Radiation dosimetry predicts IQ after conformal radiation therapy in pediatric patients with localized ependymoma

Effect of cerebellum radiation dosimetry on cognitive outcomes in children with infratentorial ependymoma

PURPOSE

Cognitive decline is a recognized effect of radiation therapy (RT) in children treated for brain tumors. The importance of the cerebellum and its contribution to cognition have been recognized; however, the effect of RT on cerebellum-linked neurocognitive deficits has yet to be explored.

METHODS AND MATERIALS

Seventy-six children (39 males) at a median 3.3 years of age (range, 1-17 years old) were irradiated for infratentorial ependymoma from 1997 to 2008. The total prescribed dose was 54 to 59.4 Gy administered to the postoperative tumor bed with 5- or 10-mm clinical target volume margin. Age-appropriate cognitive and academic testing was performed prior to the start of RT and was then repeated at 6 months and annually throughout 5 years. The anterior and posterior cerebellum and other normal brain volumes were contoured on postcontrast, T1-weighted postoperative magnetic resonance images registered to treatment planning computed tomography images. Mean doses were calculated and used with time after RT and other clinical covariates to model their effect on neurocognitive test scores.

RESULTS

Considering only the statistically significant rates in longitudinal changes for test scores and models that included mean dose, there was a correlation between mean infratentorial dose and intelligence quotient (IQ; -0.190 patients/Gy/year; P=.001), math (-0.164 patients/Gy/year; P=.010), reading (-0.137 patients/Gy/year; P=.011), and spelling scores (-0.147 patients/Gy/year; P=.012), where Gy was measured as the difference between the mean dose received by an individual patient and the mean dose received by the patient group. There was a correlation between mean anterior cerebellum dose and IQ scores (-0.116 patients/Gy/year; P=.042) and mean posterior cerebellum dose and IQ (-0.150 patients/Gy/year; P=.002), math (-0.120 patients/Gy/year; P=.023), reading (-0.111 patients/Gy/year; P=.012), and spelling (-0.117 patients/Gy/year; P=.015) scores.

CONCLUSIONS

Sparing portions of the cerebellum should be considered in RT planning for children with infratentorial ependymoma because of the potential impact of radiation dose on cognitive function.

A dosimetric comparison of intensity-modulated proton therapy optimization techniques for pediatric craniopharyngiomas: a clinical case study

BACKGROUND

To evaluate the dosimetric characteristics of intensity-modulated proton therapy (IMPT) optimization techniques and pencil-beam scanning (PBS) nozzle designs on pediatric craniopharyngiomas.

PROCEDURE

We compared a double-scatter (DS) plan with IMPT plans using single-field uniform dose (SFUD) optimization or multi-field optimization (MFO) and different PBS nozzles. The clinical impacts of SFUD versus MFO, range shifters, and two different PBS nozzles were compared. For target coverage assessment, the conformity index and inhomogeneity coefficient were evaluated.

RESULTS

Although both proton therapy techniques achieved adequate target coverage, IMPT achieved a better conformity index of 0.78 versus 0.60 for DS. For the inhomogeneity coefficient, IMPT with MFO performed better than using SFUD or DS. MFO with the dedicated nozzle (MFO-DN) achieved the best result of 0.023, as compared to values of 0.03 or higher for the other plans. IMPT achieved lower doses to the normal tissues, as compared to DS; MFO-DN had the best results. The DN provided the best beam-spot characteristics and the sharpest lateral penumbra. MFO reduced the need for range shifters.

CONCLUSIONS

As compared to DS proton therapy for pediatric craniopharyngiomas, IMPT achieved significantly better target coverage and dose sparing of normal tissue. Nozzle designs that provided small beam spots and sharp lateral penumbra allowed for better target coverage and reduced dose to normal tissue. In the case of shallow targets, MFO, in contrast to SFUD, required minimal use of range shifters, which preserved the penumbra and the dosimetric advantage. MFO-DN proved to be the optimal technique for IMPT.

Proton radiotherapy for pediatric central nervous system ependymoma: clinical outcomes for 70 patients

BACKGROUND

Ependymoma is treated with maximal surgical resection and localized radiotherapy. Minimizing unnecessary exposure to radiation is of paramount importance for young children. Proton radiotherapy (PRT) spares healthy tissues outside the target region, but reports of clinical outcomes are scarce. We report outcomes for 70 patients treated with PRT for intracranial ependymoma.

METHODS

Seventy patients with localized ependymoma treated with involved-field PRT at the Massachusetts General Hospital between October 2000 and February 2011 were included.

RESULTS

Median age at diagnosis was 38 months (range, 3 mo-20 y). Nineteen (27%) patients had supratentorial ependymoma and 51(73%) had infratentorial ependymoma. Forty-six (66%) had gross total resection (GTR), and 24 (34%) had subtotal resection (STR). At a median follow-up of 46 months, 3-year local control, progression-free survival, and overall survival were 83%, 76%, and 95%, respectively. STR was significantly associated with worse progression-free survival (54% vs 88%, P = .001) and overall survival (90% vs 97% for GTR, P = .001). In a subset of patients (n = 14), mean intelligence was 108.5 at baseline and 111.3 after mean 2.05 years of follow-up. In a larger group of patients (n = 28), overall adaptive skills were 100.1 at baseline and 100.8 after 2.21 years of follow-up. Few patients developed evidence of growth hormone deficiency, hypothyroidism, or hearing loss.

CONCLUSION

Outcomes for children treated with PRT compare favorably with the literature. STR correlated with inferior outcome. The young age at diagnosis and the proximity of critical structures in patients with ependymoma make PRT an ideal radiation modality.

Supratentorial gross-totally resected non-anaplastic ependymoma: population based patterns of care and outcomes analysis

Observation following gross-total resection (GTR) for non-anaplastic supratentorial ependymomas is often advocated based on small, retrospective series. The purpose of this study is to perform a population-based analysis to examine outcomes for this rare cohort of low-risk patients. A retrospective analysis was conducted utilizing the Surveillance, Epidemiology and End Results Program of the United States National Cancer Institute. We identified patients with supratentorial non-anaplastic ependymoma who underwent GTR alone or GTR followed by radiation. We identified 92 patients who met these criteria. The median age was 17.5 years (range 1-83) with the majority female (58 %) and white (75 %). Radiotherapy (RT) was delivered in half of patients. The 5-/10-year Kaplan-Meier estimated overall survival (OS) and cause-specific survival (CSS) for the overall cohort was 83.2/71.4 and 84.1/78.0 %, respectively. There was no evidence of decreased CSS (HR 0.52 [0.18-1.51]; p = 0.23) or OS (HR 0.63 [0.25-1.59]; p = 0.33) with the omission of RT on univariate analysis. Age ≥18 years correlated with worse OS (HR 4.01 [1.45-11.11]; p = 0.008) and CSS (HR 2.86 [0.99-8.31]; p = 0.05). RT did not impact outcome for this low-risk cohort of patients. Older age correlates with poor prognosis.

