Dynamic statistical parametric mapping: combining fMRI and MEG for high-resolution imaging of cortical activity

Functional magnetic resonance imaging (fMRI) can provide maps of brain activation with millimeter spatial resolution but is limited in its temporal resolution to the order of seconds. Here, we describe a technique that combines structural and functional MRI with magnetoencephalography (MEG) to obtain spatiotemporal maps of human brain activity with millisecond temporal resolution. This new technique was used to obtain dynamic statistical parametric maps of cortical activity during semantic processing of visually presented words. An initial wave of activity was found to spread rapidly from occipital visual cortex to temporal, parietal, and frontal areas within 185 ms, with a high degree of temporal overlap between different areas. Repetition effects were observed in many of the same areas following this initial wave of activation, providing evidence for the involvement of feedback mechanisms in repetition priming.

Regional and progressive thinning of the cortical ribbon in Huntington's disease

BACKGROUND

Huntington's disease (HD) is a fatal and progressive neurodegenerative disease that is accompanied by involuntary movements, cognitive dysfunction, and psychiatric symptoms. Although progressive striatal degeneration is known to occur, little is known about how the disease affects the cortex, including which cortical regions are affected, how degeneration proceeds, and the relationship of the cortical degeneration to clinical symptoms. The cortex has been difficult to study in neurodegenerative diseases primarily because of its complex folding patterns and regional variability; however, an understanding of how the cortex is affected by the disease may provide important new insights into it.

METHODS

Novel automated surface reconstruction and high-resolution MR images of 11 patients with HD and 13 age-matched subjects were used to obtain cortical thickness measurements. The same analyses were performed on two postmortem brains to validate these methods.

RESULTS

Regionally specific heterogeneous thinning of the cortical ribbon was found in subjects with HD. Thinning occurred early, differed among patients in different clinical stages of disease, and appeared to proceed from posterior to anterior cortical regions with disease progression. The sensorimotor region was statistically most affected. Measurements performed on MR images of autopsy brains analyzed similarly were within 0.25 mm of those obtained using traditional neuropathologic methods and were statistically indistinguishable.

CONCLUSIONS

The authors propose that the cortex degenerates early in disease and that regionally selective cortical degeneration may explain the heterogeneity of clinical expression in HD. These measures might provide a sensitive prospective surrogate marker for clinical trials of neuroprotective medications.

Retinotopy and color sensitivity in human visual cortical area V8

Prior studies suggest the presence of a color-selective area in the inferior occipital-temporal region of human visual cortex. It has been proposed that this human area is homologous to macaque area V4, which is arguably color selective, but this has never been tested directly. To test this model, we compared the location of the human color-selective region to the retinotopic area boundaries in the same subjects, using functional magnetic resonance imaging (fMRI), cortical flattening and retinotopic mapping techniques. The human color-selective region did not match the location of area V4 (neither its dorsal nor ventral subdivisions), as extrapolated from macaque maps. Instead this region coincides with a new retinotopic area that we call 'V8', which includes a distinct representation of the fovea and both upper and lower visual fields. We also tested the response to stimuli that produce color afterimages and found that these stimuli, like real colors, caused preferential activation of V8 but not V4.

Functional analysis of primary visual cortex (V1) in humans

Human area V1 offers an excellent opportunity to study, using functional MRI, a range of properties in a specific cortical visual area, whose borders are defined objectively and convergently by retinotopic criteria. The retinotopy in V1 (also known as primary visual cortex, striate cortex, or Brodmann's area 17) was defined in each subject by using both stationary and phase-encoded polar coordinate stimuli. Data from V1 and neighboring retinotopic areas were displayed on flattened cortical maps. In additional tests we revealed the paired cortical representations of the monocular "blind spot." We also activated area V1 preferentially (relative to other extrastriate areas) by presenting radial gratings alternating between 6% and 100% contrast. Finally, we showed evidence for orientation selectivity in V1 by measuring transient functional MRI increases produced at the change in response to gratings of differing orientations. By systematically varying the orientations presented, we were able to measure the bandwidth of the orientation "transients" (45 degrees).

