Objectives All organizations seek to minimize the risks that their operations pose to public safety. This task is especially significant if they deal with complex or hazardous technologies. Five decades of research in quantitative risk analysis have generated a set of risk management frameworks and practices that extend across a range of such domains. Here, we investigate the risk culture in three commercial enterprises that require exceedingly high standards of execution: radiation oncology, aviation, and nuclear power. Methods One of the characteristics of high reliability organizations is their willingness to learn from other such organizations. We investigate the extent to which this is true by compiling a database of the major publications on risk within each of the three fields. We conduct a bibliographic coupling analysis on the combined database to identify connections among publications. This analysis reveals the strength of engagement across disciplinary boundaries and the extent of cross-adoption of best practices. Results Our results show that radiation oncology is more insulated than the other two fields in its adoption and propagation of state-of-the-art risk management tools and frameworks that have transformed aviation and nuclear power into high reliability enterprises with actuarially low risk. Conclusions Aviation and nuclear power have established risk cultures that cross-pollinate. In both nature and extent, we found a distinct difference in radiation oncology's engagement with the risk community, and it lags behind the other two fields in implementing best practices that might mitigate or eliminate risks to patient safety.

PURPOSE:This study aimed to determine the feasibility and maximally tolerated dose of hypofractionated, conformal radiation therapy (RT) in patients with liver metastases. METHODS AND MATERIALS:Nonsurgical patients with ≤5 liver metastases (sum of maximal diameter of all lesions ≤8 cm) were included in the study. There were 4 dose levels: 35 Gy, 40 Gy (starting level), 45 Gy, and 50 Gy, in 10 fractions. The clinical target volume included metastases identified on contrast computed tomography or magnetic resonance imaging with a 5-mm margin within the liver. The planning target volume margin ranged from 4 to 30 mm, depending on breathing motion. Dose-limiting toxicities were defined as RT-related grade ≥4 hepatic or gastrointestinal toxicities or thrombocytopenia occurring within 90 days of the start of RT. RESULTS:A total of 26 patients with metastases from colorectal (8 patients), breast (7 patients) and other malignancies (11 patients) were enrolled between November 2005 and December 2010. Twenty-three patients were evaluable (8, 7, and 8 on the 40, 45, and 50 Gy dose levels, respectively). Two patients assigned to 50 Gy received 35 Gy owing to normal tissue limits, so 2 additional patients were treated to 50 Gy. There were no dose-limiting toxicities on any of the dose levels. On the 45 Gy dose level, 1 patient developed reversible grade 3 enteritis (37 days from RT start) and diarrhea (22 days); another patient developed grade 3 lymphopenia (23 days). At the 50 Gy dose level, 1 patient had grade 3 hyperglycemia (74 days), and another patient developed grade 3 lymphopenia (13 days), colonic hemorrhage (325 days), and colonic gastrointestinal obstruction (325 days). With a potential median follow-up of 66.1 months (range, 34.6-89.0 months), no other late toxicities were observed. CONCLUSIONS:Treatment of liver metastases with 50 Gy in 10 fractions was feasible and safe in a multi-institutional setting.

