International Journal of Radiation Oncology � Biology � PhysicsS38

Results: Freedom from BNI III-IV failure at 1, 2, and 5 years (yrs) was

73.3%, 64.5%, and 41.8%, respectively. Freedom from salvage surgery at

1, 2, and 5 yrs was 82%, 72%, and 50%, respectively. Freedom from BNI

III-IV failure at 1, 2, and 5 yrs was 68%, 47%, and 25% for type II TN (log

rank p < 0.001), and 46%, 41%, and 17% for atypical facial pain (log-rank

p < 0.001). A total of 42% of patients developed post-GRS trigeminal

dysfunction. Multivariate analysis revealed that development of post-

GKRS numbness (HR Z 0.47, p Z < 0.0001), and improved post-GRS

BNI score at 6 mos (HR Z 0.009, p Z < 0.0001) were the dominant

factors predictive of a durable response. For each increasing level of re-

ported pain relief, we observed a corresponding decrease in the hazard for

TTR. Non-Burchiel type I TN (HR Z 1.64, p Z 0.019) predicted for

decreased durability of response. A logistic regression analysis was per-

formed for the dominant factors predictive of GRS complications showed

that increasing DREZ dose (OR 1.024, p Z 0.01) and the presence of

paroxysmal sharp pain prior to treatment (OR 1.93, p Z 0.01) were

associated with an increased risk of post-GRS trigeminal dysfunction.

Conclusions: The durability of GRS for TN depends predominantly on the

Burchiel pain type at presentation, post treatment BNI score, and the

development of facial numbness after GRS.

Author Disclosure: J. Lucas: None. K. Marshall: None. D. Bourland:

None. E. Shaw: None. T. Ellis: None. S. Tatter: None. M.D. Chan: None.

93Single Fraction Proton Beam Stereotactic Radiosurgery (PSRS) forInoperable Cerebral Arteriovenous Malformations (AVMs)J.A. Hattangadi,1 P. Chapman,2 D. Kim,2 M. Bussiere,2 A. Niemierko,2

A. Rowell,2 J. Daartz,2 C. Ogilvy,2 J. Loeffler,2 and H. Shih2; 1Harvard

Radiation Oncology Program, Boston, MA, 2Massachusetts General

Hospital, Boston, MA

Purpose/Objective(s): To evaluate AVM obliteration and post-treatment

hemorrhage rates in a large single-institution experience of patients with

inoperable cerebral AVMs who underwent PSRS.

Materials/Methods: From 1991-2010, 242 consecutive patients with 254

cerebral AVMs received single fraction PSRS. Median age of the cohort

was 39 years, 55% presented with neurologic deficits, and 22% had prior

unsuccessful surgery or embolization. Twenty-three percent of AVMs were

in high-risk areas (basal ganglia, thalamus, or brainstem). Median AVM

target volume was 3.5 cc (range, 0.1-28.1) and the most common

prescription dose was 15 Gray radiobiologic equivalent, prescribed to the

90% isodose. Univariable (UVA) and multivariable analyses (MVA) were

performed to assess factors associated with obliteration and hemorrhage.

Results: Median follow-up was 33 months (range, 12-195 months).

Median time to total obliteration was 27 months (range, 2-174 months) and

the 5- and 10-year cumulative incidence of total obliteration was 68% and

88%, respectively. On UVA, smaller target volume (hazard ratio [HR] 0.89,

95% confidence interval [CI] 0.85-0.93, p < 0.0001), smaller treatment

volume (HR Z 0.93, 95% CI 0.90-0.96, p < 0.0001), and higher

prescription dose (HR Z 1.16, 95% CI 1.07-1.26, p Z 0.001) were

associated with total obliteration. On MVA, high risk location (adjusted

HR Z [AHR] 0.46, 95% CI 0.29-0.75, p Z 0.002) and smaller target

volume (AHR Z 0.86, 95% CI 0.81-0.92, p < 0.0001) were associated

with total obliteration. There were 9 cases of post-treatment hemorrhage

and cumulative incidence at 5 years was 7%. All hemorrhagic events

occurred among patients with less than total obliteration, and three of these

events were fatal. Larger target volume (HR Z 1.07, 95% CI 1.01-1.15,

p Z 0.037) and larger treatment volume (HR Z 1.05, 95% CI 1.01-1.10,

p Z 0.024) were associated with increased risk of hemorrhage. The most

common complication was seizure, controlled with medications, both

acutely (7%) and long-term (9.1%).