Monte Carlo simulation studies of EEG and MEG localization accuracy

Both electroencephalography (EEG) and magnetoencephalography (MEG) are currently used to localize brain activity. The accuracy of source localization depends on numerous factors, including the specific inverse approach and source model, fundamental differences in EEG and MEG data, and the accuracy of the volume conductor model of the head (i.e., the forward model). Using Monte Carlo simulations, this study removes the effect of forward model errors and theoretically compares the use of EEG alone, MEG alone, and combined EEG/MEG data sets for source localization. Here, we use a linear estimation inverse approach with a distributed source model and a realistic forward head model. We evaluated its accuracy using the crosstalk and point spread metrics. The crosstalk metric for a specified location on the cortex describes the amount of activity incorrectly localized onto that location from other locations. The point spread metric provides the complementary measure: for that same location, the point spread describes the mis-localization of activity from that specified location to other locations in the brain. We also propose and examine the utility of a "noise sensitivity normalized" inverse operator. Given our particular forward and inverse models, our results show that 1) surprisingly, EEG localization is more accurate than MEG localization for the same number of sensors averaged over many source locations and orientations; 2) as expected, combining EEG with MEG produces the best accuracy for the same total number of sensors; 3) the noise sensitivity normalized inverse operator improves the spatial resolution relative to the standard linear estimation operator; and 4) use of an a priori fMRI constraint universally reduces both crosstalk and point spread.

Spatiotemporal imaging of human brain activity using functional MRI constrained magnetoencephalography data: Monte Carlo simulations

The goal of our research is to develop an experimental and analytical framework for spatiotemporal imaging of human brain function. Preliminary studies suggest that noninvasive spatiotemporal maps of cerebral activity can be produced by combining the high spatial resolution (millimeters) of functional MRI (fMRI) with the high temporal resolution (milliseconds) of electroencephalography (EEG) and magnetoencephalography (MEG). Although MEG and EEG are sensitive to millisecond changes in mental activity, the ability to resolve source localization and timing is limited by the ill-posed "inverse" problem. We conducted Monte Carlo simulations to evaluate the use of MRI constraints in a linear estimation inverse procedure, where fMRI weighting, cortical location and orientation, and sensor noise statistics were realistically incorporated. An error metric was computed to quantify the effects of fMRI invisible ("missing") sources, "extra" fMRI sources, and cortical orientation errors. Our simulation results demonstrate that prior anatomical and functional information from MRI can be used to regularize the EEG/MEG inverse problem, giving an improved solution with high spatial and temporal resolution. An fMRI weighting of approximately 90% was determined to provide the best compromise between separation of activity from correctly localized sources and minimization of error caused by missing sources. The accuracy of the estimate was relatively independent of the number and extent of the sources, allowing for incorporation of physiologically realistic multiple distributed sources. This linear estimation method provides an operator-independent approach for combining information from fMRI, MEG, and EEG and represents a significant advance over traditional dipole modeling.

The representation of the ipsilateral visual field in human cerebral cortex

Previous studies of cortical retinotopy focused on influences from the contralateral visual field, because ascending inputs to cortex are known to be crossed. Here, functional magnetic resonance imaging was used to demonstrate and analyze an ipsilateral representation in human visual cortex. Moving stimuli, in a range of ipsilateral visual field locations, revealed activity: (i) along the vertical meridian in retinotopic (presumably lower-tier) areas; and (ii) in two large branches anterior to that, in presumptive higher-tier areas. One branch shares the anterior vertical meridian representation in human V3A, extending superiorly toward parietal cortex. The second branch runs antero-posteriorly along lateral visual cortex, overlying motion-selective area MT. Ipsilateral stimuli sparing the region around the vertical meridian representation also produced signal reductions (perhaps reflecting neural inhibition) in areas showing contralaterally driven retinotopy. Systematic sampling across a range of ipsilateral visual field extents revealed significant increases in ipsilateral activation in V3A and V4v, compared with immediately posterior areas V3 and VP. Finally, comparisons between ipsilateral stimuli of different types but equal retinotopic extent showed clear stimulus specificity, consistent with earlier suggestions of a functional segregation of motion vs. form processing in parietal vs. temporal cortex, respectively.

