Treatment outcome of single or hypofractionated single-isocentric stereotactic irradiation (STI) using a linear accelerator for intracranial arteriovenous malformation

Efficacy of Dose-Escalated Hypofractionated Radiosurgery for Arteriovenous Malformations

There is considerable controversy about the management of arteriovenous malformations (AVMs) that are high risk for surgical resection. Stereotactic radiosurgery (SRS) has a reported success rate of less than 50% with unacceptably high rates of radiation necrosis with larger AVM volumes. Neither volume staging nor hypo-fractionated SRS have conclusively been demonstrated to improve results. We hypothesized that the failure of previous hypo-fractionation SRS trials was due to an insufficient biologically effective dose (BED) of radiation. We initiated a pilot study of treating AVM patients with a total dose divided into three or five fractions designed to deliver the equivalent BED of 20 Gy in a single fraction (α/β =3). We performed a retrospective analysis of 37 AVM patients who had a minimum of two years of follow-up or underwent obliteration. Patients were treated with 30 Gy/3 fractions, 33 Gy/3 fractions, or 40 Gy/5 fractions using a CyberKnife device (Accuracy Incorporated, Madison, Wisconsin, United States). The primary endpoint was complete AVM obliteration, determined by MRA imaging. Most obliterations were confirmed with diagnostic cerebral angiography. Secondary endpoints were post-radiosurgery hemorrhage and radiation-related necrosis. Kaplan-Meier analysis was used to determine obliteration rates. From 2013 to 2021, 37 patients fitting inclusion criteria were identified (62% male, average age at treatment = 48.88 years). Fifteen (41%) patients had prior treatment (surgery, radiosurgery, embolization) for their AVM, 32 (86%) had AVMs in eloquent locations, 17 (46%) had high-risk features, and 14 (38%) experienced AVM rupture prior to treatment. The average modified radiosurgery-based AVM score (mRBAS) was 1.81 (standard deviation (SD)= 0.52), and the mean AVM volume was 6.77 ccs (SD = 6.09). Complete AVM obliteration was achieved in 100% of patients after an average of 26.13 (SD = 14.62) months. The Kaplan-Meier analysis showed AVM obliteration rates at one, two, and three years to be 16.2%, 46.9%, and 81.1%, respectively. Post-operative AVM rupture or hemorrhage occurred in one (2.7%) patient, after nine months. Radiation necrosis occurred in four (11%) patients after an average period of 17.3 (SD =14.7) months. The SRS dose used in this study is the highest BED of any AVM hypofractionation trial in the published literature. This study suggests that dose-escalated hypofractionated radiosurgery can be a successful strategy for AVMs with acceptable long-term complication rates. Further investigation of this treatment regimen should be performed to assess its efficacy.

Hypofractionated Stereotactic Radiotherapy with CyberKnife for Large Arteriovenous Malformations and Arteriovenous Malformations Located in Eloquent Areas

Literature has yet to establish an appropriate treatment strategy for large arteriovenous malformations (AVMs) and AVMs located in eloquent areas. In this study, the treatment outcomes of hypofractionated stereotactic radiotherapy (HSRT) with CyberKnife (CK) for large AVMs and AVMs in eloquent areas were evaluated. This study retrospectively evaluated 38 consecutive patients with AVMs treated with HSRT in the Japanese Red Cross Medical Center between August 2010 and July 2015. Obliteration rates and hemorrhage rates at 3- and 5-years of follow-up were calculated. Factors for hemorrhage and obliteration were analyzed with logistic regression analysis. Fourteen (36.8%) patients had a history of hemorrhage. Twenty (52.6%) AVMs were larger than 10 mL, and 34 (89.5%) AVMs were located in eloquent areas. The majority of the AVMs (84.2%) were classified into high grades (grades 3, 4, and 5) using the Spetzler-Martin grading scale. The median modified radiosurgery-based AVM score was 2.05, and the median Virginia Radiosurgery AVM Score was 3. The mean marginal dose was 24.5 ± 2.5 Gy. Twenty-three and 15 patients received three- and five-fraction stereotactic radiotherapy, respectively. At 3 and 5 years posttreatment, two (2.0%/year) and six (6.7%/year) patients had hemorrhage with obliteration rates of 15.2% and 16.7%, respectively. AVM localization in eloquent areas was a risk factor for obliteration failure. This study revealed that HSRT with CK for large AVMs and AVMs located in eloquent areas contributed to hemorrhage risk reduction and obliteration, at least in the early stages.

Cognitive and psychosocial outcomes following stereotactic radiosurgery for acoustic neuroma

BACKGROUND

Acoustic Neuroma (AN) is a benign tumour of the eighth cranial nerve. Stereotactic Radiosurgery (SRS) is a common treatment approach. Studies have explored the primary effects of SRS and documented equivalent efficacy for tumour control compared to neurosurgery.

OBJECTIVE

Examine the longer term cognitive and psychosocial outcomes of SRS in non-Neurofibromatosis Type II patients utilising both objective and subjective cognitive outcomes associated with quality of life and health related distress.

METHODS

Nineteen individuals treated via SRS were assessed using a battery of standardised psychometric tests as well as measures of quality of life and psychological distress.

RESULTS

Participants had largely preserved cognitive function except for processing speed, aspects of attention and visual memory relative to age norms. Self-reported quality of life was better than in other AN population studies. Level of psychological distress was equivalent to general population norms. More than half of participants reported subjective cognitive decline though this was not fully supported by objective testing. Subjective cognitive complaints may be associated with lower reported quality of life.

CONCLUSIONS

Results are largely consistent with previous findings on the effects of SRS in other clinical groups, which supports SRS as a targeted radiation treatment for AN.

Radiotherapy of non-tumoral refractory neurological pathologies

Intracranial radiotherapy has been improved, primarily because of the development of stereotactic approaches. While intracranial stereotactic body radiotherapy is mainly indicated for treatment of benign or malignant tumors, this procedure is also effective in the management of other neurological pathologies; it is delivered using GammaKnife® and linear accelerators. Thus, brain arteriovenous malformations in patients who are likely to experience permanent neurological sequelae can be managed by single session intracranial stereotactic body radiotherapy, or radiosurgery, in specific situations, with an advantageous benefit/risk ratio. Radiosurgery can be recommended for patients with disabling symptoms, which are poorly controlled by medication, such as trigeminal neuralgia, and tremors, whether they are essential or secondary to Parkinson's disease. This literature review aims at defining the place of intracranial stereotactic body radiotherapy in the management of patients suffering from non-tumoral refractory neurological pathologies. It is clear that the multidisciplinary collaboration of experienced teams from Neurosurgery, Neurology, Neuroradiology, Radiation Oncology and Medical Physics is needed for the procedures using high precision radiotherapy techniques, which deliver high doses to locations near functional brain areas.

