Single-dose Radiosurgery Research Articles

Fractionated Stereotactic Radiotherapy Compared to Stereotactic Radiosurgery for Vestibular Schwannoma in Patients with Type 2 Neurofibromatosis

The use of radiotherapy (RT) for the treatment of vestibulocochlear schwannomas is standard in patients with type 2 neurofibromatosis (NF2). In the general population, fractionated RT (FRT) can achieve good results compared to single-dose radiosurgery (SRS). We aimed to assess whether this is true for NF2 patients as well. This retrospective cohort study included 34 patients and 54 lesions treated between 2010 and 2023 in a single university hospital. Thirty-four patient charts were assessed. The median follow-up was 62.6 months (range, 7.1-135.8 months). Lesion size (median larger diameter, 2.5 cm) was correlated with the use of FRT (P > 0.001). Younger age also was correlated with FRT (P= 0.006). Median overall survival and progression-free survival (PFS) were not reached. The overall control rate was 76.5%, and the mean PFS was 49.8 months, compared with . 90.5% and 57.2 months, respectively, for SRS and 66.7% and 44.9 months, respectively, for FRT. There were no differences between the 2 groups in hearing loss, tinnitus, and facial palsy. In the NF2 population, FRT may yield worse control rates than SRS. Whenever possible, it is preferable to not fractionate treatment for these patients. Nevertheless, the FRT results were still good. More and larger prospective trials are warranted.

Radiosurgery for classical trigeminal neuralgia: impact of the shot size on clinical outcome

BackgroundThis study compares the outcome of patients suffering from medically refractory classical trigeminal neuralgia (TN) after treatment with radiosurgery using two different shot sizes (5- and 6-mm).MethodsAll patients included in this open, prospective, non-controlled study were treated in a single institution for TN (95 cases in 93 patients) with LINear ACcelerators (LINAC) single-dose radiosurgery using a 5-mm shot (43 cases) or 6-mm shot (52 cases). The target was positioned on the intracisternal part of the trigeminal nerve.ResultsThe mean Dmax (D0.035) to the brainstem was higher in the 6-mm group: 12.6 vs 21.3 Gy (p < 0.001). Pain relief was significantly better in the 6-mm group: at 12 and 24 months in the 6-mm group the rate of pain-free patients was 90.2 and 87.8%, respectively vs. 73.6 and 73.6% in the 5-mm group (p = 0.045). At 12 and 24 months post-radiosurgical hypoesthesia was more frequent in the 6-mm group: 47.0 and 58% vs.11.3 and 30.8% in the 5-mm group (p = 0.002). To investigate the effect of cone diameter and the dose to the brainstem on outcomes, patients were stratified into three groups: group 1 = 5-mm shot, (all Dmax < 25 Gy, 43 cases), group 2 = 6-mm shot, Dmax < 25 Gy (32 cases), group 3 = 6-mm shot Dmax > 25 Gy (20 cases). At 12 months the rates of hypoesthesia were 11.3, 33.5 and 76.0%, respectively in groups 1, 2 and 3 (p < 0.001) and the rates of recurrence of pain were 26.4, 16.5 and 5%, respectively, (p = 0.11).ConclusionLINAC treatment with a 6-mm shot provided excellent control of pain, but increased the rate of trigeminal nerve dysfunction, especially when the maximum dose to the brainstem was higher than 25 Gy.

Outcome after Radiotherapy for Vestibular Schwannomas (VS)-Differences in Tumor Control, Symptoms and Quality of Life after Radiotherapy with Photon versus Proton Therapy.

Simple SummaryThe standard of care for radiotherapy of symptomatic or progressive vestibular schwannomas (VS) is photon beam single-dose radiosurgery (applying 1 × 12 Gy) or (hypo)fractionated radiotherapy (applying 3 × 6 Gy up to 32 × 1.8 Gy). Only few centers also enable irradiation with protons. Proton therapy offers unique physical properties whereby healthy tissue around the tumor can be protected although a very high dose is applied to the target lesion. In patients with benign brain tumors such as vestibular schwannomas reduction of treatment-related side effects is very important. Few data comparing photon vs. proton beam radiotherapy for patients with VS are available. Thus, a detailed evaluation of differences in tumor control, symptoms and quality of life in patients with VS after photon beam vs. proton beam radiotherapy is needed.Background: To evaluate differences in local tumor control (LC), symptoms and quality of life (QOL) of 261 patients with VS after stereotactic radiosurgery/hypofractionated stereotactic radiotherapy (SRS/HFSRT) vs. fractionated radiotherapy (FRT) vs. fractionated proton therapy (FPT) were studied. Methods: For SRS/HFSRT (n = 149), the median fraction dose applied was 12 Gy. For FRT (n = 87) and FPT (n = 25), the median cumulative doses applied were 57.6 Gy and 54 Gy (RBE), respectively. FRT and FPT used single median doses of 1.8 Gy/Gy (RBE). Median follow-up was 38 months. We investigated dosimetry for organs at risk and analyzed toxicity and QOL by sending out a questionnaire. Results: LC was 99.5% at 12 months after RT with no statistical difference between treatment groups (p = 0.19). LC was significantly lower in NF2 patients (p = 0.004) and in patients with higher tumor extension grade (p = 0.039). The hearing preservation rate was 97% at 12 months after RT with no statistical difference between treatment groups (p = 0.31). Facial and trigeminal nerve affection after RT occurred as mild symptoms with highest toxicity rate in FPT patients. Conclusion: SRS/HFSRT, FRT and FPT for VS show similar overall clinical and functional outcomes. Cranial nerve impairment rates vary, potentially due to selection bias with larger VS in the FRT and FPT group.