Spatiotemporal activity of a cortical network for processing visual motion revealed by MEG and fMRI

A sudden change in the direction of motion is a particularly salient and relevant feature of visual information. Extensive research has identified cortical areas responsive to visual motion and characterized their sensitivity to different features of motion, such as directional specificity. However, relatively little is known about responses to sudden changes in direction. Electrophysiological data from animals and functional imaging data from humans suggest a number of brain areas responsive to motion, presumably working as a network. Temporal patterns of activity allow the same network to process information in different ways. The present study in humans sought to determine which motion-sensitive areas are involved in processing changes in the direction of motion and to characterize the temporal patterns of processing within this network of brain regions. To accomplish this, we used both magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). The fMRI data were used as supplementary information in the localization of MEG sources. The change in the direction of visual motion was found to activate a number of areas, each displaying a different temporal behavior. The fMRI revealed motion-related activity in areas MT+ (the human homologue of monkey middle temporal area and possibly also other motion sensitive areas next to MT), a region near the posterior end of the superior temporal sulcus (pSTS), V3A, and V1/V2. The MEG data suggested additional frontal sources. An equivalent dipole model for the generators of MEG signals indicated activity in MT+, starting at 130 ms and peaking at 170 ms after the reversal of the direction of motion, and then again at approximately 260 ms. Frontal activity began 0-20 ms later than in MT+, and peaked approximately 180 ms. Both pSTS and FEF+ showed long-duration activity continuing over the latency range of 200-400 ms. MEG responses in the region of V3A and V1/V2 were relatively small, and peaked at longer latencies than the initial peak in MT+. These data revealed characteristic patterns of activity in this cortical network for processing sudden changes in the direction of visual motion.

Design of 4D treatment planning target volumes

PURPOSE

When using non-patient-specific treatment planning margins, respiratory motion may lead to geometric miss of the target while unnecessarily irradiating normal tissue. Imaging different respiratory states of a patient allows patient-specific target design. We used four-dimensional computed tomography (4DCT) to characterize tumor motion and create treatment volumes in 10 patients with lung cancer. These were compared with standard treatment volumes.

METHODS AND MATERIALS

Four-dimensional CT and free breathing helical CT data of 10 patients were acquired. Gross target volumes (GTV) were delineated on the helical scan as well as on each phase of the 4D data. Composite GTVs were defined on 4DCT. Planning target volumes (PTV) including clinical target volume, internal margin (IM), and setup margin were generated. 4DPTVs with different IMs and standard PTVs were compared by computing centroid positions, volumes, volumetric overlap, and bounding boxes.

RESULTS

Four-dimensional PTVs and conventional PTVs differed in volume and centroid positions. Overlap between 4DPTVs generated from two extreme tumor positions only compared with 10 respiratory phases was 93.7%. Comparing PTVs with margins of 15 mm (IM 5 mm) on composite 4D target volumes to PTVs with 20 mm (IM 10 mm) on helical CT data resulted in a decrease in target volume sizes by 23% on average.

CONCLUSION

With patient-specific characterization of tumor motion, it should be possible to decrease internal margins. Patient-specific treatment volumes can be generated using extreme tumor positions on 4DCT. To date, more than 150 patients have been treated using 4D target design.

Spatiotemporal Brain Imaging of Visual-Evoked Activity Using Interleaved EEG and fMRI Recordings

Combined analysis of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has the potential to provide higher spatiotemporal resolution than either method alone. In some situations, in which the activity of interest cannot be reliably reproduced (e.g., epilepsy, learning, sleep states), accurate combined analysis requires simultaneous acquisition of EEG and fMRI. Simultaneous measurements ensure that the EEG and fMRI recordings reflect the exact same brain activity state. We took advantage of the spatial filtering properties of the bipolar montage to allow recording of very short (125--250 ms) visual-evoked potentials (VEPs) during fMRI. These EEG and fMRI measurements are of sufficient quality to allow source localization of the cortical generators. In addition, our source localization approach provides a combined EEG/fMRI analysis that does not require any manual selection of fMRI activations or placement of source dipoles. The source of the VEP was found to be located in the occipital cortex. Separate analysis of EEG and fMRI data demonstrated good spatial overlap of the observed activated sites. As expected, the combined EEG/fMRI analysis provided better spatiotemporal resolution than either approach alone. The resulting spatiotemporal movie allows for the millisecond-to-millisecond display of changes in cortical activity caused by visual stimulation. These data reveal two peaks in activity corresponding to the N75 and the P100 components. This type of simultaneous acquisition and analysis allows for the accurate characterization of the location and timing of neurophysiological activity in the human brain.

