[Medulloblastomas: review]

Survival and prognostic factors in adult medulloblastoma: the Salah Azaiz Institute experience

BACKGROUND

Medulloblastoma is the most common malignant brain tumor in children. This entity in adulthood is rare. The aim of our study is to evaluate therapeutic results and prognostic factors of adult medulloblastoma treated at our institute with post-operative radiotherapy.

METHODS

We retrospectively reviewed a cohort of 55 patients with medulloblastoma who underwent radiation in the department of radiation oncology of institute Salah Azaiz (Tunis) over a 18-year period (1994-2012).

RESULTS

The surgery was total or subtotal resection in 73% of cases. Forty-eight patients received radiotherapy to the entire craniospinal axis as part of the curative treatment. The median interval from surgery to the initiation of radiotherapy was 83 days. Etoposide-cisplatin chemotherapy was only performed in metastatic patients (n = 4). The 5-years and 10-years overall survival rates were respectively 53 and 34%. The dose of radiotherapy to the craniospinal axis was a prognostic factor. The 5-years and 10-years event-free-survival rates were 64 and 41%. Reduction in the dose of radiotherapy to the craniospinal axis and fourth ventricular floor involvement were correlated with a worse event-free survival.

CONCLUSION

Our results, compared to those of the literature, conclude that the reduction in the dose of radiotherapy to the craniospinal axis (<34 Gy) in the standard risk group of adult medulloblastoma could not be done without chemotherapy. In the high-risk group of adult medulloblastoma, radiotherapy to the cerebrospinal axis at the dose of 36 Gy with chemotherapy, is required for disease control.

[Medulloblastoma: The latest major advances]

Medulloblastoma (MB) is a malignant brain tumor that mainly affects children. It is rarely found in adults. Among the four groups of MB defined today according to molecular characteristics, group 3 is the least favorable with an overall survival rate of 50 %. Current treatments, based on surgery, radiotherapy, and chemotherapy, are not sufficiently adapted to the different characteristics of the four MB groups. However, the use of new cellular and animal models has opened new doors to interesting therapeutic avenues. In this review, we detail recent advances in MB research, with a focus on the genes and pathways that drive tumorigenesis, with particular emphasis on the animal models that have been developed to study tumor biology, as well as advances in new targeted therapies.

Medulloblastoma: optimizing care with a multidisciplinary approach

Medulloblastoma is a malignant tumor of the cerebellum and the most frequent malignant brain tumor in children. The standard of care consists of maximal resection surgery, followed by craniospinal irradiation and chemotherapy. Such treatment allows long-term survival rates of nearly 70%; however, there are wide disparities among patient outcomes, and in any case, major long-term morbidity is observed with conventional treatment. In the last two decades, the molecular understanding of medulloblastoma has improved drastically, allowing us to revolutionize our understanding of medulloblastoma pathophysiological mechanisms. These advances led to an international consensus in 2010 that defined four prognostic molecular subgroups named after their affected signaling pathways, that is, WNT, SHH, Group 3 and Group 4. The molecular understanding of medulloblastoma is starting to translate through to clinical settings due to the development of targeted therapies. Moreover, recent improvements in radiotherapy modalities and the reconsideration of craniospinal irradiation according to the molecular status hold promise for survival preservation and the reduction of radiation-induced morbidity. This review is an overview of the current knowledge of medulloblastoma through a molecular approach, and therapeutic prospects currently being developed in surgery, radiotherapy and targeted therapies to optimize the treatment of medulloblastoma with a multidisciplinary approach will also be discussed.

[Pediatric medulloblastoma: Retrospective series of 52 patients]

PURPOSE

Retrospective analysis of the results of 52 children irradiated for a medulloblastoma.

PATIENTS AND METHODS

Between 1974 and 2012, 52 children with an average age of 6 years and a half (11 months-17 years and a half) were treated with surgery then with radiotherapy at the Comprehensive Cancer Centre of Strasbourg (France). For 44 children, the treatment consisted of a chemotherapy.