Radiation therapy (RT) tumor volumes have become more personalized to anatomical differences between patients, yet the empiric one size fits all method of RT dose remains standard. We previously employed the Genomic Adjusted Radiation Dose (GARD) to show that tumor biology drives physical dose effect and derived a biologically optimized dose for each patient (RxRSI). That genomics allows for derivation of optimal dose, yet all patients are treated uniformly leads naturally to the hypothesis that the current empiric RT dose approach is biologically imprecise. To test this, we develop a method to quantify the inefficiencies in outcome resulting from a failure to account for the biological heterogeneity in RT-treated patients. We use 2 cohorts of NSCLC patients from an IRB-approved de-identified institutional biorepository: the 1st (clinical cohort) includes 60 patients with stage III NSCLC treated with post-op RT (dose range 45-70Gy); the 2nd (modeling cohort) consists of 1,747 NSCLC patients with known tumor genomics. We integrated GARD into a commercial treatment planning system to create personalized genomic RT plans using standard optimizations for both standard of care and RxRSI doses. To estimate the clinical potential for genomic based RT, we built a model to quantify the impact of optimal RT dose on local control and radiation-associated toxicity: the radiation-specific predicted event free survival (pEFS). The model incorporates a relative penalization scheme based on the added toxicity (modeled from QUANTEC) to which patients are potentially exposed when their RxRSI is exceeded. To validate this precision RxRSI model, we ran an in silico clinical trial similar to RTOG 0617 (empiric 60 vs 74Gy) in the modeling cohort. Comparing RxRSI to dose prescribed, we observe that 75% of patients were not treated optimally (either over- or under-dosed, amounting to quantifiable excess dosing to lung, esophagus and heart). Of these patients, we find that 2/3 could be optimized using dosing within NCCN guidelines. We validate our pEFS model by demonstrating the 'no benefit' result from the empiric dose escalation in RTOG0617. The pEFS model identifies only an additional 16.2% of patients in the cohort who would achieve RxRSI by receiving 74 Gy (beyond 60Gy). A genomic-based strategy to deliver 74 Gy to only those patients while the rest receive 60 Gy could have produced a 6.3% benefit for the whole population (p<0.05). With a penalized model of radiation outcome, we accurately predict the results of a recent empiric failed dose-escalation study and show how a genomic strategy could have produced superior outcomes. When optimal tumor dose is derived, our model shows a majority of NSCLC patients are sub-optimally over- or under-dosed, a biological imprecision which yields inferior outcomes which could be ameliorated with genomic stratification.

Background: Percutaneous trigeminal rhizotomy or balloon compression for trigeminal neuralgia carries a potential risk for the brainstem, the carotid artery, and the basilar artery. Objective: To detail the relation of critical neural and vascular structures to expanded balloons used for percutaneous compression of the trigeminal ganglion. Method: A retrospective analysis of preprocedural magnetic resonance imaging (MRI) and procedural X-ray-based imaging for 9 patients detailed balloon proximity to the brainstem, carotid artery, and basilar artery. Results: Balloons extended 10.96 ± 5.54 mm (mean ± SD) posterior to the clival line. The average distance from the balloon to the brainstem was 6.89 mm, and that to the basilar artery was 12.12 mm (range: 0–18.2). The medial edge of the balloon was an average distance of 1.39 mm from the baseline position of the carotid lumen. Conclusion: Preprocedural MRI, merged with 3-D rotational angiography suite imaging, detailed the proximity of the balloon to critical neural and vascular structures. Our study found that the standard technique for percutaneous trigeminal compression, with balloon placement at an average depth of 10.96 mm posterior to the clival line, on average, provided an additional 6.89 mm of space before the brainstem would have been encountered, demonstrating safe positioning.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline (MPPG) represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiation requires specific training, skills, and techniques as described in each document. As the review of the previous version of AAPM Professional Policy (PP)-17 (Scope of Practice) progressed, the writing group focused on one of the main goals: to have this document accepted by regulatory and accrediting bodies. After much discussion, it was decided that this goal would be better served through a MPPG. To further advance this goal, the text was updated to reflect the rationale and processes by which the activities in the scope of practice were identified and categorized. Lastly, the AAPM Professional Council believes that this document has benefitted from public comment which is part of the MPPG process but not the AAPM Professional Policy approval process. The following terms are used in the AAPM's MPPGs: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