Local and global attention are mapped retinotopically in human occipital cortex

Clinical evidence suggests that control mechanisms for local and global attention are lateralized in the temporal-parietal cortex. However, in the human occipital (visual) cortex, the evidence for lateralized local/global attention is controversial. To clarify this matter, we used functional MRI to map activity in the human occipital cortex, during local and global attention, with sustained visual fixation. Data were analyzed in a flattened cortical format, relative to maps of retinotopy and spatial frequency peak tuning. Neither local nor global attention was lateralized in the occipital cortex. Instead, local attention and global attention appear to be special cases of visual spatial attention, which are mapped consistently with the maps of retinotopy and spatial frequency tuning, in multiple visual cortical areas.

Molecular sub-group-specific immunophenotypic changes are associated with outcome in recurrent posterior fossa ependymoma

Better understanding of ependymoma (EPN) biology at relapse is needed to improve therapy at this critical event. Convincing data exist defining transcriptionally distinct posterior fossa (PF) sub-groups A and B at diagnosis. The clinical and biological consequence of these sub-groups at recurrence has not yet been defined. Genome and transcriptome microarray profiles and clinical variables of matched primary and first recurrent PF EPN pairs were used to identify biologically distinct patterns of progression between EPN sub-groups at recurrence. Key findings were validated by histology and immune function assays. Transcriptomic profiles were partially conserved at recurrence. However, 4 of 14 paired samples changed sub-groups at recurrence, and significant sub-group-specific transcriptomic changes between primary and recurrent tumors were identified, which were predominantly immune-related. Further examination revealed that Group A primary tumors harbor an immune gene signature and cellular functionality consistent with an immunosuppressive phenotype associated with tissue remodeling and wound healing. Conversely, Group B tumors develop an adaptive, antigen-specific immune response signature and increased T-cell infiltration at recurrence. Clinical distinctions between sub-groups become more apparent after first recurrence. Group A tumors were more often sub-totally resected and had a significantly shorter time to subsequent progression and worse overall survival. Minimal tumor-specific genomic changes were observed for either PF Groups A or B at recurrence. Molecular sub-groups of PF EPN convey distinct immunobiologic signatures at diagnosis and recurrence, providing potential biologic rationale to their disparate clinical outcomes. Immunotherapeutic approaches may be warranted, particularly in Group A PF EPN.

Pediatric low-grade ganglioglioma: epidemiology, treatments, and outcome analysis on 348 children from the surveillance, epidemiology, and end results database

BACKGROUND

Low-grade gangliogliomas/gangliocytomas (GGs) are rare tumors of the central nervous system that occur mostly in young people. Because of their rarity, large-scale, population-based studies focusing on epidemiology and outcomes are lacking.

OBJECTIVE

To use the Surveillance, Epidemiology, and End Results (SEER) data sets of the National Cancer Institute to study demographics, tumor location, initial treatment, and outcome data on low-grade GGs in children.

METHODS

SEER-STAT v8.1.2 identified all patients aged 0 to 19 years in the SEER data sets with low-grade GGs. Using the Kaplan-Meier method and Cox proportional hazard regression, we examined associations between these characteristics and survival.

RESULTS

There were 348 children with low-grade GGs diagnosed from 2004 to 2010, with a median follow-up of 37 months. Tumors were more prevalent in males (n = 208, 59.8%) than females (n = 140, 40.2%) (P < .001). Almost 63% occurred in children >10 years, whereas only 3.5% were found in those <1 year old. Approximately 50% were located in the temporal lobes, and only 3.7% and 3.5% were located in the brainstem and spinal cord, respectively. Surgery was performed on 91.6% of cases, with gross total resection achieved in 68.3%. Radiation was used in 3.2%. Young age (<1 year) and brainstem location were associated with worse overall survival.

CONCLUSION

This study shows that low-grade GGs occur in older children with a male preference. Gross total resection is achieved in the majority of cases, and radiation is rarely used. Although the majority of patients have an excellent prognosis, infants and patients with brainstem tumors have worse survival rates.

Late effects of total body irradiation and hematopoietic stem cell transplant in children under 3 years of age

BACKGROUND

Total body irradiation (TBI) is an important component of hematopoietic stem cell transplant (SCT) for pediatric malignancies. With increasing survival rates, late effects of SCT become more important. Younger children may be at particular risk of late effects of radiation and SCT.

METHODS

We retrospectively reviewed outcomes of children less than 3 years of age who received TBI as part of their preparative regimen for SCT at Children's Hospital Colorado. Clinical information including the date of last follow-up, most recent lab values, and physiologic tests were extracted from the medical record.

