Search

Background There is no consensus regarding the optimal management of inoperable high-grade arteriovenous malformations (AVMs). This long-term study of 42 patients with high-grade AVMs reports obliteration and adverse event (AE) rates using planned multistage repeat stereotactic radiosurgery (SRS). Objective To evaluate the efficacy and safety of multistage SRS with treatment of the entire AVM nidus at each treatment session to achieve complete obliteration of high-grade AVMs. Methods Patients with high-grade Spetzler-Martin (S-M) III-V AVMs treated with at least 2 multistage SRS treatments from 1989 to 2013. Clinical outcomes of obliteration rate, minor/major AEs, and treatment characteristics were collected. Results Forty-two patients met inclusion criteria (n = 26, S-M III; n = 13, S-M IV; n = 3, S-M V) with a median follow-up was 9.5 yr after first SRS. Median number of SRS treatment stages was 2, and median interval between stages was 3.5 yr. Twenty-two patients underwent pre-SRS embolization. Complete AVM obliteration rate was 38%, and the median time to obliteration was 9.7 yr. On multivariate analysis, higher S-M grade was significantly associated ( P = .04) failure to achieve obliteration. Twenty-seven post-SRS AEs were observed, and the post-SRS intracranial hemorrhage rate was 0.027 events per patient year. Conclusion Treatment of high-grade AVMs with multistage SRS achieves AVM obliteration in a meaningful proportion of patients with acceptable AE rates. Lower obliteration rates were associated with higher S-M grade and pre-SRS embolization. This approach should be considered with caution, as partial obliteration does not protect from hemorrhage.

OBJECT The number of patients with spinal tumors is rapidly increasing; spinal metastases develop in more than 30% of cancer patients during the course of their illness. Such lesions can significantly decrease quality of life, often necessitating treatment. Stereotactic radiosurgery has effectively achieved local control and symptomatic relief for these patients. The authors determined prognostic factors that predicted pain palliation and report overall institutional outcomes after spine stereotactic body radiation therapy (SBRT). METHODS Records of patients who had undergone treatment with SBRT for either primary spinal tumors or spinal metastases from June 2008 through June 2013 were retrospectively reviewed. Data were collected at the initial visit just before treatment and at 1-, 3-, 6-, and 12-month follow-up visits. Collected clinical data included Karnofsky Performance Scale scores, pain status, presence of neurological deficits, and prior radiation exposure at the level of interest. Radiation treatment plan parameters (dose, fractionation, and target coverage) were recorded. To determine the initial extent of epidural spinal cord compression (ESCC), the authors retrospectively reviewed MR images, assessed spinal instability according to the Bilsky scale, and evaluated lesion progression after treatment. RESULTS The study included 99 patients (mean age 60.4 years). The median survival time was 9.1 months (95% CI 6.9–17.2 months). Significant decreases in the proportion of patients reporting pain were observed at 3 months (p < 0.0001), 6 months (p = 0.0002), and 12 months (p = 0.0019) after treatment. Significant decreases in the number of patients reporting pain were also observed at the last follow-up visit (p = 0.00020) (median follow-up time 6.1 months, range 1.0–56.6 months). Univariate analyses revealed that significant predictors of persistent pain after intervention were initial ESCC grade, stratified by a Bilsky grade of 1c (p = 0.0058); initial American Spinal Injury Association grade of D (p = 0.011); initial Karnofsky Performance Scale score, stratified by a score of 80 (p = 0.002); the presence of multiple treated lesions (p = 0.044); and prior radiation at the site of interest (p < 0.0001). However, when multivariate analyses were performed on all variables with p values less than 0.05, the only predictor of pain at last follow-up visit was a prior history of radiation at the site of interest (p = 0.0038), although initial ESCC grade trended toward significance (p = 0.073). Using pain outcomes at 3 months, at this follow-up time point, pain could be predicted by receipt of radiation above a threshold biologically effective dose of 66.7 Gy. CONCLUSIONS Pain palliation occurs as early as 3 months after treatment; significant differences in pain reporting are also observed at 6 and 12 months. Pain palliation is limited for patients with spinal tumors with epidural extension that deforms the cord and for patients who have previously received radiation to the same site. Further investigation into the optimal dose and fractionation schedule are needed, but improved outcomes were observed in patients who received radiation at a biologically effective dose (with an a/b of 3.0) of 66.7 Gy or higher.

