Proceedings of the 51st Annual ASTRO Meeting S503

time to any failure was 16.3 months for previously irradiated vs. 25.6 months for unirradiated lesions (log–rank p = 0.06). Mediantime to failure when radiation was .12 months prior was 22.3 months, vs. 4.7 months for less (log–rank p = 0.08). No neurologicdeficit was noted clinically. Of 17 SRS (16 patients) where both kidneys were contoured and both pre- and post-SRS creatinine (Cr)labs were available, 2 patients had Cr increases of .20%. A breast cancer pt with lesion radiation 5 years prior had a Cr increasefrom 0.7 pre- to 1.1 at 6-months post-SRS, with 29%, 21%, 11% and 4% of the kidneys receiving .4, .6, .8 and .10 Gy. Aprostate cancer pt with lumbosacral SRS 2 years prior and 1 month later, both with unknown kidney doses, had a Cr increase from1.0 pre- to 1.8 at 1 month and 1.5 at 6 months post-SRS, with 7%, 4%, 2% and 0% of the kidneys receiving .4, .6, .8 and .10Gy. No renal failure was noted.

Conclusion: Single-fraction lumbo-sacral SRS appears to be safe and effective. The effect of renal radiation, and in particular cu-mulative doses over multiple treatments, needs to be considered when planning SRS.

Author Disclosure: O. Marina, None; L. Angelov, None; T. Djemil, None; J.H. Suh, Medtronic, Schering Plough, D. SpeakersBureau/Honoraria; S.T. Chao, None.

2714 Factors Influencing Referral for Palliative Radiotherapy

A. M. Fairchild S. Ghosh

Cross Cancer Institute, Edmonton, AB, Canada

Purpose/Objective(s): In Canada, patients with incurable or metastatic cancer are commonly followed by Medical Oncologists(MO) or Palliative Care physicians, or discharged to the care of their General Practitioners (GP). Relying on other physiciansto refer symptomatic patients for palliative radiotherapy (PRT) presumes a familiarity with the efficacy of PRT. Our objectiveswere to assess patterns in referral and knowledge about the indications for PRT.

Materials/Methods: 1360 GPs, MOs, and Palliative Care specialists practicing in our catchment area were faxed or mailed a 23-item questionnaire. Respondents answered questions on demographics, and rated on a four-point scale how much certain patient-,tumor- and treatment-related factors influenced their decision to refer. Respondents estimated their level of PRT knowledge andanswered questions regarding its efficacy. Completed surveys were anonymized and descriptive statistics compiled. Chi-square testwas used for categorical and t test for continuous variables.

Results: The overall eligible response rate was 31.8% (412/1294), of whom 85.4% of respondents were GPs, 65.3% were male,and 44.9% practiced in a rural setting. 97.6% had seen cancer patients in the last month, 80.5% sometimes or often provided end-of-life care, and 71.0% had referred patients for PRT in the last year. Factors taken into account in referring for PRT most often werefunctional status, by 93.1% (349/375) of respondents, histology (75.4%; 285/378), and concern about side effects (75.3%; 281/373). Logistic concerns, such as need for out-of-town patients to stay in the city and travel distance, were taken into account ‘‘alot’’ by 11% or fewer. Wait times for PRT consultation and delivery were considered important by just over half of physicians.Respondents’ self-rated knowledge was poor for 74.0% (305/412), fair for 24.5% (101/412), and good (6/412) for 1.5%. Actualknowledge score was classified as poor for 46.6%, fair for 36.7%, and good for 16.7%. Practitioners referring for PRT were inpractice significantly longer, saw significantly more cancer patients per month, provided palliative care more frequently, andhad significantly higher self-rated and actual PRT knowledge.

Conclusions: Cancer- and patient-related factors outweighed concerns about convenience and wait times for physicians referringpatients for PRT. Although our results suggest that referring practitioners have less than optimal knowledge about common PRTindications, they are more well-informed than they believe themselves to be. Lack of education may be a barrier to referral of ap-propriate patients for PRT.

Author Disclosure: A.M. Fairchild, Unrestricted educational grant, G. Other; S. Ghosh, None.

2715 Predictors of Symptomatic Failure after Palliative Radiation Therapy for Multiple Myeloma

S. R. Alcorn1,2, P. M. Mauch1, A. Ng1, A. K. E. Oppenheimer1, B. T. Webber1, T. A. Balboni1

1Dana-Farber Cancer Institute/Brigham and Women’s Hospital, Boston, MA, 2Harvard Medical School, Boston, MA

Purpose/Objective(s): Advances in therapy for multiple myeloma (MM) have resulted in greater patient life expectancy. Durablelocal control with palliative radiation therapy (PRT) is therefore of increasing importance. Preliminary data suggest that PRTcourses with higher biological equivalent dose (BED) may improve MM response. This study aimed to examine the relationshipsof BED and other potential predictors of failure after PRT for MM.