Efficacy and comorbidities of hypofractionated and single-dose radiosurgery for vestibular schwannomas: a systematic review and meta-analysis.

Vestibular schwannomas (VS) are tumors of the cerebellopontine angle with significant morbidity, causing hearing loss, tinnitus, and trigeminal and facial nerve compromise. An effective alternative to microsurgical resection is stereotactic radiosurgery (SRS), which can be delivered in either single-fraction (SRS) or hypofractionated stereotactic radiotherapy (hSRT) (3-5 treatments) regimens. It remains unclear which fractionation regimen provides superior outcomes. Ovid MEDLINE, EMBASE, CINAHL, and Cochrane Reviews were searched for studies either comparing hSRT with SRS or focusing on hSRT alone in treating VS. Primary endpoints included tumor control, serviceable hearing, tinnitus, and cranial nerve V and VII symptoms. A random-effects analysis was employed to compare pre- and post-treatment effects (hSRT alone) or SRS and hSRT outcomes (two-arm studies). This analysis included 21 studies focusing on hSRT alone and 13 studies comparing SRS and hSRT. Significant heterogeneity was observed. Overall, when hSRT was analyzed alone, crude tumor control was achieved in 94% (95% CI: 88%, 99%) of 1571 patients. There was no difference between pre- and post-treatment odds ratios (OR) of tinnitus, facial, or trigeminal impairment. Serviceable hearing was diminished following hSRT (OR = 0.60, 95% CI: 0.44, 0.83). Comparison with SRS showed no difference with respect to tumor control, serviceable hearing, trigeminal or facial nerve impairment. hSRT achieved excellent tumor control and, with the exception of serviceable hearing, did not result in worse post-treatment cranial nerve symptomatology. Analysis of comparative studies between hSRT and SRS did not reveal any significant difference in either tumor control or treatment morbidities.

Brain metastases: Single dose radiosurgery versus hypofractionated stereotactic radiotherapy: a retrospective study

Radiosurgery is employed for the treatment of brain metastases. The aim of this study is to evaluate the efficacy and tolerability of single-dose radiosurgery (SRS) compared to hypofractionated stereotactic radiotherapy (hFSRT). Between 2004 and 2018, we analyzed treatments of 97 patients with 135 brain metastases. Fifty-six patients were treated with SRS, and 41 patients were treated with hFSRT. Median dose was 16 Gy (12-20 Gy) for the SRS group and 30 Gy in 5-6 fractions for the hFSRT group. hFSRT was used for larger lesions and lesions located near critical structures. Kaplan-Meier curves were constructed for overall survival (OS) and local control (LC). Median age was 64 years (range, 32-89 years). Median survival was 10 months (1-68 months). With a median follow-up of 10 months, no significant differences in OS between groups were found (P=0.21). LC for all patients was 67%. Local progression-free survival (LPFS) at 6 months and 1 year was 71% and 60% for the SRS group, respectively, and 80% and 69% for the hFSRT group, respectively (P=0.93). Although hFSRT was used for larger lesions and lesions in adverse locations, LPFS was not inferior compared to lesions treated with SRS. We observed acute toxicity grade 1-2 in 25 patients (25.8%). Late complications were observed in 11 patients (11.3%). Acute and late toxicity was similar in the SRS- and hFSRT-treated patients (P=0.63 and P=0.11, respectively). Brain recurrence occurred in 37.5% and 14.6% in the hFSRT and SRS group, respectively (P=0.06). Since patients treated with hFSRT exhibited similar survival and LPFS rates without differences in toxicity compared to those treated with SRS, hFSRT can be beneficial, particularly for patients with brain metastases. Hypofractionated schemes in stereotactic radiosurgery offers treatment alternatives to patients with large lesions or lesions near critical structures.