Current treatment options for pediatric and adult patients with ependymoma

OPINION STATEMENT

Survival rates for patients with ependymoma, a glial tumor arising from the ependymal cells lining the ventricles of the brain and spinal cord canal, have changed little during the past decade. Contemporary "standard" therapy for children and adults with ependymoma consists of maximal surgical resection followed by focal irradiation except in cases of disseminated disease. Despite refinements in radiotherapy techniques and improvements in survival for patients with gross totally resected, nonanaplastic disease, many therapeutic challenges remain, especially for patients with unresectable, macroscopic, metastatic, or anaplastic disease. Moreover, radiotherapy to the developing central nervous system, especially in patients younger than age 5 years, can have potential long-term neurocognitive and neuroendocrine sequelae. Chemotherapy has not played a role in most treatment regimens for ependymoma to date, but due to the ongoing therapeutic challenges for a subset of patients, this modality is being reinvestigated in a few ongoing studies. Early recognition of patients who will not respond to primary therapy is imperative to modify treatment regimens, such as intensification with the addition of adjuvant chemotherapy, the use of novel experimental therapies, or their combination. Refinements in patient stratification schemes that are based on a combination of clinical variables and molecular profiles also require improved knowledge of tumor biology. Several molecular alterations have been identified already, some of which may be of prognostic significance. Furthermore, disruption of molecular alterations in signaling pathways involved in the development and maintenance of ependymoma by using novel molecularly targeted therapies may improve outcomes and reduce toxicity for patients with ependymoma.

Neuroanatomical target theory as a predictive model for radiation-induced cognitive decline

OBJECTIVE

In a retrospective review to assess neuroanatomical targets of radiation-induced cognitive decline, dose volume histogram (DVH) analyses of specific brain regions of interest (ROI) are correlated to neurocognitive performance in 57 primary brain tumor survivors.

METHODS

Neurocognitive assessment at baseline included Trail Making Tests A/B, a modified Rey-Osterreith Complex Figure, California or Hopkins Verbal Learning Test, Digit Span, and Controlled Oral Word Association. DVH analysis was performed for multiple neuroanatomical targets considered to be involved in cognition. The %v10 (percent of ROI receiving 10 Gy), %v40, and %v60 were calculated for each ROI. Factor analysis was used to estimate global cognition based on a summary of performance on individual cognitive tests. Stepwise regression was used to determine which dose volume predicted performance on global factors and individual neurocognitive tests for each ROI.

RESULTS

Regions that predicted global cognitive outcomes at doses <60 Gy included the corpus callosum, left frontal white matter, right temporal lobe, bilateral hippocampi, subventricular zone, and cerebellum. Regions of adult neurogenesis primarily predicted cognition at %v40 except for the right hippocampus which predicted at %v10. Regions that did not predict global cognitive outcomes at any dose include total brain volume, frontal pole, anterior cingulate, right frontal white matter, and the right precentral gyrus.

CONCLUSIONS

Modeling of radiation-induced cognitive decline using neuroanatomical target theory appears to be feasible. A prospective trial is necessary to validate these data.

Prospective study of health-related quality of life for children with brain tumors treated with proton radiotherapy

PURPOSE

We describe the health-related quality of life (HRQoL) of a cohort of children with brain tumors treated with proton radiotherapy.

PATIENTS AND METHODS

We recruited 142 pediatric patients with brain tumors (age 2 to 18 years) and parents of such patients treated with proton radiation at Massachusetts General Hospital from 2004 to 2010. HRQoL was assessed using the PedsQL core, brain tumor, and cancer modules (range, 0 to 100). Assessments took place during radiation and annually thereafter. We examined correlations of HRQoL with disease, treatment, and cognitive and behavioral data.

RESULTS

Overall reports of HRQoL during treatment were 74.8 and 78.1 for child self-report (CSR) and 67.0 and 74.8 for parent proxy report (PPR) for the core and brain tumor modules, respectively. PPR demonstrated lower HRQoL scores than CSR, but the two were highly correlated. Higher HRQoL scores were significantly associated with Wechsler Full Scale Intelligence Quotient scores (administered via the age-appropriate version) and better scores on two behavioral measures. Disease type also correlated with PPR core total HRQoL score at the beginning of treatment: medulloblastoma or primitive neuroectodermal tumors, 57.8; germ cell tumors, 63.5; ependymoma or high-grade glioma, 69.8; low-grade glioma, 71.5; and other low-grade neoplasms, 78.0 (P = .001). Craniospinal irradiation and chemotherapy were negatively correlated with HRQoL.

CONCLUSION

This is the first study to our knowledge of HRQoL in a cohort of children with brain tumors treated with proton radiation. This prospective study demonstrates the effect of disease type and intensity of treatment on HRQoL. It further suggests that where CSR is not possible, PPR is appropriate in most circumstances.

A 5-year investigation of children's adaptive functioning following conformal radiation therapy for localized ependymoma

PURPOSE

Conformal and intensity modulated radiation therapies have the potential to preserve cognitive outcomes in children with ependymoma; however, functional behavior remains uninvestigated. This longitudinal investigation prospectively examined intelligence quotient (IQ) and adaptive functioning during the first 5 years after irradiation in children diagnosed with ependymoma.

METHODS AND MATERIALS

The study cohort consisted of 123 children with intracranial ependymoma. Mean age at irradiation was 4.60 years (95% confidence interval [CI], 3.85-5.35). Serial neurocognitive evaluations, including an age-appropriate IQ measure and the Vineland Adaptive Behavior Scales (VABS), were completed before irradiation, 6 months after treatment, and annually for 5 years. A total of 579 neurocognitive evaluations were included in these analyses.

RESULTS

Baseline IQ and VABS were below normative means (P<.05), although within the average range. Linear mixed models revealed stable IQ and VABS across the follow-up period, except for the VABS Communication Index, which declined significantly (P=.015). Annual change in IQ (-.04 points) did not correlate with annual change in VABS (-.90 to +.44 points). Clinical factors associated with poorer baseline performance (P<.05) included preirradiation chemotherapy, cerebrospinal fluid shunt placement, number and extent of surgical resections, and younger age at treatment. No clinical factors significantly affected the rate of change in scores.

CONCLUSIONS

Conformal and intensity modulated radiation therapies provided relative sparing of functional outcomes including IQ and adaptive behaviors, even in very young children. Communication skills remained vulnerable and should be the target of preventive and rehabilitative interventions.