Radiosurgery for Cerebral Arteriovenous Malformation (AVM) : Current Treatment Strategy and Radiosurgical Technique for Large Cerebral AVM

Arteriovenous malformations (AVMs) are congenital anomalies of the cerebrovascular system. AVM harbors 2.2% annual hemorrhage risk in unruptured cases and 4.5% annual hemorrhage risk of previously ruptured cases. Stereotactic radiosurgery (SRS) have been shown excellent treatment outcomes for patients with small- to moderated sized AVM which can be achieved in 80–90% complete obliteration rate with a 2–3 years latency period. The most important factors are associated with obliteration after SRS is the radiation dose to the AVM. In our institutional clinical practice, now 22 Gy (50% isodose line) dose of radiation has been used for treatment of cerebral AVM in single-session radiosurgery. However, dose-volume relationship can be unfavorable for large AVMs when treated in a single-session radiosurgery, resulting high complication rates for effective dose. Thus, various strategies should be considered to treat large AVM. The role of pre-SRS embolization is permanent volume reduction of the nidus and treat high-risk lesion such as AVM-related aneurysm and high-flow arteriovenous shunt. Various staging technique of radiosurgery including volume-staged radiosurgery, hypofractionated radiotherapy and dose-staged radiosurgery are possible option for large AVM. The incidence of post-radiosurgery complication is varied, the incidence rate of radiological post-radiosurgical complication has been reported 30–40% and symptomatic complication rate was reported from 8.1% to 11.8%. In the future, novel therapy which incorporate endovascular treatment using liquid embolic material and new radiosurgical technique such as gene or cytokine-targeted radio-sensitization should be needed.

The use of Hypofractionated Radiosurgery for the Treatment of Intracranial Lesions Unsuitable for Single-Fraction Radiosurgery

Stereotactic radiosurgery (SRS) is commonly used in the treatment of brain metastases, benign tumors, and arteriovenous malformations (AVM). Single-fraction radiosurgery, though ubiquitous, is limited by lesion size and location. In these cases, hypofractionated radiosurgery (hfSRS) offers comparable efficacy and toxicity. We review the recent literature concerning hfSRS in the treatment of brain metastases, benign tumors, and AVMs that are poorly suited for single-fraction SRS. Published retrospective analyses suggest that local control rates for brain metastases and benign tumors, as well as the rates of AVM obliteration, following hfSRS treatment are comparable to those reported for single-fraction SRS. Additionally, the toxicities from hypofractionated treatment appear comparable to those seen with single-fractioned SRS to small lesions.

Hypofractionated stereotactic radiosurgery for dural arteriovenous fistula in the superior sagittal sinus: case report and review of the literature

Stereotactic radiosurgery (SRS) for dural arteriovenous fistula (dAVF) in the superior sagittal sinus (SSS) is not an established treatment because of relatively poor efficacy and a latency period for treatment effects. Hypofractionated SRS for these lesions has not yet been reported. A 65-year-old man presented with intermittent paraparesis. Brain magnetic resonance imaging (MRI) revealed acute infarction in the premotor and motor cortex of both frontal convexities. Cerebral angiography demonstrated extensive dAVF in the middle and posterior third SSS, associated with an occlusion in the middle third. Transfemoral arterial Onyx embolization was performed through the right middle meningeal arteries, and cerebral venous reflux (CVR) disappeared from the middle third of the SSS. However, the remnant dAVF in the posterior third of the SSS and CVR in the posterior parietal and occipital lobes remained. Novalis SRS was performed on remnant the dAVF with 35 Gy in 5 fractions. Seven months after Novalis SRS, symptoms improved and cortical engorged vessel gradually disappeared on brain MRI. The patient recovered completely at 22 months post-radiosurgery. SRS for dAVF in the SSS could provide an alternative treatment option. Hypofractionated SRS showed a good result in our case.

Severe adverse radiation effects complicating radiosurgical treatment of brain arteriovenous malformations and the potential benefit of early surgical treatment

Treatment of brain arteriovenous malformations (AVM) with stereotactic radiosurgery is rarely complicated by severe adverse radiation effects (ARE). The treatment of these sequelae is varied and often ineffectual. We present three cases of brain AVMs treated with SRS, all complicated by severe AREs. All three cases failed to respond to what is currently considered the standard treatment - corticosteroids - and indeed one patient died as a result of the side effects of their extended use. Two cases were successfully treated with surgical excision of the necrotic lesion resulting in immediate clinical improvement. Having considered the experience described in this paper and reviewed the published literature to date we suggest that surgical treatment of AREs should be considered early in the management of this condition should steroid therapy not result in early improvement.

Long-term Outcomes With Planned Multistage Reduced Dose Repeat Stereotactic Radiosurgery for Treatment of Inoperable High-Grade Arteriovenous Malformations: An Observational Retrospective Cohort Study

BACKGROUND

There is no consensus regarding the optimal management of inoperable high-grade arteriovenous malformations (AVMs). This long-term study of 42 patients with high-grade AVMs reports obliteration and adverse event (AE) rates using planned multistage repeat stereotactic radiosurgery (SRS).

OBJECTIVE

To evaluate the efficacy and safety of multistage SRS with treatment of the entire AVM nidus at each treatment session to achieve complete obliteration of high-grade AVMs.

METHODS

Patients with high-grade Spetzler-Martin (S-M) III-V AVMs treated with at least 2 multistage SRS treatments from 1989 to 2013. Clinical outcomes of obliteration rate, minor/major AEs, and treatment characteristics were collected.

RESULTS

Forty-two patients met inclusion criteria (n = 26, S-M III; n = 13, S-M IV; n = 3, S-M V) with a median follow-up was 9.5 yr after first SRS. Median number of SRS treatment stages was 2, and median interval between stages was 3.5 yr. Twenty-two patients underwent pre-SRS embolization. Complete AVM obliteration rate was 38%, and the median time to obliteration was 9.7 yr. On multivariate analysis, higher S-M grade was significantly associated ( P = .04) failure to achieve obliteration. Twenty-seven post-SRS AEs were observed, and the post-SRS intracranial hemorrhage rate was 0.027 events per patient year.

CONCLUSION

Treatment of high-grade AVMs with multistage SRS achieves AVM obliteration in a meaningful proportion of patients with acceptable AE rates. Lower obliteration rates were associated with higher S-M grade and pre-SRS embolization. This approach should be considered with caution, as partial obliteration does not protect from hemorrhage.

Volume-staged versus dose-staged stereotactic radiosurgery outcomes for large brain arteriovenous malformations: a systematic review

OBJECTIVE Several recent studies have improved our understanding of the outcomes of volume-staged (VS) and dose-staged (DS) stereotactic radiosurgery (SRS) for the treatment of large (volume > 10 cm3) brain arteriovenous malformations (AVMs). In light of these recent additions to the literature, the aim of this systematic review is to provide an updated comparison of VS-SRS and DS-SRS for large AVMs. METHODS A systematic review of the literature was performed using PubMed to identify cohorts of 5 or more patients with large AVMs who had been treated with VS-SRS or DS-SRS. Baseline data and post-SRS outcomes were extracted for analysis. RESULTS A total of 11 VS-SRS and 10 DS-SRS studies comprising 299 and 219 eligible patients, respectively, were included for analysis. The mean obliteration rates for VS-SRS and DS-SRS were 41.2% (95% CI 31.4%-50.9%) and 32.3% (95% CI 15.9%-48.8%), respectively. Based on pooled individual patient data, the outcomes for patients treated with VS-SRS were obliteration in 40.3% (110/273), symptomatic radiation-induced changes (RICs) in 13.7% (44/322), post-SRS hemorrhage in 19.5% (50/256), and death in 7.4% (24/323); whereas the outcomes for patients treated with DS-SRS were obliteration in 32.7% (72/220), symptomatic RICs in 12.2% (31/254), post-SRS hemorrhage in 10.6% (30/282), and death in 4.6% (13/281). CONCLUSIONS Volume-staged SRS appears to afford higher obliteration rates than those achieved with DS-SRS, although with a less favorable complication profile. Therefore, VS-SRS or DS-SRS may be a reasonable treatment approach for large AVMs, either as stand-alone therapy or as a component of a multimodality management strategy.