RESULTS

Of 81 patients who underwent SCT, 19 received TBI and of those, 15 were long-term survivors available for review. Late effects occurring in greater than 50% of the children included abnormalities involving endocrine, metabolic, renal, cataracts, and neurocognitive systems. Other organs involved less commonly included liver, skeletal, and cardiac abnormalities. Solid tumors were a rare finding with only one patient developing a benign osteochondroma and no identified secondary malignancies.

CONCLUSIONS

TBI has been shown to be an important part of the preparative regimen for patients undergoing SCT. Our results, similar to other studies, suggest TBI in patients less than 3 years of age will likely result in multi-organ dysfunction including endocrine, metabolic, renal, eye, and neurocognitive abnormalities. A longitudinal study with standardized testing of these systems would further clarify the late effects concerns in this patient population.

Bevacizumab as therapy for radiation necrosis in four children with pontine gliomas

PURPOSE

Diffuse pontine gliomas are a pediatric brain tumor that is fatal in nearly all patients. Given the poor prognosis for patients with this tumor, their quality of life is very important. Radiation therapy provides some palliation, but can result in radiation necrosis and associated neurologic decline. The typical treatment for this necrosis is steroid therapy. Although the steroids are effective, they have numerous side effects that can often significantly compromise quality of life. Bevacizumab, an antibody against vascular endothelial growth factor, has been suggested as a treatment for radiation necrosis. We report on our initial experience with bevacizumab therapy for radiation necrosis in pediatric pontine gliomas.

MATERIALS AND METHODS

Four children with pontine gliomas treated at the Children's Hospital in Denver and the University of Colorado Denver developed evidence of radiation necrosis both clinically and on imaging. Those 4 children then received bevacizumab as a treatment for the radiation necrosis. We reviewed the clinical outcome and imaging findings.

RESULTS

After bevacizumab therapy, 3 children had significant clinical improvement and were able to discontinue steroid use. One child continued to decline, and, in retrospect, had disease progression, not radiation necrosis. In all cases, bevacizumab was well tolerated.

CONCLUSIONS

In children with pontine gliomas, bevacizumab may provide both therapeutic benefit and diagnostic information. More formal evaluation of bevacizumab in these children is needed.

Pediatric choroid plexus tumors: epidemiology, treatments, and outcome analysis on 202 children from the SEER database

Choroid plexus papillomas (CPPs) and carcinomas (CPCs) are rare neoplasms that affect mostly children. Due to their rarity, their epidemiology and outcomes are incompletely understood. The National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program is a well-established population-based group of registries that collects and publishes cancer incidence and survival data representing approximately 28 % of the US population. SEER-STAT v8.1.2 was used to identify patients with ICD-O-3 codes for choroid plexus tumors in patients aged 0-19. Demographics, initial treatment, and follow-up data were collected. Statistical methods including Kaplan-Meier curves, log rank tests, and Cox proportional hazards regression were used to estimate associations between independent variables and survival. The SEER registries contained 107 CPPs (2004-2010) and 95 CPCs (1978-2010). Median follow-up was 38 and 40 months, respectively. More than 75 % of CPCs were diagnosed before the age of 5 years, versus 48 % for CPPs. Sixty-five percent of CPCs and 57 % of CPPs occurred in males. In both groups at least 90 % of children underwent surgical resection. Gross total resection (GTR) was achieved in 67.0 % of CPCs and 63.6 % of CPPs. Almost 17 % of CPCs were treated with radiation versus only 0.9 % of CPPs. More than 98 % of patients with CPP were alive at the last follow-up, versus 62 % of CPC patients. For CPC, surgery was significantly associated with increased overall survival, but contrary to previous reports, extent of surgical resection was not associated with survival. Age, sex, race, and radiation treatment also had no effect on survival. This report, using the SEER datasets, corroborates many findings of previous smaller studies on CPTs. CPC occurs in younger children, with a male predominance, and a much worse prognosis than CPP. As such, these tumors have been treated aggressively with high rates of GTR and radiation treatment. Despite these treatments, overall survival for CPC remains poor.

Patient-reported outcomes and survivorship in radiation oncology: overcoming the cons

PURPOSE

Although patient-reported outcomes (PROs) have become a key component of clinical oncology trials, many challenges exist regarding their optimal application. The goal of this article is to methodically review these barriers and suggest strategies to overcome them. This review will primarily focus on radiation oncology examples, will address issues regarding the "why, how, and what" of PROs, and will provide strategies for difficult problems such as methods for reducing missing data. This review will also address cancer survivorship because it closely relates to PROs.