BACKGROUND: Optimal doses for single-fraction stereotactic radiosurgery (SRS) in the treatment of brain metastases are not well established. Our institution utilized conservative dosing compared to maximum-tolerated doses from the Radiation Therapy Oncology Group 90-05 Phase I study. OBJECTIVE: To report individual lesion control (LC) from conservative single-fraction doses and determine factors affecting LC. METHODS: From 2003 to 2015, patients who underwent linear accelerator-based single-fraction SRS for cerebral/cerebellar metastases and receiving at least 1 follow-up magnetic resonance imaging (MRI) were identified. Lesion response was assessed by a size-based rating system and modified "Response Assessment in Neuro-Oncology Brain Metastases" (RANO-BM) criteria. RESULTS: Among 188 patients with 519 lesions, median survival was 13.1 mo; median follow-up time with MRI was 9.6 mo per course. Median tumor-periphery dose was 15 Gy (range: 7.5-20.7). Median lesion volume was 0.5 cc and diameter was 9 mm (range: 2-45). Concordance between RANO-BM and size-based system was 93%. Crude 1-yr LC was 80%, 73%, 56%, and 38% for lesions 1 to 10, 11 to 20, 21 to 30, > 31 mm, respectively. On multivariate analysis, increased size, melanoma and colorectal histology, and progression after whole brain radiation therapy predicted worse LC. When excluding lesions treated as a boost, dose was a significant predictor of LC in multivariate models (hazard ratio 0.89, P = .01). Symptomatic radiation necrosis occurred in 10 lesions in 10 patients. CONCLUSION: Histology predicts LC after conservative SRS doses with evidence of a dose-response relationship. Conservative single-fraction SRS doses confer minimal toxicity and acceptable control in certain subgroups (breast cancer, <5 mm), with suboptimal control in larger lesions and in combination with whole brain radiation therapy.

Stereotactic body radiation therapy (SBRT) has been developed as a novel modality for early stage non–small cell lung cancer (NSCLC) and has emerged as a standard treatment option for medically inoperable patients. We report here our institutional experience with SBRT for stage I NSCLC. We retrospectively analyzed 106 consecutive stage I (T1a, T1b, T2a N0) NSCLC patients treated at an institution from January 2008 through December 2012 with a 5-fraction SBRT regimen. Patients were treated using the ExacTrac® system on a Novalis LINAC. Survival and loco-regional control were calculated from the date of completion of SBRT to last date of follow-up/death. There were 58 males and 48 females with median age of 76.5 years (range 50-91 years). Pulmonary and/or cardiac co-morbidity was the most common reason for patients not undergoing surgery. Eighty-seven percent (n=93) had a pathologic diagnosis whereas 13 refused biopsy. Adenocarcinoma (51%) was the most common histology followed by squamous cell (19.8%), BAC, and large cell. Sixty-nine percent (n=74) were 11-20 mm in size, 20.8% (n=22) were 21-30 mm, 2.8% (n=3) were 31-40 mm, and 6.6% (n=7) were <10 mm. Ninety-eight percent (n=104) of tumors were peripherally located whereas 1.9% (n=2) were central or para-spinal in location. The 1-, 2-, and 5-year local control (LC) rates were 98%, 90%, and 88% with all local failures (LF) occurring within 2 years. Age, gender, tumor size, tumor histology, prescribed dose, patient age, prior RT, or surgery had no significant impact on LC rates. The overall survival (OS) rates and cause specific survival (CSS) were 95%, 85%, 73%, and 41% (median survival of 42.7 months) and 98%, 91%, 81%, and 58% (median survival was not reached) at 6 months, 1 year, 2 year, and 5 years, respectively. On univariate analysis, age, gender, prescribed dose, size of tumor, and prior treatment were not significant; progression of disease was the only significant factor for OS (P<.0004) and CSS (P<.00001). Six of 106 developed LF and 13 developed distant failure (of whom 5 also developed LF). Five died from NSCLC and 2 died from causes other than NSCLC. All patients tolerated SBRT well: 21% (n=19) patients developed grade II radiation changes on follow-up CT and 12% (n=12) patients developed symptomatic radiation pneumonitis requiring medical treatment. No patient died from treatment-related toxicity. For patients with stage I NSCLC, SBRT results in excellent LC, OS, and DSS at 1, 2, and 5 years with no grade ≥III toxicity.

