Surveillance neuroimaging of intracranial medulloblastoma in children: how effective, how often, and for how long?

Optimizing reirradiation for relapsed medulloblastoma: identifying the ideal patient and tumor profiles

BACKGROUND

First-line therapies for medulloblastoma(MBL) are obtaining higher survival-rates while decreasing late-effects, but treatment at relapse is not standardized. We report here the experience with MBL re-irradiation(re-RT), its timing and outcome in different clinical settings and tumor groups.

METHODS

Patient's staging/treatment at diagnosis, histotypes/molecular subgroups, relapse site/s, re-treatments outcome are reported.

RESULTS

25 patients were included, with a median age of 11.4 years; 8 had metastases. According to 2016-2021 WHO-classification, 14 had SHH subgroup tumors(six TP53 mutated,one + MYC,one + NMYC amplification), 11 non-WNT/non-SHH (two with MYC/MYCN amplification).Thirteen had received HART-CSI, 11 standard-CSI, one HFRT; all post-radiation chemotherapy(CT), 16 also pre-RT. Median time to relapse (local-LR in nine, distant-DR in 14, LR + DR in two) was 26 months. Fourteen patients were re-operated, in five cases excising single DR-sites, thereafter three received CT, two after re-RT; out of 11 patients not re-operated, four had re-RT as first treatment and seven after CT. Re-RT was administered at median 32 months after first RT: focally in 20 cases, craniospinal-CSI in five. Median post-relapse-PFS/after re-RT was 16.7/8.2 months, while overall survival-OS was 35.1/23.9 months, respectively. Metastatic status both at diagnosis/relapse negatively affected outcome and re-surgery was prognostically favorable. PD after re-RT was however significantly more frequent in SHH (with a suggestive association with TP53 mutation, p = 0.050). We did not observe any influence of biological subgroups on PFS from recurrence while SHH showed apparently worse OS compared to non-WNT/non-SHH group.

CONCLUSIONS

Re-surgery + reRT can prolong survival; a substantial fraction of patients with worse outcome belongs to the SHH-subgroup.

Hypercarbia in a Pediatric Patient With Relapsed Medulloblastoma

Pediatric medulloblastoma is a common form of pediatric brain tumor and typically presents with progressive signs of increased intracranial pressure and ataxia. Relapse of the disease is most often diagnosed on surveillance imaging. We present the case of a 13-year-old boy with a previous history of medulloblastoma who presented with chronic hypercarbic respiratory failure as a symptom of a recurrent tumor. Imaging demonstrated a left cerebellar enhancing mass with leptomeningeal thickness and extension to the posterior medulla oblongata, which is the center for respiratory control. His hypercarbic respiratory failure represents a unique presentation of a central nervous system (CNS) tumor. Thus, this case illustrates the importance of thorough evaluation for CNS tumors involving the brainstem in patients with respiratory acidosis and no clear pulmonary etiology. 

Magnetic Resonance Imaging in the Contemporary Management of Medulloblastoma: Current and Emerging Applications

Medulloblastoma, the most common malignant primary brain tumor in children, is now considered to comprise of four distinct molecular subgroups-wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4 medulloblastoma, each associated with distinct developmental origins, unique transcriptional profiles, diverse phenotypes, and variable clinical behavior. Due to its exquisite anatomic resolution, multiparametric nature, and ability to image the entire craniospinal axis, magnetic resonance imaging (MRI) is the preferred and recommended first-line imaging modality for suspected brain tumors including medulloblastoma. Preoperative MRI can reliably differentiate medulloblastoma from other common childhood posterior fossa masses such as ependymoma, pilocytic astrocytoma, and brainstem glioma. On T1-weighted images, medulloblastoma is generally iso- to hypointense, while on T2-weighted images, the densely packed cellular component of the tumor is significantly hypointense and displays restricted diffusion on diffusion-weighted imaging. Following intravenous gadolinium, medulloblastoma shows significant but variable and heterogeneous contrast enhancement. Given the propensity of neuraxial spread in medulloblastoma, sagittal fat-suppressed T1-postcontrast spinal MRI is recommended to rule out leptomeningeal metastases for accurate staging. Following neurosurgical excision, postoperative MRI done within 24-48 h confirms the extent of resection, accurately quantifying residual tumor burden imperative for risk assignment. Post-treatment MRI is needed to assess response and effectiveness of adjuvant radiotherapy and systemic chemotherapy. After completion of planned therapy, surveillance MRI is recommended periodically on follow-up for early detection of recurrence for timely institution of salvage therapy, as well as for monitoring treatment-related late complications. Recent studies suggest that preoperative MRI can reliably identify SHH and Group 4 medulloblastoma but has suboptimal predictive accuracy for WNT and Group 3 tumors. In this review, we focus on the role of MRI in the diagnosis, staging, and quantifying residual disease; post-treatment response assessment; and periodic surveillance, and provide a brief summary on radiogenomics in the contemporary management of medulloblastoma.

