Hippocampal-sparing radiotherapy: the new standard of care for World Health Organization grade II and III gliomas?

Neuropsychological performances in patients with infiltrative non-GBM gliomas after postoperative adjuvant photon or proton radiotherapy: A prospective and preliminary investigation

Infiltrative non-GBM gliomas are common primary intracranial malignancies, and postoperative adjuvant radiotherapy is recommended for most adult patients diagnosed with this disease to enhance local control and prolong intracranial progression-free survival (PFS). However, RT-related neurocognitive function (NCF) consequences should not be ignored. Early neurocognitive decline principally includes episodic memory, associated significantly with functions of the hippocampus. This prospective study aims to investigate the impact of adjuvant brain irradiation on neurocognitive performances and relevant oncological outcomes.Twenty-five patients with intracranial infiltrative non-GBM gliomas were enrolled when postoperative adjuvant RT was recommended. All recruited patients should receive baseline brain magnetic resonance imaging, and neuropsychological assessments before and 4 months after the RT course. A battery of neuropsychological measures, mainly including executive functions, memory, psychomotor speed and visuoconstructive ability, was used to evaluate NCFs of interest.Analyzing the delta values between post-irradiation and baseline NCF scores, we observed a robust trend reflecting cognitive stabilization rather than deterioration in almost all NCF. Both verbal and visual memory functions exhibited significant differences in the corresponding scaled scores (Z = -2.722, p = .006, regarding verbal memory; Z = -2.246, p = .025, concerning non-verbal memory). Moreover, patients' neuropsychological performances associated with psychomotor speed and executive functions also disclosed a tendency toward stabilization/improvement.This prospective study demonstrated that patients with infiltrative non-GBM exhibited a marked tendency toward neurocognitive stabilization after receiving postoperative adjuvant RT. Clinical trial registration: Trial Registration with ClinicalTrials.gov identifier: NCT03534050.

Total scalp irradiation: A study comparing multiple types of bolus and VMAT optimization techniques

PURPOSE

To investigate bolus design and VMAT optimization settings for total scalp irradiation.

METHODS

Three silicone bolus designs (flat, hat, and custom) from .decimal were evaluated for adherence to five anthropomorphic head phantoms. Flat bolus was cut from a silicone sheet. Generic hat bolus resembles an elongated swim cap while custom bolus is manufactured by injecting silicone into a 3D printed mold. Bolus placement time was recorded. Air gaps between bolus and scalp were quantified on CT images. The dosimetric effect of air gaps on target coverage was evaluated in a treatment planning study where the scalp was planned to 60 Gy in 30 fractions. A noncoplanar VMAT technique based on gEUD penalties was investigated that explored the full range of gEUD alpha values to determine which settings achieve sufficient target coverage while minimizing brain dose. ANOVA and the t-test were used to evaluate statistically significant differences (threshold = 0.05).

RESULTS

The flat bolus took 32 ± 5.9 min to construct and place, which was significantly longer (p < 0.001) compared with 0.67 ± 0.2 min for the generic hat bolus or 0.53 ± 0.10 min for the custom bolus. The air gap volumes were 38 ± 9.3 cc, 32 ± 14 cc, and 17 ± 7.0 cc for the flat, hat, and custom boluses, respectively. While the air gap differences between the flat and custom boluses were significant (p = 0.011), there were no significant dosimetric differences in PTV coverage at V57Gy or V60Gy. In the VMAT optimization study, a gEUD alpha of 2 was found to minimize the mean brain dose.

CONCLUSIONS

Two challenging aspects of total scalp irradiation were investigated: bolus design and plan optimization. Results from this study show opportunities to shorten bolus fabrication time during simulation and create high quality treatment plans using a straightforward VMAT template with simple optimization settings.

Dose-Volume Constraints fOr oRganS At risk In Radiotherapy (CORSAIR): An "All-in-One" Multicenter-Multidisciplinary Practical Summary

BACKGROUND

The safe use of radiotherapy (RT) requires compliance with dose/volume constraints (DVCs) for organs at risk (OaRs). However, the available recommendations are sometimes conflicting and scattered across a number of different documents. Therefore, the aim of this work is to provide, in a single document, practical indications on DVCs for OaRs in external beam RT available in the literature.