Predictors for occlusion of cerebral AVMs following radiation therapy : Radiation dose and prior embolization, but not Spetzler-Martin grade

BACKGROUND

Intracranial arteriovenous malformations (AVMs) may show a harmful development. AVMs are treated by surgery, embolization, or radiation therapy.

OBJECTIVE

This study investigated obliteration rates and side effects in patients with AVMs treated by radiation therapy.

METHODS

A total of 40 cases treated between 2005 and 2013 were analyzed. Single-dose stereotactic radiosurgery (SRS) was received by 13 patients and 27 received hypofractionated stereotactic radiation therapy (HSRT). In 20 patients, endovascular embolization had been performed prior to irradiation and 24 patients (60 %) had a history of previous intracranial hemorrhage.

RESULTS

Treatment resulted in complete obliteration (CO) in 23/40 cases and partial obliteration in 8/40. CO was achieved in 85 % of patients receiving SRS compared to 44 % of those receiving HSRT. In the HSRT group, a first indication of an influence of AVM volume on obliteration rate was found. Equivalent 2 Gy fraction doses (EQD2) >70 Gy showed an obliteration rate of 50 %. Prior embolization was significantly associated with a higher portion of CO (p = 0.032). Median latency period (24.2 vs. 26 months) until CO was similar in both groups (SRS vs. HSRT). The rate of intracranial hemorrhage in patients with no prior bleeding events was 0 %.

CONCLUSION

Excellent obliteration rates were achieved by SRS. Consistent with the literature, this data analysis suggests that the results of HSRT are volume-dependent. Furthermore, regimens with EQD2 doses >70 Gy appear more likely to achieve obliteration than schemes with lower doses. The findings indicate that radiation therapy does not increase the risk of bleeding. Prior embolization may have a good prognostic impact.

Improvement of cerebral hypometabolism after resection of radiation-induced necrotic lesion in a patient with cerebral arteriovenous malformation

A 55-year-old woman underwent radiosurgery for a left cerebral hemisphere arteriovenous malformation (AVM) and developed radiation-induced necrosis causing a massive edema in the surrounding brain tissues. Despite various therapies, the edema expanded to the ipsilateral hemisphere and induced neurological symptoms. The radiation-induced necrotic lesion was surgically removed 4 years after radiosurgery. While the preoperative FDG PET revealed severe hypometabolism in the left cerebrum, the necrotomy significantly ameliorated the brain edema, glucose metabolism (postoperative FDG PET), and symptoms. This case indicates that radiation necrosis-induced neurological deficits may be associated with brain edema and hypometabolism, which could be reversed by appropriate necrotomy.

Brain arteriovenous malformations

An arteriovenous malformation is a tangle of dysplastic vessels (nidus) fed by arteries and drained by veins without intervening capillaries, forming a high-flow, low-resistance shunt between the arterial and venous systems. Arteriovenous malformations in the brain have a low estimated prevalence but are an important cause of intracerebral haemorrhage in young adults. For previously unruptured malformations, bleeding rates are approximately 1% per year. Once ruptured, the subsequent risk increases fivefold, depending on associated aneurysms, deep locations, deep drainage and increasing age. Recent findings from novel animal models and genetic studies suggest that arteriovenous malformations, which were long considered congenital, arise from aberrant vasculogenesis, genetic mutations and/or angiogenesis after injury. The phenotypical characteristics of arteriovenous malformations differ among age groups, with fistulous lesions in children and nidal lesions in adults. Diagnosis mainly involves imaging techniques, including CT, MRI and angiography. Management includes observation, microsurgical resection, endovascular embolization and stereotactic radiosurgery, alone or in any combination. There is little consensus on how to manage patients with unruptured malformations; recent studies have shown that patients managed medically fared better than those with intervention at short-term follow-up. By contrast, interventional treatment is preferred following a ruptured malformation to prevent rehaemorrhage. Management continues to evolve as new mechanistic discoveries and reliable animal models raise the possibility of developing drugs that might prevent the formation of arteriovenous malformations, induce obliteration and/or stabilize vessels to reduce rupture risk. For an illustrated summary of this Primer, visit: http://go.nature.com/TMoAdn.

Volume-staged versus dose-staged radiosurgery outcomes for large intracranial arteriovenous malformations

OBJECT

The aim in this paper was to compare the outcomes of dose-staged and volume-staged stereotactic radio-surgery (SRS) in the treatment of large (> 10 cm(3)) arteriovenous malformations (AVMs).

METHODS

A systematic literature review was performed using PubMed. Studies written in the English language with at least 5 patients harboring large (> 10 cm(3)) AVMs treated with dose- or volume-staged SRS that reported post-treatment outcomes data were selected for review. Demographic information, radiosurgical treatment parameters, and post-SRS outcomes and complications were analyzed for each of these studies.

RESULTS

The mean complete obliteration rates for the dose- and volume-staged groups were 22.8% and 47.5%, respectively. Complete obliteration was demonstrated in 30 of 161 (18.6%) and 59 of 120 (49.2%) patients in the dose- and volume-staged groups, respectively. The mean rates of symptomatic radiation-induced changes were 13.5% and 13.6% in dose- and volume-staged groups, respectively. The mean rates of cumulative post-SRS latency period hemorrhage were 12.3% and 17.8% in the dose- and volume-staged groups, respectively. The mean rates of post-SRS mortality were 3.2% and 4.6% in dose- and volume-staged groups, respectively.

CONCLUSIONS

Volume-staged SRS affords higher obliteration rates and similar complication rates compared with dose-staged SRS. Thus, volume-staged SRS may be a superior approach for large AVMs that are not amenable to single-session SRS. Staged radiosurgery should be considered as an efficacious component of multimodality AVM management.

Advances in Radiosurgery for Arteriovenous Malformations of the Brain

Arteriovenous malformations of the brain are a considerable source of morbidity and mortality for patients who harbor them. Although our understanding of this disease has improved, it remains in evolution. Advances in our ability to treat these malformations and the modes by which we address them have also improved substantially. However, the variety of patient clinical and disease scenarios often leads us into challenging and complex management algorithms as we balance the risks of treatment against the natural history of the disease. The goal of this article is to provide a focused review of the natural history of cerebral arteriovenous malformations, to examine the role of stereotactic radiosurgery, to discuss the role of endovascular therapy as it relates to stereotactic radiosurgery, and to look toward future advances.

Neuropsychological outcomes of stereotactic radiotherapy for cerebral arteriovenous malformations

To our knowledge, this is the first study to investigate cognitive outcome in patients with large or surgically inaccessible cerebral arteriovenous malformations (AVMs), who were treated with hypo-fractionated stereotactic radiotherapy (HSRT). A sample of 10 patients with AVMs was assessed up to 3.5 years post-HSRT. All patients were treated with HSRT to a total dose of 55 Gy in 11 fractions over a treatment period of 2.5 weeks. Neuropsychological assessments were given prior to radiotherapy and then at three time points following radiotherapy: 6 weeks, 6 months and 2.5-3.5 years post-treatment. The cognitive domains of attention, processing speed, learning, memory, semantic processing, naming, verbal fluency, visuospatial and executive function were assessed. Findings revealed that prior to radiotherapy the patient group was impaired in five of the nine cognitive domains. Post-treatment performances remained stable in the majority of domains; however, there was some fluctuation in semantic processing and memory performances. At 6 weeks post-treatment, a mild decrement was found in semantic processing ability; however, restoration to baseline levels was observed from 6 months onwards. At 2.5-3.5 years post-treatment, improvement was seen in the cohort's ability to remember new information when performances were compared with earlier time points. This study demonstrated improvements in memory several years after HSRT treatment. Further, this form of treatment was not associated with long-term, harmful cognitive side effects for these 10 patients encouraging further study of this treatment method. Further evaluation of the entire cohort is required to assess efficacy in terms of AVM obliteration and other potential side effects.