Relapsed Medulloblastoma in Pre-Irradiated Patients: Current Practice for Diagnostics and Treatment

Relapsed medulloblastoma (rMB) accounts for a considerable, and disproportionate amount of childhood cancer deaths. Recent advances have gone someway to characterising disease biology at relapse including second malignancies that often cannot be distinguished from relapse on imaging alone. Furthermore, there are now multiple international early-phase trials exploring drug-target matches across a range of high-risk/relapsed paediatric tumours. Despite these advances, treatment at relapse in pre-irradiated patients is typically non-curative and focuses on providing life-prolonging and symptom-modifying care that is tailored to the needs and wishes of the individual and their family. Here, we describe the current understanding of prognostic factors at disease relapse such as principal molecular group, adverse molecular biology, and timing of relapse. We provide an overview of the clinical diagnostic process including signs and symptoms, staging investigations, and molecular pathology, followed by a summary of treatment modalities and considerations. Finally, we summarise future directions to progress understanding of treatment resistance and the biological mechanisms underpinning early therapy-refractory and relapsed disease. These initiatives include development of comprehensive and collaborative molecular profiling approaches at relapse, liquid biopsies such as cerebrospinal fluid (CSF) as a biomarker of minimal residual disease (MRD), modelling strategies, and the use of primary tumour material for real-time drug screening approaches.

EANO-EURACAN clinical practice guideline for diagnosis, treatment, and follow-up of post-pubertal and adult patients with medulloblastoma

The European Association of Neuro-Oncology (EANO) and EUropean RAre CANcer (EURACAN) guideline provides recommendations for the diagnosis, treatment, and follow-up of post-pubertal and adult patients with medulloblastoma. The guideline is based on the 2016 WHO classification of tumours of the CNS and on scientific developments published since 1980. It aims to provide direction for diagnostic and management decisions, and for limiting unnecessary treatments and cost. In view of the scarcity of data in adults with medulloblastoma, we base our recommendations on adult data when possible, but also include recommendations derived from paediatric data if justified. Our recommendations are a resource for professionals involved in the management of post-pubertal and adult patients with medulloblastoma, for patients and caregivers, and for health-care providers in Europe. The implementation of this guideline requires multidisciplinary structures of care, and defined processes of diagnosis and treatment.

The utility of routine surveillance screening with magnetic resonance imaging to detect tumor recurrence/progression in children with high-grade central nervous system tumors: a systematic review

BACKGROUND

Surveillance magnetic resonance imaging (MRI) is routinely used to detect recurrence in children with high-grade central nervous system (CNS) tumors, although no consensus has been reached regarding its effectiveness and whether earlier detection is associated with improved patient outcomes. This review aimed to evaluate this practice and any associated benefits and harms.

METHODS

Systematic searches for relevant studies were undertaken in a number of databases, including MEDLINE and EMBASE, from 1985 to August 2018. Study selection and data extraction was undertaken independently by two reviewers. Due to heterogeneity between studies, no pooling of data was undertaken. Reporting followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

No comparative studies were identified. Three retrospective observational studies involving 306 patients were reviewed. All had high risk of bias by virtue of study design. Two studies reported outcomes by symptomatic status-both recurrence rates and overall survival for asymptomatic patients were comparable with those for clinically symptomatic patients. No quality-of-life outcomes were reported.