Assessment of the alpha/beta ratio of the optic pathway to adjust hypofractionated stereotactic radiosurgery regimens for perioptic lesions

Hypofractionation has been recently considered as an alternative to improve stereotactic radiosurgery treatments of lesions close to the optic pathways. To estimate the intrinsic benefit from fractionation versus single-dose radiosurgery for perioptic lesions, the value of the alpha/beta ratio of the optic pathways needs to be known. Based on the linear quadratic (LQ) model, hypofractionation versus single-fraction SRS can be justified in cases where parts of the optic apparatus necessarily receive the full therapeutic peripheral dose, if there is a positive difference between α/s of the lesion and the α/s of the surrounding organs at risk. Furthermore, the knowledge of α/s ratios is required to calculate radiobiological dose parameters, such as the biologically effective dose (BED) and single fraction equivalent dose (SFED), and helps estimate normal tissue complication probability (NTCP), dose constraints, and retreatment doses. Only 3 alpha/beta ratios for the visual system have been published so far, varying between -0.6 and 3.06 Gy. The alpha/beta ratio of the optic pathways was estimated from a fraction equivalent plot based on a meta-analysis of 429 studies published between 2000 and June 2018. We included 15 studies with fraction sizes between 1 and 31, considering the following inclusion criteria: at least one well-documented RION case with detailed dosimetric analysis for the visual system, follow-up period (FUP) of at least 24 months, no tumor progression, no prior radiation. Additionally, we included results from our center on 68 hypofractionated treatments and 161 single-fraction SRS treatments for perioptic lesions. The fraction equivalent (FE) plot method revealed an alpha/beta ratio of the optic pathway of 1.03 Gy, confidence interval [-0.38–1.60]. Well-documented RION cases are rare in the literature; there is still not enough data to distinguish between alpha/beta ratios of the optic chiasm, the nerves, and the tracts. Optimized hypofractionation schedules were calculated for the treatment of meningiomas, chordomas, and brain metastases. Compared to single-fraction SRS, a significant intrinsic benefit from hypofractionation can be achieved, not only for perioptic malignant tumors, but for benign lesions as well, because of the very low alpha/beta ratio of the optic system of 1.03 Gy. An increased single fraction equivalent dose of up to 10% for perioptic meningiomas and of more than 25% for malignant tumors can be reached with optimized hypofractionated stereotactic radiosurgery schedules.

MON-457 One in Five Patients Develop Multiple Hormone Deficiencies Following Radiotherapy for Acromegaly or Cushing's Disease

Aim: To characterise the use of radiotherapy (RTx) for corticotropinomas and somatotropinomas and the long-term clinical outcome for these patients. Methods: All patients with corticotropinomas (CD) and somatotropinomas (AC) who were treated at the Royal Melbourne and the Royal Adelaide Hospitals between 1980 and 2017 were included. Long-term clinical outcome data were obtained via a clinical database (Biogrid) and medical records from the respective hospitals. There were no standard guidelines for recommending RTx during this period at either institution, however, it was considered in the presence of non-operable persistent or relapsed disease. Statistical analyses applied included binary logistic regression, propensity score matching and Fisher’s exact test. Results In total, 171 patients were assessed and 30 patients were excluded due to insufficient data. Of the 141 patients included, 32 patients (23%) received RTx (20 - AC, 12 - CD). The non-RTx group (n=109) consisted of 78 CD and 31 AC patients. Patients with macroadenomas were significantly more likely to receive RTx (OR 5.93, p < 0.05, CI 1.9-18.3). Details regarding the modality of RTx were recorded in 18 of 32 patients: 9 fractionated stereotactic, 7 single dose radiosurgery, 2 deep-radiotherapy. Twenty-nine (21%) patients in this study had evidence of persistent ACTH or GH hyper-secretion post initial surgery and 14 received RTx. Amongst 9 AC patients who required medical therapy for disease control, 6 patients (67%) were able to stop their medication post RTx. The median time for medication cessation was 78 months (IQR 31, 106). None of the patients (n=12, 2 had CD, 10 had AC) in non-RTx group were able to cease medication (p < 0.05). After adjustment for tumour size, number of surgeries and surgery performed within the past 10 years, RTx was independently associated with increasing risk of hypopituitarism (adjusted OR 3.04, CI 1.01-9.17, p = 0.048). Overall, 11 out of 32 patients (34%) in the RTx group developed hypopituitarism. The median time to onset of first hormone deficiency post RTx was 36 months (IQR 7-60). Hypogonadotrophic hypogonadism was the most common deficiency detected (n=7), followed by ACTH (n=5) and TSH deficiency (n=4). Seven patients (22%) developed more than one hormone axis deficiency and 2 patients (6%) developed panhypopituitarism. Conclusion In this study, approximately 1 in 5 (22%) corticotropinoma and somatotropinoma patients developed multiple hormone deficiency post RTx. The median time to develop first hormone deficit was 36 months, confirming that long-term follow-up is required for these patients. Further studies are needed to compare mortality and cost-effectiveness of RTx versus medical therapy for persistent or recurrent corticotropinomas and somatotropinomas.