To examine and identify predictors of local control and incidence of radiation necrosis with single fraction SRS using conservative dosing techniques and identify minimum effective doses based on these variables. Patients who from 2004-2014 received single fraction LINAC-based SRS treatment for brain metastases from breast, non-small cell lung (NSCLC), colorectal, and melanoma primaries were identified. Lesion response was defined based on RANO-BM criteria with serial MRI scans. Patients followed with MRI >= 90 days after first treatment course were analyzed. Lesion size, primary histology, dose, normal tissue dose-volume exposure, previous therapy (WBRT or surgery), and incidence of symptomatic radiation necrosis were recorded. A total of 167 patients (with >=90 day follow up) who underwent 502 treatment courses were identified. Median age at time of first SRS was 61 years, with median KPS of 80 at time of each course. There were 128 lesions from breast, 271 from NSCLC, 70 from melanoma, and 34 from colorectal primaries. One to 7 lesions (median of 2) were treated per SRS course. Each lesion was planned as a separate isocenter. 239 lesions were treated with up front SRS alone, 65 as a planned boost after WBRT (median dose 30 Gy), and 199 as progressive / new lesions after prior WBRT. Median follow up time with imaging was 7.2 months (0.8 – 128 mo) per lesion. Median survival after first SRS course 14.4 months. Mean lesion volume was 2.16 cc (0.006 – 27.2 cc). Median dose to isocenter and 99% of the target volume (GTV = PTV) was 17.8 Gy (10-26.5 Gy) and 15.2 Gy (9-24 Gy). NSCLC local control was 84% at 6-months and 62% at 1 year. On univariate analysis increasing lesion size was associated with worse LC HR 1.05 (1.02-1.08), while >16 Gy peripheral dose (covering 99% PTV) was associated with improved control HR 0.65 (0.46 – 0.93). Lesions treated with SRS for progression after previous WBRT had worse LC HR 1.84 (1.3-2.56). Histology was a significant variable for LC: breast cancer was most sensitive; relative to breast cancer, NSCLC was not significantly different HR 1.28 (0.88 – 1.88), while both colorectal 4.8 (2.33-10.3) and melanoma 4.1 (2.62 – 6.42) primaries were significantly worse. On multivariate analysis, histology remained the most significant variable for LC. When examining breast histology alone, a dose cut off of 16 Gy to the periphery was no longer significant on univariate 1.00 (0.46 – 2.16), and on multivariate analysis with size 0.88 (HR 0.42 – 1.91). Twenty patients had symptomatic radiation necrosis, confirmed by pathology (n = 6), MR perfusion/spectroscopy (n = 5), or clinical/MRI characteristics (n = 9). Overall control was comparable to other series. Histology was a major predictive variable and lesions from breast primary may respond well to more conservative dosing. Ongoing work to evaluate a combination of dose, size, and conformity index is ongoing to identify a threshold effective dose, and predictors of symptomatic radiation necrosis.

OBJECTIVE:To report our institutional experience with five fractions of daily 8-12 Gy stereotactic body radiotherapy (SBRT) for the treatment of oligometastatic cancer to the lung.METHODS:Thirty-four consecutive patients with oligometastatic cancers to the lung were treated with image-guided SBRT between 2008 and 2011. Patient age ranged from 38 to 81 years. There were 17 males and 17 females. Lung metastases were from the following primary cancer types: colon cancer (n=13 patients), head and neck cancer (n=6), breast cancer (n=4), melanoma (n=4), sarcoma (n=4) and renal cell carcinoma (n=3). The median prescription dose was 50 Gy in five fractions (range, 40-60 Gy) to the isocenter, with the 80% isodose line encompassing the planning target volume (PTV) [defined as gross tumor volume (GTV) + 7-11 mm volumetric expansion]. The follow-up interval ranged from 2.4-54 months, with a median of 16.7 months.RESULTS:The 1-, 2-, and 3-year patient local control (LC) rates for all patients were 93%, 88%, and 80% respectively. The 1-, 2-, and 3-year overall survival (OS) rates were 62%, 44%, and 23% respectively. The 1- and 2-year patient LC rates were 95% and 88% for tumor size 1-2 cm (n=25), and 86% for tumor size 2-3 cm (n=7). The majority (n=4) of local failures occurred within 12 months. No patient experienced local failure after 12 months except for one patient with colon cancer whose tumors progressed locally at 26 months. All five patients with local recurrences had colorectal cancer. Statistical analyses showed that age, gender, previous chemotherapy, previous surgery or radiation had no significant effect on LC rates. No patient was reported to have any symptomatic pneumonitis at any time point.CONCLUSIONS:SBRT for oligometastatic disease to the lung using 8-12 Gy daily fractions over five treatments resulted in excellent 1- and 2-year LC rates. Most local failures occurred within the first 12 months, with five local failures associated with colorectal cancer. The treatment is safe using this radiation fractionation schedule with no therapy-related pneumonitis.