CONCLUSION

There is a paucity of evidence to guide clinical practice as to the effectiveness of MRI surveillance in pediatric patients with high-grade CNS tumors. These studies do not clearly demonstrate benefit or harm for the practice. With more research needed, there is a role for researchers to build into future trials data collection on surveillance imaging to give more information for the assessment of imaging frequency and duration in asymptomatic patients. This is an important question not only to clinicians and patients and their families but also from a health service resource perspective.

Imaging features of medulloblastoma: Conventional imaging, diffusion-weighted imaging, perfusion-weighted imaging, and spectroscopy: From general features to subtypes and characteristics

Medulloblastoma is a frequent high-grade neoplasm among pediatric brain tumours. Its classical imaging features are a midline tumour growing into the fourth ventricle, hyperdense on CT-scan, displaying a hypersignal when using diffusion-weighted imaging, with a variable contrast enhancement. Nevertheless, atypical imaging features have been widely reported, varying according to the age of the patient, and histopathological subtype. In this study, we review the classical and atypical imaging features of medulloblastomas, with emphasis on advanced MRI techniques, histopathological and molecular subtypes and characteristics, and follow-up modalities.

Medulloblastoma

Medulloblastoma accounts for nearly 10% of all childhood brain tumors. These tumors occur exclusively in the posterior fossa and have the potential for leptomeningeal spread. Treatment includes a combination of surgery, radiation therapy (in patients >3 years old). Patients >3 years old are stratified based on the volume of postoperative residual tumor and the presence or absence of metastases into "standard risk" and "high risk" categories with long-term survival rates of approximately 85% and 70%, respectively. Outcomes are inferior in infants and children younger than 3 years with exception of those patients with the medulloblastoma with extensive nodularity histologic subtype. Treatment for medulloblastoma is associated with significant morbidity, especially in the youngest patients. Recent molecular subclassification of medulloblastoma has potential prognostic and therapeutic implications. Future incorporation of molecular subgroups into treatment protocols will hopefully improve both survival outcomes and posttreatment quality of life.

The impact of routine surveillance screening with magnetic resonance imaging (MRI) to detect tumour recurrence in children with central nervous system (CNS) tumours: protocol for a systematic review and meta-analysis

BACKGROUND

The aim of this study is to assess the impact of routine MRI surveillance to detect tumour recurrence in children with no new neurological signs or symptoms compared with alternative follow-up practices, including periodic clinical and physical examinations and the use of non-routine imaging upon presentation with disease signs or symptoms.

METHODS

Standard systematic review methods aimed at minimising bias will be employed for study identification, selection and data extraction. Ten electronic databases have been searched, and further citation searching and reference checking will be employed. Randomised and non-randomised controlled trials assessing the impact of routine surveillance MRI to detect tumour recurrence in children with no new neurological signs or symptoms compared to alternative follow-up schedules including imaging upon presentation with disease signs or symptoms will be included. The primary outcome is time to change in therapeutic intervention. Secondary outcomes include overall survival, surrogate survival outcomes, response rates, diagnostic yield per set of images, adverse events, quality of survival and validated measures of family psychological functioning and anxiety. Two reviewers will independently screen and select studies for inclusion. Quality assessment will be undertaken using the Cochrane Collaboration's tools for assessing risk of bias. Where possible, data will be summarised using combined estimates of effect for time to treatment change, survival outcomes and response rates using assumption-free methods. Further sub-group analyses and meta-regression models will be specified and undertaken to explore potential sources of heterogeneity between studies within each tumour type if necessary.

DISCUSSION

Assessment of the impact of surveillance imaging in children with CNS tumours is methodologically complex. The evidence base is likely to be heterogeneous in terms of imaging protocols, definitions of radiological response and diagnostic accuracy of tumour recurrence due to changes in imaging technology over time. Furthermore, the delineation of tumour recurrence from either pseudo-progression or radiation necrosis after radiotherapy is potentially problematic and linked to the timing of follow-up assessments. However, given the current routine practice of MRI surveillance in the follow-up of children with CNS tumours in the UK and the resource implications, it is important to evaluate the cost-benefit profile of this practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016036802.