Hypofractionated stereotactic radiotherapy for large or involving critical organs cerebral arteriovenous malformations

Background

The treatment of large arteriovenous malformations (AVMs) or AVMs involving eloquent regions of the brain remains a challenge. For inoperable lesions, observation, volume-staged radiosurgery or hypofractionated stereotactic radiotherapy (HFSRT) are proposed. The aim of our study was to assess the safety and efficiency of HFSRT for large AVMs located in eloquent areas of the brain.

Materials and methods

An analysis of records of 49 patients irradiated for cerebral AVMs with a mean dose of 19.9 Gy (12–28 Gy) delivered in 2–4 fractions with planned gap (at least one week) between fractions. Actuarial obliteration rates and annual bleeding hazard were calculated using Kaplan-Meier survival analysis and life tables.

Results

Annual bleeding hazard rates were 4.5% and 1.6% after one and two years of the follow-up, respectively. Actuarial total obliteration rates were 7%, 11%, and 21% and total response rate (total and partial obliterations) 22%, 41%, and 55% after one, two and three years of the follow-up, respectively. There was a trend towards larger total obliteration rate in patients irradiated with fraction dose ≥ 8 Gy and total dose > 21 Gy for lesions of volume ≤ 8.18 cm³ which was not observed in case of partial obliterations.

Conclusions

HFSRT results with relatively low obliteration rate but is not associated with a significant risk of permanent neurological deficits if both total and fraction doses are adjusted to size and location of the lesion. Predictive factors for total and partial obliterations can be different; this observation, however, is not firmly supported and requires further studies.

Hypofractionated stereotactic radiotherapy for large arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are abnormal connections between the arteries and veins, with possible serious consequences of intracranial hemorrhage. The curative treatment for AVMs includes microsurgery and radiosurgery, sometimes with embolization as an adjunct. However, controversies exist with the treatment options available for large to giant AVMs. Hypofractionated stereotactic radiotherapy (HSRT) is one treatment option for such difficult lesions. We aim to review recent literature, looking at the treatment outcome of HSRT in terms of AVM obliteration rate and complications. The rate of AVM obliteration utilizing HSRT as a primary treatment was comparable with that of stereotactic radiosurgery (SRS). For those not totally obliterated, HSRT makes them smaller and turns some lesions manageable by single-dose SRS or microsurgery. Higher doses per fraction seemed to exhibit better response. However, patients receiving higher total dose may be at risk for higher rates of complications. Fractionated regimens of 7 Gy × 4 and 6–6.5 Gy × 5 may be accepted compromises between obliteration and complication. Embolization may not be beneficial prior to HSRT in terms of obliteration rate or the volume reduction. Future work should aim on a prospectively designed study for larger patient groups and long-term follow-up results.

[Hypofractionated stereotactic radiotherapy for brain metastases]

PURPOSE

A survey of the literature has been performed to find arguments in order to help the choice between radiosurgery and hypofractionated stereotactic radiotherapy in the treatment of brain metastases.

PATIENTS AND METHODS

A comparison of two groups of brain metastases treated with hypofractionated stereotactic radiotherapy or radiosurgery, with or without WBRT was performed. Hypofractionated stereotactic radiotherapy: there were eight series including 448 patients published from 2000 to 2009; treated with 5-6 MV X-Rays, non invasive head immobilization, a margin 2 to 10mm; 24 to 40Gy in three to five fractions; a 5 to 8 days duration in six series and 15-16 days in two other series. WBRT (30%) ; radiosurgery: there were 12 series (1994 to 2005) including 2157 patients; an invasive head immobilization, no margin; doses from 10 to 25 Gy; six series over 12 had Gamma Knife radiosurgery and six had Linacs X-Rays. WBRT (30 Gy/10 F/12 days) associated to radiosurgery in several series. The following parameters were compared: median GTV, median survival, 1-year survival rate, local control rate, necrosis and WBRT rates.

RESULTS

Hypofractionated stereotactic radiotherapy series: the parameters were respectively: 0,52-4,47 cm(3) (median 2,8 cm(3)); 5-16 months (median 8,7 months); 68,2-93% (median 82,5%); necrosis rate 3,1%; associated WBRT 30%. Radiosurgery series: the parameters were respectively: 1,3 to 5,5 cm(3) (median 2 cm(3)); 5,5 to 22 months (median 11 months); 71 to 95% (median 85%); 0,5 to 6% (median 2,4%); associated WBRT 58%. Results seem similar in the two groups: Hypofractionated stereotactic radiotherapy with non invasive immobilization could theoretically treat all brain metastases sizes except lesions<10 mm (500 mm(3)). In large volumes,>4200 mm(3) GTV, the toxicity of hypofractionated stereotactic radiotherapy was not reported, thus it was difficult to compare its results with the published reports of radiosurgery toxicity. WBRT was a confusing parameter. Obviously, this initial survey has important limitations, specifically its methodology.

CONCLUSION

Radiosurgery and hypofractionated stereotactic radiotherapy could be used to treat brain metastases with GTV>500 mm(3) and < or = 4200 mm(3) (Ø 20mm); for GTV<500 mm(3) (Ø 10mm) an invasive procedure with radiosurgery is necessary. For GTV>4200 mm(3) (Ø 20mm), hypofractionated stereotactic radiotherapy could be proposed, provided further studies, using 4 to 6 Gy fractions, a duration less or equal to 10-12 days and a margin of 2mm will be performed.

Semiautomatic tractography: motor pathway segmentation in patients with intracranial vascular malformations

Object

The visualization of white matter tracts using tractography has previously been achieved by displaying streamlines that pass between regions of interest (ROIs). These techniques require a significant amount of user interaction, and their results are entirely dependent on the positioning of the ROIs. Furthermore, in patients with intracerebral hemorrhage secondary to intracranial vascular malformation, there is often significant cerebral edema and susceptibility artifact from the hematoma, which degrade the reliability of tractography. In this paper, the authors' objectives were to visualize the motor pathways of patients with hemorrhagic and nonhemorrhagic vascular malformations by using a novel semiautomated technique that functions without the need for multiple ROIs.

Methods

The authors investigated the tractography appearance of the descending motor pathways in 6 patients with intracranial vascular malformations. Of these patients 4 presented with a spontaneous intracranial hemorrhage, 2 of whom were clinically hemiparetic. Diffusion tensor imaging was performed using a 1.5-T clinical MR imaging system, and whole-brain tractography was performed after reconstruction of the data. A fractional anisotropy threshold of 0.05 was used to terminate the tractography. The semiautomatic motor pathway segmentation technique required definition of a single voxel within the corticospinal tract of the medulla from which the descending motor pathways were automatically defined by grouping together all streamlines within the entire image with a geometry similar to that of the single streamline generated from this initial voxel. The results of this segmentation were then visually assessed and compared with the patient's motor function.