Intensity-modulated arc therapy for pediatric posterior fossa tumors

PURPOSE

To compare intensity-modulated arc therapy (IMAT) to noncoplanar intensity-modulated radiation therapy (IMRT) in the treatment of pediatric posterior fossa tumors.

METHODS AND MATERIALS

Nine pediatric patients with posterior fossa tumors, mean age 9 years (range, 6-15 years), treated using IMRT were chosen for this comparative planning study because of their tumor location. Each patient's treatment was replanned to receive 54 Gy to the planning target volume (PTV) using five different methods: eight-field noncoplanar IMRT, single coplanar IMAT, double coplanar IMAT, single noncoplanar IMAT, and double noncoplanar IMAT. For each method, the dose to 95% of the PTV was held constant, and the doses to surrounding critical structures were minimized. The different plans were compared based on conformity, total linear accelerator dose monitor units, and dose to surrounding normal tissues, including the entire body, whole brain, temporal lobes, brainstem, and cochleae.

RESULTS

The doses to the target and critical structures for the various IMAT methods were not statistically different in comparison with the noncoplanar IMRT plan, with the following exceptions: the cochlear doses were higher and whole brain dose was lower for coplanar IMAT plans; the cochleae and temporal lobe doses were lower and conformity increased for noncoplanar IMAT plans. The advantage of the noncoplanar IMAT plan was enhanced by doubling the treatment arc.

CONCLUSION

Noncoplanar IMAT results in superior treatment plans when compared to noncoplanar IMRT for the treatment of posterior fossa tumors. IMAT should be considered alongside IMRT when treatment of this site is indicated.

Proton beam therapy in pediatric oncology

Pediatric caregivers and parents are eager to know the role of proton beam therapy (PBT) in the treatment of children with brain and solid tumors and other diseases for which radiation therapy is indicated. Although the number of children treated with PBT for the most common pediatric tumors is relatively small and outcome data are clearly lacking, modeling radiation dose, volume, and outcomes based on photon benchmark data and clinical experience suggest an advantage for PBT and an opportunity to reduce or eliminate many of the early and late effects of radiation therapy. As the number of centers available to treat children increases, it is incumbent on those with access to this modality to optimize other critical aspects of radiotherapy and cancer care and follow-up that are requisite to achieving disease control and high-quality survivorship. Even though the focus of pediatric radiation oncology is weighted toward side effect reduction, there is an opportunity for dose escalation or biologically optimized radiotherapy in a number of diseases or settings in which high-dose irradiation is considered unapproachable. Justification for PBT in pediatric patients should be realized once the costs of treating acute symptoms, growth hormone deficiency, orthopedic deformities, and secondary malignancies are studied and reduced.

Region-specific radiotherapy and neuropsychological outcomes in adult survivors of childhood CNS malignancies

Childhood cancer survivors exposed to CNS irradiation are at increased risk for neurocognitive deficits; however, limited data exist linking outcomes with region-specific exposure to CNS irradiation. We report associations between region-specific radiation dose and self-reported neurocognitive and health-related quality of life (HRQOL) outcomes in 818 adult survivors of childhood central nervous system (CNS) malignancies from the Childhood Cancer Survivor Study. Survivors were compared with a sibling group and national normative samples to calculate standardized scores. Cumulative radiation dose was calculated for 4 specific brain regions. Logistic regression was used to estimate the association between radiation dose to specific brain regions and outcome measures of functional impairment adjusted for clinical and demographic factors, including sex and age at diagnosis. High radiation dose levels to temporal regions were associated with a higher risk for memory impairment (radiation doses ≥30 to <50 Gy: OR, 1.95; 95% CI, 1.01-3.78; dose ≥50 Gy: OR, 2.34; 95% CI, 1.25-4.39) compared with those with no radiation exposure. No such association was seen with radiation exposure to other regions. Exposure to temporal regions was associated with more social and general health problems, whereas exposure to frontal regions was associated with general health problems and physical performance limitations. Adult survivors of childhood CNS malignancies report higher rates of neuropsychological and HRQOL outcomes, which vary as a function of dose to specific neuroanatomical regions. Survivors with a history of radiation exposure to temporal brain regions are at increased risk for impairment in memory and social functioning.

Cognitive Sparing during the Administration of Whole Brain Radiotherapy and Prophylactic Cranial Irradiation: Current Concepts and Approaches

Whole brain radiotherapy (WBRT) for the palliation of metastases, or as prophylaxis to prevent intracranial metastases, can be associated with subacute and late decline in memory and other cognitive functions. Moreover, these changes are often increased in both frequency and severity when cranial irradiation is combined with the use of systemic or intrathecal chemotherapy. Approaches to preventing or reducing this toxicity include the use of stereotactic radiosurgery (SRS) instead of WBRT; dose reduction for PCI; exclusion of the limbic circuit, hippocampal formation, and/or neural stem cell regions of the brain during radiotherapy; avoidance of intrathecal and/or systemic chemotherapy during radiotherapy; the use of high-dose, systemic chemotherapy in lieu of WBRT. This review discusses these concepts in detail as well as providing both neuroanatomic and radiobiologic background relevant to these issues.

Inter- and intrafractional positional uncertainties in pediatric radiotherapy patients with brain and head and neck tumors

PURPOSE

To estimate radiation therapy planning margins based on inter- and intrafractional uncertainty for pediatric brain and head and neck tumor patients at different imaging frequencies.

METHODS

Pediatric patients with brain (n = 83) and head and neck (n = 17) tumors (median age = 7.2 years) were enrolled on an internal review board-approved localization protocol and stratified according to treatment position and use of anesthesia. Megavoltage cone-beam CT (CBCT) was performed before each treatment and after every other treatment. The pretreatment offsets were used to calculate the interfractional setup uncertainty (SU), and posttreatment offsets were used to calculate the intrafractional residual uncertainty (RU). The SU and RU are the patient-related components of the setup margin (SM), which is part of the planning target volume (PTV). SU data was used to simulate four intervention strategies using different imaging frequencies and thresholds.

RESULTS

The SM based on all patients treated on this study was 2.1 mm (SU = 0.9 mm, RU = 1.9 mm) and varied according to treatment position (supine = 1.8 mm, prone = 2.6 mm) and use of anesthesia (with = 1.7 mm, without = 2.5 mm) because of differences in the RU. The average SU for a 2-mm threshold based on no imaging, once per week imaging, initial five images, and daily imaging was 3.6, 2.1, 2.2, and 0.9 mm, respectively.