PURPOSEMD Anderson Radiological Physics Center (RPC) routinely evaluates the calibration of linear accelerators using thermoluminescent dosimeters (TLDs) and more recently optically-stimulated luminescence dosimeters (OSLDs).The RPC continues to use TLDs for the annual TomoTherapy audits.In the past, an RPC measurement was 6.2% low compared to our institution planned dose.Therefore, we have constructed an RPC duplicate phantom and we have altered the design to accommodate an OSLD and an A1SL ionization chamber in order to examine the quality of the RPC TomoTherapy audit.METHODSThe RPC TomoTherapy Calibration Phantom consists of an acrylic cylinder with TLD capsules inserted in the center of the cylinder.A TomoTherapy treatment plan is generated to deliver a uniform dose of 600 cGy to an approximately 10 cm long by 2.5 cm diameter target that holds the TLDs.Two more treatment plans are generated for the in-house TomoTherapy Calibration Phantom; one for the OSLD and another for the A1SL ionization chamber. The beam energy and output calibration were checked prior to irradiating the phantoms. All Plans are delivered at the same time the RPC Phantom is irradiated for consistent comparison of the results.RESULTSThe results obtained with the in-house phantom were well within 2% of the calculated dose. The OSLD dose measurement was 1.8% from the dose calculated by the treatment planning system (TPS). The dose measured by the A1SL ionization chamber was only 1% from calculated. The repeated RPC measurement differed by only 2.8% from the calculated one.CONCLUSIONWe have manufactured an independent and similar dose verification phantom for testing the quality and reproducibility of the RPC TomoTherapy Calibration results. The phantom proved to be well suited for the evaluation of the overall machine calibration and for benchmarking the results of the RPC QA Audit. Institutions preparing for participation in the credentialing process will find this tool very helpful.

Stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) for spinal metastases are emerging treatment paradigms in the multidisciplinary management of metastases located within or adjacent (paraspinal) to the vertebral bodies/spinal cord. In this review, we provide a brief overview of spine SBRT/SRS indications, technology, planning, and treatment delivery; review the current state of the literature; and discuss the radiobiology, toxicity, and limitations of SBRT/SRS for metastatic disease of the spine.

Purpose: To establish institutionally specific action levels for quality assurance (QA) ofintensity‐modulated radiation therapy (IMRT) treatment plans based on the guidelines andstatistical principles presented by Howell et al. in 2008 for the University of Texas MD Anderson. Methods: A review of 3937 fields of 364 patients treatment plans was undertaken to findinstitutional action level values unique to this clinic. Data analysis focused on the commonlyused gamma parameter. Institutional averages and standard deviations were found formaximum gamma, average gamma, and percentage of a field's fluence area exhibiting a gammavalue greater than 1.0. Additional analysis reviewed action level dependence on disease site and EPID acquisition software version. Results: These observations were used to create action levels specific to this clinic and which were found to be substantially stricter than those recorded by Howell et al; this difference perhaps reflects institution‐specific aspects such as updated acquisition software and individual treatment planning styles. Conclusion: Results suggest that action levels for Portal Dosimetry‐based IMRT QA should beadjusted based on individual institutional experience.