RESULTS

After a mean follow-up of 106.6 months (7-446 months), 13 relapses and 24 deaths were observed. Overall survival at 5 years and 10 years were 62% and 57%, respectively. Disease-free survival at 5 years and 10 years were 80% and 63%, respectively. Univariate analysis found the following adverse prognostic factors: the existence of a postoperative residue, the positivity of the cerebrospinal fluid, the metastatic status and medulloblastoma of high-risk. Positivity of the cerebrospinal fluid remains a negative factor in multivariate analysis.

CONCLUSION

These results confirm the survival rate obtained by a conventional approach (surgery then irradiation). Insufficiency of results and rarity of medulloblastoma require the establishment of international protocols.

[Therapeutic outcomes of medulloblastoma in Casablanca from 2000 to 2012]

PURPOSE

To describe the therapeutic results, with the aim to contribute to improving the care of patients with medulloblastoma.

PATIENTS AND METHODS

A retrospective study of 69 cases of medulloblastoma collected in the university hospital Ibn Rochd of Casablanca between 2000 and 2012.

RESULTS

Fifty-three children with an average age of 9 years and 16 adults with an average age of 32.4 years were included in the study. Thirty-seven children and eight adults suffered from a high-risk tumour. The radiotherapy was received by all patients with a mean dose of 36 Gy to the whole brain and 54 Gy in the posterior fossa. All patients in the paediatric group and 10 patients in the adult group received concomitant chemotherapy, 44 children and four adults received adjuvant chemotherapy. Tumour recurrence was observed in 17 children after a mean follow-up period of 38 months. These recurrences were observed in five adults after a mean follow-up period of 42 months. The posterior fossa was the main site of relapses. Overall survival was 77.7% for the children and 61% for the adults. Overall survival was better (70% versus 25%) when the interval between radiotherapy and surgery was less than 40 days in the paediatric group. The recurrence rate was significantly higher for the high-risk group: 41% versus 13% for the standard risk. In the adult group, overall survival differences according to the risk group were significant (100% for the standard risk versus 37.5% for the high risk).

CONCLUSION

The overall survival and recurrences rate obtained are encouraging. The risk group and time between surgery and radiotherapy were prognostic factors with significant impact on survival depending on the age group. We recommend reducing these times to improve therapeutic results.

[Medulloblastoma in adults: report of 13 cases and literature review]

Le médulloblastome est une tumeur neuro-ectodermique primitive maligne. Il s'agit d'une tumeur rare chez l'adulte, représentant moins de 1% des tumeurs cérébrales. Nous proposons une étude rétrospective réalisée au sein du service d'Oncologie-Radiothérapie du CHU Mohamed VI de Marrakech sur une période de 13 ans. Le but de notre travail est de déterminer le profil épidémioclinique, thérapeutique, évolutif ainsi que les facteurs pronostiques de cette entité pathologique avec une revue de la littérature. Notre série comportait 13 patients, 10 hommes et 3 femmes, l’âge médian a été 20,8 ans. Le tableau clinique a été révélé par un syndrome d'hypertension intracrânienne (100%), associée à un syndrome cérébelleux (84%). La localisation était hémisphérique (31%) et vermio-hémisphérique (54%). 31% des patients ont bénéficié d'une exérèse chirurgicale totale. 85% des cas avaient une variante classique et 15% une variante desmoplasique. 30% des cas avaient été classés à «risque standard» et 70% à «haut risque». La chirurgie avait été complétée d'une radiothérapie de l'ensemble du névraxe selon la technique de «jonctions mobiles» dans tous les cas. Le délai moyen était de 73 jours. Une chimiothérapie adjuvante avait été réalisée chez 9 cas. Avec un recul moyen de 21.3 mois, l’évolution a été marquée par une récidive tumorale (4 cas), une toxicité auditive (6 cas) et des troubles cognitifs chez un cas. La prise en charge du médulloblastome doit être multidisciplinaire associant neurochirurgiens et oncologues radiothérapeutes. Cette collaboration est le seul garant d'une amélioration de son pronostic.