METHODS

Key articles focusing on PROs, quality of life, and survivorship issues in oncology trials are highlighted, with an emphasis on radiation oncology clinical trials. Publications and Web sites of various governmental and regulatory agencies are also reviewed.

RESULTS

The study of PROs in clinical oncology trials has become well established. There are guidelines provided by organizations such as the US Food and Drug Administration that clearly indicate the importance of and methodology for studying PROs. Clinical trials in oncology have repeatedly demonstrated the value of studying PROs and suggested ways to overcome some of the key challenges. The Radiation Therapy Oncology Group (RTOG) has led some of these efforts, and their contributions are highlighted. The current state of cancer survivorship guidelines is also discussed.

CONCLUSION

The study of PROs presents significant benefits in understanding and treating toxicities and enhancing quality of life; however, challenges remain. Strategies are presented to overcome these hurdles, which will ultimately improve cancer survivorship.

Targeting Aurora Kinase A enhances radiation sensitivity of atypical teratoid rhabdoid tumor cells

Atypical teratoid/rhabdoid tumors (ATRT) are rare, highly malignant, embryonal CNS tumors with a poor prognosis. Therapy relies on highly toxic chemotherapy and radiotherapy. To improve outcomes and decrease morbidity, more targeted therapy is required. Gene expression analysis revealed elevated expression of multiple kinases in ATRT tissues. Aurora Kinase A was one of the candidate kinases. The objective of this study was to evaluate the impact of Aurora Kinase A inhibition in ATRT cell lines. Our analysis revealed that inhibition of Aurora Kinase A induces cell death in ATRT cells and the small molecule inhibitor MLN 8237 sensitizes these cells to radiation. Furthermore, inhibition of Aurora Kinase A resulted in decreased activity of pro-proliferative signaling pathways. These data indicate that inhibition of Aurora Kinase A is a promising small molecule target for ATRT therapy.

Radiosurgery alone is associated with favorable outcomes for brain metastases from small-cell lung cancer

INTRODUCTION

Whole-brain radiation therapy (WBRT) is the standard approach for brain metastases (BM) arising in patients with small-cell lung cancer (SCLC), but the neurocognitive toxicities of WBRT are well documented. For this reason, stereotactic radiosurgery (SRS) alone is the preferred modality for limited BM in most histologies, but in SCLC there are few data exploring this approach.

METHODS

We queried the National Cancer Database (NCDB) for patients with SCLC with BM at diagnosis and stratified by upfront SRS compared with upfront WBRT ± SRS. We utilized multivariate Cox regression and propensity score matching (PSM) to determine the impact on overall survival (OS) of each approach.

RESULTS

5952 eligible patients (WBRT: 5752; SRS: 200) were identified from 2010 to 2014 with a median follow-up of 40.0 months. Upfront SRS was associated with superior OS (median 10.8 vs 7.1 months, HR 0.65, 95% CI 0.55-0.75, p < 0.001), which persisted on multivariate analysis controlling for comorbidities, extracranial metastases, age, race/ethnicity, and gender (HR 0.70, 95% CI 0.60-0.81, p < 0.001). These results were confirmed in PSM analysis. A subset analysis comparing outcomes after SRS vs SRS + WBRT showed no differences in OS (p = .601).

CONCLUSIONS

To our knowledge, this is the largest dataset of patients treated with SRS alone for SCLC. The observation of favorable OS with SRS alone in this contemporary dataset suggests that SRS alone may be appropriate for some patients with SCLC. Prospective investigations of SRS in SCLC are warranted.

Sarcomas of the aorta: a systematic review and pooled analysis of published reports

BACKGROUND

Aortic sarcomas are rare and aggressive tumors with a propensity for arterial embolization, disseminated metastases, and rapid clinical deterioration. Overall, little is known about the evaluation and management of this disease.

METHODS

A systematic review and pooled analysis were performed from a comprehensive search of the MEDLINE database for reports of primary aortic sarcomas published in the English language.