CONCLUSION

On the basis of this study, the SM component of the PTV may be reduced to 2 mm for daily CBCT compared with 3.5 mm for weekly CBCT. Considering patients who undergo daily pretreatment CBCT, the SM is larger for those treated in the prone position or smaller for those treated under anesthesia because of differences in the RU.

Dosimetric effect of setup motion and target volume margin reduction in pediatric ependymoma

PURPOSE

Quantify the dosimetric effect of inter- and intrafractional motion on intensity-modulated radiation therapy (IMRT) and three-dimensional (3D) planning via changes in the generalized equivalent uniform dose (gEUD), predicted tumor control probability (TCP) and normal tissue complication probability (NTCP) for pediatric ependymoma.

METHODS AND MATERIALS

Twenty patients treated between 1998 and 2002 with a 3D plan (CTV = 1 cm, PTV = 5 mm) were selected. Two IMRT plans were created for the 1 cm CTV (PTV = 5 mm and PTV = 0 mm), and a third IMRT plan for a 5 mm CTV (PTV = 0 mm). Direct simulation with inter- and intrafractional motion was performed for 3D and IMRT plans based on daily pre and post-treatment cone beam CT information obtained from 20 well-matched patients (age, supine/prone, use of GA) on a localization protocol. Calculated TCP, NTCP, Conformity Index (CI), and predictive IQ were compared.

RESULTS

IMRT improved the calculated TCP by 2.8+/-2.8 vs. 3D (p<0.001). Inter- and intrafractional motion results in a TCP loss of 0.4+/-0.7 (p=0.02) and 0.0+/-0.1 (p=0.14) for the IMRT plan with PTV = 0 mm. Mean NTCP for 3D and IMRT with PTV = 5 mm, PTV = 0 mm, and CTV = 5 mm for the cochlea was: 66.6, 29.4, 8.7. Mean NTCP change due to motion was <5%. CI was 0.70+/-0.06 for IMRT and 0.5+/-0.10 for 3D. Predictive IQ was 10.0+/-10.3 points higher for IMRT vs. 3D.

CONCLUSIONS

IMRT improves calculated TCP vs. 3D. Daily localization can allow for a safe reduction in the PTV margin, while maintaining target coverage; reducing the CTV margin can further reduce NTCP and may reduce future side-effects.

Proton beam therapy following resection for childhood ependymoma

INTRODUCTION

Proton radiation therapy is a form of radiation with physical properties that can provide an advantage in normal tissue sparing compared to the more commonly used photon therapy.

DISCUSSION

The greatest benefit may be for young patients with tumors requiring relatively high doses of radiation and adjacent to critical structures. Children with central nervous system ependymomas meet these criteria and have a very high likelihood of benefit from proton radiation. At present, proton radiation is limited to select centers. However, knowledge of many of the physical advantages of proton therapy has spread rapidly over the past several years, and its availability is becoming more widespread.

Radiation therapy for pediatric central nervous system tumors

Radiation therapy is an important component of treatment of many pediatric central nervous system tumors. The radiation treatment target is determined by tumor histology, extent of disease, anticipated pattern of spread, and expected pattern of failure. Children cured of their tumors live to experience the long-term sequelae of radiation treatment, including developmental, neurocognitive, neuroendocrine, and hearing late effects. The development of more conformal radiation techniques has decreased inadvertent radiation dose to normal tissues and should decrease long-term treatment sequelae that are the result of normal tissue radiation. Intensity-modulated radiation therapy improves treatment conformity and decreases high dose to nearby normal tissues; however, it delivers a larger volume of low- and intermediate-dose radiation. Proton radiation eliminates exit dose to normal tissues, thereby eliminating approximately 50% of unnecessary radiation to normal tissues. The long-term clinical benefits of proton radiation in the pediatric population are just beginning to be reported in the literature.

Neuropsychological sequelae and quality of life following treatment of posterior fossa ependymomas in children

INTRODUCTION

Modern treatment of posterior fossa ependymomas in children has improved the overall survival, but as more children live longer, the neuropsychological problems that they endure as result of the disease and its treatment become more the focus of attention.

MATERIAL

Early problems such as cerebellar mutism appear to be related to surgery and do not seem to be influenced in their incidence or outcome by the otherwise beneficial effect of oncological treatment. Indeed, the cause of cerebellar mutism is still elusive. While it was originally believed to be totally reversible, it is increasingly realized that it may be related to more complex delayed neuropsychological problems. Late problems such as the cerebellar cognitive affective syndrome are increasingly being recognized. The deleterious effect of both surgery and radiotherapy that is commonly administered afterwards is now well appreciated.

CONCLUSION

Careful neuropsychological assessment of these children and early intervention will maximize chances for recovery and improvement of academic functions and quality of life issues.

The genetic and epigenetic basis of ependymoma

INTRODUCTION

Although ependymoma is the third most common pediatric brain tumor, we know little about the genetic/epigenetic basis of its initiation, maintenance, or progression. This is due in part to the heterogeneity of the disease, as well as the small sample size of the cohorts analyzed in most studies.

METHODS

Many of the genetic aberrations identified to date are large genomic regions, making the differentiation between passenger and driver genes difficult. The finding of a balanced karyotype in a significant subset of pediatric posterior fossa ependymomas increases the difficulty of identifying targets for rationale therapy.

CONCLUSION

The paucity of in vitro and in vivo model systems for ependymoma compound the difficulties outlined above. In this review, we discuss the published literature on ependymoma genetics and epigenetics and discuss possible future directions for the field.

Three-dimensional conformal radiation therapy for ependymoma

INTRODUCTION

The application of conformal radiation therapy in the treatment of pediatric ependymoma is a success story resulting from advances in radiation therapy planning and delivery. These advances occurred at a time when clinical trial results confirmed that radiotherapy avoidance strategies were unsuccessful.

DISCUSSION

Investigators have been keen to confirm the promise of newer radiation therapy methods even for the youngest children. When preliminary results suggested that high-dose focal irradiation could be safely administered through systematic targeting and that cognitive function could be preserved, investigators moved to include conformal therapy in the frontline management of children regardless of age. The results with postoperative conformal radiation therapy were further enhanced when neurosurgeons increased the rate of gross-total resection and recognized that second surgery could be safely accomplished after incomplete initial resection. With more than a decade of experience, the role of conformal radiation therapy in the treatment of childhood ependymoma has been firmly established as investigators consider new trials to increase disease control and improve functional outcomes.

Investigating verbal and visual auditory learning after conformal radiation therapy for childhood ependymoma

PURPOSE

The primary objective of this study was to determine whether children with localized ependymoma experience a decline in verbal or visual-auditory learning after conformal radiation therapy (CRT). The secondary objective was to investigate the impact of age and select clinical factors on learning before and after treatment.