[Evolution of the management of pediatric and adult medulloblastoma]

Medulloblastoma are cerebellar tumours belonging to the group of primitive neuroectodermal tumours (PNET) and are the most common malignant brain tumours of childhood. These tumours are rare and heterogeneous, requiring some multicentric prospective studies and multidisciplinary care. The classical therapeutic approaches are based on clinical, radiological and surgical data. They involve surgery, radiation therapy and chemotherapy. Some histological features were added to characterize risk. More recently, molecular knowledge has allowed to devise risk-adapted strategies and helped to define groups with good outcome and reduce long-term sequelae, improve the prognostic of high-risk medulloblastoma and develop new therapeutic tools.

Heme Oxygenase-1 Influences Apoptosis via CO-mediated Inhibition of K+ Channels

Hypoxic/ischemic episodes can trigger oxidative stress-mediated loss of central neurons via apoptosis, and low pO2 is also a feature of the tumor microenvironment, where cancer cells are particularly resistant to apoptosis. In the CNS, ischemic insult increases expression of the CO-generating enzyme heme oxygenase-1 (HO-1), which is commonly constitutively active in cancer cells. It has been proposed that apoptosis can be regulated by the trafficking and activity of K(+) channels, particularly Kv2.1. We have explored the idea that HO-1 may influence apoptosis via regulation of Kv2.1. Overexpression of Kv2.1 in HEK293 cells increased their vulnerability to oxidant-induced apoptosis. CO (applied as the donor CORM-2) protected cells against apoptosis and inhibited Kv2.1 channels. Similarly in hippocampal neurones, CO selectively inhibited Kv2.1 and protected neurones against oxidant-induced apoptosis. In medulloblastoma sections we identified constitutive expression of HO-1 and Kv2.1, and in the medulloblastoma-derived cell line DAOY, hypoxic HO-1 induction or exposure to CO protected cells against apoptosis, and also selectively inhibited Kv2.1 channels expressed in these cells. These studies are consistent with a central role for Kv2.1 in apoptosis in both central neurones and cancer cells. They also suggest that HO-1 expression can strongly influence apoptosis via CO-mediated regulation of Kv2.1 activity.

Disrupted sensorimotor synchronization, but intact rhythm discrimination, in children treated for a cerebellar medulloblastoma

The aim of this study was to investigate the temporal abilities of children treated by surgery for a malignant tumor in the cerebellum, both in the perception and the production of rhythm. Children with a diagnosed medulloblastoma and age-matched control children were tested in a rhythm discrimination task and a sensorimotor synchronization task. Their motor and cognitive capabilities were also assessed through a battery of age-adapted neuropsychological tests. The results did not show any significant difference in performance between groups for the discrimination task. On the contrary, children with cerebellar lesions produced longer and more variable inter-tap intervals (ITI) in their spontaneous motor tempo (SMT) than did the control children. However, the length and, to a lesser extent, the variability of their SMT decreased after a synchronization phase, when they had been instructed to tap in synchrony with a beep. During the synchronization task, the children with medulloblastoma succeeded to modify the length of their ITI in response to an auditory rhythm, although with better success when the inter-stimuli intervals (ISI) were shorter than when they were longer than the ITIs of their own SMT. Correlational analyses revealed that children's poorer synchronization performance was related to lower scores in neuropsychological tests assessing motor dexterity and processing speed.

Cognitive disorders in pediatric medulloblastoma: what neuroimaging has to offer

Medulloblastomas are the most common malignant childhood brain tumors arising in the posterior fossa. Treatment improvements for these tumors have meant that there are a greater number of survivors, but this long-term patient survival has increased the awareness of resulting neurocognitive deficits. Impairments in attention, memory, executive functions, and intelligence quotient demonstrate that the cerebellum likely plays a significant role in numerous higher cognitive functions such as language, cognitive, and emotional functions. In addition, children with medulloblastoma not only have cerebellar lesions but also brain white matter damages due to radiation and chemotherapy. Functional neuroimaging, a noninvasive method with many advantages, has become the standard tool in clinical and cognitive neuroscience research. By reviewing functional neuroimaging studies, this review aims to clarify the role of the cerebellum in cognitive function and explain more clearly cognitive sequelae due to polytherapy in children with medulloblastoma. This review suggests that the posterior cerebellar lobes are crucial to maintaining cognitive performance. Clinical investigations could help to better assess the involvement of these lobes in cognitive functions.