Relapse patterns and outcome after relapse in standard risk medulloblastoma: a report from the HIT-SIOP-PNET4 study

The HIT-SIOP-PNET4 randomised trial for standard risk medulloblastoma (MB) (2001–2006) included 338 patients and compared hyperfractionated and conventional radiotherapy. We here report the long-term outcome after a median follow up of 7.8 years, including detailed information on relapse and the treatment of relapse. Data were extracted from the HIT Group Relapsed MB database and by way of a specific case report form. The event-free and overall (OS) survival at 10 years were 76 ± 2 % and 78 ± 2 % respectively with no significant difference between the treatment arms. Seventy-two relapses and three second malignant neoplasms were reported. Thirteen relapses (18 %) were isolated local relapses in the posterior fossa (PF) and 59 (82 %) were craniospinal, metastatic relapses (isolated or multiple) with or without concurrent PF disease. Isolated PF relapse vs all other relapses occurred at mean/median of 38/35 and 28/26 months respectively (p = 0.24). Late relapse, i.e. >5 years from diagnosis, occurred in six patients (8 %). Relapse treatment consisted of combinations of surgery (25 %), focal radiotherapy (RT 22 %), high dose chemotherapy with stem cell rescue (HDSCR 21 %) and conventional chemotherapy (90 %). OS at 5 years after relapse was 6.0 ± 4 %. In multivariate analysis; isolated relapse in PF, and surgery were significantly associated with prolonged survival whereas RT and HDSCR were not. Survival after relapse was not related to biological factors and was very poor despite several patients receiving intensive treatments. Exploration of new drugs is warranted, preferably based on tumour biology from biopsy of the relapsed tumour.

Postoperative Surveillance Magnetic Resonance Imaging for Cerebellar Astrocytoma

Introduction:

Patients with low grade astrocytomas generally have good prognosis when total resection can be achieved, but surveillance neuroimaging is commonly performed to detect recurrence or progression. This study evaluated the utility and yield of such strategy for pilocytic and non-pilocytic cerebellar astrocytomas.

Methods:

A 20-year retrospective review was performed of patients undergoing resection of cerebellar astrocytoma at a single institution. A negative MRI string (NMS) ratio was computed as the fraction of total follow-up period over which surveillance neuroimaging was negative for recurrence or progression. Chi-squared analysis differentiated NMS ratio by resection extent and lesion histopathology.

Results:

Twenty-eight patients with pilocytic (n=15) and non-pilocytic (n=13) astrocytoma underwent 34 craniotomies, with total resection in 19 cases. Surveillance MRIs (n=167) among total resection patients were uniformly negative for recurrent disease at average seven years follow-up (NMS ratio = 1.0). The 43 surveillance MRIs among subtotal resection patients revealed disease progression in two patients within six months of operation (NMS ratio = 0.78, p<0.05). No differences in NMS ratio were observed between pilocytic and non-pilocytic astrocytoma subtypes.

Discussion:

This study illustrates pediatric patients with low-grade cerebellar astrocytomas undergoing total resection may not benefit from routine surveillance neuroimaging, primarily because of low recurrence likelihood. Patients with subtotal resection may benefit from surveillance of residual disease, with further work aimed at exploring the schedule of such follow-up.

Neuro-oncological disorders of the cerebellum

This article provides an overview of the intra-axial tumors that affect the cerebellum, which can be categorized by location and age. For each tumor, we review conventional neuroimaging findings and discuss the value of more advanced neuroimaging techniques. Current management strategies are also briefly discussed. Finally, cerebellar paraneoplastic disorders and medication-induced cerebellar disorders are discussed.

