S104 I. J. Radiation Oncology d Biology d Physics Volume 69, Number 3, Supplement, 2007

Materials/Methods: Adult patients with and without brain metastases (n = 44) were prospectively evaluated with serial cognitivetesting, before (T0), after starting (T1), at the end (T2), and 6–8 weeks (T3) after the completion of radiotherapy. The neuropsy-chological assessment consisted of the Auditory Verbal Learning Test (AVLT), the Medical College of Georgia (MCG) ComplexFigures, and a highly sensitive, computerized test battery developed for the assessment of attentional deficits in patients with ce-rebral lesions in the German-speaking part (Test for Attentional Performance, TAP). Only standardized neuropsychological instru-ments (all with published normative data) were used. Premorbid intellectual functioning, emotional distress, Karnofskyperformance status, and chemotherapy status were controlled.

Results: Data were obtained from 1) small cell lung cancer patients treated with prophylactic cranial irradiation (PCI), 2) patientswith brain metastases treated with therapeutic cranial irradiation (TCI), and 3) breast cancer patients treated with non-CNS-RT.Group information is presented in the table (memory results are given in percentile scores). At baseline, PCI patients performedworse on almost all test scores, although these patients had a higher Karnofsky score and no brain metastases on imaging studies.Univariate analyses of covariance with baseline score as covariate showed significant main effects of both pretreatment cognitivestatus, and to a lesser extent, WBRT. At T1, the TCI patients had lower verbal memory scores than the PCI and control groups(F = 3.8; p = 0.031). At T3, both the TCI and PCI patients had lower verbal memory scores compared to the control group(F = 6.3; p = 0.006).

Conclusions: Our data support the hypothesis that WBRT is one cause of cognitive dysfunction immediately after the beginning ofRT in patients with brain metastases. In addition, our data show that verbal memory 6–8 weeks after the end of WBRT is influencedby both pretreatment cognitive status, and WBRT. Because WBRT is far less relevant than pretreatment cognitive status, we thinkthat patients should not avoid palliative or prophylactic WBRT due to fear of potential neurocognitive side effects.

Author Disclosure: G. Welzel, None; K. Fleckenstein, None; S.K. Mai, None; B. Hermann, None; U. Kraus-Tiefenbacher, None;J. Schaefer, None; F. Wenz, None.

186 Spinal Cord Astrocytomas: Treatment Considerations

K. J. Minehan, P. D. Brown, B. W. Scheithauer, M. P. Wright, W. E. Krauss

Mayo Clinic, Rochester, MN

Purpose/Objective(s): To identify prognostic factors and to determine the impact of surgery and radiotherapy upon outcome ofspinal cord astrocytomas.

Patients/Methods: The study consists of 136 consecutively operated patients with spinal cord astrocytoma treated at Mayo Clinicbetween 1962 and 2005. Extent of surgery included incisional biopsy (59%), subtotal resection (25%), and gross total resection(16%). Postoperative radiotherapy was delivered in 75% of cases.

Results: The 136 cases included 69 pilocytic and 67 infiltrative astrocytomas with a median follow-up of 8.2 years (range37.6–0.08 years). Patients with pilocytic tumors had a significantly better median overall survival as compared to those infiltrativeastrocytomas (39.9 vs 1.85 years; p = \0.0001). For both pilocytic and infiltrative astrocytomas, patients who underwent moreextensive resections had a worse outcome (pilocytic 39.7 vs 18.1 years, p = .066; infiltrative 42 vs 25 months, p = 0.137). Post-operative radiotherapy did not result in a significant survival benefit for pilocytic tumors but did for the infiltrative astrocytomas(pilocytic 39.8 vs 18.1 years; p = 0.329; infiltrative 24 vs 3 months; p = .006). Multivariate analyses found pilocytic histology,diagnosis in the MRI era, longer symptom duration, younger age, minimal extent of surgery, post-operative radiotherapy to be pre-dictive of a better outcome.

Conclusions: Histology is the most important prognostic variable affecting spinal cord astrocytomas. Surgical resection exceedingbiopsy results in less favorable survival and thus remains an unproven treatment. Postoperative radiation therapy significantlyimproves survival of patients with infiltrative fibrillary astrocytomas but not for those with pilocytic tumors.

Author Disclosure: K.J. Minehan, None; P.D. Brown, None; B.W. Scheithauer, None; M.P. Wright, None; W.E. Krauss, None.

187 Radiosurgery for Spinal Cord Arteriovenous Malformations

S. G. Soltys, J. R. Adler, J. D. Borchers, S. D. Chang, I. C. Gibbs

Stanford University, Stanford, CA

Purpose/Objective(s): Intramedullary arteriovenous malformations (AVMs), given their intrinsic location within the spinal cordand involvement of normal spinal cord vasculature, are often not amenable to endovascular or microsurgical therapy. Untreated,these lesions can lead to significant neurologic morbidity due to hemorrhage or from chronic ischemia due to vascular shunting.Based on the success of radiosurgical obliteration of intra-cranial AVMs, the use of radiosurgery to treat selected spinal cord AVMswas investigated. We retrospectively analyze and present updated results on our preliminary experience with this technique.

Materials/Methods: From 2000–2006, 24 patients with unresectable intramedullary spinal cord AVMs were treated by image-guided stereotactic radiosurgery (SRS). The presenting symptoms were hemorrhage in 14 patients (58%) or progressive myelop-athy in 10 patients (42%). Treatment was delivered in one to four sessions (median two) to a mean marginal dose of 20 Gy to a meantumor volume of 2.8 cm3 (range 0.3–15.0 cm3). Prescribed dose has been gradually escalated over the course of the study; the mostcommon schedules were 21 Gy in 3 sessions (n = 9), 20 Gy in 2 sessions (n = 11), with single session treatments in selected patients(n = 3). Mean maximal dose was 25.8 Gy (range 22.5–30.0 Gy). Patients were followed with annual MRIs, with angiographyrepeated at 3 years.