Results

The authors' semiautomatic algorithm consistently visualized the location of the descending motor pathways in patients with nonhemorrhagic and hemorrhagic vascular malformations. In 1 patient whose complete right hemiplegia (complete paralysis) was caused by a large left frontal hematoma that bisected the descending motor pathways, the authors were unable to reconstruct the motor pathways due to severe tract degeneration. However, in all cases in which motor function was intact or only mildly impaired, the technique clearly delineated the motor pathways, even in the presence of large anatomical displacement by the vascular abnormality or associated hemorrhage.

Conclusions

Semiautomatic tractography allows consistent and rapid demonstration of the descending motor pathways in patients with hemorrhagic and nonhemorrhagic intracranial vascular malformations. The technique allows the use of a comparatively low fractional anisotropy threshold and does not require the definition of multiple ROIs. These techniques may help to improve the clinical feasibility and potentially the reliability of tractography for the evaluation of patients with intracranial vascular malformations as well as other space-occupying lesions of the brain.

Reproducibility and geometric accuracy of the Fixster system during hypofractionated stereotactic radiotherapy

Background

Hypofractionated radiotherapy has been used for the treatment of AVMs and brain metastases. Hypofractionation necessitates the use of a relocatable stereotactic frame that has to be applied on several occasions. The stereotactic frame needs to have a high degree of reproducibility, and patient positioning is crucial to achieve a high accuracy of the treatment.

Methods

In this study we have, by radiological means, evaluated the reproducibility of the isocenter in consecutive treatment sessions using the Fixster frame. Deviations in the X, Y and Z-axis were measured in 10 patients treated with hypofractionated radiotherapy.

Results

The mean deviation in the X-axis was 0.4 mm (range -2.1 – 2.1, median 0.7 mm) and in the Y-axis -0.3 mm (range -1.4 – 0.7, median -0.2 mm). The mean deviation in the Z-axis was -0.6 (range -1.4 – 1.4, median 0.0 mm).

Conclusion

There is a high degree of reproducibility of the isocenter during successive treatment sessions with HCSRT using the Fixster frame for stereotactic targeting. The high reducibility enables a safe treatment using hypofractionated stereotactic radiotherapy.

Advances in the radiosurgical treatment of large inoperable arteriovenous malformations

Radiosurgery has proven useful in the treatment of small arteriovenous malformations (AVMs) of the brain. However, the volume of healthy tissue irradiated around large lesions is rather significant, necessitating reduced radiation doses to avoid complications. As a consequence, this can produce poorer obliteration rates. Several strategies have been developed in the past decade to circumvent dose-volume problems with large AVMs, including repeated treatments as well as dose, and volume fractionation schemes. Although success on par with that achieved in lesions smaller than 3 ml remains elusive, improvements over the obliteration rate, the complication rate or both have been reported after conventional single-dose stereotactic radiosurgery (SRS). Radiosurgery with a marginal dose or peripheral dose < 15 Gy rarely obliterates AVMs, yet most lesions diminish in size posttreatment. Higher doses may then be reapplied to any residual nidi after an appropriate follow-up period. Volume fractionation divides AVMs into smaller segments to be treated on separate occasions. Doses > 15 Gy irradiate target volumes of only 5-15 ml, thereby minimizing the radiation delivered to the surrounding brain tissue. Fewer adverse radiological effects with the use of fractionated radiosurgery over standard radiosurgery have been reported. Advances in AVM localization, dose delivery, and dosimetry have revived interest in hypofractionated SRS. Investigators dispensing >or= 7 Gy per fraction minimum doses have achieved occlusion with an acceptable number of complications in 53-70% of patients. The extended latency period between treatment and occlusion, about 5 years for emerging techniques (such as salvage, staged volume, and hypofractionated radiotherapy), exposes the patient to the risk of hemorrhage during that period. Nevertheless, improvements in dose planning and target delineation will continue to improve the prognosis in patients harboring inoperable AVMs.

Possible fractionated regimens for image-guided intensity-modulated radiation therapy of large arteriovenous malformations

The aim of this study was to estimate a plausible alpha/beta ratio for arteriovenous malformations (AVMs) based on reported clinical data, and to design possible fractionation regimens suitable for image-guided intensity-modulated radiation therapy (IG-IMRT) for large AVMs based on the newly obtained alpha/beta ratio. The commonly used obliteration rate (OR) for AVMs with a three year angiographic follow-up from many institutes was fitted to linear-quadratic (LQ) formalism and the Poisson OR model. The determined parameters were then used to calculate possible fractionation regimens for IG-IMRT based on the concept of a biologically effective dose (BED) and an equivalent uniform dose (EUD). The radiobiological analysis yields a alpha/beta ratio of 2.2 +/- 1.6 Gy for AVMs. Three sets of possible fractionated schemes were designed to achieve equal or better biological effectiveness than the single-fraction treatments while maintaining the same probability of normal brain complications. A plausible alpha/beta ratio was derived for AVMs and possible fractionation regimens that may be suitable for IG-IMRT for large AVM treatment are proposed. The sensitivity of parameters on the calculation was also studied. The information may be useful to design new clinical trials that use IG-IMRT for the treatment of large AVMs.

Calculation of isoeffective doses and the α /β value by comparing results following radiosurgery and radiotherapy for arteriovenous malformations of the brain

Object

The authors sought to assess the relationship between obliteration rate and different dose parameters following fractionated radiotherapy for arteriovenous malformations (AVMs). A comparison of the results of radiosurgery and radiotherapy for AVMs was made to calculate the best fit α/β value, which would then be used as a model for predicting the treatment outcome, independent of the number of fractions applied.

Methods

Data from 1453 patients were analyzed: 1154 treated with radiosurgery and 300 with fractionated radiotherapy. The relationships between dose and obliteration rate after 3 years were calculated, and the best fit curve to the empirical results was defined. The higher the dose per fraction, biologically effective dose, and the lower the total dose, the higher the obliteration rate. The isoeffective doses when comparing radiotherapy and radiosurgery independent of the α/β value could not be defined. The dose per fraction had the best predictive value, independent of the number of fractions.

Conclusions

Dose per fraction seems to be the decisive parameter for the treatment response following both radiotherapy and radiosurgery. A larger number of fractions did not increase the obliteration rate. The data indicate that higher doses per fraction should be used when irradiating AVMs.

Outcomes of Surgery for Resection of Regions of Symptomatic Radiation Injury After Stereotactic Radiosurgery for Arteriovenous Malformations

OBJECTIVE:

Although radiation injury after stereotactic radiosurgery (SRS), including radiation necrosis (RN), is often treated with surgical resection, detailed outcome data are lacking after resection of symptomatic radiation-injured regions with imaging characteristics suspicious for RN after SRS for arteriovenous malformations (AVM). We present outcomes in seven such patients.

METHODS:

We conducted a retrospective chart review of seven patients with AVMs of Spetzler-Martin Grades II (n = 1), III (n = 2), and IV (n = 4) who underwent helium ion, proton beam, or gamma knife SRS and required resection of RN-suspicious tissue 1 to 24 months after post-SRS symptom onset. Postoperative outcomes included Karnofsky Performance Scale (KPS) score and time to symptomatic improvement.

RESULTS:

Symptomatic improvement required at least 9 months in the three patients with large regions suspicious for RN (≥4 cm), whereas of four patients with smaller regions (&lt;4 cm), three showed improvement within 2 months (P &lt; 0.05). The remaining patient, who showed no benefit, underwent resection 2 years after the onset of RN symptoms (compared with ≤ 8 mo for the other six patients). Surgery improved KPS scores in four patients with a preoperative KPS score of 50 or lower, but not in three patients with preoperative KPS scores greater than 70 (P &lt; 0.05). Outcomes were not consistently associated with AVM size or location, SRS treatment volume or dose, associated aneurysm, or residual AVM.