Surveillance imaging in children with malignant CNS tumors: low yield of spine MRI

Magnetic resonance imaging (MRI) is routinely obtained in patients with central nervous system (CNS) tumors, but few studies have been conducted to evaluate this practice. We assessed the benefits of surveillance MRI and more specifically spine MRI in a contemporary cohort. We evaluated MRI results of children diagnosed with CNS tumors from January 2000 to December 2011. Children with at least one surveillance MRI following the diagnosis of medulloblastoma (MB), atypical teratoid rhabdoid tumor (ATRT), pineoblastoma (PB), supratentorial primitive neuroectodermal tumor, supratentorial high-grade glioma (World Health Organization grade III-IV), CNS germ cell tumors or ependymoma were included. A total of 2,707 brain and 1,280 spine MRI scans were obtained in 258 patients. 97% of all relapses occurred in the brain and 3% were isolated to the spine. Relapse was identified in 226 (8%) brain and 48 (4%) spine MRI scans. The overall rate of detecting isolated spinal relapse was 9/1,000 and 7/1,000 for MB patients. MRI performed for PB showed the highest rate for detecting isolated spinal recurrence with 49/1,000. No initial isolated spinal relapse was identified in patients with glioma, supratentorial primitive neuroectodermal tumor and ATRT. Isolated spinal recurrences are infrequent in children with malignant CNS tumors and the yield of spine MRI is very low. Tailoring surveillance spine MRI to patients with higher spinal relapse risk such as PB, MB with metastatic disease and within 3 years of diagnosis could improve allocation of resources without compromising patient care.

Efficacy of temozolomide for recurrent embryonal brain tumors in children

OBJECTIVE

The salvage therapy of recurrent embryonal brain tumors in children is disappointing. Temozolomide is a newly developed chemotherapeutic agent in central nervous system tumors. This study analyzed the efficacy of temozolomide on the treatment of recurrent embryonal brain tumors in children.

MATERIALS AND METHODS

There were eight patients, including four with medulloblastoma (MB), three with atypical teratoid/rhabdoid tumor (AT/RT) and one with supratentorial primitive neuroectodermal tumor, whose tumors recurred after surgery and radiotherapy, with or without conventional intravenous cisplatin-based chemotherapy. They all received once daily oral temozolomide (150 mg/m(2)/day) for five consecutive days in a 28-day cycle. The responsiveness of the tumors to temozolomide was judged by magnetic resonance imaging (MRI) during regular follow-up.

RESULTS

The median treatment cycles received by these eight patients were 17 (range from two to 59 cycles). The follow-up MRI showed no tumor progression in five patients at 6 months and four patients at 12 months. The median progression-free survival (PFS) of the eight patients was 15.7 months (range from 0 to 59 months). Complete response was achieved in one patient with MB accompanying with a long period of PFS for 26 months. Another patient with AT/RT showed partial response accompanying with a long period of PFS for 59 months. The observed adverse effects of temozolomide included nausea, vomiting, headache, constipation, mild marrow suppression, and decreased activity; none of them was severe enough to discontinue the treatment. No patient experienced moderate or severe marrow suppression in this series.

CONCLUSION

In this preliminary study, oral temozolomide shows promising results on recurrent embryonal brain tumors in children. The adverse effects of temozolomide are mild and tolerable. When conventional chemotherapy fails and/or the adverse response is too severe to tolerate, temozolomide is a reasonable alternative. However, a further well-designed, controlled study and more long-term follow-up are needed to assess the exact role of temozolomide in children with embryonal tumors in brain.

Imaging of central nervous system tumors in children: advances and limitations

Magnetic resonance technology is continually improving. Functional imaging techniques such as magnetic resonance spectroscopy, perfusion imaging, diffusion imaging, and diffusion tensor imaging are increasingly used in the diagnosis and treatment of brain tumors in children. However, estimate of tumor size remains the primary imaging endpoint in the evaluation of response to treatment, and validation across institutions and vendor platforms of magnetic resonance imaging functional parameters is necessary given the relatively uncommon occurrence of brain tumors in children. Pediatric neuroimaging can be challenging, and the optimal way to image children with tumors of the central nervous system is not uniformly applied across all centers. Application of proper scanning techniques and validation of functional imaging techniques should lead to improved care of children with central nervous system tumors.

Hypofractionated stereotactic radiotherapy in the management of recurrent or residual medulloblastoma/PNET

PURPOSE

To evaluate the efficacy and toxicity of hypofractionated stereotactic radiotherapy in the management of locally recurrent or residual central nervous system (CNS) primitive neuroectodermal tumors (PNETs).