Background Patients with melanoma can present with a hemorrhagic intracranial lesion. Upon resection, pathology reports may not detect any malignant cells. However, the hemorrhage may obscure their presence and so physicians may still decide whether adjuvant radiotherapy should be applied. Here, we report on the outcomes of a series of patients with melanoma with hemorrhagic brain lesions that returned with no tumor cells. Methods All melanoma patients who had craniotomies from 2008 to 2017 at a single institution for hemorrhagic brain lesions were identified through retrospective chart review. Those who had pathology reports with no malignant cells were analyzed. Recurrence at the former site of hemorrhage and resection was the primary outcome. Results Ten patients met inclusion criteria, and the median follow-up time was 8.5 (1.8-27.3) months. At the time of craniotomy, the median number of brain lesions was 3 (1-25). Two patients had prior craniotomies, eight had prior radiation, and six had prior immunotherapy to the lesion of interest. After surgery, one patient received stereotactic radiosurgery (SRS) to the resection bed. Only one patient developed subsequent melanoma at the resection site; this patient developed the lesion recurrence once and had not received postoperative SRS. Conclusion Although small foci of metastatic disease as a source of bleeding for some patients cannot be excluded, melanoma patients with a suspected hemorrhagic brain metastasis that shows no tumor cells on pathology may benefit from close observation. The local recurrence risk in such cases appears to be low, even without adjuvant radiation.

We present a case report of a patient with glioblastoma multiforme (GBM) complicated by extracranial metastasis (ECM) whose survival of nearly four years surpassed the anticipated life expectancy given numerous negative prognostic factors including EGFRvIII-mutation, unmethylated MGMT promoter status, and ECM. Interestingly, while this patient suffered from locally aggressive disease with multiple intracranial recurrences, the proximal cause of death was progressive extracranial disease and complications related to pulmonary metastases. Herein, we review potential mechanisms of ECM with an emphasis upon glioblastoma molecular and genetic profiles and the potential implications of targeted agents such as bevacizumab.

Re-irradiation for recurrent HGG remains controversial, although several studies have now suggested a dose of 36 Gy as standard for re-treatment. We retrospectively evaluated outcomes and toxicity following re-irradiation for recurrent HGG, in many cases to higher than 36 Gy. Ninety-six patients, median KPS 80 [range 40-100]), were retreated at a median of 29 months following initial radiation (4.8-203.3 months). The median re-irradiation dose was 41.4 Gy (12.6-54 Gy) to a median lesion volume of 185.5 cm3 (20-901 cm3). Of evaluable treatment plans, the median cumulative (initial- and re-irradiation combined) maximum brainstem dose was 76.6 Gy (6.2-103.4 Gy) and to the optic apparatus 54.9 Gy (5.5-90.9 Gy). Concurrent temozolomide (TMZ) alone was given with 55% of re-irradiation treatments, bevacizumab (BEV) alone with 14%, TMZ+BEV with 12%, and no chemotherapy with 20%. Planned re-irradiation was completed by 90% of patients and was not affected by concurrent chemotherapy. Median overall survival (OS) from primary diagnosis was 108, 73, and 33 months for patients with initial grade I-II, grade III, and grade IV gliomas, respectively (p36 Gy were safe, well tolerated, and completed in the majority of patients with recurrent HGG. More study is needed to define the optimal re-irradiation dose, the maximal safe dose to critical structures, the role of systemic therapy, and efficacy.