MATERIAL AND METHODS

A multidisciplinary team collected bibliographic information on the anatomical definition of OaRs, on the imaging methods needed for their definition, and on DVCs in general and in specific settings (curative RT of Hodgkin's lymphomas, postoperative RT of breast tumors, curative RT of pediatric cancers, stereotactic ablative RT of ventricular arrythmia). The information provided in terms of DVCs was graded based on levels of evidence.

RESULTS

Over 650 papers/documents/websites were examined. The search results, together with the levels of evidence, are presented in tabular form.

CONCLUSIONS

A working tool, based on collected guidelines on DVCs in different settings, is provided to help in daily clinical practice of RT departments. This could be a first step for further optimizations.

Memantine in the Prevention of Radiation-Induced Brain Damage: A Narrative Review

Simple Summary

Decline in cognitive function is a major problem for patients undergoing whole-brain radiotherapy (WBRT). Scientific interest has increased due to the high dropout rate of patients in the first months after WBRT and the early onset of cognitive decline. Therefore, the study of antiglutamatergic pharmacological prophylaxis and hippocampal-sparing WBRT techniques has been deepened based on the knowledge of the mechanisms of hyperglutamatergic neurotoxicity and the role of some hippocampal areas in cognitive decline. In order to provide a summary of the evidence in this field, and to foster future research in this setting, this literature review presents current evidence on the prevention of radiation-induced cognitive decline and particularly on the role of memantine.

Abstract

Preserving cognitive functions is a priority for most patients with brain metastases. Knowing the mechanisms of hyperglutamatergic neurotoxicity and the role of some hippocampal areas in cognitive decline (CD) led to testing both the antiglutamatergic pharmacological prophylaxis and hippocampal-sparing whole-brain radiotherapy (WBRT) techniques. These studies showed a relative reduction in CD four to six months after WBRT. However, the failure to achieve statistical significance in one study that tested memantine alone (RTOG 0614) led to widespread skepticism about this drug in the WBRT setting. Moreover, interest grew in the reasons for the strong patient dropout rates in the first few months after WBRT and for early CD onset. In fact, the latter can only partially be explained by subclinical tumor progression. An emerging interpretation of the (not only) cognitive impairment during and immediately after WBRT is the dysfunction of the limbic and hypothalamic system with its immune and hormonal consequences. This new understanding of WBRT-induced toxicity may represent the basis for further innovative trials. These studies should aim to: (i) evaluate in greater detail the cognitive effects and, more generally, the quality of life impairment during and immediately after WBRT; (ii) study the mechanisms producing these early effects; (iii) test in clinical studies, the modern and advanced WBRT techniques based on both hippocampal-sparing and hypothalamic-pituitary-sparing, currently evaluated only in planning studies; (iv) test new timings of antiglutamatergic drugs administration aimed at preventing not only late toxicity but also acute effects.

Multi-Planar VMAT Plans for High-Grade Glioma and Glioblastoma Targeting the Hypothalamic-Pituitary Axis Sparing

