of this substitution in driving the epigenetic phenotype. This work considerably expands the number of potential treatment targets and further justifies pretreatment biopsy in pediatric mHGA as a means to orient therapeutic efforts in this disease.

Moyamoya following cranial irradiation for primary brain tumors in children

Objective: To study the risk factors for the development of moyamoya syndrome after cranial irradiation for primary brain tumors in children. Methods: We reviewed neuroimaging studies and dosimetry data for 456 children who were treated with radiation for a primary brain tumor and who were prospectively evaluated with serial neuroimaging studies and neurologic evaluations. A total of 345 patients had both adequate neuroimaging and radiation dosimetry data for further analysis. We used survival analysis techniques to examine the relationship of clinically important variables as risk factors for the development of moyamoya over time. Results: Overall, 12 patients (3.5%) developed evidence of moyamoya. The onset of moyamoya was more rapid for patients with neurofibromatosis type 1 (NF1) (median of 38 vs 55 months) and for patients who received >5,000 cGy of radiation (median of 42 vs 67 months). In a multiple Cox proportional hazards regression analysis controlling for age at start of radiation, each 100-cGy increase in radiation dose increased the rate of moyamoya by 7% (hazard ratio [HR] = 1.07, 95% CI: 1.02 to 1.13, p = 0.01) and the presence of NF1 increased the rate of moyamoya threefold (HR = 3.07, 95% CI: 0.90 to 10.46, p = 0.07). Conclusions: Moyamoya syndrome is a potentially serious complication of cranial irradiation in children, particularly for those patients with tumors in close proximity to the circle of Willis, such as optic pathway glioma. Patients who received higher doses of radiation to the circle of Willis and with neurofibromatosis type 1 have increased risk of the development of moyamoya syndrome.

Genomic analysis of diffuse pediatric low-grade gliomas identifies recurrent oncogenic truncating rearrangements in the transcription factor MYBL1

Pediatric low-grade gliomas (PLGGs) are among the most common solid tumors in children but, apart from BRAF kinase mutations or duplications in specific subclasses, few genetic driver events are known. Diffuse PLGGs comprise a set of uncommon subtypes that exhibit invasive growth and are therefore especially challenging clinically. We performed high-resolution copy-number analysis on 44 formalin-fixed, paraffin-embedded diffuse PLGGs to identify recurrent alterations. Diffuse PLGGs exhibited fewer such alterations than adult low-grade gliomas, but we identified several significantly recurrent events. The most significant event, 8q13.1 gain, was observed in 28% of diffuse astrocytoma grade IIs and resulted in partial duplication of the transcription factor MYBL1 with truncation of its C-terminal negative-regulatory domain. A similar recurrent deletion-truncation breakpoint was identified in two angiocentric gliomas in the related gene v-myb avian myeloblastosis viral oncogene homolog (MYB) on 6q23.3. Whole-genome sequencing of a MYBL1-rearranged diffuse astrocytoma grade II demonstrated MYBL1 tandem duplication and few other events. Truncated MYBL1 transcripts identified in this tumor induced anchorage-independent growth in 3T3 cells and tumor formation in nude mice. Truncated transcripts were also expressed in two additional tumors with MYBL1 partial duplication. Our results define clinically relevant molecular subclasses of diffuse PLGGs and highlight a potential role for the MYB family in the biology of low-grade gliomas.

Stereotactic radiotherapy for pediatric and adult brain tumors : preliminary report

PURPOSE Stereotactic radiotherapy is a new modality that combines the accurate focal dose delivery of stereotactic radiosurgery with the biological advantages of conventional radiotherapy (1.8-2.0 Gy/day using 25-30 fractions). The modality requires sophisticated treatment planning, dedicated high-energy linear accelerator, and relocatable immobilization devices. We report here our early experience using stereotactic radiotherapy for intracranial neoplasms. METHODS AND MATERIALS Between June 1992 and September 1993, we treated 82 patients with central nervous system lesions using stereotactic radiotherapy, delivered from a dedicated 6 MV stereotactic linear accelerator. A head fixation frame provided daily relocatable setup using a dental plate for all patients over 8 years of age. A modified head frame, which does not require a mouthpiece, was used for children requiring anesthesia. The patients ranged in age from 9 months to 76 years. Thirty-three patients were children less than 21 years of age. Selection criteria for the protocol included: (a) focal, small (< 5 cm) radiographically distinct lesions known to be radiocurable (pituitary adenoma, craniopharyngioma, meningioma, acoustic neuroma, pilocytic astrocytoma, retinoblastoma), and (b) lesions located in regions not amenable to surgery or radiosurgery such as the brain stem or chiasm. Standard fractionation and conventional doses were delivered. Patients with low-grade astrocytoma, oligodendroglioma, or ependymoma were treated using a dose escalation regime consisting of conventional doses plus a 10% increase. RESULTS Although follow-up is 16 months (range 3-16 months), posttreatment radiographic studies in 77 patients have been consistent with changes similar to those found after conventional radiation therapy. To date, reduction of up to 50% of the original volume has been noted in 19 out of 77 patients, and 4 patients had a complete response, 2 with dysgerminoma, and 1 each with astrocytoma and retinoblastoma. In 56 patients disease was either stable or the follow-up was too short for evaluation. While the follow-up is relatively short, there have been no in-field or marginal recurrences. The only unexpected radiographic findings were in three patients with pilocytic astrocytomas, who developed asymptomatic edema in the treatment volume. Accuracy in daily fractionation was excellent. In over 2000 patient setups with 41,000 scalp measurements, reproducibility was found to be within 0.41 mm (median) of baseline readings, allowing for precise immobilization throughout the treatment course. The treatment in all cases was well tolerated with minimal acute effects. Our stereotactic radiotherapy facility can provide fractionated therapy for 10-12 patients a day efficiently and accurately. CONCLUSIONS The treatment and relocatable stereotactic head frames were well tolerated with minimal acute effects. No long-term sequelae have been noted, although the observation period is short. To fully define the role of stereotactic radiotherapy, we are conducting prospective studies to evaluate neurocognitive and neuroendocrine effects. We expect that this innovative approach will make a significant impact on the treatment of intracranial neoplasms, particularly in children.