Tumor treating fields (TTFields) is a noninvasive, regional antimitotic treatment approved for the treatment of newly-diagnosed and recurrent glioblastoma (GBM) including use concurrent with temozolomide. As anti-mitotic therapies may have synergy with radiotherapy, we have developed a plan to implement use of this therapy during radiotherapy and to test safety and tolerability. In preparation for the clinical trial, we plan tests evaluating impact of placement of the applicator (transducer array) on RT targeting and dosimetry using an anthropomorphic phantom, aquaplast immobilization, and intensity-modulated radiotherapy. In this first test, several strategies were employed to ensure minimal degradation of targeting accuracy: 1) the CT scan artifacts due to the array were reduced by use of the Metal Artifact Reduction for Orthopedic Implants (O-MAR) algorithm, 2) radiation was delivered to a tumor location that did not require the radiation beam to pass through the array, by using an arrangement of six noncoplanar intensity modulated radiation therapy (IMRT) beams entering inferiorly, 3) the cone beam CT (CBCT) alignment was performed with a region of interest box that excluded any of the arrays. The end result was an X,Y,Z targeting error of 0.58 mm, -0.59 mm, 0.40 mm, for a 3D Euclidean error of 0.92 mm, well within the acceptable range for GBM irradiation. An extensive series of systematic tests of comprehensive geometries is planned to determine the accuracy in various tumor locations and geometries including dosimetric effects. The data obtained from these preclinical investigations, when completed, will support optimal testing of concurrent TTFields and radiation for safety/tolerability and ultimately efficacy.

Glioblastoma (GBM) cancer stem cells and their neural stem cell counterparts are hypothesized to contribute to tumor progression. We examined whether GBM contrast enhancement contact with neurogenic regions (NR) affect recurrence patterns, as contrast enhancement reflects regions of blood-brain barrier breakdown.102 patients with primary GBM, treated at Johns Hopkins Hospital between 2006 and 2009, were included. All patients underwent surgical resection followed by adjuvant IMRT (60 Gy/30 fractions) and concomitant temozolomide. Initial and recurrent tumor distance from the subventricular zone (SVZ) or subgranular zone (SGZ) was measured. Tumors were categorized as NR contacting or non-contacting. The chi-square test was used to analyze the association between tumor contact and recurrence pattern.49 of 102 (48.0%, 95% CI: 0.386-0.576) tumors contacted NRs at initial presentation, and, of these tumors, 49/49 (100%) contacted NRs at recurrence. Of 53 tumors that were initially non-contacting, 37/53 (69.8%, 95% CI: 0.565-0.804) recurred contacting NRs. In total, 86/102 (84.3%, 95% CI: 0.760-0.901) recurrent GBM contacted NRs compared with 49/102 (48%, 95% CI: 0.386-0.576) at initial presentation. Of the recurrent tumors that did not contact NRs, 16/53 (30.1%, 95% CI: 0.195-0.435) recurred medially toward NRs with a significant decrease in distance between tumor contrast enhancement and NRs. 16/49 (32.6%, 95% CI: 0.212-0.466) initially NR-contacting GBMs recurred out-of field while 7/53 (13.2%, 95% CI: 0.0655-0.248) initially non-contacting recurred out of the radiation treatment field (p=0.0315, Odds ratio: 3.19, 95% CI: 1.18-8.62).GBM contrast-enhancing recurrence is significantly associated with proximity to NRs. NR-contacting initial tumors were more likely to recur out of radiation treatment fields.

PURPOSE: This study examines white matter integrity as measured by DTI and proton MR spectroscopy (MRS) and their associations with region specific radiation dose and neuropsychological functioning in children treated with cranial irradiation. METHODS: 20 patients and 34 age-& sex-matched controls participated. MRS and DTI and neuropsychological assessment were conducted at baseline, 6, 15, 27 months (times 1-4) following RT and compared to a single visit in controls. Neuro-psychological battery included: motor dexterity, visual attention/processing speed, visual and verbal working memory. White matter regions contoured and apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were recorded for each. Concentrations of neuro-metabolites were expressed as ratios N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr. Linear mixed effects (LME) regression models were used to examine associations among ADC, FA, metabolite ratios, RT dose to contoured structures, and performance on testing, and to compare findings for patients versus controls. RESULTS: Mean prescription dose: 44.2 Gy (range 2-59.4 Gy). LME analyses demonstrated significant differences between patients and controls in NAA/Cr and ADC, with the greatest difference at time 4 (p =