Surgery versus stereotactic radiotherapy for people with single or solitary brain metastasis.

Brain metastases occur when cancer cells spread from their original site to the brain and are a frequent cause of morbidity and death in people with cancer. They occur in 20% to 40% of people during the course of their disease. Brain metastases are also the most frequent type of brain malignancy. Single and solitary brain metastasis is infrequent and choosing the most appropriate treatment is a clinical challenge. Surgery and stereotactic radiotherapy are two options. For surgery, tumour resection is performed using microsurgical techniques, while in stereotactic radiotherapy, external ionising radiation beams are precisely focused on the brain metastasis. Stereotactic radiotherapy may be given as a single dose, also known as single dose radiosurgery, or in a number of fractions, also known as fractionated stereotactic radiotherapy. There is uncertainty regarding which treatment (surgery or stereotactic radiotherapy) is more effective for people with single or solitary brain metastasis. To assess the effectiveness and safety of surgery versus stereotactic radiotherapy for people with single or solitary brain metastasis. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 3, March 2018), MEDLINE and Embase up to 25 March 2018 for relevant studies. We also searched trials databases, grey literature and handsearched relevant literature. We included randomised controlled trials (RCTs) comparing surgery versus stereotactic radiotherapy, either a single fraction (stereotactic radiosurgery) or multiple fractions (fractionated stereotactic radiotherapy) for treatment of single or solitary brain metastasis. Two review authors screened all references, evaluated the quality of the included studies using the Cochrane tool for assessing risk of bias, and performed data extraction. The primary outcomes were overall survival and adverse events. Secondary outcomes included progression-free survival and quality of life . We analysed overall survival and progression-free survival as hazard ratios (HRs) with 95% confidence intervals (CIs), and analysed adverse events as risk ratios (RRs). For quality of life we used mean difference (MD). Two RCTs including 85 participants met our inclusion criteria. One study included people with single untreated brain metastasis (n = 64), and the other included people with solitary brain metastasis (22 consented to randomisation and 21 were analysed). We identified a third trial reported as completed and pending results this may be included in future updates of this review. The two included studies were prematurely closed due to poor participant accrual. One study compared surgery plus whole brain radiotherapy (WBRT) versus stereotactic radiosurgery alone, and the second study compared surgery plus WBRT versus stereotactic radiosurgery plus WBRT. Meta-analysis was not possible due to clinical heterogeneity between trial interventions. The overall certainty of evidence was low or very low for all outcomes due to high risk of bias and imprecision.We found no difference in overall survival in either of the two comparisons. For the comparison of surgery plus WBRT versus stereotactic radiosurgery alone: HR 0.92, 95% CI 0.48 to 1.77; 64 participants, very low-certainty evidence. We downgraded the certainty of the evidence to very low due to risk of bias and imprecision. For the comparison of surgery plus WBRT versus stereotactic radiosurgery plus WBRT: HR 0.53, 95% CI 0.20 to 1.42; 21 participants, low-certainty evidence. We downgraded the certainty of the evidence to low due to imprecision. Adverse events were reported in both trial groups in the two studies, showing no differences for surgery plus WBRT versus stereotactic radiosurgery alone (RR 0.31, 95% CI 0.07 to 1.44; 64 participants) and for surgery plus WBRT versus stereotactic radiosurgery plus WBRT (RR 0.37, 95% CI 0.05 to 2.98; 21 participants). Most of the adverse events were related to radiation toxicities. We considered the certainty of the evidence from the two comparisons to be very low due to risk of bias and imprecision.There was no difference in progression-free survival in the study comparing surgery plus WBRT versus stereotactic radiosurgery plus WBRT (HR 0.55, 95% CI 0.22 to 1.38; 21 participants, low-certainty evidence). We downgraded the evidence to low certainty due to imprecision. This outcome was not clearly reported for the other comparison. In general, there were no differences in quality of life between the two studies. The study comparing surgery plus WBRT versus stereotactic radiosurgery plus WBRT found no differences after two months using the QLQ-C30 global scale (MD -10.80, 95% CI -44.67 to 23.07; 14 participants, very low-certainty evidence). We downgraded the certainty of evidence to very low due to risk of bias and imprecision. Currently, there is no definitive evidence regarding the effectiveness and safety of surgery versus stereotactic radiotherapy on overall survival, adverse events, progression-free survival and quality of life in people with single or solitary brain metastasis, and benefits must be decided on a case-by-case basis until well powered and designed trials are available. Given the difficulties in participant accrual, an international multicentred approach should be considered for future studies.