Presentation and Management of Chiari I Malformation in Children

To determine the efficacy of operative treatment for children with Chiari I malformation, the medical records and magnetic resonance imaging (MRI) studies of 68 consecutive patients cared for at The Childrens Hospital, Boston, Mass., USA, from December, 1988 to November, 1996 were retrospectively reviewed. All patients underwent suboccipital craniectomy, C1 laminectomy, and dural grafting. Bipolar coagulation to shrink and reduce the volume of the cerebellar tonsils was carried out in 40 patients. In 32 of 40 patients with associated syringomyelia, the procedure included placement of a IVth ventricle to cervical subarachnoid space shunt. Twenty-three patients with syringomyelia also had plugging of the obex. There was no operative mortality. Morbidity included a 22% incidence of nausea/vomiting and a 10% incidence of headache, both limited to the immediate postoperative period. Within the first postoperative month, all patients or their parents reported clear improvement in their presenting symptoms and 93% were found to have clear improvement in their presenting signs. In follow-up periods of 6-70 months, all patients had continued unequivocal symptom improvement and all patients were found on examination to have clear improvement in neurological signs. In patients with syringomyelia, MRI studies carried out at least 6 months postoperatively revealed near total or total syrinx resolution in 80% of the cases. This study demonstrates that a standard bony and dural decompression of the foramen magnum region with modifications designed to maximize the restoration of CSF circulation across the foramen magnum is a safe, effective operative treatment for Chiari I malformation in children.

Treatment of Hydrocephalus with Third Ventriculocisternostomy: Outcome and CSF Flow Patterns

Third ventriculocisternostomy was performed in 23 patients for management of hydrocephalus. The procedure was offered as the first treatment in 18 cases and in lieu of a shunt revision in 4 cases. Median follow-up was 17 months (range 7-44 months). In 16 patients the operation was successful in treating their symptoms (73%). Cine MRI was helpful in evaluating patients with persistent ventriculomegaly. Resolution of symptoms in association with decreased ventricular size correlated best with outcome following this procedure. Third ventriculocisternostomy is technically safe and minimally invasive and should be offered as the first procedure in the management of noncommunicating hydrocephalus.

RADIOSURGERY IN THE MANAGEMENT OF PEDIATRIC BRAIN TUMORS

OBJECTIVE To describe the outcome of pediatric brain tumor patients following stereotactic radiosurgery (SRS), and factors associated with progression-free survival. METHODS We reviewed the outcome of 90 children treated with SRS for recurrent (n = 62) or residual (n = 28) brain tumors over a 10-year period. Median follow-up from SRS was 24 months for all patients and 55.5 months for the 34 patients currently alive. RESULTS The median progression-free survival (PFS) for all patients was 13 months. Median PFS according to tumor histology was medulloblastoma = 11 months, ependymoma = 8.5 months, glioblastoma and anaplastic astrocytoma = 12 months. Median PFS in patients treated to a single lesion was 15.4 months. No patient undergoing SRS to more than 1 lesion survived disease free beyond 2 years. After adjusting for histology and other clinical factors, SRS for tumor recurrence (RR = 2.49) and the presence of > 1 lesion (RR = 2.3) were associated with a significantly increased rate of progression (p < 0.05). Three-year actuarial local control (LC) was as follows: medulloblastoma = 57%, ependymoma = 29%, anaplastic astrocytoma/glioblastoma = 60%, other histologies = 56%. Nineteen patients with radionecrosis and progressive neurologic symptoms underwent reoperation after an interval of 0.6-62 months following SRS. Pathology revealed necrosis with no evidence of tumor in 9 of these cases. CONCLUSION SRS can be given safely to selected children with brain tumors. SRS appears to reduce the proportion of first failures occurring locally and is associated with better outcome when given as a part of initial management. Some patients with unresectable relapsed disease can be salvaged with SRS. SRS to multiple lesions does not appear to be curative. Serious neurologic symptoms requiring reoperation is infrequently caused by radionecrosis alone.