CONCLUSION:

After SRS for AVMs, resection of symptomatic RN-suspicious tissue areas is beneficial in reversing neurological deficits and improving KPS scores in selected patients. Times to improvement were longer when larger areas were resected. Delaying such surgery after symptom onset may negatively affect improvement.

Update of radiosurgery at the Royal Adelaide Hospital

This is an update of the Royal Adelaide Hospital radiosurgery experience between November 1993 and December 2004 comprising 165 patients with 168 intracranial lesions. Including re-treatment, there were 175 treatment episodes (163 radiosurgery and 12 stereotactic radiotherapy) at an average of 1.3 per month. The commonest lesions were acoustic neuroma (65), arteriovenous malformation (58), solitary brain metastasis (23) and meningioma (14). The clinical features, treatment details and outcome are described. Our results continue to be well within the range reported in the published work. Radiosurgery provides an elegant, non-invasive alternative to neurosurgery and conventional external beam radiotherapy for many benign and malignant brain tumours.

Linac-based radiosurgery or hypofractionated stereotactic radiotherapy in the treatment of large cerebral arteriovenous malformations

PURPOSE

We investigate retrospectively clinical outcome after radiosurgery (RS) or hypofractionated stereotactic radiotherapy (HSRT) in patients with large cerebral arteriovenous malformations (AVMs).

METHODS AND MATERIALS

This analysis is based on 48 patients with cerebral AVM greater than 4 cm treated with HSRT or RS at our institution. Fifteen patients received HSRT, with 26 Gy median total dose in 4 to 5 fractions, and 33 patients received RS with 17 Gy median total dose in 4 to 5 fractions. Median target volume was 27 cc in HSRT and 7 cc in RS; median maximum diameter was 6 cm and 5 cm, respectively. Seventeen patients experienced intracranial hemorrhage before treatment. Median follow-up was 2.6 years.

RESULTS

The 3-year and 4-year actuarial complete obliteration (CO) after HSRT was 17% and 33% and after RS was 47% and 60%, respectively. Actuarial CO was higher in AVMs less than 5 cm (66% vs. 37% after 4 years). Intracranial hemorrhage after HSRT occurred in 3 of 15 patients after 18 months median, and after RS in 7 of 33 patients after 17 months median. Bleeding risk was significantly higher in patients with prior hemorrhage (p < 0.04). Preexisting neurologic dysfunction improved/dissolved in 50% and remained stable in 45%.

CONCLUSIONS

Large AVMs need a long time period to obliterate and show a high bleeding risk. Multimodal treatment strategies are required to reduce treatment volume before radiotherapy.

Combined effects of embolization and hypofractionated conformal stereotactic radiotherapy in arteriovenous malformations of the brain

SUMMARY

There are three major treatment options for cerebral AVMs; surgery, embolization and radiosurgery. Embolization may be effective to reduce the size and density but completely obliterates AVMs only in a minority of cases. Radiosurgery may be an alternative to resection, especially in smaller AVMs. Large AVMs have been considered difficult to treat safely and effectively with single fraction radiosurgery. Hypofractionated conformal stereotactic radiotherapy (HCSRT) alone or in combination with embolization may be an alternative treatment. Embolization may reduce the volume and density of AVMs, followed by HCSRT, allowing a safe delivery of a higher total dose of radiation than possible with a single fraction. Sixteen patients with AVMs were treated with embolization and HCSRT. Embolization was performed in 1-6 (median 2) sessions. HCSRT was delivered in 5 fractions with 6-7 Gy each to the total dose of 30-35 Gy. Cerebral angiographies before and after embolization were digitally compared for calculation of volume reduction and luminescence as a measure of AVM density. The mean AVM volume in 15 patients was reduced from 11.9 +/- 2.1 (1-29, median 10.0) ml to 6.5 +/- 2.0 (0.5-28, median 3) ml by embolization. The luminescence for all AVMs was significantly higher after than before embolization, indicating that all AVMs were less dense after embolization. Thirteen out of 16 patients (13/16, 81%) treated with embolization and HCSRT have so far shown obliteration of their AVMs 2-9 (median 4) years after HCSRT. Three patients experienced neurological sequele after embolization, and three patients developed radionecrosis after HCSRT. Using a new method to compare cerebral angiographies in AVMs we report reduction in density and volume after embolization. The obliteration rate of a combined treatment with embolization and HCSRT seems comparable with single fraction radiosurgery although the AVMs in our series are larger than reported in most series treated with single fraction radiosurgery.

Intracranial arteriovenous malformations treated utilizing a linear accelerator-based patient rotator or commercially available radiosurgery system

PURPOSE

To report a single-institution experience with intracranial arteriovenous malformations (AVMs) treated utilizing a linear accelerator-based patient rotator (PR) or BrainLAB (BL) radiosurgery system (BrainLAB AG, Heimstetten, Germany).

METHODS AND MATERIALS

Since 1989, 84 evaluable patients were treated. PR patients (n = 45) were planned/localized on the basis of biplane angiography and treated between 1989 and 2000. BL patients (n = 39) were planned/localized on the basis of CT/MRI and treated since 2000. Kaplan-Meier analyses of survival, nidus obliteration (NO), and any radiographic improvement were undertaken with Cox regression of dose and volume effects.

RESULTS

No significant complication, survival, previous embolization incidence, AVM location or size differences existed between BL/PR patients. The groups differed significantly in prescribed dose (PR: 16.2 Gy, BL: 17.3 Gy, p = 0.004) and isodose (PR: 62%, BL: 79%, p < 0.0001). Estimated 2-year NO rate was 87% for BL patients, 12% for PR patients (p < 0.0001). Ultimate PR NO rate was 67% at 6 years. Dose (p = 0.037) and isodose (p = 0.014) significantly affected PR NO outcome; volume was of borderline significance (p = 0.069). No factors significantly affected BL outcome. Analyses of small (< or = 4.0 cm3), high-dose (> or = 17.0 Gy) PR patients (PR1 group) vs. BL patients still demonstrated greater NO (p = 0.04) and radiographic improvement (p = 0.0004) rates for the BL group. PR1 patients had a 76% 3-year NO rate.

CONCLUSIONS

BL-based radiosurgery achieved a high NO rate, the PR method did not. Differences in outcomes between PR/BL groups may be due to localization methods or an inherent advantage with the BL system.

Comparison of imaging modalities for the accurate delineation of arteriovenous malformation, with reference to stereotactic radiosurgery

PURPOSE

To investigate the discrepancy between the arteriovenous malformations seen on magnetic resonance angiography (MRA) and on stereotactic digital subtracted angiography (DSA).

METHODS AND MATERIALS

The target volume on stereotactic DSA (V(DSA)) and the target volume on MRA (V(MRA)) were separately delineated in 28 intracranial arteriovenous malformations. The coordinates of the center and the outer edges of V(DSA) and V(MRA) were calculated and used for the analyses.

RESULTS

The standard deviations (mean value) of the displacement of centers of V(MRA) from V(DSA) were 2.67 mm (-1.82 mm) in the left-right direction, 3.23 mm (-0.08 mm) in the anterior-posterior direction, and 2.16 mm (0.91 mm) in the craniocaudal direction. V(MRA) covered less than 80% of V(DSA) in any dimensions in 9 cases (32%), although no significant difference was seen in the target volume between each method, with a mean value of 11.9 cc for V(DSA) and 12.3 cc for V(MRA) (p = 0.948).