Results: Mean clinical follow-up was 34.0 months (range 3.5–86.4 months), with mean radiologic follow-up of 29.1 months(range 5.7–83.9 months). Serial MRIs displayed reduction in nidus size in all AVMs. Of 8 patients with post-treatment spinal an-giography, 3 have displayed complete obliteration. 2 patients with absence of flow voids on MRI await angiography to confirmnidus obliteration. No patients have experienced a repeat bleeding episode following SRS. Calculation of the Biologically EffectiveDose (BED), with an alpha/beta ratio of 2, yielded a mean single session equivalent dose of 14 Gy (range 11.4–18.0 Gy) and a mean2 Gy-per-day fractionated equivalent dose of 56.6 Gy (range 38.1–90.0 Gy). Only one patient (4%), with a history of pre-SRS

Proceedings of the 49th Annual ASTRO Meeting S105

myelopathy, had clinical deterioration at 9 months post-SRS; no treatment parameters based on spinal cord dose volume histogramanalysis correlated with this probable case of radiation myelopathy.

Conclusions: With modest follow-up, SRS for otherwise untreatable spinal cord AVMs appears to be effective, with no re-bleed-ing episodes as well as the potential for complete nidus obliteration. Stereotactic irradiation of small volumes of the spinal cordbeyond its traditionally cited tolerance appears to be safe, although longer surveillance is needed given the latency of radiationmyelopathy.

Author Disclosure: S.G. Soltys, None; J.R. Adler, Shareholder–Accuray, E. Ownership Interest; J.D. Borchers, None; S.D. Chang,None; I.C. Gibbs, Clincial Advisory Board–Accuray, F. Consultant/Advisory Board.

188 Risk Factors for Inter-fraction Tissue Motion during Cranial Radiation Therapy

T. P. Jenkins, H. Gay, C. Sibata, R. Allison

The Brody School of Medicine, ECU, Greenville, NC

Purpose/Objective(s): Inter-fraction tissue motion in the brain has been observed at our institution during image-guided radiationtherapy (IGRT). This motion, sometimes as much as two centimeters, was associated with post-surgical healing, tumor growth, tu-mor destruction, brain edema, hydrocephalus, and reabsorption of pneumocephalus. Patients with tissue motion require special con-sideration to ensure that tumor volumes and critical structures are targeted accurately. The goal of this study was to determine riskfactors associated with cranial tissue motion so that future patients could receive followup imaging during therapy when appropriate.

Materials/Methods: Two CT scans, one showing showing baseline anatomy and the second captured several weeks later, were ret-rospectively collected for each of the 63 patients previously treated with cranial IGRT at our institution. The baseline scans were theimages used for treatment planning and the followup scans were images acquired during IGRT using an in-room CT scanner on thelast day of therapy. The baseline and followup CT for each patient were fused based on bony anatomy, each fused slice was inspectedfor soft-tissue changes, and the maximum displacement of cranial tissue was recorded. Examples of anatomy visible in the CT data weresurgical cavities, surrounding normal brain tissue, areas of pneumocephalus, and gross tumor volumes (sometimes visible even withoutcontrast). Ventricle displacement was also occasionally used as a surrogate measurement for changes in the adjacent tissue. Statisticalsoftware (SPSS) was used to identify risk factors associated with tissue motion. This study received IRB approval.

Results: Eighteen patients (29%) had changes 5 mm or greater, seven patients (11%) had changes 10 mm or greater, and two pa-tients (3%) had changes 20 mm or greater. The largest recorded displacement was 22 mm. Most patients (71%) had changes 4 mmor smaller. Patients with surgery prior to radiation experienced larger changes than those who did not (p\0.01). Patients treated forprimary tumors also had larger changes than those with metastases (p\0.01). Age, pneumocephalus, gender, and the presence ofimplanted chemotherapy wafers were not factors associated with larger average inter-fraction motion.

Conclusions: Patients with surgery prior to radiation therapy and those being treated for primary lesions experienced significantlylarger average tissue motion in this study. The data suggests that followup imaging during therapy should be used for this group ofpatients to monitor for large changes that could affect tumor coverage (Fig.).

Author Disclosure: T.P. Jenkins, None; H. Gay, None; C. Sibata, None; R. Allison, None.

189 Modification of Brain Tumor Microenvironment by Applying Cervical Spinal Cord Stimulation (cSCS)

B. Clavo1,2, F. Robaina1,2, B. Balcarcel3, L. Catala1, J. L. Perez1, A. Cabezon1, I. J. Jorge1, M. A. Hernandez1, R. Jover4,J. L. Carreras5

1Dr. Negrin University Hospital, Las Palmas, Spain, 2ICIC (Canary Islands Institute for Cancer Research), Las Palmas, Spain,3DIMEC Center, Las Palmas, Spain, 4P.E.T. Technological Institute, Madrid, Spain, 5P.E.T. FOCUSCAN Institute, Madrid,Spain

Purpose/Objective(s): The effect of radiotherapy and chemotherapy in high grade gliomas (HGG) depends of tumor microenvi-ronment. This work summarizes our experience about the effect of cervical spinal cord stimulation (cSCS) on brain tumor micro-environment.