Materials/Methods: This retrospective analysis identified 74 patients treated with PRT for MM from 01/1998 to 06/2006 at Brig-ham and Women’s Hospital and Dana-Farber Cancer Institute; 60 (79%) had sufficient follow-up data to be included in the anal-ysis. BED was calculated assuming a/b = 10 for tumor. Local failure was defined as increasing symptoms at the prior PRT site with(1) radiographic evidence of progression or (2) medical intervention (e.g. surgery, re-irradiation) initiated due to progressive symp-toms at the site. Univariable (UVA) and multivariable (MVA) logistic regression characterized the relationships between baselinepredictors and RT failure.

Results: At the time of PRT, mean age was 61 years (SD 12), mean Karnofsky performance status (PS) was 68 (SD 15), and mediantime since MM diagnosis was 18 months. Fifty-three percent of the 60 patients were female. A total of 117 sites were treated (me-dian follow-up 32 months). PRT sites were 45% spine, 9% pelvis, 18% extremities, and 28% other. The median dose was 30 (range,8–40) Gy, with a median BED of 39 Gy10. A total of 31 sites (26%) recurred at a median of 35 (interquartile range, 8.2 to 79.1)months after PRT. Of 53 sites receiving RT of BED\39 Gy10, 18 (34%) recurred, compared to 13 of 64 (20%) sites receiving BED$39 Gy10 (OR = 2.02, 95% CI = 0.88–4.64, p = 0.10). Of 62 spine and pelvis sites treated, 25 (40%) failed, compared to 6 of 55(11%) non-spine/pelvis sites (OR = 5.52, 95% CI = 2.05–14.82, p = .0007). On UVA, age, gender, PS, duration of MM diagnosis,presence of an associated soft tissue mass, prior systemic therapy and surgery immediately prior to RT did not predict for localfailure following RT. On MVA adjusted for age, gender, PS, prior surgery, and presence of a soft tissue mass, spine/pelvic site(OR = 8.99, 95% CI = 2.85–28.39, p = .0002) and BED\39 Gy10 (OR = 2.79, 95% CI = 1.08–7.22, p = 0.03) predicted for a higherrisk of recurrence.

S504 I. J. Radiation Oncology d Biology d Physics Volume 75, Number 3, Supplement, 2009

Conclusions: This retrospective analysis suggests that MM patients receiving PRT with BED\39 Gy10 (equivalent to 30 Gy in 10fractions) have a higher risk of symptomatic failure after RT than those treated with a higher BED. Spine and pelvic sites appear toincrease the risk of developing symptomatic failure after PRT. Though prospective data are required to confirm these findings,doses of at least BED 39 Gy10 should be considered for PRT in MM patients, particularly for spine and pelvic sites.

Author Disclosure: S.R. Alcorn, None; P.M. Mauch, None; A. Ng, None; A.K.E. Oppenheimer, None; B.T. Webber, None; T.A.Balboni, None.

2716 Stereotactic Body Radiotherapy (SBRT) for Spinal Metastases

A. E. Kretzler, M. Bassetti, J. M. Balter, C. I. Tsien

University of Michigan, Ann Arbor, MI

Purpose/Objective(s): A retrospective review was performed to determine the rate of pain relief, toxicity, and local progression inpatients treated with SBRT for spinal tumors.

Material/Methods: From 2006–2009, SBRT was performed for bone metastasis in 22 patients for a total of 30 lesions. Patientswere selected for SBRT based on one of the following criteria: (1) Prior RT to the same site. (2) Renal cell ca. or melanoma, with upto 3 spinal metastases and a life expectancy of greater than 2 months. (3) Other histologies, with up to 3 spinal metastases and a lifeexpectancy of greater than 9 months, as predicted based on the score developed by Van der Linden et al. 2005. Pain outcome wasmeasured according to the International consensus on palliative radiotherapy endpoints (Chow et al. 2002). Acute effects werescored according to CTC v. 3. Median age was 55 years (33–72 years), median KPS 90% (60–90%). 17 patients had received priorRT to the same area. Patients received 1–5 fractions with a median of 3 fractions, median total dose 24 Gy (14–35 Gy) and mediandose per fraction 7 Gy (4–16 Gy), depending on spine level treated and history of prior RT to the same site. The PTV typicallyencompassed the GTV + 2mm and the remainder of the anterior vertebral body for targets in the vertebral body, or the GTV +2–5mm for paraspinal tumors. Dose was typically prescribed to the lowest isodose surface covering 99% of the GTV and 95%of the PTV.