The purpose of this critical review is to explore the controversy regarding the relationship between radiation dose to the neural progenitor cell (NPC) niches and patient outcomes, in terms of both toxicity and tumor control. NPCs in the subventricular zone (SVZ) and hippocampus are paradoxically associated with long-term neurocognitive sequelae of brain irradiation, as well as resistance to therapy and tumor recurrence. The reconciliation of these somewhat opposing functions is challenging. Current literature suggests that radiation and other treatments against the NPC in the hippocampus and the SVZ may influence patient outcome. As a result, both the SVZ and the hippocampus could have important implications on radiation treatment planning strategies, and future laboratory and clinical evaluations will be critical in designing studies to optimize treatment outcome, effectiveness, and safety.

Invasive pituitary adenomas and pituitary carcinomas are clinically indistinguishable until identification of metastases. Optimal management and survival outcomes for both are not clearly defined. The purpose of this study is to use the Surveillance, Epidemiology, and End Results (SEER) database to report patterns of care and compare survival outcomes in a large series of patients with invasive adenomas or pituitary carcinomas. One hundred seventeen patients diagnosed between 1973 and 2008 with pituitary adenomas/adenocarcinomas were included. Eighty-three invasive adenomas and seven pituitary carcinomas were analyzed for survival outcomes. Analyzed prognostic factors included age, sex, race, histology, tumor extent, and treatment. A significant decrease in survival was observed among carcinomas compared to invasive adenomas at 1, 2, and 5 years (p = 0.047, 0.001, and 0.009). Only non-white race, male gender, and age ≥65 were significant negative prognostic factors for invasive adenomas (p = 0.013, 0.033, and

Cancers, such as melanoma, that are associated with immune deficiencies are a major cause of morbidity and mortality in HIV-infected patients. Once patients develop melanoma metastases to the brain, treatment is often limited to palliative surgery and/or radiation. Ipilimumab, a CTLA-4 antagonist, has been shown to improve the median survival of patients with metastatic melanoma. However, available data regarding the safety and efficacy of ipilimumab in HIV-infected patients who develop intracranial melanoma metastases is limited. Here we report our experience administering ipilimumab to a patient with HIV-AIDS who developed multiple intracranial melanoma metastases. Following treatment, our patient showed improvement in systemic tumor control without any apparent interference with antiretroviral treatment.

Purpose Neural progenitor cells in the subventricular zone (SVZ) have a controversial role in glioblastoma multiforme (GBM) as potential tumor-initiating cells. The purpose of this study was to examine the relationship between radiation dose to the SVZ and survival in GBM patients. Methods and Materials The study included 116 patients with primary GBM treated at the Johns Hopkins Hospital between 2006 and 2009. All patients underwent surgical resection followed by adjuvant radiation therapy with intensity modulated radiation therapy (60 Gy/30 fractions) and concomitant temozolomide. Ipsilateral, contralateral, and bilateral SVZs were contoured on treatment plans by use of coregistered magnetic resonance imaging and computed tomography. Multivariate Cox regression was used to examine the relationship between mean SVZ dose and progression-free survival (PFS), as well as overall survival (OS). Age, Karnofsky Performance Status score, and extent of resection were used as covariates. The median age was 58 years (range, 29-80 years). Results Of the patients, 12% underwent biopsy, 53% had subtotal resection (STR), and 35% had gross total resection (GTR). The Karnofsky Performance Status score was less than 90 in 54 patients and was 90 or greater in 62 patients. The median ipsilateral, contralateral, and bilateral mean SVZ doses were 48.7 Gy, 34.4 Gy, and 41.5 Gy, respectively. Among patients who underwent GTR, a mean ipsilateral SVZ dose of 40 Gy or greater was associated with a significantly improved PFS compared with patients who received less than 40 Gy (15.1 months vs 10.3 months; P =.028; hazard ratio, 0.385 [95% confidence interval, 0.165-0.901]) but not in patients undergoing STR or biopsy. The subgroup of GTR patients who received an ipsilateral dose of 40 Gy or greater also had a significantly improved OS (17.5 months vs 15.6 months; P =.027; hazard ratio, 0.385 [95% confidence interval, 0.165-0.895]). No association was found between SVZ radiation dose and PFS and OS among patients who underwent STR or biopsy. Conclusion A mean radiation dose of 40 Gy or greater to the ipsilateral SVZ was associated with a significantly improved PFS and OS in patients with GBM after GTR.