RESULTS

One hundred sixty-five cases were analyzed. The median age was 60 years, and the male:female ratio was 1.5:1. High tumor grade (87.3%), arterial embolization (46.7%), and metastatic disease at diagnosis (44.8%) were common. Typical histologies were undifferentiated (39.4%), angiosarcomatous (37%), leiomyosarcomatous (13.3%), and fibroblastic (7.3%). Management was diverse and included combinations of surgical resection (46.7%), palliative vascular surgeries (37.7%), chemotherapy (28.7%), and radiotherapy (14.7%). The median survival was 11 months, and the 1-, 3-, and 5-year survival rates were 46.7%, 17.1%, and 8.8%, respectively. On univariate analyses, metastatic disease at diagnoses, surgical resection, and chemotherapy were associated with survival. On multivariate analysis, only metastatic disease remained significant (P < 0.001).

CONCLUSIONS

Aortic tumors are devastating malignancies with distinct clinical features from sarcomas at other sites. Although prognosis is poor overall, long-term survivors have been reported, and aggressive management with surgical resection and adjuvant therapy should be considered in medically suitable patients. High embolic rates suggest a potential role for prophylactic anticoagulation.

Vascular abnormalities in pediatric craniopharyngioma patients treated with radiation therapy

BACKGROUND

Craniopharyngioma is a benign brain tumor that can be treated with some combination of surgery, intracystic chemotherapy and radiation therapy. Treatment for craniopharyngioma, especially radiation therapy, is associated with a variety of long-term toxicities including vascular abnormalities. We report on the incidence of vascular abnormalities seen in the children with craniopharyngioma who received radiation therapy at our institution.

PROCEDURE

We reviewed our experience with craniopharyngioma patients who received radiation therapy from 1995 to 2008. We reviewed clinical data including surgery, chemotherapy, radiation therapy and imaging for vasculopathy.

RESULTS

Twenty of the 22 children with craniopharyngioma who received radiation therapy had imaging available. Six of the 20 were found to have some type of vasculopathy. One had bilateral temporal cavernomas, one had moyamoya syndrome, one had an aneurysm of the internal carotid artery and three children had decreases in the caliber of the carotid or cerebral arteries, but were asymptomatic. Two of the six children with abnormalities also received intracystic bleomycin prior to radiation therapy.

CONCLUSIONS

We report a high incidence of vascular abnormalities in children with craniopharyngioma. The data suggest that intracystic bleomycin may contribute to radiation-related vasculopathy. We now include magnetic resonance angiography as part of our routine follow up in these children.

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.

Fractionated stereotactic radiosurgery for recurrent ependymoma in children

Outcomes for children with relapsed ependymoma are poor. Re-irradiation is a potentially viable salvage option in these patients. Data were reviewed for 12 patients (median age 5.6 years) with relapsed ependymoma who received fractionated stereotactic radiosurgery (fSRS) following maximal surgical resection from 1995 to 2012. Four patients experienced a second recurrence, including 2 in-field and 2 distant failures. Median time to second recurrence (32 months) was significantly longer than time to first recurrence (24 months) (p = 0.008). Three-year local control was 89 %, and median event free survival from fSRS was 3.4 years. Radiation necrosis was observed in 6 patients, 3 who were symptomatic. In conclusion, fSRS offers durable response with a tolerable toxicity profile in children with recurrent EPN.

Maximally safe resection followed by hypofractionated re-irradiation for locally recurrent ependymoma in children

BACKGROUND

Treatment failure in children with ependymoma is relatively common, with the majority of events consisting of local failure. Salvage therapy for these children historically had poor results, with repeated local recurrences. To improve these outcomes, we began to offer hypofractionated re-irradiation after resection at first local recurrence. To minimize the duration of therapy, we chose a hypofractionated regimen that has been shown to be well tolerated in adult patients.

PROCEDURE

We performed a review of the experience at the Children's Hospital in Denver and at the Department of Radiation Oncology at the University of Colorado Denver from 1995 to 2008 with hypofractionated re-irradiation after maximally safe resection in children with locally recurrent ependymoma.

RESULTS

Six children with locally recurrent ependymoma were seen in that time period. After maximally safe resection, all six received hypofractionated radiation therapy of 24-30 Gy delivered in three fractions. With a median follow-up of 28 months from the time of re-irradiation, all six children are alive with no evidence of disease. Three children had evidence of radiation necrosis, either clinically or based on imaging, but none required significant intervention.

CONCLUSIONS

Hypofractionated re-irradiation after resection for locally recurrent ependymoma is well tolerated. This approach also appears to provide good local control. Additional follow-up is required to determine the efficacy and potential late effects of hypofractionated re-irradiation in this patient population.