Background: This study aimed to identify the better arc configuration of volumetric modulated arc therapy (VMAT) for high-grade glioma and glioblastoma, focusing on a dose reduction to the hypothalamic–pituitary axis through an analysis of dose-volumetric parameters, as well as a correlation analysis between the planned target volume (PTV) to organs at risk (OAR) distance and the radiation dose. Method: Twenty-four patients with 9 high-grade glioma and 15 glioblastomas were included in this study. Identical CT, MRI and structure sets of each patient were used for coplanar VMAT (CO-VMAT), dual planar VMAT (DP-VMAT) and multi-planar VMAT (MP-VMAT) planning. The dose constraints adhered to the RTOG0825 and RTOG9006 protocols. The dose-volumetric parameters of each plan were collected for statistical analysis. Correlation analyses were performed between radiation dose and PTV-OARs distance. Results: The DP-VMAT and MP-VMAT achieved a significant dose reduction to most nearby OARs when compared to CO-VMAT, without compromising the dose to PTV, plan homogeneity and conformity. For centrally located OARs, including the hypothalamus, pituitary, brain stem and optic chiasm, the dose reductions ranged from 2.65 Gy to 3.91 Gy (p < 0.001) in DP-VMAT and from 2.57 Gy to 4 Gy (p < 0.001) in MP-VMAT. Similar dose reduction effects were achieved for contralaterally located OARs, including the hippocampus, optic nerve, lens and retina, ranging from 1.06 Gy to 4.37 Gy in DP-VMAT and from 0.54 Gy to 3.39 Gy in MP-VMAT. For ipsilaterally located OARs, DP-VMAT achieved a significant dose reduction of 1.75 Gy to D_max for the optic nerve. In the correlation analysis, DP-VMAT and MP-VMAT showed significant dose reductions to centrally located OARs when the PTV-OAR distance was less than 4 cm. In particular, DP-VMAT offered better sparing to the optic chiasm when it was located less than 2 cm from the PTV than that of MP-VMAT and CO-VMAT. DP-VMAT and MP-VMAT also showed better sparing to the contralateral hippocampus and retina when they were located 3–8 cm from the PTV. Conclusion: The proposed DP-VMAT and MP-VMAT demonstrated significant dose reductions to centrally located and contralateral OARs and maintained the high plan qualities to PTV with good homogeneity and conformity when compared to CO-VMAT for high-grade glioma and glioblastoma. The benefit in choosing DP-VMAT and MP-VMAT over CO-VMAT was substantial when the PTV was located near the hypothalamus, pituitary, optic chiasm, contralateral hippocampus and contralateral retina.

Feasibility of hippocampus-sparing VMAT for newly diagnosed glioblastoma treated by chemoradiation: pattern of failure analysis

Background

To identify the pattern of failure and oncological safety of hippocampus (HC)-sparing IMRT (HSRT) in newly diagnosed glioblastoma (GBM) patients.

Materials and methods

Eighty-two GBM patients treated with temozolomide-based chemoradiation using HSRT between 2014 and 2018 were retrospectively reviewed. HSRT consisted of a sparing of D_max of the contralateral HC < 17 Gy. Fifteen patients were unable to achieve the dose-constraints for adequate target coverage. The dose to ipsilateral HC was kept as low as possible. The pattern of failure was investigated, focusing on the area in the vicinity of the spared HC (organ and + 1 cm area). The median HSRT dose was 60 Gy in 30 fractions.

Results

The median follow-up for survivors was 11.7 months. The median progression-free and overall survival were 9.7 and 23.5 months, respectively. Six (7.3%) and eight (9.8%) patients eventually demonstrated progressive disease at the contralateral HC and HC + 1 cm, respectively. The 12-month contralateral HC and HC + 1 cm failure-free rate were 97.2 and 93.4%, respectively. However, no patient (0%) and two patients (2.4%) showed failure at contralateral HC and HC + 1 cm at initial progression, respectively. The dominant pattern of failure at the contralateral HC was by subependymal seeding (66.7%).

Conclusion

The incidence of failure at the contralateral HC and HC + 1 cm is very low and mostly accompanied by disseminated disease progression after HSRT. Since HSRT does not compromise oncological outcomes, it could be considered especially for GBM patients who are expected to have favorable survival outcomes.

Long-term outcomes and late adverse effects of a prospective study on proton radiotherapy for patients with low-grade glioma

BACKGROUND

Patients with low-grade gliomas (LGG) can survive years with their illness. Proton radiotherapy (PRT) can reduce off-target dose and decrease the risk of treatment-related morbidity. We examined long-term morbidity following proton therapy in this updated prospective cohort of patients with LGG.

METHODS

Twenty patients with LGG were enrolled prospectively and received PRT to 54 Gy(RBE) in 30 fractions. Comprehensive baseline and longitudinal assessments of toxicity, neurocognitive and neuroendocrine function, quality of life, and survival outcomes were performed up to 5 years following treatment.