Background: To examine outcomes and prognostic factors in a large prospectively collected database of patients treated with Gamma Knife (GK) radiosurgery for breast cancer metastases to the brain. Methods: All patients were treated with GK radiosurgery for brain metastases from breast cancer between 1993 and 2009. Overall survival time was calculated from the time of GK radiosurgery to the time of death from any cause. Kaplan-Meier analysis was applied to calculate overall median time to failure and clinical and radiologic features of the study population. Multivariate analysis was performed using Cox Proportional Hazards regression analysis to calculate relative risk for mortality. Results: Two hundred and ninety-two patients with were analyzed over a median follow-up of 8.53 months (reverse Kaplan-Meier follow-up of 66.81 months). The median overall survival for the entire cohort from the time of GK radiosurgery was 9.08 months (95% CI, 7.86-10.63 months). There was a significantly greater median overall survival in patients that had KPS > 70, age 65) and multiple lesions (> 3 lesions) were independent predictors of poor prognosis. The risk of mortality in patients with low KPS, multiple lesions, and older age (as defined above) was 300%, 80%, 50% greater than their counterparts, respectively. Conclusion: Patients with poor performance status and multiple brain metastases from breast cancer have worse outcomes and may be candidates for conservative management. Categories: Radiation Oncology, Neurosurgery

Radiation is used in the study of neurogenesis in the adult mouse both as a model for patients undergoing radiation therapy for CNS malignancies and as a tool to interrupt neurogenesis. We describe the use of a dedicated CT-guided precision device to irradiate specific sub-regions of the adult mouse brain. Improved CT visualization was accomplished with intrathecal injection of iodinated contrast agent, which enhances the lateral ventricles. T2-weighted MRI images were also used for target localization. Visualization of delivered beams (10 Gy) in tissue was accomplished with immunohistochemical staining for the protein γ-H2AX, a marker of DNA double-strand breaks. γ-H2AX stains showed that the lateral ventricle wall could be targeted with an accuracy of 0.19 mm (n = 10). In the hippocampus, γ-H2AX staining showed that the dentate gyrus can be irradiated unilaterally with a localized arc treatment. This resulted in a significant decrease of proliferative neural progenitor cells as measured by Ki-67 staining (P < 0.001) while leaving the contralateral side intact. Two months after localized irradiation, neurogenesis was significantly inhibited in the irradiated region as seen with EdU/NeuN double labeling (P < 0.001). Localized radiation in the rodent brain is a promising new tool for the study of neurogenesis.