METHODS AND MATERIALS

Learning in a sample of 71 patients with localized ependymoma was assessed with the California Verbal Learning Test (CVLT-C) and the Visual-Auditory Learning Test (VAL). Learning measures were administered before CRT, at 6 months, and then yearly for a total of 5 years.

RESULTS

There was no significant decline on measures of verbal or visual-auditory learning after CRT; however, younger age, more surgeries, and cerebrospinal fluid shunting did predict lower scores at baseline. There were significant longitudinal effects (improved learning scores after treatment) among older children on the CVLT-C and children that did not receive pre-CRT chemotherapy on the VAL.

CONCLUSION

There was no evidence of global decline in learning after CRT in children with localized ependymoma. Several important implications from the findings include the following: (1) identification of and differentiation among variables with transient vs. long-term effects on learning, (2) demonstration that children treated with chemotherapy before CRT had greater risk of adverse visual-auditory learning performance, and (3) establishment of baseline and serial assessment as critical in ascertaining necessary sensitivity and specificity for the detection of modest effects.

Conformal radiotherapy after surgery for paediatric ependymoma: a prospective study

BACKGROUND

Therapy for ependymoma includes aggressive surgical intervention and radiotherapy administered by use of methods that keep the risk of side-effects to a minimum. We extended this treatment approach to include children under the age of 3 years with the aim of improving tumour control.

METHODS

Between July 11, 1997, and Nov 18, 2007, 153 paediatric patients (median age 2.9 years [range 0.9-22.9 months]) with localised ependymoma were treated. 85 patients had anaplastic ependymoma; the tumours of 122 were located in the infratentorial region, and 35 had received previous chemotherapy. Patients received conformal radiotherapy after definitive surgery (125 patients had undergone gross total, 17 near total, and 11 subtotal resection). Doses of 59.4 Gy (n=131) or 54.0 Gy (n=22) were prescribed to a 10 mm margin around the target volume. Disease control, patterns of failure, and complications were recorded for patients followed over 10 years. Overall survival, event-free survival (EFS), cumulative incidence of local recurrences, and cumulative incidence of distant recurrences were assessed. Variables considered included tumour grade, tumour location, ethnic origin, sex, age when undergoing conformal radiotherapy, total radiotherapy dose, number of surgical procedures, surgery extent, and preradiotherapy chemotherapy.

FINDINGS

After a median follow-up of 5.3 years (range 0.4-10.4), 23 patients had died and tumour progression noted in 36, including local (n=14), distant (n=15), and combined failure (n=7). 7-year local control, EFS, and overall survival were 87.3% (95% CI 77.5-97.1), 69.1% (56.9-81.3), and 81.0% (71.0-91.0), respectively. The cumulative incidences of local and distant failure were 16.3% (9.6-23.0) and 11.5% (5.9-17.1), respectively. In the 107 patients treated with immediate postoperative conformal radiotherapy (without delay or chemotherapy), 7-year local control, EFS, and overall survival were 88.7% (77.9-99.5), 76.9% (63.4-90.4), and 85.0% (74.2-95.8), respectively; the cumulative incidence of local and distant failure were 12.6% (5.1-20.1), and 8.6% (2.8-14.3), respectively. The incidence of secondary malignant brain tumour at 7 years was 2.3% (0-5.6) and brainstem necrosis 1.6% (0-4.0). Overall survival was affected by tumour grade (anaplastic vs differentiated: HR 3.98 [95% CI 1.51-10.48]; p=0.0052), extent of resection (gross total vs near total or subtotal: 0.16 [0.07-0.37]; p<0.0001), and ethnic origin (non-white vs white: 3.0 [1.21-7.44]; p=0.018). EFS was affected by tumour grade (anaplastic vs differentiated: 2.52 [1.2705.01]; p=0.008), extent of resection (gross total vs near total or subtotal: 0.20 [0.11-0.39]; p<0.0001]), and sex (male vs female: 2.19 [1.03-4.66]; p=0.042). Local failure was affected by extent of resection (gross total vs near total or subtotal: 0.16 [0.067-0.38]; p<0.0001), sex (male vs female: 3.85 [1.10-13.52]; p=0.035), and age (<3 years vs >/=3 years: 3.25 [1.30-8.16]; p=0.012). Distant recurrence was only affected by tumour grade (anaplastic vs differentiated: 4.1 [1.2-14.0]; p=0.017).

INTERPRETATION

Treatment of ependymoma should include surgery with the aim of gross-total resection and conformal, high-dose, postoperative irradiation. Future trials might consider treatment stratification based on sex and age.

Dynamic contrast-enhanced magnetic resonance imaging as a biomarker for prediction of radiation-induced neurocognitive dysfunction

PURPOSE

To determine whether early assessment of cerebral microvessel injury can predict late neurocognitive dysfunction after brain radiation therapy (RT).

EXPERIMENTAL DESIGN

Ten patients who underwent partial brain RT participated in a prospective dynamic contrast-enhanced magnetic resonance imaging (MRI) study. Dynamic contrast-enhanced MRI was acquired prior to, at weeks 3 and 6 during, and 1 and 6 months after RT. Neuropsychological tests were done pre-RT and at the post-RT MRI follow-ups. The correlations between early delayed changes in neurocognitive functions and early changes in vascular variables during RT were analyzed.

RESULTS

No patients had tumor progression up to 6 months after RT. Vascular volumes and blood-brain barrier (BBB) permeability increased significantly in the high-dose regions during RT by 11% and 52% (P<0.05), respectively, followed by a decrease after RT. Changes in both vascular volume and BBB permeability correlated with the doses accumulated at the time of scans at weeks 3 and 6 during RT and 1 month after RT (P<0.03). Changes in verbal learning scores 6 months after RT were significantly correlated with changes in vascular volumes of left temporal (P<0.02) and frontal lobes (P<0.03), and changes in BBB permeability of left frontal lobes during RT (P<0.007). A similar correlation was found between recall scores and BBB permeability.

CONCLUSION

Our data suggest that the early changes in cerebral vasculature may predict delayed alterations in verbal learning and total recall, which are important components of neurocognitive function. Additional studies are required for validation of these findings.

Predicting change in academic abilities after conformal radiation therapy for localized ependymoma

PURPOSE

Conformal radiation therapy (CRT) aims to limit the highest radiation dose to the tissue volume at risk while sparing surrounding normal tissues. This study investigated whether treatment of childhood ependymoma with CRT would preserve cognitive function. Academic competence was chosen as the primary outcome measure given it is a measure of applied cognitive abilities in a child's natural setting.