PATIENTS AND METHODS

Between 1991 and 2005, 12 patients with locally recurrent medulloblastoma and two patients with residual supratentorial PNET were treated with hypofractionated stereotactic conformal radiotherapy (SCRT). Nine patients were treated for first recurrence, two patients after the 2nd, and one patient after 3rd recurrence. Median age at diagnosis was 20 years (range: 4-35 years) and median age at SCRT 25 years (range: 7-41 years). Nine of 12 patients underwent resection at recurrence and 13 patients received at least one cycle of chemotherapy prior to SCRT. All received focal SCRT (30-40 Gy/6-8 #) using non-coplanar arcs (n = 6) or fixed conformal non-coplanar fields (n = 8).

RESULTS

Median overall survival was 29 months (95% CI: 6-51 months) and median progression-free survival was 12 months (95% CI: 5-19 months). Local progression-free survival at 1 and 3 years was 80% (95% CI: 55-100%) and 48% (95% CI: 11-85%). Causes of death were recurrent CNS disease (n = 7), herpes encephalitis (n = 1), and metastatic PNET outside the CNS (n = 1).

CONCLUSION

Hypofractionated SCRT provides effective local control with acceptable toxicity for patients with recurrent localized PNET. However, overall long-term disease control is rare and limited by the occurrence of CSF mediated relapses, which thus could benefit from intensive systemic chemotherapy as part of the primary relapse strategy even in local recurrences. Larger multi-national studies will be necessary to assess the value of such combined treatment approaches.

Impact of site of tumor recurrence upon survival for children with recurrent or progressive medulloblastoma

OBJECT

The object of this study was to identify prognostic factors for survival among children with recurrent medulloblastoma.

METHODS

Postprogression survival and patient, tumor, and treatment factors were examined in 46 cases of recurrent medulloblastoma (mean age of patients at diagnosis 6.5 years, mean age at progression 8.4 years). Differences were calculated by Kaplan-Meier log-rank analysis. Multivariate analysis was performed using the Cox proportional hazard model.

RESULTS

The probability of 5-year survival was 26.3%. Forty-one patients received salvage therapy and five patients received hospice care only. Log-rank analysis showed an association between prolonged patient survival and recurrence limited to the primary site (p = 0.008), initial therapy including the Pediatric Oncology Group (POG) regimen for the treatment of brain tumors in infants ("Baby POG;" p = 0.037), and treatment with radiation therapy (RT) following initial progression (p = 0.015). Cox regression analysis showed a significant association between prolonged survival and only one variable--tumor recurrence restricted to the primary site (p = 0.037). There was no significant association between prolonged survival and any other variables, including patient sex, age at progression, interval from tumor diagnosis to progression, initial tumor stage, and salvage treatment with chemotherapy. Subgroup analysis revealed that site of tumor progression was also prognostic for survival among the subgroup of patients older than 3 years of age at diagnosis who were initially treated with RT and chemotherapy (p = 0.017, log-rank test).

CONCLUSIONS

Some children with recurrent medulloblastoma will be long-term survivors, and certain features are associated with likelihood of survival. Patients whose tumors recur at only the primary tumor site have an increased chance of prolonged survival.

Magnetic resonance imaging protocols for paediatric neuroradiology

Increasingly, radiologists are encouraged to have protocols for all imaging studies and to include imaging guidelines in care pathways set up by the referring clinicians. This is particularly advantageous in MRI where magnet time is limited and a radiologist's review of each patient's images often results in additional sequences and longer scanning times without the advantage of improvement in diagnostic ability. The difficulties of imaging small children and the challenges presented to the radiologist as the brain develops are discussed. We present our protocols for imaging the brain and spine of children based on 20 years experience of paediatric neurological MRI. The protocols are adapted to suit children under the age of 2 years, small body parts and paediatric clinical scenarios.