CONCLUSION

The shift of centers between each modality is not negligible. Considering no significant difference between V(DSA) and V(MRA), but inadequate coverage of the V(DSA) by V(MRA), it is reasonable to consider that the target on MRA might include the feeding artery and draining vein and possibly miss a portion of the nidus.

Stereotactic proton beam therapy for intracranial arteriovenous malformations

PURPOSE

To investigate hypofractionated stereotactic proton therapy of predominantly large intracranial arteriovenous malformations (AVMs) by analyzing retrospectively the results from a cohort of patients.

METHODS AND MATERIALS

Since 1993, a total of 85 patients with vascular lesions have been treated. Of those, 64 patients fulfilled the criteria of having an arteriovenous malformation and sufficient follow-up. The AVMs were grouped by volume: <14 cc (26 patients) and > or =14 cc (38 patients). Treatment was delivered with a fixed horizontal 200 MeV proton beam under stereotactic conditions, using a stereophotogrammetric positioning system. The majority of patients were hypofractionated (2 or 3 fractions), and the proton doses are presented as single-fraction equivalent cobalt Gray equivalent doses (SFEcGyE). The overall mean minimum target volume dose was 17.37 SFEcGyE, ranging from 10.38-22.05 SFEcGyE.

RESULTS

Analysis by volume group showed obliteration in 67% for volumes <14 cc and 43% for volumes > or =14 cc. Grade IV acute complications were observed in 3% of patients. Transient delayed effects were seen in 15 patients (23%), becoming permanent in 3 patients. One patient also developed a cyst 8 years after therapy.

CONCLUSIONS

Stereotactic proton beam therapy applied in a hypofractionated schedule allows for the safe treatment of large AVMs, with acceptable results. It is an alternative to other treatment strategies for large AVMs. AVMs are likely not static entities, but probably undergo vascular remodeling. Factors influencing angiogenesis could play a new role in a form of adjuvant therapy to improve on the radiosurgical results.

A simple method for predicting imaging-based complications following gamma knife surgery for cerebral arteriovenous malformations

Object.The authors studied the relationship between dose planning parameters and complications in the treatment of cerebral arteriovenous malformations (AVMs).

Methods.There were 41 continuous unselected patients. The mean follow-up period was 19 months; the mean age was 28 years; the male/female ratio was 2.2:1.0; the median prescription dose was 25 Gy (range 14–25 Gy); the median prescription isodose was 50%. The median lesion volume was 4.4 cm3. The median lesion coverage was 93%; and the mean conformity index was 1.22.

The authors found no relationship between lesion volume or integral dose and the development of the clinical effects based on the adverse radiation effects (AREs); however, there was a significant relationship between both target volume and integral dose with the development of AREs as well as the severity of the AREs.

Conclusions.The integral dose could be used as a guideline for the prescription dose. Arguments are made for maximizing the prescription dose for the long-term safety of the patient.

A simple method for predicting imaging-based complications following gamma knife surgery for cerebral arteriovenous malformations

Object. The authors studied the relationship between dose planning parameters and complications in the treatment of cerebral arteriovenous malformations (AVMs).

Methods. There were 41 continuous unselected patients. The mean follow-up period was 19 months; the mean age was 28 years; the male/female ratio was 2.2:1.0; the median prescription dose was 25 Gy (range 14–25 Gy); the median prescription isodose was 50%. The median lesion volume was 4.4 cm3. The median lesion coverage was 93%; and the mean conformity index was 1.22.

The authors found no relationship between lesion volume or integral dose and the development of the clinical effects based on the adverse radiation effects (AREs); however, there was a significant relationship between both target volume and integral dose with the development of AREs as well as the severity of the AREs.

Conclusions. The integral dose could be used as a guideline for the prescription dose. Arguments are made for maximizing the prescription dose for the long-term safety of the patient.

Stereotactic irradiation for intracranial arteriovenous malformation using stereotactic radiosurgery or hypofractionated stereotactic radiotherapy

PURPOSE

To investigate the appropriateness of the treatment policy of stereotactic irradiation using both hypofractionated stereotactic radiotherapy (HSRT) and stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs) located in an eloquent region or for large AVMs and using SRS alone for the other AVMs.

METHODS AND MATERIALS

Included in this study were 75 AVMs in 72 patients, with a mean follow-up of 52 months. Of the 75 AVMs, 33 were located in eloquent regions or were >2.5 cm in maximal diameter and were given 25-35 Gy (mean, 32.4 Gy) in four daily fractions at a single isocenter if the patient agreed to prolonged wearing of the stereotactic frame for 5 days. The other 42 AVMs were treated with SRS at a dose of 15-25 Gy (mean, 24.1 Gy) at the isocenter. The 75 AVMs were classified according to the Spetzler-Martin grading system; 21, 23, 28, 2, and 1 AVM were Grade I, II, III, IV, V, and VI, respectively.

RESULTS

The overall actuarial rate of obliteration was 43% (95% confidence interval [CI], 30-56%) at 3 years, 72% (95% CI, 58-86%) at 5 years, and 78% (95% CI, 63-93%) at 6 years. The actuarial obliteration rate at 5 years was 79% for the 42 AVMs <2.0 cm and 66% for the 33 AVMs >2 cm. The 5- and 6-year actuarial obliteration rate was 61% (95% CI, 39-83%) and 71% (95% CI, 47-95%), respectively, after HSRT and 81% (95% CI, 66-96%) and 81% (95% CI, 66-96%), respectively, after SRS; the difference was not statistically significant. Radiation-induced necrosis was observed in 4 subjects in the SRS group and 1 subject in the HSRT group. Cyst formation occurred in 3 patients in the SRS group and no patient in the HSRT group. A permanent symptomatic complication was observed in 3 cases (4.2%), and 1 of the 3 was fatal. All 3 patients were in the SRS group. The annual intracranial hemorrhage rate was 5.5-5.6% for all patients.

CONCLUSION

Our treatment policy using SRS and HSRT was as effective as the policy involving SRS alone. The HSRT schedule was suggested to have a lower frequency of radiation necrosis and cyst formation than the high-dose SRS schedule. The benefit of HSRT compared with lower dose SRS has not yet been determined.

Integration of functional brain information into stereotactic irradiation treatment planning using magnetoencephalography and magnetic resonance axonography

PURPOSE

To minimize the risk of neurologic deficit after stereotactic irradiation, functional brain information was integrated into treatment planning.

METHODS AND MATERIALS

Twenty-one magnetoencephalography and six magnetic resonance axonographic images were made in 20 patients to evaluate the sensorimotor cortex (n = 15 patients, including the corticospinal tract in 6), visual cortex (n = 4), and Wernicke's area (n = 2). One radiation oncologist was asked to formulate a treatment plan first without the functional images and then to modify the plan after seeing them. The pre- and postmodification values were compared for the volume of the functional area receiving > or =15 Gy and the volume of the planning target volume receiving > or =80% of the prescribed dose.

RESULTS

Of the 21 plans, 15 (71%) were modified after seeing the functional images. After modification, the volume receiving > or =15 Gy was significantly reduced compared with the values before modification in those 15 sets of plans (p = 0.03). No statistically significant difference was found in the volume of the planning target volume receiving > or =80% of the prescribed dose (p = 0.99). During follow-up, radiation-induced necrosis at the corticospinal tract caused a minor motor deficit in 1 patient for whom magnetic resonance axonography was not available in the treatment planning. No radiation-induced functional deficit was observed in the other patients.