Acoustic Neuroma Treated with Stereotactic Radiosurgery: Follow-up of 335 Patients

To determine the clinical and radiologic outcome of patients with acoustic neuroma (AN) treated with linear accelerator (LINAC) or CyberKnife-based stereotactic radiosurgery with respect to tumor control, preservation of serviceable hearing, and toxicity. A retrospective monocentric analysis including all patients who underwent single-fraction LINAC- or CyberKnife-based radiosurgery for AN between 1991 and 2015. Patient data were analyzed in terms of radiologic and clinical tumor control (no further intervention needed), treatment-related complications, preservation of serviceable hearing, and objectified hearing loss using pure tone average levels. We included 335 patients (median age 58.2 years, treated either by LINAC-based [n= 270] or CyberKnife [n= 65] stereotactic radiosurgery). The median tumor volume was 1.1 mL (0.1-23.7 mL). The median radiation dose was 12 Gy (LINAC 12 Gy, 11-20 Gy; CyberKnife 13 Gy, 12-13 Gy) at an isodose level of 71.7% (LINAC 68.3%, 31.9%-86.2%; CyberKnife 80%, 65%-81%). The median follow-up was 30 months (LINAC 43 months, 2-224 months; CyberKnife 13 months, 4-37 months). Clinical tumor control was 98%, 89%, and 88% at 2, 5, and 10 years. The objective actuarial hearing preservation rate was 89%, 80%, and 55% at 1, 2, and 5 years. New symptoms were observed in 11.3% and classified as Common Terminology Criteria for Adverse Events grade 1/2, apart from 4 patients (1.2%), who developed Common Terminology Criteria for Adverse Events grade3. Our study shows that in AN, high tumor control and considerable hearing preservation rates can be achieved by single-dose radiosurgery at low toxicity rates, resulting in a positive impact on long-term clinical outcome.

Updates in outcomes of stereotactic radiation therapy in acromegaly.

Purpose Treatment of acromegaly has undergone important progress in the last 20years mainly due to the development of new medical options and advances in surgical techniques. Pituitary surgery is usually first-line therapy, and medical treatment is indicated for persistent disease, while radiation (RT) is often used as third-line therapy. The benefits of RT (tumor volume control and decreased hormonal secretion) are hampered by the long latency of the effect and the high risk of adverse effects. Stereotactic RT methods have been developed with the aim to provide more precise targeting of the tumor with better control of the radiation dose received by the adjacent brain structures. The purpose of this review is to present the updates in the efficacy and safety of pituitary RT in acromegalic patients, with an emphasis on the new stereotacticradiation techniques. Methods A systematic review was performed using PubMed and articles/abstracts and reviews detailing RT in acromegaly from 2000 to 2016 were included. Results Stereotactic radiosurgery and fractionated stereotactic RT (FSRT) for patients with persistent active acromegaly after surgery and/or during medical therapy provide comparable high rates of tumor control, i.e. stable or decrease in size of the tumor in 93-100% of patients at 5-10 years and endocrinological remission in 40-60% of patients at 5years. Hypofractionated RT is an optimal option for tumors located near the optic structures, due to its lower toxicity for the optic nerves compared to single-dose radiosurgery. The rate of new hypopituitarism varies from 10 to 50% at 5 years and increases with the duration of follow-up. The risk for other radiation-induced complications is usually low (0-5% for new visual deficits, cranial nerves damage or brain radionecrosis and 0-1% for secondary brain tumors) and risk of stroke may be higher in FSRT. Conclusion Although the use of radiotherapy in patients with acromegaly has decreased with advances in medical treatments, it remains an effective treatment option after unsuccessful surgery and/or resistance or unavailability of medical therapy. Long-term studies evaluating secondary morbidity and mortality rate after the new stereotactic techniques are needed, in order to evaluate their potential brain-sparing effect.

P13.11 Outcome evaluation of oligometastatic patients with single, large brain metastases treated with gross total resection (GTR) followed by hypofractionated stereotactic radiosurgery (HSRS) on the tumor bed