Incidence of cavernoma development in children after radiotherapy for brain tumors

OBJECT

Cavernous hemangiomas (cavernomas) are benign vascular malformations that may cause seizures and/or hemorrhage when they develop in the brain. The incidence of cavernoma development after brain radiotherapy is unknown. The aim of this study was to assess the prevalence of cavernoma formation in patients who had previously received radiotherapy for brain tumors during childhood.

METHODS

All patients were identified who were younger than 16 years of age and had undergone radiotherapy for brain tumors within a 16-year period (January 1, 1988-December 31, 2003). The patient data that were ascertained included age at diagnosis, sex, histopathology results, initial preoperative magnetic resonance (MR) imaging results, date of radiotherapy, and date of detection of cavernoma. Children who were followed up for less than 1 month after radiotherapy or who died during treatment were excluded, as were children with brainstem tumors. All patients had undergone diagnostic MR imaging before receiving radiotherapy, and no vascular malformations were revealed. Of the 379 patients identified, 297 satisfied the inclusion criteria. Ten patients (3.4%) developed cavernomas after radiation therapy. The ages of these patients ranged from 2 to 11 years at the time of radiotherapy (median 7 years), and the latency interval between radiotherapy and cavernoma development was 3 to 102 months (median 37 months).

CONCLUSIONS

The prevalence of cavernomas in the present study was more than six times greater than the prevalence rate cited in the literature for this population. The authors conclude that there is an increased risk of developing an intracranial cavernoma after radiotherapy for brain tumors. The possibility of this complication arising should be mentioned when informed consent is sought before treatment using radiotherapy.

Infratentorielle Tumoren

This article gives an overview concerning the typical infratentorial tumors of adults.

Role of spinal MRI in the follow-up of children treated for medulloblastoma

BACKGROUND

The purpose of the current study was to describe the usefulness of spinal magnetic resonance imaging (MRI) in children with medulloblastoma or primitive neuroectodermal tumor (PNET) of the posterior fossa.

METHODS

Children consecutively diagnosed with medulloblastoma/PNET and followed in the Hospital for Sick Children/Toronto were identified. A homogenous cohort of children treated with craniospinal irradiation as part of their initial treatment was considered. Contrast-enhanced spinal MRIs done concomitantly with cranial MRIs (doublets) were reviewed. Recurrence was defined as any new abnormal lesion (in the brain or in the spine) in symptomatic or asymptomatic patients. Doublets after the first recurrence were excluded in the final analysis. The utility of a spinal MRI in the presence of a negative cranial MRI was assessed.

RESULTS

In all, 73 patients (21 females and 52 males; median age, 6.6 years, median follow-up time, 4.3 years) had at least 1 evaluable doublet during the follow-up period. Since concomitant cranial and spinal MRI was introduced as the standard evaluation for medulloblastoma/PNET in 1991, 286 doublets were evaluable. Fourteen spinal MRIs and 25 cranial MRIs showed new nodular or leptomeningeal lesions. In 2 patients, repeat MRIs ruled out recurrence (false-positive). All confirmed spinal recurrences were associated with intracranial recurrence. Of 261 doublets with negative cranial MRI, no new lesion was identified on spinal MRI.

CONCLUSIONS

An absence of progression on cranial MRI is highly predictive of absence of progression on spinal MRI. There is little evidence that surveillance spinal MRI (in children who underwent craniospinal radiation as part of their initial treatment) improves the detection of recurrences in children with medulloblastoma.

Monitoring the growth effect of xenotransplanted human medulloblastoma in an immunocompromised mouse model using in vitro and ex vivo green fluorescent protein imaging

INTRODUCTION

Medulloblastoma (MB) is one of the most common malignant brain tumors in children. It is a radiosensitive tumor. At 5 years after radical surgical excision and craniospinal axis irradiation, the tumor-free survival rate is from 50 to 70% [Halperin EC, Constine LS, Tarbell NJ, Kun LE. Pediatric radiation oncology (2005)].

CASE REPORT

In this study, we established xenotransplanted human MB (hMB) cells - isochromosome 17q - in a severe combined immunodeficiency (SCID) mouse model. We further transduced green fluorescent protein (GFP) into hMB cells to evaluate these hMB cells grafted in SCID mice.