PATIENTS AND METHODS

Eighty-seven pediatric patients diagnosed with ependymoma received CRT in which doses ranging from 54.0 to 59.4 Gy were prescribed to the postoperative tumor bed with a 10-mm clinical target volume margin. Cognitive testing was conducted at the start of CRT, 6 months, and annually after the start of CRT. The median length of follow-up was 59.6 months. Academic testing included subtests from the Wechsler Individual Achievement Test (WIAT) and the Achenbach Child Behavior Checklist.

RESULTS

Linear mixed models with random coefficients revealed a modest but significant decline in reading scores during follow-up (WIAT slope estimate -0.064 +/- 0.028 points/month; P = .026). Math and spelling performance remained stable. Supratentorial tumor location and multiple surgeries were predictive of worse reading performance at CRT baseline. Male sex, longer symptomatic interval, pre-CRT chemotherapy, pre-existing endocrine deficiencies, hydrocephalus, and younger age at CRT (< 5 years) were predictive of a significant decline in reading scores over time.

CONCLUSION

CRT may result in better long-term cognitive outcomes when compared to conventional radiation therapy approaches. Reading appears more vulnerable than other academic skills and may decline over time despite stable intellectual functioning.

Dose-dependent effects of radiation therapy on cerebral blood flow, metabolism, and neurocognitive dysfunction

PURPOSE

A prospective study was performed to formally relate dose-dependent radiologically defined changes in normal brain induced by radiotherapy (RT) to neurocognitive dysfunction in subjects with primary brain tumors.

METHODS AND MATERIALS

Adult patients receiving three-dimensional RT for central nervous system (CNS) tumors were enrolled. Positron emission tomography (PET) scanning and neuropsychological testing were performed before RT and 3 weeks and 6 months after treatment. Analyses were performed for correlations between changes in 2-deoxy-2-[(18)F]-fluoro-d-glucose (FDG)-PET (metabolism), (15)O-PET (relative blood flow), regional radiation dose, follow-up time, and neuropsychological test scores.

RESULTS

Eleven subjects were enrolled and 6 completed follow-up studies. The PET data showed reduced FDG uptake, with average decreases of 2-6% in regions of the brain receiving greater than 40 Gy at 3 weeks' and 6 months' follow-up. The (15)O-H(2)O PET showed increases (<10%) at 3 weeks in relative regional blood flow in brain receiving greater than 30 Gy, but less at the 6-month follow-up studies. There were significant correlations between decreases in FDG uptake and increased scores from the Symptom Checklist-90-R, with an average increase in T score of 2 (p < 0.0001). The Wisconsin Card Sorting Test showed a significant correlation of decreased FDG uptake with increased errors and perseveration in test performance, with an average decrease in T score of 11 (p = 0.037).

CONCLUSIONS

A dose-dependent response of CNS tissue was detected using FDG PET in this small number of patients. Decreases in CNS metabolism correlated with decreased performance on neuropsychological tests for problem solving, cognitive flexibility, and global measures of psychopathology. Additional research is needed to verify and define these findings.

Proton versus photon radiotherapy for common pediatric brain tumors: comparison of models of dose characteristics and their relationship to cognitive function

BACKGROUND

To determine whether proton radiotherapy has clinical advantages over photon radiotherapy, we modeled the dose characteristics of both to critical normal tissue volumes using data from patients with four types of childhood brain tumors.

PROCEDURES

Three-dimensional imaging and treatment planning data, including targeted tumor and normal tissues contours, were acquired for 40 patients, 10 each with optic pathway glioma (OPG), craniopharyngioma (CR), infratentorial ependymoma (EP), or medulloblastoma (MB). Dose-volume data were collected for the entire brain, temporal lobes, cochlea, and hypothalamus from each patient. The data were averaged and compared based on treatment modality (protons vs. photons) using dose-cognitive effects models. Outcomes were estimated over 5 years.

RESULTS

Relatively small critical normal tissue volumes such as the cochlea and hypothalamus may be spared from radiation exposure when not adjacent to the primary tumor volume. Larger normal tissue volumes such as the supratentorial brain or temporal lobes receive less of the low and intermediate doses. When applied to longitudinal models of radiation dose-cognitive effects, these differences resulted in clinically significant higher IQ scores for patients with MB and CR and academic reading scores in patients with OPG. Extreme differences between proton and photon dose distributions precluded meaningful comparison of protons and photons for patients with EP.

CONCLUSIONS

Differences in the overall dose distributions, as indicated by modeling changes in cognitive function, showed that a reduction in the lower-dose volumes or mean dose would have long-term, clinical advantages for children with MB, CR, and OPG.

Differential prefrontal-like deficit in children after cerebellar astrocytoma and medulloblastoma tumor

Background

This study was realized thanks to the collaboration of children and adolescents who had been resected from cerebellar tumors. The medulloblastoma group (CE+, n = 7) in addition to surgery received radiation and chemotherapy. The astrocytoma group (CE, n = 13) did not receive additional treatments. Each clinical group was compared in their executive functioning with a paired control group (n = 12). The performances of the clinical groups with respect to controls were compared considering the tumor's localization (vermis or hemisphere) and the affectation (or not) of the dentate nucleus. Executive variables were correlated with the age at surgery, the time between surgery-evaluation and the resected volume.

Methods

The executive functioning was assessed by means of WCST, Complex Rey Figure, Controlled Oral Word Association Test (letter and animal categories), Digits span (WISC-R verbal scale) and Stroop test. These tests are very sensitive to dorsolateral PFC and/or to medial frontal cortex functions. The scores for the non-verbal Raven IQ were also obtained. Direct scores were corrected by age and transformed in standard scores using normative data. The neuropsychological evaluation was made at 3.25 (SD = 2.74) years from surgery in CE group and at 6.47 (SD = 2.77) in CE+ group.

Results

The Medulloblastoma group showed severe executive deficit (≤ 1.5 SD below normal mean) in all assessed tests, the most severe occurring in vermal patients. The Astrocytoma group also showed executive deficits in digits span, semantic fluency (animal category) and moderate to slight deficit in Stroop (word and colour) tests. In the astrocytoma group, the tumor's localization and dentate affectation showed different profile and level of impairment: moderate to slight for vermal and hemispheric patients respectively. The resected volume, age at surgery and the time between surgery-evaluation correlated with some neuropsychological executive variables.

Conclusion

Results suggest a differential prefrontal-like deficit due to cerebellar lesions and/or cerebellar-frontal diaschisis, as indicate the results in astrocytoma group (without treatments), that also can be generated and/or increased by treatments in the medulloblastoma group. The need for differential rehabilitation strategies for specific clinical groups is remarked. The results are also discussed in the context of the Cerebellar Cognitive Affective Syndrome.