Conclusions: The current series is the largest modern series of PSRS for

cerebral AVMs. We show that cerebral AVMs can be safely treated with

PSRS with a high rate of success and minimal morbidity. Post-treatment

hemorrhage remains a small but potentially fatal risk among patients who

have not responded to treatment.

Author Disclosure: J.A. Hattangadi: None. P. Chapman: None. D. Kim:

None. M. Bussiere: None. A. Niemierko: None. A. Rowell: None. J.

Daartz: None. C. Ogilvy: None. J. Loeffler: None. H. Shih: None.

94Technique for Using Dynamic CT Angiography (dCTA) for FramelessStereotactic Radiosurgical (SRS) Planning of IntracranialArteriovenous Malformations (AVM)A. Haridass, S. Chakraborty, R. Chatelain, J. Szanto, C. Lum, S. Malone,

and J. Sinclair; The Ottawa Hospital, Ottawa, ON, Canada

Purpose/Objective(s): SRS is a safe and effective means of treating

small, deep seated brain AVMs. Selective catheter angiograms continue to

be the gold standard for localizing the AVM nidus but their 2D images

makes integration into 3D radiation treatment planning(TP) difficult.

Rotational 3D DSA has poor spatial resolution than CT angiogram. The

new dynamic CTA(dCTA) is capable of imaging the whole brain with high

spatial and temporal resolution. It makes it possible to choose a volume of

brain with optimum level of contrast showing only the nidus without

significant enhancement of the adjacent draining veins. The aim of our

research is to define the utility of dCTA in determining the 3D contour of

the nidus for accurate SRS targeting. We describe a technique for inte-

gration of dCTA into SRS TP for intracranial AVMs.

Materials/Methods: The patients were scanned on a 320 slice CT scanner

that has 16 cm of coverage to image the entire brain in a single rotation.

For dCTA, following a timing bolus, the scan sequence and injection of the

contrast (@ 5 mL/s, 35 mL) were started. At 7 seconds, a ‘mask’ non-

contrast scan (300 mA 80 KV) was obtained to enable digital subtraction

from the angiographic datasets. The angiographic acquisition was started

1s before the contrast arrival at the skull base as determined by the timing

bolus. Dynamic continuous acquisition (100 mA 80 KV, 1/sec) of whole

brain images were obtained for 16 seconds, allowing imaging to start with

no contrast, continuing to peak arterial enhancement and end with the

venous return phase. A complete data volume was reconstructed every 0.5

seconds (temporal resolution of 2 images/sec). The spatial resolution of

each slice was 512 x 512 pixels with a 0.5 mm thickness. The data volumes

are processed to create a digitally subtracted dCTA. The datasets were

reviewed by the Neuroradiologist, Neurosurgeon and Radiation Oncologist

to determine the temporal phase (T + 0s to T + 16s) of imaging best

demonstrating the AVM nidus without contrast highlighting the draining

veins of the AVM. This volume was then reformatted to the TP specifi-

cations (1 x 1 x 1 mm voxels) and the DICOM data was imported to the TP

system for coregistration with the MRI to contour the nidus and treated to

a dose of 12-20 Gy. This method adds more certainty in differentiating the

nidus from the draining venous structures than using standard CTA that

gives a snapshot view of the AVM.

Results: Between October 2010 and November 2011, 9 patients were

treated for inoperable small AVMs on a robotic radiosurgery system.

Conclusions: We have described a technique for use of dynamic CT

Angiograms in SRS treatment planning for AVMs. Further research

regarding its utility in supplementing catheter angiograms in this setting is

ongoing.

Author Disclosure: A. Haridass: None. S. Chakraborty: None. R. Chate-

lain: None. J. Szanto: None. C. Lum: None. S. Malone: None. J. Sinclair:

None.

95Long-term Outcomes of Low-dose Fractionated StereotacticRadiation Therapy of 46.8 Gy for Acoustic SchwannomasC.E. Champ, S. Mayekar, M.V. Mishra, D.W. Andrews, M. Werner-Wasik,

K. Chapman, V. Gunn, H. Liu, J.J. Evans, and W. Shi; Thomas Jefferson

University Hospital, Philadelphia, PA

Purpose/Objective(s): Fractionated Stereotactic Radiation therapy

(FSRT) is a noninvasive treatment for acoustic schwannomas (AS). An

initial report from our institution has shown that a lower radiation treat-

ment dose of 46.8 Gy results in improved hearing preservation when

Volume 84 � Number 3S � Supplement 2012 Oral Scientific Sessions S39

compared to 50.4 Gy. In this retrospective study, we report the long term

tumor control rate, symptomatic outcome, and hearing preservation rate in

patients treated with lower dose FSRT.