RESULTS

The result of an ex vivo GFP imaging system showed that a small lesion of the third-week-hMB-transplanted graft presented "green" signals with a clear tumor margin before any tumor-related symptoms were noted. We also demonstrated that the tumor progression could be monitored by GFP imaging for up to 12 weeks post-transplantation.

CONCLUSIONS

This novel approach of GFP imaging assessment provides more accurate information of tumor status for experimental brain tumor studies. Because MB is sensitive to radiation and also response to chemotherapy, this SCID mouse model will be helpful for preclinical studies in the future.

Spontaneous regression of residual low-grade cerebellar pilocytic astrocytomas in children

BACKGROUND

Cerebellar low-grade astrocytomas (CLGAs) of childhood are benign tumours and are usually curable by surgical resection alone or combined with adjuvant radiotherapy.

OBJECTIVE

To undertake a retrospective study of our children with CLGA to determine the optimum schedule for surveillance imaging following initial surgery. In this report we describe the phenomenon of spontaneous regression of residual tumour and discuss its prognostic significance regarding future imaging.

MATERIALS AND METHODS

A retrospective review was conducted of children treated for histologically proven CLGA at Great Ormond Street Hospital from 1988 to 1998.

RESULTS

Of 83 children with CLGA identified, 13 (15.7%) had incomplete resections. Two children with large residual tumours associated with persistent symptoms underwent additional treatment. Eleven children were followed by surveillance imaging alone for a mean of 6.83 years (range 2-13.25 years). Spontaneous tumour regression was seen in 5 (45.5%) of the 11 children. There were no differences in age, gender, symptomatology, histological grade or Ki-67 fractions between those with spontaneous tumour regression and those with progression. There was a non-significant trend that larger volume residual tumours progressed.

CONCLUSIONS

Residual tumour followed by surveillance imaging may either regress or progress. For children with residual disease we recommend surveillance imaging every 6 months for the first 2 years, every year for years 3, 4 and 5, then every second year if residual tumour is still present 5 years after initial surgery. This would detect not only progressive or recurrent disease, but also spontaneous regression which can occur later than disease progression.

Surveillance imaging strategies following surgery and/or radiotherapy for childhood cerebellar low-grade astrocytoma

OBJECT

The authors sought to evaluate surveillance strategies for the detection and monitoring of residual and recurrent disease in children with cerebellar low-grade astrocytomas (CLGAs) treated surgically or with radiotherapy. Patients were divided into three groups: (1) those in whom a "complete" resection was achieved; (2) those with residual disease with no immediate adjuvant therapy; and (3) those who received radiotherapy for residual/recurrent disease.

METHODS

Magnetic resonance (MR) imaging studies and clinical data obtained in children with CLGA who presented between January 1988 and September 1998 were reviewed. Eighty-four children were followed for a mean period of 73 months (range 2-159 months). One child died. Of the 70 children in whom a complete resection was achieved, nine (13%) developed a recurrence detected by surveillance imaging at 6, 8, 9, 9, 13, 27, 39, 44, and 47 months, respectively. Following an incomplete resection, radiologically detected tumor progression leading to further treatment was detected at 7, 9, 12, 13, and 20 months, respectively, and an additional six tumors regressed or stablized. In 11 of 12 children treated with radiotherapy, stabilization/regression occurred radiologically at a mean of 14.9 months.

CONCLUSIONS

The authors recommend surveillance MR imaging in children treated for CLGA at 6 months and 1, 2, 3.5, and 5 years following a complete resection and after radiotherapy performed either initially or following recurrence. For follow up of residual tumor, 6-month interval imaging for at least 3 years, yearly images for another 2 years, and subsequent 2-year imaging is recommended.

Brain tumors in children

Pediatric brain tumors are a challenging group of very divergent diseases. Considerable controversy exists concerning the accurate diagnosis and treatment of these patients. Aggressive therapy is often needed to cure aggressive and potentially lethal disease, yet late effects, especially injury to the developing brain, remain a profound problem. The discipline of pediatric neuro-oncology remains one of the most productive areas for continued clinical and basic research because of these and other challenges.