Proton radiotherapy for childhood ependymoma: initial clinical outcomes and dose comparisons

PURPOSE

To report preliminary clinical outcomes for pediatric patients treated with proton beam radiation for intracranial ependymoma and compare the dose distributions of intensity-modulated radiation therapy with photons (IMRT), three-dimensional conformal proton radiation, and intensity-modulated proton radiation therapy (IMPT) for representative patients.

METHODS AND MATERIALS

All children with intracranial ependymoma confined to the supratentorial or infratentorial brain treated at the Francis H. Burr Proton Facility and Harvard Cyclotron between November 2000 and March 2006 were included in this study. Seventeen patients were treated with protons. Proton, IMRT, and IMPT plans were generated with similar clinical constraints for representative infratentorial and supratentorial ependymoma cases. Tumor and normal tissue dose-volume histograms were calculated and compared.

RESULTS

At a median follow-up of 26 months from the start date of radiation therapy, local control, progression-free survival, and overall survival rates were 86%, 80%, and 89%, respectively. Subtotal resection was significantly associated with decreased local control (p = 0.016). Similar tumor volume coverage was achieved with IMPT, proton therapy, and IMRT. Substantial normal tissue sparing was seen with proton therapy compared with IMRT. Use of IMPT will allow for additional sparing of some critical structures.

CONCLUSIONS

Preliminary disease control with proton therapy compares favorably with the literature. Dosimetric comparisons show the advantage of proton radiation compared with IMRT in the treatment of ependymoma. Further sparing of normal structures appears possible with IMPT. Superior dose distributions were accomplished with fewer beam angles with the use of protons and IMPT.

Intensity-modulated radiation therapy in childhood ependymoma

PURPOSE

To determine the patterns of failure after intensity-modulated radiation therapy (IMRT) for localized intracranial ependymoma.

METHODS AND MATERIALS

From 1994 to 2005, 22 children with pathologically proven, localized, intracranial ependymoma were treated with adjuvant IMRT. Of the patients, 12 (55%) had an infratentorial tumor and 14 (64%) had anaplastic histology. Five patients had a subtotal resection (STR), as evidenced by postoperative magnetic resonance imaging. The clinical target volume encompassed the tumor bed and any residual disease plus margin (median dose 54 Gy). Median follow-up for surviving patients was 39.8 months.

RESULTS

The 3-year overall survival rate was 87% +/- 9%. The 3-year local control rate was 68% +/- 12%. There were six local recurrences, all in the high-dose region of the treatment field. Median time to recurrence was 21.7 months. Of the 5 STR patients, 4 experienced recurrence and 3 died. Patients with a gross total resection had significantly better local control (p = 0.024) and overall survival (p = 0.008) than those with an STR. At last follow-up, no patient had developed visual loss, brain necrosis, myelitis, or a second malignancy.

CONCLUSIONS

Treatment with IMRT provides local control and survival rates comparable with those in historic publications using larger treatment volumes. All failures were within the high-dose region, suggesting that IMRT does not diminish local control. The degree of surgical resection was shown to be significant for local control and survival.

Radiotherapy for pediatric brain tumors: when and how

Radiotherapy plays a central role in the treatment of pediatric brain tumors. Historically, surgical resection alone was the mainstay of treatment for pediatric CNS malignancies. During the past 75 years, radiotherapy has been incorporated into the upfront treatment of many pediatric brain tumors either as adjuvant therapy for resected tumors, definitive treatment for unresectable malignancies or as prophylactic therapy for occult microscopic disease. Many CNS malignancies, which were once universally fatal are now curable with multimodality approaches that integrate surgery, chemotherapy and radiotherapy. Unfortunately, the long-term CNS side effects of radiotherapy remain a major obstacle for survivors of childhood tumors. In this article we will discuss these issues in detail and summarize the ongoing efforts to reduce the risks of these toxicities.

Impairment of intellectual functions after surgery and posterior fossa irradiation in children with ependymoma is related to age and neurologic complications

Background

To investigate the neuropsychological outcome of children treated with surgery and posterior fossa irradiation for localized infratentorial ependymoma.

Methods

23 patients (age 0.3 – 14 years at diagnosis) who were treated with local posterior fossa irradiation (54 Gy) underwent one (4 patients) or sequential (19 patients) neuropsychologic evaluation. The last evaluation was performed at a median of 4.5 (1 to 15.5) years after RT.

Results

Mean last full scale IQ (FSIQ), verbal IQ (VIQ) and PIQ were 89.1, 94.0, and 86.2 respectively. All patients had difficulties with reading, and individual patients showed deficits in visuospatial, memory and attentional tasks. There was no trend for deterioration of intellectual outcome over time. All 5 children with IQ scores ≤ 75 were under the age of four at diagnosis. There was a significant association between the presence of cerebellar deficits and impaired IQ (72.0 vs 95.2, p < 0,001). The absence of hydrocephalus was an indicator of better neuropsychologic outcome (mean FSIQ of 102.6 vs 83.9, p = 0.025).

Conclusion

Within the evaluated cohort, intellectual functions were moderately impaired. Markedly reduced IQ scores were only seen with early disease manifestation and treatment, and postoperative neurological deficits had a strong impact on intellectual outcome.

High-grade astrocytoma in very young children

BACKGROUND

High-grade astrocytomas are rare in young children, but have been reported to have a better prognosis than similar tumors in older patients.

PROCEDURE

We retrospectively reviewed the clinical characteristics, survival, and long-term sequelae for patients younger than 3 years old with high-grade astrocytoma, treated at a single institution between 1984 and 2005.

RESULTS

Sixteen patients were included. Histology included anaplastic astrocytoma (n = 9), glioblastoma multiforme (n = 5), and malignant glioma (n = 2). All patients underwent biopsy or resection, followed by chemotherapy. Six patients received scheduled irradiation and six were irradiated at the time of disease progression. Ten patients are alive at a median follow-up of 11.6 years (range, 1.7-21.6 years). 5-year overall survival (OS) was 66.3% (SE 12.2%), and 5-year event-free survival (EFS) was 28.6% (SE 12.1%). Age at diagnosis was a significant predictor of the hazard of death in a Cox model (HR 2.871, 95%CI 1.015-8.123). Gender and histology did not predict OS or EFS. Trends toward improved OS were detected for patients with hemispheric tumors and those undergoing complete resection. All evaluable survivors (n = 9) had some neurocognitive impairment, with estimated overall cognitive ability ranging from significantly delayed to average; all survivors attending school (n = 5) performed below grade level on achievement testing. Seven of nine evaluable survivors had endocrine dysfunction.