This study was designed to examine the effect of adjuvant 5-FU-based chemoradiation therapy (CRT) after distal pancreatectomy for adenocarcinoma of the distal pancreas.All patients underwent curative resection for adenocarcinoma of the distal pancreas between December 1985 and June 2006. Patients who received adjuvant CRT were compared with those who underwent surgery alone. A Kaplan-Meier estimate of the survival curve was used to determine estimates of the median survival and proportion alive at 1 and 2 years; log-rank tests were used to make comparisons between groups.A total of 123 patients underwent distal pancreatectomy; 29 patients were excluded for distant metastases at the time of surgery (n = 12, 10%) or before adjuvant therapy (n = 11, 9%), death within 2 months of surgery (n = 2, 2%), or if CRT treatment status was unknown (n = 4, 3%). Of the remaining 94 patients, 72% received adjuvant 5-FU-based CRT and 28% underwent surgery alone. Overall median survival was 16.2 (95% confidence interval (CI), 13.1-18.9) months. The groups were similar with respect to tumor size, nodal status, and margin status. There was no significant difference in overall survival between patients treated with adjuvant CRT versus surgery alone (p = 0.23). An exploratory subgroup analysis suggested a potential survival benefit of adjuvant CRT in patients with lymph node metastases (16.7 vs. 12.1 months, p0.01).Adjuvant CRT did not increase survival compared with surgery alone; however, patients with node-positive disease appear to benefit from adjuvant CRT.

Purpose To determine whether lung tumor respiratory excursion at simulation is predictive of excursion during radiation and whether phase offsets between tumor and surrogate markers are constant throughout treatment. Methods and Materials Respiration-correlated CT scans and two rescans (using a Brilliance Big Bore spiral CT simulator; Philips, Inc.) were obtained from 20 patients at simulation. Gross tumor volume (GTV) was contoured on 10 phases of the respiratory cycle, and excursions were calculated. Diaphragm and xyphoid motion were quantified. Phase offsets, ΔΦ, were calculated for patients with a GTV motion of >3 mm. Interfraction differences in excursions between simulation and rescans and magnitudes of variation in phase offset between fractions were evaluated. Results Mean GTV excursions at simulation in superior-inferior, anterior-posterior, and medial-lateral directions were 0.67, 0.29, and 0.21 cm, respectively. The magnitude of superior-inferior GTV excursion correlated with tumor location (upper vs. lower lobe, p = 0.011). GTV excursions between simulation and rescan 1 ( p = 0.115) and between simulation and rescan 2 ( p = 0.071) were stable. Fourteen patients were analyzed for variations in phase offsets. GTV–xyphoid phase offset changed significantly between simulation and rescan 1 ( p = 0.007) and simulation and rescan 2 ( p = 0.008), with mean ΔΦ values of 13.2% (rescan 1) and 14.3% (rescan 2). Xyphoid–diaphragm offset changed between simulation and rescan 1 ( p = 0.004) and between simulation and rescan 2 ( p = 0.012), with mean ΔΦ values of 14.5% (rescan 1) and 7.6% (rescan 2). Conclusions Interfraction consistency in tumor excursion suggests tumor excursion at simulation may direct therapy. Significant variations in phase lag between GTV and other anatomic structures throughout treatment have important implications for techniques that rely on surrogate structures to predict tumor motion

Purpose/Objective(s): Radiation is hypothesized to potentiate the efficacy of the immune response to tumor cells. Here, we aim to retrospectively characterize the treatment effect of stereotactic radiosurgery (SRS) and whole brain radiation therapy (WBRT) in a cohort of patients with intracranial metastases. Specifically we examined intracranial disease progression following radiation with and without concurrent immunotherapy. Materials/Methods: We identified metastatic non-small cell lung cancer (NSCLC) and metastatic melanoma patients who had intracranial metastases treated with radiation. Radiation treatments consisted of WBRT or SRS at a single institution from 2011-2014. We retrospectively reviewed patient demographics, pathology, oncologic treatment course, and radiographic imaging. Patients were defined as having concurrent immunotherapy if a cycle of Ipilimumab or Nivolumab was given within thirty days pre or post-radiation. Progression free survival (PFS) was defined from date of intracranial radiation to intracranial progression and overall survival (OS) was defined from date of intracranial radiation to date of death. Patients were categorized as having no intracranial progression, local progression within the treatment field, and/or new metastatic disease. The absolute number of new intracranial metastases was recorded following RT. Data was analyzed using Kaplan-Meier survival curves, unpaired two-tailed t-test and Fisher’s exact test. Results: We included 74 adults with metastatic melanoma (nZ51) or NSCLC (nZ23) treated for intracranial metastases with SRS (nZ46) or WBRT (nZ28). In total 23 patients were treated with Ipilimumab or Nivolumab and 17 of these patients were treated concurrently with radiation. PFS and OS for this cohort was a median of 15 months (range:1-51 mo) and 27 months (range:6-76mo). At the time of intracranial progression, 93%of SRS patients who received SRS alone had new intracranial metastases compared to 53% in patients who received concurrent immunotherapy (pZ0.0006, OR 17.14, 95% CI:2.97-99.1). SRS patients who did not receive concurrent immunotherapy had a mean of 7 (range 0-35, SEM 1.49) subsequent brain metastases compared to amean of 1 (range 0-5, SEMZ0.43) in patients who received concurrent immunotherapy (p