RESULTS

Six patients died (all of disease) and six had progression of disease. Median follow-up was 6.8 years for the 14 patients alive at time of reporting. Median progression-free survival (PFS) was 4.5 years. Of tumors tested for molecular markers, 71% carried the IDH1-R132H mutation and 29% had 1p/19q co-deletion. There was no overall decline in neurocognitive function; however, a subset of five patients with reported cognitive symptoms after radiation therapy had progressively worse function by neurocognitive testing. Six patients developed neuroendocrine deficiencies, five of which received Dmax ≥20 Gy(RBE) to the hypothalamus-pituitary axis (HPA). Most long-term toxicities developed within 2 years after radiation therapy.

CONCLUSIONS

The majority of patients with LGG who received proton therapy retained stable cognitive and neuroendocrine function. The IDH1-R132H mutation was present in the majority, while 1p/19q loss was present in a minority. A subset of patients developed neuroendocrine deficiencies and was more common in those with higher dose to the HPA.

Long-term cognitive dysfunction after radiation therapy for primary brain tumors

Background: The extent of radiation therapy (RT)-induced changes in cognitive function is unknown. RT with protons instead of photons spares the healthy brain tissue more and is believed to reduce the risk of cognitive dysfunction. There is modest knowledge on which parts of the brain we need to spare, to prevent cognitive dysfunction. To uncover which cognitive domains is most affected, we compared cognitive functioning in brain tumor patients treated with neurosurgery and RT with brain tumor patients treated with neurosurgery alone. Methods: A cross-sectional study assessing cognitive function in 110 patients with a primary brain tumor grades I-III or medulloblastoma (grade IV) treated at Aarhus University Hospital (AUH), Denmark between 2006 and 2016. Two cohorts were established: a cohort of 81 brain tumor patients who had received neurosurgery followed by RT (RT+), and a cohort of 29 brain tumor patients who had only received neurosurgery (RT-). The patients underwent questionnaires and neuropsychological assessment with standardized tests. Results: Mean age was 53.5 years with an average time since diagnosis of 7.3 years. Compared with normative data, lower average scores were observed for the entire group on domains concerning of verbal learning and memory (p < .001), attention and working memory (p < .001), processing speed (p < .001), and executive functioning (p < .001). Compared to RT- patients, RT + patients scored lower on domains concerning processing speed (p = .04) and executive function (p = .05) and had higher impairment frequency on verbal fluency (p = .02) with 16% of patients exceeding 1.5 SD below normative data. Conclusions: Our results indicate that treatment, including RT, for a primary brain tumor may have negative long-term impact on cognitive function, especially on processing speed and executive function.

Advantages of intensity modulated proton therapy during hippocampal avoidance whole brain radiation therapy

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Whole-brain intensity modulated proton therapy capably spares hippocampal volumes.

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Hippocampal avoidance whole-brain radiotherapy may benefit pediatric populations.

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Intensity modulated proton therapy provides superior target-dose homogeneity relative to modulated x-rays.

Background and purpose

Intensity modulated proton therapy (IMPT) allows for modulation parameterized for individual beamlets by position, intensity, and depth. This modulation capability is ideally suited for sparing organs at risk intermediate of the radiation target, such as hippocampal volumes within the whole brain. This work compared IMPT relative to volumetric modulated arc therapy (VMAT) during hippocampal avoidance whole brain radiation therapy (HA WBRT).

Materials and methods

Ten adult and ten pediatric patients previously treated for central nervous system malignancies were identified. IMPT and VMAT treatment plans employing HA WBRT were generated for each patient, delivering 30 GyE (Gray Equivalent) in 10 fractions for adults and 36 GyE in 20 fractions for pediatrics. Dose indices, including dose volume histogram metrics and homogeneity index HI = [D5% − D95%]/[D_mean] × 100, were used to assess plan quality and describe target coverage and normal-tissue sparing.

Results

IMPT offered significant benefits relative to VMAT for hippocampal sparing. Hippocampal mean dose was reduced from 13.7 ± 0.8 Gy with VMAT to 5.4 ± 0.3 GyE using IMPT for pediatrics, and was reduced from 11.7 ± 0.9 Gy with VMAT to 4.4 ± 0.2 GyE using IMPT for adults. IMPT similarly lowered left hippocampal mean dose. Dose to 95% of the clinical target volume was statistically equivalent for both groups; however IMPT reduced the homogeneity index by roughly half.