Materials/Methods: After obtaining IRB approval, we analyzed all

patients (pts) diagnosed with AS and treated at our institution from 2002 to

2011. All pts received 46.8 Gy in 1.8 Gy fractions. After treatment, follow-

up audiogram and MRI were performed in �1-year intervals. Tumor

control was defined as � 1mm increase in tumor size in any dimension on

multiple MRIs to allow for operator-dependent differences. Tumor control

and hearing preservation were calculated by the Kaplan-Meier (KM)

method. Analysis of hearing preservation, defined as Gardner-Robertson

value �2, excluded pts with prior surgery, no initial documented hearing

test, or non-serviceable hearing. Non-hearing related symptoms were

defined by Common Terminology Criteria for Adverse Events (CTCAE)

version 4. Symptomatic control was evaluated using descriptive statistics.

Results: In total, 127 pts were analyzed. At a median follow-up time of 35

months (range, 4-108 months) tumor control was achieved in 95% of pts (n

Z 121/127). Tumor control at 3- and 5-years was 100 and 93%, respec-

tively. For hearing evaluation, 77 pts had a median audiogram follow-up of

28 months (range, 3-90 months). Functional hearing preservation at 3- and

5-years was 83.5 and 64.8%, respectively. Median time to functional

hearing loss was 87.5 months. Crude pure tone average at last follow-up

was decreased by an average of 12 decibels (db) in all pts and 19 db in pts

with over 2 years of follow-up (n Z 42). At last follow-up, 18% (n Z 23)

of pts experienced ataxia, vertigo, paresthesia, or pain symptom

improvement, 8.7% (n Z 11) had worsening of symptoms, and 81% had

no change in symptoms. Of pts with worsening symptoms, 2.4% (n Z 3)

experienced cranial nerve dysfunction of the trigeminal or facial nerve (1

Z CTCAE grade 1 and 2Z CTCAE grade 2 toxicity). There was no grade

3 or higher toxicities.

Conclusions: Lower dose FSRT to 46.8 Gy for AS provides excellent local

control and functional hearing preservation rates with limited toxicity. The

local control rate is similar to reported outcomes for pts receiving radio-

surgery. The functional hearing preservation rate appears to compare

favorable to pts who received radiosurgery. Future attempts of dose

reduction to 45 Gy may potentially increase hearing preservation and

warrant prospective evaluation.

Author Disclosure: C.E. Champ: None. S. Mayekar: None. M.V. Mishra:

None. D.W. Andrews: None. M. Werner-Wasik: None. K. Chapman: None.

V. Gunn: None. H. Liu: None. J.J. Evans: None. W. Shi: None.

96The Role of Proton Radiation Therapy for Multiple MeningiomasE.D. Tanzler, D. Yeung, Z. Li, Z. Su, W.M. Mendenhall, and R. Malyapa;

University of Florida Proton Therapy Institute, Jacksonville, FL

Purpose/Objective(s): To compare the dose delivered by proton radiation

therapy to the dose delivered by intensity modulated radiation therapy

(IMRT) for patients presenting with multiple intracranial meningiomas.

Materials/Methods: We compared proton radiation therapy and non-

coplanar IMRT plans for 4 patients who presented with multiple simul-

taneous meningiomas. We required that each plan deliver the prescription

dose (50.4 Gy at 1.8 Gy per fraction for WHO Grade I meningiomas and

61.2 Gy at 1.8 Gy per fraction for WHO Grade II meningiomas) to 95% of

the planning target volume. We compared the dose to 0.1 cc of the critical

normal tissue structures (brainstem, optic nerves, and optic chiasm), the

mean dose to the brain, the V50, V20, and V30 of the brain, and the

integral dose received by each patient.

Results: The normal-tissue dose constraints were met for each structure

using either IMRT or proton radiation therapy. With the IMRT plans, the

integral dose received by each of the 4 patients was 62.3 J, 94.5 J, 66.2 J,

and 40.2 J. The integral dose with the proton plan was significantly

reduced; the integral dose for each patient was 22.4 J, 26.6 J, 22.1 J, and

16.2 J. The mean dose to the brain delivered by the IMRT plans for each of

the 4 patients was 26.92 Gy, 32.71 Gy, 17.58 Gy, and 18.75 Gy. The mean

dose delivered to the brain using the proton plans for each of the 4 patients

was 12.76 Gy, 8.96 Gy, 11.64 Gy, and 8.92 Gy. In addition, the V20, V30,

and V50 of the brain were either the same or better when comparing the

proton plans to the IMRT plans.