CONCLUSIONS

Young children with high-grade astrocytoma have better long-term overall survival than older patients, but recurrence is common, and most children require irradiation. Long-term complications are frequent and often severe.

Childhood intracranial ependymoma: twenty-year experience from a single institution

BACKGROUND

Because few large studies of pediatric ependymoma treatment are available, the authors believed that a retrospective review of treatment outcomes from a single institution would yield potentially valuable information regarding potential prognostic factors. In this article, they report their 20-year institutional experience with this disease.

METHODS

Medical records were reviews of patients with intracranial ependymoma who received their initial treatment at the Children's Hospital of Philadelphia (CHOP)/Hospital of the University of Pennsylvania (HUP) between January 1980 and December 2000. Of the 61 patients who were identified, 49 patients underwent primary therapy at CHOP/HUP and formed the basis for the study. Actuarial overall survival (OS) and progression-free survival (PFS) were determined by the Kaplan-Meier method. Univariate and multivariate analyses were performed using the log-rank test and Cox proportional-hazards models.

RESULTS

With median follow-up of 110.2 months, the 5-year OS and PFS rates were 66.2% and 40.7%, respectively. Older age and higher radiation dose significantly predicted for improved OS. Anaplastic histology predicted for decreased PFS. Cervical spinal cord extension resulted in decreased OS primarily caused by failures outside the primary site. Patients who had a favorable prognosis (aged >/=3 years, no dissemination or cord extension, complete resection, and radiation dose >/=54 grays [Gy]) had 5-year OS and PFS rates of 83.1% and 60.6%, respectively.

CONCLUSIONS

In this study of patients with pediatric intracranial ependymoma, OS and PFS rates were concordant with the rates published in other modern series. The finding of a dose response up to 54 Gy supported the current trend toward dose escalation. Tumor extension to the cervical spine was identified as a predictor for failure outside of the primary site. Although the survival rates were encouraging, there is still significant room for improvement in the management of this disease.

Changes in Cerebral Cortex of Children Treated for Medulloblastoma

PURPOSE

Children with medulloblastoma undergo surgery, radiotherapy, and chemotherapy. After treatment, these children have numerous structural abnormalities. Using high-resolution magnetic resonance imaging, we measured the thickness of the cerebral cortex in a group of medulloblastoma patients and a group of normally developing children.

METHODS AND MATERIALS

We obtained magnetic resonance imaging scans and measured the cortical thickness in 9 children after treatment of medulloblastoma. The measurements from these children were compared with the measurements from age- and gender-matched normally developing children previously scanned. For additional comparison, the pattern of thickness change was compared with the cortical thickness maps from a larger group of 65 normally developing children.

RESULTS

In the left hemisphere, relatively thinner cortex was found in the perirolandic region and the parieto-occipital lobe. In the right hemisphere, relatively thinner cortex was found in the parietal lobe, posterior superior temporal gyrus, and lateral temporal lobe. These regions of cortical thinning overlapped with the regions of cortex that undergo normal age-related thinning.

CONCLUSION

The spatial distribution of cortical thinning suggested that the areas of cortex that are undergoing development are more sensitive to the effects of treatment of medulloblastoma. Such quantitative methods may improve our understanding of the biologic effects that treatment has on the cerebral development and their neuropsychological implications.

Neural Stem Cells: Implications for the Conventional Radiotherapy of Central Nervous System Malignancies

Advances in basic neuroscience related to neural stem cells and their malignant counterparts are challenging traditional models of central nervous system tumorigenesis and intrinsic brain repair. Neurogenesis persists into adulthood predominantly in two neurogenic centers: subventricular zone and subgranular zone. Subventricular zone is situated adjacent to lateral ventricles and subgranular zone is confined to the dentate gyrus of the hippocampus. Neural stem cells not only self-renew and differentiate along multiple lineages in these regions, but also contribute to intrinsic brain plasticity and repair. Ionizing radiation can depopulate these exquisitely sensitive regions directly or impair in situ neurogenesis by indirect, dose-dependent and inflammation-mediated mechanisms, even at doses <2 Gy. This review discusses the fundamental neural stem cell concepts within the framework of cumulative clinical experience with the treatment of central nervous system malignancies using conventional radiotherapy.

Role of radiation therapy in pediatric cancer

Whether in its preventive role of CNS prophylaxis for high-risk ALL, its central role in brain tumors, its adjunct role combined with chemotherapy for disease such as Hodgkin's lymphoma, Ewing's sarcoma, and rhabdomyosarcoma, or its palliative role for metastatic disease, radiation remains an important therapy for pediatric cancers.

Current developments in radiotherapy for paediatric brain tumours

This review summarises current developments in radiation oncology and how they impact on the management of children with brain tumours. Improved understanding of radiobiology has led to attempts to improve the therapeutic ratio with hyperfractionated radiotherapy. Recent advances in planning and delivery of radiotherapy, including three-dimensional conformal radiotherapy, intensity modulated radiotherapy, and proton therapy allow a more precise localisation of the maximum dose region with maximum sparing of normal brain. Increasingly interactions between drugs and radiotherapy are exploited, but it is important to evaluate toxicity of combined modality therapy. The introduction of models to predict the impact of radiotherapy dose-volume parameters on long-term neuropsychological function will hopefully lead to further benefit with respect to sparing of normal tissue morbidity.

Modeling radiation dosimetry to predict cognitive outcomes in pediatric patients with CNS embryonal tumors including medulloblastoma

PURPOSE

Model the effects of radiation dosimetry on IQ among pediatric patients with central nervous system (CNS) tumors.

METHODS AND MATERIALS

Pediatric patients with CNS embryonal tumors (n = 39) were prospectively evaluated with serial cognitive testing, before and after treatment with postoperative, risk-adapted craniospinal irradiation (CSI) and conformal primary-site irradiation, followed by chemotherapy. Differential dose-volume data for 5 brain volumes (total brain, supratentorial brain, infratentorial brain, and left and right temporal lobes) were correlated with IQ after surgery and at follow-up by use of linear regression.

RESULTS

When the dose distribution was partitioned into 2 levels, both had a significantly negative effect on longitudinal IQ across all 5 brain volumes. When the dose distribution was partitioned into 3 levels (low, medium, and high), exposure to the supratentorial brain appeared to have the most significant impact. For most models, each Gy of exposure had a similar effect on IQ decline, regardless of dose level.

CONCLUSIONS

Our results suggest that radiation dosimetry data from 5 brain volumes can be used to predict decline in longitudinal IQ. Despite measures to reduce radiation dose and treatment volume, the volume that receives the highest dose continues to have the greatest effect, which supports current volume-reduction efforts.