Conclusion

This manuscript demonstrates that HA IMPT can match or exceed dosimetric benefits offered with modulated X-rays. Inclusion of IMPT in future prospective studies is warranted.

Hippocampus-sparing radiotherapy using volumetric modulated arc therapy (VMAT) to the primary brain tumor: the result of dosimetric study and neurocognitive function assessment

Background

We hypothesized that hippocampal-sparing radiotherapy via volumetric modulated arc therapy (VMAT) could preserve the neurocognitive function (NCF) of patients with primary brain tumors treated with radiotherapy.

Methods

We reviewed data from patients with primary brain tumors who underwent hippocampal-sparing brain radiotherapy via VMAT between February 2014 and December 2015. The optimization criteria for the contralateral hippocampus was a maximum dose (D_max) of less than 17 Gy. For NCF evaluations, the Seoul Verbal Learning Test for total recall, delayed recall, and recognition (SVLT-TR, DR, and Recognition) was performed at baseline and at seven months after radiotherapy.

Results

A total of 26 patients underwent NCF testing seven months after radiotherapy. Their median age was 49.5 years (range 26–77 years), and 14 (53.8%) had grade III/IV tumors. The median D_max to the contralateral hippocampus was 16.4 Gy (range 3.5-63.4). The median mean dose to the contralateral hippocampus, expressed as equivalent to a 2-Gy dose (EQD_2/2), was 7.4 Gy₂ (0.7–13.1). The mean relative changes in SVLT-TR, SVLT-DR, and SVLT-Recognition at seven months compared to the baseline were − 7.7% (95% confidence interval [CI], − 19.6% to 4.2%), − 9.2% (95% CI, − 25.4% to 7.0%), and − 3.4% (− 12.7% to 5.8%), respectively. Two patients (7.7%) showed deteriorated NCF in the SVLT-TR and SVLT-DR, and three (11.5%) in the SVLT-Recognition. The mean dose of the left hippocampus and bilateral hippocampi were significantly higher in patients showing deterioration of the SVLT-TR and SVLT-Recognition than in those without deterioration.

Conclusions

The contralateral hippocampus could be effectively spared in patients with primary brain tumor via VMAT to preserve the verbal memory function. Further investigation is needed to identify those patients who will most benefit from hippocampal-sparing radiotherapy of the primary brain tumor.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-0975-4) contains supplementary material, which is available to authorized users.

Ionizing Radiation-Induced Immune and Inflammatory Reactions in the Brain

Radiation-induced late brain injury consisting of vascular abnormalities, demyelination, white matter necrosis, and cognitive impairment has been described in patients subjected to cranial radiotherapy for brain tumors. Accumulating evidence suggests that various degrees of cognitive deficit can develop after much lower doses of ionizing radiation, as well. The pathophysiological mechanisms underlying these alterations are not elucidated so far. A permanent deficit in neurogenesis, chronic microvascular alterations, and blood–brain barrier dysfunctionality are considered among the main causative factors. Chronic neuroinflammation and altered immune reactions in the brain, which are inherent complications of brain irradiation, have also been directly implicated in the development of cognitive decline after radiation. This review aims to give a comprehensive overview on radiation-induced immune alterations and inflammatory reactions in the brain and summarizes how these processes can influence cognitive performance. The available data on the risk of low-dose radiation exposure in the development of cognitive impairment and the underlying mechanisms are also discussed.

A prospective study on neurocognitive effects after primary radiotherapy in high-grade glioma patients

BACKGROUND

Neurocognition is a very important aspect of a brain tumor patient's quality of life following radiotherapy. The aim of the present study was to assess neurocognitive functions of patients diagnosed with high-grade gliomas undergoing radiotherapy by using the NeuroCogFx(®) test and to examine relevant dose/volume parameters as well as patient characteristics potentially influencing the neurological baseline status and subsequent outcome.

METHODS

The cohort consisted of 44 astrocytoma World Health Organization grade III/IV patients. The NeuroCogFx(®) test was carried out on patients during (N = 44) and after (N = 21) irradiation. The test examines verbal/figural/short-term/working memory, psychomotorical speed, selective attention and verbal speed. The results were compared with regular patient and treatment data with an emphasis on the dose applied to the hippocampus.