Purpose/Objective(s): Observation after detection is now frequently selected as a primary management option for vestibular schwannoma (VS). It is uncertain whether this approach affects patient outcomes. It is possible that patients treated at time of progression are at an increased risk of treatment failure compared to patients treated at the time of initial detection, even among patients who may not have progressed for many years without treatment. In this study, we explore whether the decision for early or delayed treatment impacts treatment success among patients treated with hypofractionated stereotactic radiation therapy (HSRT). Materials/Methods: A retrospective review of 432 VS patients treated with HSRT regimens of 25Gy in 5 fractions or 12-15Gy in 1 fraction was performed. Patients were stratified as: (1) Early (nZ291, 67.4%), patients treated at time of initial presentation and (2) Delayed (nZ141, 32.6%), patients with radiological and/or clinical progression during a period of observation. Continuous data are summarized using median (interquartile range) and categorical data via frequency (percentage). Outcomes were measured from the date of treatment. Results: The median follow-up was 73.3 (48.7-102.9) months in the early group and 61.5 (41.0-88.7) months in the Delayed group. Baseline demographics and median baseline tumor volume (BTV) between the two groups were similar, except for older age at treatment (P 0.05). No significant differences were observed between groups with regards to median tumor volume at last follow-up, treatment failure requiring salvage microsurgery, or rate of clinical/radiological progression after treatment. Of note, a greater reduction in baseline tumor volume was observed in the Delayed group (median: -41.1%, IQR: -66.7% 9.4%) compared to the Early group (median: -32.5%, IQR: -66.7% 11.0%); however, this finding was not significant (P>0.05). Salvage microsurgery was required in 11 (3.8%) patients in the early group and 3 (2.1%) patients in the Delayed group. Ultimately, radiation therapy was equally successful in most patients in both groups (Early: nZ280, 96.2% vs Delayed: nZ138, 97.9%, PZ0.6). Conclusion: We report no difference in treatment failure rates among VS patients treated at time of initial detection versus those treated at time of progression. These data suggest that delaying RT-related toxicity by postponing RT until progression may be a reasonable approach. Author Disclosure: E.W. Sankey: None. A.E. Marciscano: None. I. Jusue-Torres: Research Grant; Salisbury Family Foundation. A. Liu: None. H.W. Francis: None. M. Lim: None. K.J. Redmond: Research Grant; Elekta Ab oligometastases research consortium. D. Rigamonti: Research Grant; Nicholl Family Foundation, Salisbury Family Foundation. L.R. Kleinberg: None.

Figure 1 in the above-referenced article was publishedwithout an acknowledgment in error. The figure should have been credited as follows:© 2006MediVisuals Inc. Reprintedwith permission fromBarani IJ, Benedict SH, Lin PS, “Neural stem cells: implications for the conventional radiotherapy of central nervous systemmalignancies,” Int J RadiatOncol Biol Phys 68(2):324-333, 2007.We regret the omission.

2098 Background: In patients with low-grade gliomas, pathologic grade at time of progression has important therapeutic and prognostic implications. Whether surrogate radiographic variables such as ...