CONCLUSION

Integration of magnetoencephalography and magnetic resonance axonography in treatment planning has the potential to reduce the risk of radiation-induced functional dysfunction without deterioration of the dose distribution in the target volume.

Hypofractionated Conformal Stereotactic Radiotherapy for Arteriovenous Malformations

OBJECTIVE

Arteriovenous malformations (AVMs) are congenital vascular lesions that are associated with high morbidity and mortality if left untreated. There are several options for treatment, including radiotherapy. Safe and effective single-fraction radiotherapy for patients with large AVMs has been considered difficult.

METHODS

Between December 1986 and June 2001, 36 patients with cerebral AVMs were treated with hypofractionated conformal stereotactic radiotherapy at Umeå University Hospital. Twenty-nine patients have been followed angiographically to date and are reported in this study.

RESULTS

Twenty-four (83%) of 29 patients (mean AVM volume, 11.5 cm3) underwent complete obliteration of their AVMs. The rates of angiographically verified total obliteration at 2 years after treatment were 56% for AVMs 4 to 10 cm3 and 50% for AVMs larger than 10 cm3. The obliteration rate increased considerably with extended follow-up. Five years after treatment, the obliteration rates were 81% for AVMs 4 to 10 cm3 and 70% for AVMs larger than 10 cm3.

CONCLUSION

Hypofractionated conformal stereotactic radiotherapy may be an important alternative to single-fraction radiotherapy in patients with large AVMs or AVMs located in eloquent areas, because it allows the administration of a higher radiation dose than is possible to deliver in single-fraction radiosurgery. With our technique of hypofractionated conformal stereotactic radiotherapy, the rate of obliterating AVMs was comparable to that of single-dose radiosurgery, although the volumes of the irradiated AVMs in our study were larger than those reported previously.

Radiosurgery of cerebral arteriovenous malformations in children: a series of 57 cases

PURPOSE

To evaluate the efficacy and outcome of Linac radiosurgery (RS) as treatment of cerebral arteriovenous malformations (cAVM) in a series of 57 children.

METHODS AND MATERIALS

Between 1984 and 2000, we used Linac radiosurgery to treat 792 patients with cAVM. This series included 57 children (7.2%) under the age of 15 years at the time of RS (range = 7-15 years, median = 12 years). We were able to evaluate 49 of the children (86%) by angiography, 21 boys and 28 girls (sex ratio = 0.75). First symptoms were: hemorrhage, 34 patients (69.4%); seizures, 6 patients (12.5%); headache, 6 patients (12.5%); and progressive neurologic deficit, 1 patient (2.1%). Nidus size ranged from 5 to 50 mm (median = 20 mm). Nidus volume ranged from 0.6 to 16 cc (median = 3.5 cc). Patient distribution according to Spetzler-Martin grade was as follows: Grade 1, n = 5 (11%); Grade 2, n = 18 (35%); Grade 3, n = 21 (40%,); Grade 4, n = 5 (14%); and Grade 5, n = 0%. Twenty-seven patients (55.1%) had other treatment before RS: embolization, n = 14 (31.1%); neurosurgery, n = 9 (20.5%); embolization and neurosurgery, n = 3 (6.1%). RS was performed with the system used for adults. Patients were seated in a Betti armchair. Circular 15 MV X-ray minibeams (6 to 20 mm) were delivered in coronal arcs by a GECGR Saturne 43 Linac. Planification and dosimetry were carried out using the Associated Target Methodology and Dosigray TPS dosimetric systems. The dose at the peripheral isodose (50-70%) ranged from 18 to 28 Gy. Median and mean doses were 25 Gy and 23.8 Gy. Mono-isocentric planification was used in 25 patients (53.2%) and multi-isocentric in 24 patients (2 to 5 isocenters). The overall follow-up ranged from 7 to 172 months (mean 40 months, median 34 months).

RESULTS

The overall rate of obliteration (OR) was 30/49 (61.2%). Mean time to obliteration was 34 months (range = 7 to 172 months). OR varied according to nidus size and volume: OR was 80% for nidus <15 mm, 67% for nidus between 15 and 25 mm, and 42% for nidus >25 mm (p = 0.058). OR was 100% for nidus <1 cc, 73% for nidus between 1 and 4 cc, and 40% for nidus of 4 to 10 cc (p = 0.019). OR according to patient gender was 84.2% for boys and 40% for girls. OR according to minimum dose (Dmin) was 44% for Dmin < 15 Gy (p = 0.01), 89% for D min from 15 to 20 Gy, and 100% for Dmin > 20 Gy (p = 0.01). OR was 62% in nonembolized AVM and 58% in previously embolized AVM (NS). OR according to the number of isocenters was 68.2%, 55.6%, 80%, 50%, and 0% for 1, 2, 3, 4, and 5 isocenters, respectively. After multivariate analysis, only Dmin closely correlated with OR (beta = 0.462; SE = 0.244, p = 0.057). Of the 6 patients with seizures before RS, 5 (80%) were seizure-free without medication after RS. One patient died of pneumonia.

MORBIDITY

Four patients (8.2%) had bleeding after RS at 39, 45, 51, and 59 months. No new neurologic deficit was found during the follow-up period. Twenty-nine patients underwent magnetic resonance imaging. Thirteen patients (44.8%) showed no parenchymal changes. Thirteen patients (44.8%) had Grade 2 changes, that is, T2 hypersignals. Two patients (6.9%) had Grade 3 changes, and 1 patient (3.4%) had Grade 4 "necrosis-like" changes.

CONCLUSION

In our experience, Linac RS has proven to be a safe and effective method to treat cerebral AVM in children <15 years, whether used alone or in association with embolization and/or neurosurgery.

Focal fractionated radiotherapy for intramedullary spinal arteriovenous malformations: 10-year experience

OBJECT

Radiosurgical treatment of spinal arteriovenous malformations (AVMs) is becoming a practical therapeutic option as methodology improves, but no comparative study has yet been published on focal fractionated radiotherapy. The authors report their experience with conventional and hypofractionated radiotherapy for spinal AVM.

METHODS

Candidates for this study were patients who experienced symptoms due to an intramedullary AVM but were ineligible for embolization or surgery. Of 21 patients with spinal AVMs, 10 cases in a 10-year period met this criterion. Angiography and contrast-enhanced computerized tomography scanning were used for treatment planning in all cases. Fractionated radiotherapy was performed using a linear accelerator, extracranial immobilization system, and frequent orthogonal linacographic verification. The starting radiation dose was 32 Gy in two, 36 Gy in three, and 40 Gy in two patients, in a regimen involving 1.8 to 2-Gy daily fractions; this was recently changed to a hypofractionation schedule of 30 Gy (in eight sessions) in one and 20 Gy (in four sessions) in two patients.

RESULTS

The follow-up period ranged from 26 to 124 months (median of 49 months). There were no hemorrhages nor any adverse reactions attributable to irradiation. Of the seven patients who consented to undergo follow-up angiography, the nidus size decreased in five, but complete obliteration did not occur in any patient.

CONCLUSIONS

Because no patient experienced adverse effects, the maximum tolerable radiation dose for the spinal cord associated with an AVM could not be identified, although it presumably is higher than those administered. The lack of rebleeding in patients in whom complete angiographic occlusion was absent suggests that the natural history of spinal AVMs may be less aggressive than previously reported.