AbstractIntroduction:In case of large brain metastases (BMs), treatment option include whole-brain-radiation-therapy (WBRT), surgery, single dose radiosurgery (SRS) or Hypofractionated stereotactic radiosurgery (HSRS). None of these, when given as a single modality are able to obtain and adequate local control rate. Therefore a combined approach, if feasible, is recommended. The aim of this study was to evaluate the benefit of a combined treatment, gross total resection (GTR) followed by adjuvant hypofractionated-stereotactic-radiosurgery (HSRS) on the tumor bed, in oligometastatic patients with single, large BMs.Methods and Materials:From January 2011 to March 2015, 69 patients with single, large BMs, controlled primary tumor and extracranial disease were treated. All patients underwent gross total resection (GTR) followed by HSRS on the tumor bed with a total dose of 30 Gy in 3 daily fractions. Clinical outcome was evaluated by neurological examination and MRI 2 months after RT and then every 3 months. Local progression was defined as radiographic increase of the enhancing abnormality in the treated brain volume and brain distant progression (BDP) as the presence of new brain metastases or leptomeningeal enhancement outside the treated brain volume. Surgical morbidity and radiation-therapy toxicity, local control (LC), brain distant progression (BDP), and overall survival (OS) were evaluated.Results:The median preoperative volume and maximum diameter of BMS was 18.45 cm3 (range 4.06–64.23 cm3) and 3.6 cm (range 2.1–5.4 cm); the median clinical target volume (CTV) was 29 cm3 (range 4.06–203.10 cm3) and the median planning target volume (PTV) was 55.19 cm3 (range 17.18–282.90 cm3). The median follow-up was 24 months (range 4–33 months). The 1-and 2-year LC in site of treatment was 100%; the median, 1-and 2-year BDP was 11.9 months, 19.6% and 33 %; the median, 1-and 2-year OS was 24 months (range 4–33 months), 91.3% and 73%. No severe postoperative morbidity or radiation toxicity occurred in our series.Conclusions:Multimodal approach, surgery followed by HSRS, can be an effective treatment option for selected patients with single, large brain metastases from different solid tumors.Keywords: brain metastases, surgical resection, hypofractionated-stereotactic-radiosurgery

Comparative Analysis of Efficacy and Safety of Multisession Radiosurgery to Single Dose Radiosurgery for Metastatic Brain Tumors.

BackgroundThe purpose of this study is to compare the efficacy and safety of multisession radiosurgery to those of single dose radiosurgery for metastatic brain tumors.MethodsBetween February 2008 and February 2012, 90 patients with 196 metastatic brain tumors were treated with cyberknife radiosurgery, and we reviewed these patients retrospectively. Among them, 57 patients underwent single dose radiosurgery, and 33 patients multisession radiosurgery. Tumors involving the eloquent area and large tumors (>5 cc) were treated with multisession radiosurgery. The median tumor volume and the median treatment dose of single dose radiosurgery were 2.05±0.72 cc and 19.76±1.54 Gy respectively, and in the case of multisession radiosurgery, 5.30±1.70 cc and 29.6±1.70 Gy respectively. The frequency of multisession dose was 3 to 5 times, on average 3.55 times, and 8.91 Gy were given per 1 session on average.ResultsThe overall survival (OS) of multisession radiosurgery was 16.0 months, whereas that of single dose radiosurgery was 11.5 months. The radiologic tumor response rates were 90% in single dose radiosurgery and 95.4% in multisession radiosurgery, respectively. Over 6-month and 1-year periods, the OS rates of single dose radiosurgery were 71.4% and 44.9%, whereas those of multisession radiosurgery were 69.1% and 58.3%, respectively (p=0.83). Toxicities were seen in 18.1% in the single dose radiosurgery group versus 4% in the multisession radiosurgery group. The difference was significant (p<0.05).ConclusionIn this study, the multisession radiosurgery group, despite the location and size constraints, did not differ from the single dose radiosurgery group when comparing the survival and recurrence rates, but complications and toxicity were lower. Thus, multisession radiosurgery is thought to be beneficial for treatment of large tumors and tumors located in the eloquent area.

SP-0002 WHEN IS HYPOFRACTIONATION MANDATORY: THE RADIOBIOLOGIST'S AND CLINICAL POINT OF VIEW?

In the field of radiation oncology, equipments for fractionated stereotactic radiotherapy and single-dose radiosurgery have become increasingly accurate. Out of brain lesions, extracranial stereotactic treatments are more and more frequently considered. New imaging techniques (spect MRI, PET) provide further relevant information to slice images (CT-Scan, MRI). However, the treatment of extracranial lesions needs to take into account organ mobility (tumor and healthy tissue) whilst retaining the ability of stereotactically locating the target. Real time tracking systems allow to keep high conformality to moving and deforming targets. Currently, the most significant developments are in the field of extracranial stereotactic radiotherapy in lung, liver and prostate cancers, together with re-irradiation and oligo metastases. Recent data will be presented.

SP-0001 EXTRA CRANIAL STEREOTACTIC RADIOTHERAPY: FROM TECHNICAL AVAILABILITIES TO CLINICAL OPPORTUNITIES

In the field of radiation oncology, equipments for fractionated stereotactic radiotherapy and single-dose radiosurgery have become increasingly accurate. Out of brain lesions, extracranial stereotactic treatments are more and more frequently considered. New imaging techniques (spect MRI, PET) provide further relevant information to slice images (CT-Scan, MRI). However, the treatment of extracranial lesions needs to take into account organ mobility (tumor and healthy tissue) whilst retaining the ability of stereotactically locating the target. Real time tracking systems allow to keep high conformality to moving and deforming targets. Currently, the most significant developments are in the field of extracranial stereotactic radiotherapy in lung, liver and prostate cancers, together with re-irradiation and oligo metastases. Recent data will be presented.