Abstract Background: A previous phase III RTOG study subset analysis demonstrated improvement in overall survival (OS) with the addition of SRS to WBRT in NSCLC patients with 1 to 3 brain metastases. As both TMZ and erlotinib are known to cross the blood brain barrier (potentially providing radiosensitization), and have documented activity in NSCLC, a phase III study was designed to test whether either of these drugs would improve outcome of WBRT/SRS. Methods: NSCLC patients (n=126) with 1-3 brain metastases were randomized (10/2005 to 8/2009; study closed prematurely due to slow accrual) to receive WBRT (2.5 Gy x 15 to 37.5Gy) + SRS alone, vs. WBRT/SRS with TMZ (75mg/m2/D x 21) or erlotinib (150mg/D). Erlotinib or TMZ (150-200 mg/m2/D x 5/mo) could be given in the drug arms post-WBRT/SRS at the discretion of the investigator. The primary endpoint was overall survival (OS). Results: Arms were stratified by RTOG recursive partitioning analysis (RPA) class and balanced for prognostic variables including the Graded Prognostic Assessment (GPA) score. Neither the addition of erlotinib nor TMZ to WBRT/SRS resulted in an improvement in OS, or time to CNS progression compared to WBRT/SRS alone. Patients in the WBRT/SRS arm had longer MST (Median Survival Time) (13.4 mo, 95% CI = 6.5-20.8 mo.) compared to the WBRT+SRS+ erlotinib (6.1 mo, 95% CI = 3.6-12.1 mo)[Hazard ratio (≥2 / α1) and 95% CI; 1.47 (0.92 to 2.36)], or TMZ (6.3 mo, 95% CI= 3.4-10.1 mo.) [Hazard ratio (β3 / α1) and 95% CI; 1.43 (0.89 to 2.31)]. This surprising result was not related to excess toxicity. In fact, patients experiencing grade 3+ Adverse Events (AE) appear to have longer OS than those patients without grade 3+ AE for both drug arms. The WBRT/SRS arm had significantly less deterioration in performance status at 6 mo. There were no significant differences between arms for steroid dependence at 6 mo, or causes of death. Conclusion: The addition of either TMZ or erlotinib to WBRT/SRS in this unselected population of NSCLC patients with 1-3 brain metastases provided no clinical advantage. Treatment with WBRT/SRS alone appeared to result in superior outcome data (compared to the addition of TMZ or erlotinib) relative to OS in this limited data set. Detailed analysis to date provides no obvious explanation for these unexpected results. Support: RTOG grant U10 CA21661, and CCOP grant U10 CA37422 from the National Cancer Institute (NCI) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 736. doi:1538-7445.AM2012-736

257 Background: This multi-institutional phase I trial was conducted to determine the maximally tolerated dose (MTD) of hypofractionated, highly conformal radiation therapy (RT) in patients (pts) with liver metastases. Methods: Eligibility criteria included non-surgical pts with ≤ 5 liver metastases; total measurement for all lesions ≤ 8 cm. There were four dose levels (DLs) escalating from 35 Gy to 50 Gy in 5 Gy increments given in 10 fractions with defined normal tissue dose limits. Accrual began at 40 Gy. The clinical target volume (CTV) included all metastases identified on contrast CT/MRI with a 5 mm margin. The planning target margin ranged from 4 to 30 mm around the CTV. For quality assurance the Image-Guided Therapy Center (ITC) remote review tool was used to evaluate treatment planning images and dosimetry information. Dose limiting toxicities (DLTs) were defined as treatment-related grade (Gr) ≥ 4 hepatic, gastrointestinal (GI), thrombocytopenia, or radiation induced liver disease (RILD) within 90 days (dys) of the start of RT. Results: 26 pts were enrolled between 11/05 and 12/10, and 23 were evaluable; 8, 7, and 8 on the 40, 45, and 50 Gy DLs respectively. Two pts assigned to the 50 Gy DL received 35 Gy because of normal tissue constraints, therefore an additional 2 pts were accrued and treated at the 50 Gy DL. The study was temporarily closed for toxicity evaluation after 6 pts on each DL were followed for a minimum of 90 dys from start of treatment. There were no DLTs observed on any of the DLs. Four pts developed treatment-related Gr 3 toxicities; 2 each on the 45 and 50 Gy DLs. On the 45 Gy DL, 1 pt had two Gr 3 GI toxicities: enteritis (37 dys from RT start) and diarrhea (22 dys) while another pt had Gr 3 lymphopenia (23 dys). On the 50 Gy DL, 1 pt had Gr 3 hyperglycemia (74 dys) and another pt had three Gr 3 toxicities: lymphopenia (13 dys), colonic hemorrhage (325 dys), and GI obstruction (325 dys). Conclusions: When normal tissue constraints could be met, treatment of liver metastases with 50 Gy in 5 Gy/fx is feasible and safe in a multi-institutional setting. Further studies looking at higher doses and alternate fractionation regimens are warranted. Supported by RTOG U10 CA21661, CCOP U10 CA37422 and ATC U24 CA 81647 NCI grants.