Conclusions: Compared to IMRT, proton radiation therapy allows for

a significantly lower dose to the brain and optic structures when treating

multiple brain lesions because of the proton’s Bragg peak. More specifi-

cally, with proton therapy, the integral dose to the brain and optic struc-

tures is reduced as is the mean dose to the brain, allowing for fewer

toxicities and the safer treatment of patients with multiple meningiomas.

Author Disclosure: E.D. Tanzler: None. D. Yeung: None. Z. Li: None. Z.

Su: None. W.M. Mendenhall: None. R. Malyapa: None.

97Dynamic Contrast Enhanced Magnetic Resonance Imaging-basedAssessment of Tumor Response to High-dose Spine StereotacticRadiosurgeryY. Yamada, S. Karimi, P. Kyung, E. Lis, J. Lyo, M. Bilsky, B. Cox,

and A. Holodny; Memorial Sloan-Kettering Cancer Center, New York, NY

Purpose/Objective(s): Endothelial damage is thought to be an important

mechanism of tumor response to high dose stereotactic radiosurgery

(SRS). Dynamic contrast enhanced MRI (DCE) was utilized to assess the

changes in blood flow in tumors over time that achieved long term control

as well as tumors that eventually failed spine SRS.

Materials/Methods: Nineteen spine metastases (19 locally controlled, 2

with local recurrence) treated with SRS (600 cGy x 5 [N Z 4], 900 cGy x

3 [NZ 1], 2,400 cGy x 1 [NZ 14]) who underwent pretreatment and post

treatment T1 DCE studies were identified. Plasma volume (Vp), perme-

ability (Ktrans), area under the curve (AUC), and peak enhancement (PE)

perfusion parameters were assessed. Images were acquired on 1.5 Tesla

scanner with an 8 channel spinal coil. A two-compartment model (intra-

vascular and extra vascular, extracellular space) was assumed.

Results: Median follow-up was 17 months (range, 8-48 months). Reduced

Vp was the best predictor of response. In lesions that achieved local

control, mean Vp was -66% (range, -21% to -99%), whereas the lesions

that ultimately recurred were found to have marked increases in Vp

(+145% and +207%). The differences in between Vp for locally controlled

and local failures was highly significant (p > 0.0001) and the calculated

rate of a false positive was 9.38 x 10�9 and a false negative rate of 0.055.

The differences in Ktrans, AUC, and PE were not significantly different

between locally controlled and locally recurrent lesions.

Conclusions: Vp was found to be highly significantly different in lesions

that were ultimately locally controlled compared to those that locally

progressed. DCE imaging can suggest treatment response even when

conventional MRI studies demonstrate minimal or no regression after

successful spine SRS. DCE also adds clinical credence to animal experi-

mental data that suggest endothelial effects are an important mechanism of

tumor response to very high dose single fraction radiation. Further work

may also prove DCE as an important predictive tool of treatment response.

AuthorDisclosure: Y. Yamada: F. Honoraria; ContinuingMedical Education

Institute. G. Consultant; Varian medical systems. Q. Leadership; American

Brachytherapy Society. S. Karimi: None. P. Kyung: None. E. Lis: None. J.

Lyo: None. M. Bilsky: None. B. Cox: None. A. Holodny: None.

98The Risk of Vertebral Compression Fracture (VCF) PostspineStereotactic Body Radiation Therapy (SBRT) and Evaluation of theSpinal Instability Neoplastic Score (SINS)A. Al-Omair,1 M. da Cunha,2 E. Atenafu,1 D. Letourneau,1 R. Korol,3,4 E. Yu,1

L. Masucci,1 L. Da Costa,4 M. Fehlings,5 and A. Sahgal6; 1Princess Margaret

Hospital, Toronto, ON, Canada, 2Sunnybrook Health Sciences Centre,

University of Toronto, Toronto, ON, Canada, 3Sunnybrook Health Sciences

Centre, Toronto, ON, Canada, 4Sunnybrook Health Sciences Centre, University

of Toronto, Toronto, ON, Canada, 5Toronto Western Hospital, University of

Toronto, Toronto, ON, Canada, 6Princess Margaret Hospital and, Sunnybrook

Health Sciences Centre, University of Toronto, Toronto, ON, Canada

Purpose/Objective(s): Vertebral compression fracture (VCF) is increas-

ingly being observed post-spine SBRT. A recent SINS classification was