Results: Pain outcome was documented in 28 lesions, with an average follow-up of 10 months (±7 months), with 18 patients pre-senting with painful metastasis, all but two with complete (6) or partial (10) pain response at the site treated, and all 10 patients whowere asymptomatic prior to SBRT remained asymptomatic. Treatment was well-tolerated with 6 patients noted to have Grade 1fatigue, nausea or chills. None of the patients developed neurotoxicity. Two patients required further treatment. One presentedwith cord compression and underwent surgery and further SBRT 10 months after his initial SBRT, the second presented withasymptomatic progression on imaging and was re-treated with SBRT 13 months after his first treatment. Follow-up imagingwas available in 24 patients, median 11 months (2–27 months). 15 patients had stable disease, 5 patients showed response, and4 patients had progression on imaging. Pattern of progression was towards the pedicles, into the spinal canal, the posterior vertebralbody or a combination.

Conclusion: SBRT for spinal metastases, as reported elsewhere, is a well-tolerated, safe and effective treatment, especially in casesof re-treatment, albeit longer follow-up for final evaluation of neurotoxicity is warranted. Definition of the CTV requires consid-eration of the potential spread along the pedicles and into the spinal canal.

Author Disclosure: A.E. Kretzler, None; M. Bassetti, None; J.M. Balter, None; C.I. Tsien, None.

2717 Treatment of Five or More Brain Metastases with Stereotactic Radiosurgery

G. K. Hunter, J. Suh, M. Vogelbaum, G. Barnett, L. Angelov, R. Weil, A. M. Reuther, G. Neyman, S. Chao

Cleveland Clinic, Cleveland, OH

Purpose/Objective(s): To examine the outcomes of patients with five or more brain metastases treated in a single session withstereotactic radiosurgery (SRS).

Materials/Methods: Sixty-four patients with radiographically diagnosed brain metastases treated with LINAC or Gamma Knifebased SRS to 5 or more lesions in a single session were reviewed. Primary disease type, number of lesions treated, SRS records,whole brain radiation (WBRT) records, Karnofsky performance score (KPS) at SRS, and status of primary disease and systemicdisease at SRS were included. Patients were treated using standard dosing defined by RTOG 90-05, with adjustments for criticalstructures and/or brainstem. We defined prior WBRT as WBRT completed .1 month prior to SRS and concurrent WBRT asWBRT completed within 1 month before or after SRS. Kaplan-Meier estimates and Cox proportional hazard regression wereused to determine which patient and treatment factors predicted overall survival.

Results: The median overall survival (OS) after SRS was 7.5 months. The median KPS was 80 (range, 60–100). KPS of .80 sig-nificantly influenced OS (median OS = 4.8 months for KPS\70 vs 8.8 months for KPS .80, p = 0.0097). The number of lesionstreated did not significantly influence OS (median OS = 6.6 months for\8 vs 9.9 months for .8, p = ns). Primary site histology didnot significantly influence median OS and was broken down as the following: breast (n = 13) vs other (11.5 months for breast vs 6.8months, p = ns), NSCLC (n = 23) vs other (9.6 months for NSCLC vs 6.8 months, p = ns), or radioresistant (RadR) histology (renalcell/melanoma, n = 20) vs. other (4.2 months for RadR vs 9.6 months, p = ns). On multivariate Cox modeling, KPS and priorWBRT significantly predicted for OS. WBRT prior to SRS compared to concurrent WBRT significantly influenced survival,with a risk ratio (RR) of 0.423 (CI = 0.191–0.936, p = 0.0338). No WBRT group compared to concurrent WBRT had a RR of0.447 (CI = 0.176–1.134, p = ns), and no WBRT group compared to prior WBRT had a RR of 1.051 (CI = 0.534–2.070,p = ns). KPS of \70 predicted for poorer outcomes, with a RR of 2.164 (CI = 1.157–4.049, p = 0.0157).

Conclusions: Stereotactic radiosurgery to 5 or more lesions is an effective palliative option, especially for patients previouslytreated with WBRT. A KPS of 80 and above is predictive of better outcomes.

Author Disclosure: G.K. Hunter, None; J. Suh, Schering Plough, D. Speakers Bureau/Honoraria; M. Vogelbaum, None; G. Barnett,Elekta, Inc., D. Speakers Bureau/Honoraria; L. Angelov, None; R. Weil, None; A.M. Reuther, None; G. Neyman, None; S. Chao,None.