RESULTS

Overall there were only slight changes in the median test results when comparing the baseline to the follow-up tests. In the 'verbal memory test' lower percentile ranks were achieved in left-sided tumors compared to right-sided tumors (p = 0.034). Dexamethasone intake during radiotherapy was significantly correlated with the difference between the two test batteries. Concerning figural memory, a correlation was detected between decreased figural recognition and the radiation dose to the left hippocampus (p = 0.045).

CONCLUSION

We conclude that tumor infiltration of the hippocampus has an impact on neurocognitive function. However, treatment with radiotherapy seems to have less influence on cognitive outcome than expected.

Donepezil for Irradiated Brain Tumor Survivors: A Phase III Randomized Placebo-Controlled Clinical Trial

PURPOSE

Neurotoxic effects of brain irradiation include cognitive impairment in 50% to 90% of patients. Prior studies have suggested that donepezil, a neurotransmitter modulator, may improve cognitive function.

PATIENTS AND METHODS

A total of 198 adult brain tumor survivors ≥ 6 months after partial- or whole-brain irradiation were randomly assigned to receive a single daily dose (5 mg for 6 weeks, 10 mg for 18 weeks) of donepezil or placebo. A cognitive test battery assessing memory, attention, language, visuomotor, verbal fluency, and executive functions was administered before random assignment and at 12 and 24 weeks. A cognitive composite score (primary outcome) and individual cognitive domains were evaluated.

RESULTS

Of this mostly middle-age, married, non-Hispanic white sample, 66% had primary brain tumors, 27% had brain metastases, and 8% underwent prophylactic cranial irradiation. After 24 weeks of treatment, the composite scores did not differ significantly between groups (P = .48); however, significant differences favoring donepezil were observed for memory (recognition, P = .027; discrimination, P = .007) and motor speed and dexterity (P = .016). Significant interactions between pretreatment cognitive function and treatment were found for cognitive composite (P = .01), immediate recall (P = .05), delayed recall (P = .004), attention (P = .01), visuomotor skills (P = .02), and motor speed and dexterity (P < .001), with the benefits of donepezil greater for those who were more cognitively impaired before study treatment.

CONCLUSION

Treatment with donepezil did not significantly improve the overall composite score, but it did result in modest improvements in several cognitive functions, especially among patients with greater pretreatment impairments.

Volumetric modulated arc therapy for hippocampal-sparing radiotherapy in transformed low-grade glioma: A treatment planning case report

Timing of radiotherapy for low-grade gliomas is still controversial due to concerns of possible adverse late effects. Prevention of possible late cognitive sequelae by hippocampal avoidance has shown promise in phase II trials. A patient with progressive low-grade glioma with gradual dedifferentiation into anaplastic astrocytoma is presented along with description of radiotherapy planning process attempting to spare the hippocampus. To our knowledge, this is the first described case using volumetric modulated arc technique to spare hippocampus during transformed low-grade glioma radiotherapy. Using modern intensity-modulated radiotherapy systems it is possible to selectively spare hippocampus together with other standard organs at risk. For selected patients, an attempt to spare hippocampus can be considered as long as other dose characteristics are not significantly compromised compared to standard treatment plan created without any effort to avoid hippocampus.

Comparison of dose distributions hippocampus in high grade gliomas irradiation with linac-based imrt and volumetric arc therapy: a dosimetric study