Personalizing the treatment of pediatric medulloblastoma: Polo-like kinase 1 as a molecular target in high-risk children

Medulloblastoma is the most common malignant brain tumor in children. This disease is heterogeneous and is composed of four subtypes of medulloblastoma [WNT, Sonic Hedgehog (SHH), Group 3, and Group 4]. An immediate goal is to identify novel molecular targets for the most aggressive forms of medulloblastoma. Polo-like kinase 1 (PLK1) is an oncogenic kinase that controls cell cycle and proliferation, making it a strong candidate for medulloblastoma treatment. In this study, pediatric medulloblastomas were subtyped in two patient cohorts (discovery cohort, n = 63 patients; validation cohort, n = 57 patients) using NanoString nCounter analysis and PLK1 mRNA was assessed. We determined that the SHH and Group 3 subtypes were independently associated with poor outcomes in children as was PLK1 using Cox regression analyses. Furthermore, we screened a library of 129 compounds in clinical trials using a model of pediatric medulloblastoma and determined that PLK1 inhibitors were the most promising class of agents against the growth of medulloblastoma. In patient-derived primary medulloblastoma isolates, the PLK1 small-molecule inhibitor BI2536 suppressed the self-renewal of cells with high PLK1 but not low PLK1 expression. PLK1 inhibition prevented medulloblastoma cell proliferation, self-renewal, cell-cycle progression, and induced apoptosis. In contrast, the growth of normal neural stem cells was unaffected by BI2536. Finally, BI2536 extended survival in medulloblastoma-bearing mice with efficacy comparable with Headstart, a standard-of-care chemotherapy regimen. We conclude that patients with medulloblastoma expressing high levels of PLK1 are at elevated risk. These preclinical studies pave the way for improving the treatment of medulloblastoma through PLK1 inhibition.

Carbon monoxide mediates the anti-apoptotic effects of heme oxygenase-1 in medulloblastoma DAOY cells via K+ channel inhibition

Tumor cell survival and proliferation is attributable in part to suppression of apoptotic pathways, yet the mechanisms by which cancer cells resist apoptosis are not fully understood. Many cancer cells constitutively express heme oxygenase-1 (HO-1), which catabolizes heme to generate biliverdin, Fe(2+), and carbon monoxide (CO). These breakdown products may play a role in the ability of cancer cells to suppress apoptotic signals. K(+) channels also play a crucial role in apoptosis, permitting K(+) efflux which is required to initiate caspase activation. Here, we demonstrate that HO-1 is constitutively expressed in human medulloblastoma tissue, and can be induced in the medulloblastoma cell line DAOY either chemically or by hypoxia. Induction of HO-1 markedly increases the resistance of DAOY cells to oxidant-induced apoptosis. This effect was mimicked by exogenous application of the heme degradation product CO. Furthermore we demonstrate the presence of the pro-apoptotic K(+) channel, Kv2.1, in both human medulloblastoma tissue and DAOY cells. CO inhibited the voltage-gated K(+) currents in DAOY cells, and largely reversed the oxidant-induced increase in K(+) channel activity. p38 MAPK inhibition prevented the oxidant-induced increase of K(+) channel activity in DAOY cells, and enhanced their resistance to apoptosis. Our findings suggest that CO-mediated inhibition of K(+) channels represents an important mechanism by which HO-1 can increase the resistance to apoptosis of medulloblastoma cells, and support the idea that HO-1 inhibition may enhance the effectiveness of current chemo- and radiotherapies.