SU-E-T-628: Dosimetric Evaluation of Proton Arc Therapy for Brain Stereotactic Radiotherapy

Purpose: The aim of this study is to evaluate the dosimetric comparison of proton arc therapy based on dose‐volume histograms (DVH) analysis obtained by brainstereotactic radiotherapy plans. Methods: Treatment plans using dynamic conformal arc therapy and proton arc therapy were generated for 10 patients with brain metastases. Single‐dose radiosurgery(SRS) and fractionated stereotactic radiotherapy (FSRT) were used. The mean doses were 13.5 Gy for the SRS group and 36 Gy in 6 fractions for the FSRT group. The delivered prescription doses to 100% isodose line were chosen on the basis of tumor size and location. The normal tissue complication probability (NTCP) and equivalent uniform dose (EUD) were investigated for each treatment plans. Results: The normal braindose at V5 and V10 was significantly decreased using proton arc therapy compare to dynamic conformal arc therapy. The radiobiological parameters of NTCP and EUD showed a complete tumorcontrol limiting the organs at risk damage. Proton arc therapy shows good target coverage compare to dynamic conformal arc therapy. Conclusions: In this study, we present that proton arc therapy was superior to dynamic conformal arc therapy in stereotactic radiotherapy. The low doseradiotherapy could be the best way for young children.

Treatment of Giant Cerebral Arteriovenous Malformation: Hypofractionated Stereotactic Radiation as the First Stage

Treatment of giant cerebral arteriovenous malformations (AVMs) remains a challenge. To propose hypofractionated stereotactic radiotherapy (HSRT) as a part of staged treatment, and evaluate its effect by analyzing AVM volume changes. From 2001 to 2007, 20 AVMs larger than 5 cm were treated by HSRT and followed up using magnetic resonance imaging. Patients' median age was 34 years (8-61 years). Eleven patients presented with hemorrhage and 9 with seizure. Ten patients had previous embolization and radiosurgery had failed in 4. Thirteen AVMs (65%) were classified as Spetzler-Martin grade V and 7 as grade IV. Median pretreatment volume was 46.84 cm³ (12.51-155.38 cm³). Dose was 25 to 30 Gy in 5 to 6 daily fractions. Median follow-up was 32 months. Median AVM volume decreased to 13.51 cm³ (range, 0.55-147.14 cm³). Residual volume varied from 1.5% to 98%. Volume decreased 44% every year on average. We noted that 6-Gy fractions were more effective (P = .040); embolized AVM tended to respond less (P = .085). After HSRT, we reirradiated 4 AVMs, with 3 amenable to single dose and one with fractions. After HSRT, one patient had an ischemic stroke and one had increased seizure frequency. One AVM bled during follow-up (2.06%/year). No complete obliteration was confirmed. HSRT can turn some giant AVMs manageable for single-dose radiosurgery. Six-Gray fractions were better than 5-Gy and routine embolization seemed unhelpful. There was no increase in bleeding risk with this approach. Future studies with longer follow-up are necessary to confirm our observation.

Single-Dose Versus Fractionated Stereotactic Radiotherapy for Brain Metastases

To evaluate the efficacy of stereotactic radiotherapy in patients with brain metastases by comparing two different treatment regimens, single-dose radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT). Between November 2003 and December 2008, 98 patients with brain metastases were included. Fifty-eight patients were treated with SRS, and forty were treated with FSRT. Fractionated stereotactic radiotherapy was used for large lesions or lesions located near critical structures. The median doses were 20 Gy for the SRS group and 36 Gy in 6 fractions for the FSRT group. With a median follow-up period of 7 months, the median survival was 7 months for all patients, with a median of 6 months for the SRS group and 8 months for the FSRT group (p = 0.89). Local progression-free survival (LPFS) rates at 6 months and 1 year were 81% and 71%, respectively, for the SRS group and 97% and 69%, respectively, for the FSRT group (p = 0.31). Despite the fact that FSRT was used for large lesions and lesions in adverse locations, LPFS was not inferior to SRS. Toxicity was more frequently observed in the SRS group than in the FSRT group (17% vs. 5%, p = 0.05). Because patients treated with FSRT exhibited similar survival times and LPFS rates with a lower risk of toxicity in comparison to those treated with SRS, despite the fact that FSRT was used for large lesions and lesions in adverse locations, we find that FSRT can particularly be beneficial for patients with large lesions or lesions located near critical structures. Further investigation is warranted to determine the optimal dose/fractionation.