The aim of this study was to assess the feasibility of sparing contralateral hippocampus during partial brain radiotherapy in high grade gliomas. 20 previously treated patients were replanned to 60 Gy in 30 fractions with sparing intensity-modulated radiotherapy (IMRT) and volumetric modulated arctherapy (VMAT) using the following planning objectives: 100 % of PTV covered by 95% isodose without violating organs at risk (OAR) and hot spot dose constraints. For each, standard intensity-modulated radiotherapy (IMRT) plans were generated, as well as sparing IMRT and VMAT plans which spared contralateral (hemispheric cases) hippocampus. When the three plans were compared, there was equivalent PTV coverage, homogeneity, and conformality. Sparing IMRT significantly reduced maximum, mean, V20, V30 and V40 hippocampus doses compared with standart IMRT and VMAT (p < 0.05). VMAT significantly reduced maximum left lens and mean eye doses compared with standart IMRT and sparing IMRT (p < 0.05). Brainstem, chiasm, left and right optic nerves, right eyes and lens doses were similar. VMAT significantly reduced monitor units compared with standart IMRT and sparing IMRT (p < 0.05). It is possible to spare contralateral hippocampus during PBRT for high grade gliomas using IMRT. This approach may reduce late cognitive sequelae of cranial radiotherapy.

Organs at risk in the brain and their dose-constraints in adults and in children: a radiation oncologist's guide for delineation in everyday practice

PURPOSE

Accurate organs at risk definition is essential for radiation treatment of brain tumors. The aim of this study is to provide a stepwise and simplified contouring guide to delineate the OARs in the brain as it would be done in the everyday practice of planning radiotherapy for brain cancer treatment.

METHODS

Anatomical descriptions and neuroimaging atlases of the brain were studied. The dosimetric constraints used in literature were reviewed.

RESULTS

A Computed Tomography and Magnetic Resonance Imaging based detailed atlas was developed jointly by radiation oncologists, a neuroradiologist and a neurosurgeon. For each organ brief anatomical notion, main radiological reference points and useful considerations are provided. Recommended dose-constraints both for adult and pediatric patients were also provided.

CONCLUSIONS

This report provides guidelines for OARs delineation and their dose-constraints for the treatment planning of patients with brain tumors.

Hippocampal EUD in primarily irradiated glioblastoma patients

BACKGROUND

Radiation delivery for malignant brain tumors is gradually becoming more precise. Particularly the possibilities of sparing adjacent normal structures such as the hippocampus are increasing. To determine its radiation exposure more exactly, the equivalent uniform dose (EUD) of the hippocampus was compared with further treatment parameters. This way sparing options could be found.

METHODS

From the database of the University hospital of Munich 61 glioblastoma patients were selected who received primary radiotherapy in 2011. General data about the etiology, treatment course, survival of the patients and dose parameters were retrieved.

RESULTS

In a linear regression analysis the side of the tumor (left hippocampus: p < 0.001/right hippocampus: p = 0.009) and its temporal location (left hippocampus: p = 0.015/right hippocampus: p = 0.033) were identified as factors with a significant influence on the EUD of the respective hippocampus. Besides this, the size of the planning target volume (PTV) and the EUD of the hippocampus correlated significantly (p = 0.027; Pearson correlation = 0.291). The median PTV size of the tumor in the right hemisphere was 386.1 ml (range 131.2-910.7 ml), and in the left hemisphere 291.3 ml (range 146.0-588.9 ml) (Kruskal-Wallis test: p = 0.048). A dose quartile analysis showed that 31 patients had a high dose exposure of the hippocampus on one side while having a moderate dose exposure in the other side.

CONCLUSIONS

The radiation exposure of the respective hippocampus is dependent on the side where the tumor is located as well as on whether it is temporally located. The exposure of the contralateral hippocampus is further dependent on multiple additional factors - nevertheless a reasonable protection seems to be possible in about half of all cases.

[Radiotherapy in central neurocytoma and review of literature]

Central neurocytoma is a rare primary central nervous system tumour of young adults with good prognosis. Typical and atypical forms are described according to various histologic and histopathologic parameters. Central neurocytoma develops in the periventricular areas and is revealed by increased intracranial pressure. The tumour exhibits typical characteristics on CT scan and MRI and a characteristic peak of glycine on spectroscopy-MRI. The main treatment is total resection, which is achievable only in half of the cases. External beam therapy improves local control of partially resected and/or atypical central neurocytoma. Many studies show that stereotactic radiotherapy can be used in the therapeutic management as exclusive treatment, in postoperatives residues and in case of distant recurrence. Chemotherapy is the last line of treatment in refractory forms, especially in the forms with extracranial and/or neuromeningeal spread and in recurrent forms after treatment with surgery and/or radiotherapy.