Differences in Clinical Results After LINAC-Based Single-Dose Radiosurgery Versus Fractionated Stereotactic Radiotherapy for Patients With Vestibular Schwannomas

To evaluate the outcomes of patients with vestibular schwannoma (VS) treated with fractionated stereotactic radiotherapy (FSRT) vs. those treated with stereotactic radiosurgery (SRS). This study is based on an analysis of 200 patients with 202 VSs treated with FSRT (n = 172) or SRS (n = 30). Patients with tumor progression and/or progression of clinical symptoms were selected for treatment. In 165 out of 202 VSs (82%), RT was performed as the primary treatment for VS, and for 37 VSs (18%), RT was conducted for tumor progression after neurosurgical intervention. For patients receiving FSRT, a median total dose of 57.6 Gy was prescribed, with a median fractionation of 5 x 1.8 Gy per week. For patients who underwent SRS, a median single dose of 13 Gy was prescribed to the 80% isodose. FSRT and SRS were well tolerated. Median follow-up time was 75 months. Local control was not statistically different for both groups. The probability of maintaining the pretreatment hearing level after SRS with doses of < or =13 Gy was comparable to that of FSRT. The radiation dose for the SRS group (< or =13 Gy vs. >13 Gy) significantly influenced hearing preservation rates (p = 0.03). In the group of patients treated with SRS doses of < or =13 Gy, cranial nerve toxicity was comparable to that of the FSRT group. FSRT and SRS are both safe and effective alternatives for the treatment of VS. Local control rates are comparable in both groups. SRS with doses of < or =13 Gy is a safe alternative to FSRT. While FSRT can be applied safely for the treatment of VSs of all sizes, SRS should be reserved for smaller lesions.

Salvage reirradiation for recurrent glioblastoma with radiosurgery: radiographic response and improved survival

To determine the radiographic and clinical efficacy of stereotactic single dose radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) as salvage therapy for glioblastoma (GBM) at recurrence. Thirty-six patients with pathologically proven recurrent GBM were treated with salvage reirradiation by either SRS or FSRT between March of 2001 and August of 2006. Thirty-one patients had an initial diagnosis of GBM. Five patients had a malignant transformation. All patients had received radiotherapy with a dose of 50-60 Gy, a median 13.6 months prior to reirradiation (range: 0.8-119 months). At the time of recurrence, 26 patients were treated with SRS with a median dose of 18 Gy (range: 12-20 Gy). FSRT was performed in ten patients with a dose of 36 Gy in six fractions, twice weekly. Follow-up included MRI and clinical examination every 2 months. Median survival time after SRS was 8.5 months, compared to 7.4 months after FSRT (P = 0.81). Of 26 patients treated with SRS, radiographic tumor response or stable disease was observed in eight (35%) patients and tumor progression was seen in 18 (65%) patients. Of 10 patients treated by FSRT, radiographic tumor response or stable disease was observed in four (40%) patients and tumor progression was observed in four (40%) patients (two lost to follow-up). Patients who responded to treatment had statistically improved survival compared to non-responders, with median survival of 15.8 vs. 7.3 months (P < 0.05). Salvage reirradiation with SRS or FSRT for recurrent GBM results in radiographic response in a proportion of patients. Survival was significantly improved among patients who either responded or had stable disease after salvage reirradiation, compared to non-responders. Further study is warranted to investigate the method and time of reirradiation for recurrent GBM.

Pain Control by Image-Guided Radiosurgery for Solitary Spinal Metastasis

Precision and accuracy of image-guided spinal radiosurgery has been previously demonstrated. This study was carried out to determine the clinical efficacy of spine radiosurgery for the treatment of solitary spinal metastases with or without cord compression. A total of 49 patients with 61 separate spinal metastases were treated with radiosurgery. All patients had pathologically proven primary cancers and had either synchronous or metachronous metastasis to the spine. The majority of the patients presented with back pain. All patients received single-dose radiosurgery to the involved spine only. The radiosurgery dose ranged from 10 to 16 Gy. The primary endpoint was pain control, but outcomes in neurological status and radiological tumor control also were assessed. The median time to pain relief was 14 days and the earliest time of pain relief was within 24 hours. Complete pain relief was achieved in 46%, partial relief in 18.9%, and stable symptoms in 16.2%. Relapse of pain at the treated spinal segment was 6.9%. Median duration of pain relief at the treated spine was 13.3 months. Overall pain control rate for one year was 84%. This experience demonstrates that spinal radiosurgery can achieve rapid and durable pain relief. Single-dose radiosurgery has a potential to be a viable treatment option for single spinal metastasis.