Predictors for long-term survival free from whole brain radiation therapy in patients treated with radiosurgery for limited brain metastases

PURPOSE: To identify predictors for prolonged survival free from salvage whole brain radiation therapy (WBRT) in patients with brain metastases treated with stereotactic radiosurgery (SRS) as their initial radiotherapy approach. MATERIALS AND METHODS: Patients with brain metastases treated with SRS from 2001 to 2013 at our institution were identified. SRS without WBRT was typically offered to patients with 1-4 brain metastases, Karnofsky performance status \u3e /=70, and life expectancy \u3e /=3 months. Three hundred and eight patients met inclusion criteria for analysis. Medical records were reviewed for patient, disease, and treatment information. Two comparison groups were identified: those with \u3e /=1-year WBRT-free survival (N = 104), and those who died or required salvage WBRT within 3 months of SRS (N = 56). Differences between these groups were assessed by univariate and multivariate analyses. RESULTS: Median survival for all patients was 11 months. Among patients with \u3e /=1-year WBRT-free survival, median survival was 33 months (12-107 months) with only 21% requiring salvage WBRT. Factors significantly associated with prolonged WBRT-free survival on univariate analysis (p \u3c 0.05) included younger age, asymptomatic presentation, RTOG RPA class I, fewer brain metastases, surgical resection, breast primary, new or controlled primary, absence of extracranial metastatic disease, and oligometastatic disease burden ( \u3c /=5 metastatic lesions). After controlling for covariates, asymptomatic presentation, breast primary, single brain metastasis, absence of extracranial metastases, and oligometastatic disease burden remained independent predictors for favorable WBRT-free survival. CONCLUSION: A subset of patients with brain metastases can achieve long-term survival after upfront SRS without the need for salvage WBRT. Predictors identified in this study can help select patients that might benefit most from a treatment strategy of SRS alone

Prescription dose evaluation for APBI with noninvasive image-guided breast brachytherapy using equivalent uniform dose

ABSTRACT PURPOSE: Noninvasive image-guided breast brachytherapy (NIBB) is an attractive novel approach to deliver accelerated partial breast irradiation (APBI). Calculations of equivalent uniform dose (EUD) were performed to identify the appropriate APBI dose for this technique. METHODS AND MATERIALS: APBI plans were developed for 15 patients: five with threedimensional conformal APBI (3D-CRT), five with multi-lumen intracavitary balloons (m-IBB), and five simulating NIBB treatment. Prescription doses of 34.0 and 38.5 Gy were delivered in 10 fractions for m-IBB and 3D-CRT, respectively. Prescription doses ranging from 34.0 to 38.5 Gy were considered for NIBB. Dose-volume histogram data from all 3D-CRT, m-IBB, and NIBB plans were used to calculate the biologically effective EUD and corresponding EUD to the PTV_eval using the following equation: ). An a/b value of 4.6 Gy was assumed for breast tumor. EUD for varying NIBB prescription doses were compared with EUD values for the other APBI techniques. RESULTS: Mean PTV_eval volume was largest for 3D-CRT (372.9 cm 3 ) and was similar for NIBB and m-IBB (88.7 and 87.2 cm 3 , respectively). The EUD value obtained by prescribing 38.5 Gy with 3D-CRT APBI was 38.6 Gy. The EUD value of 34.0 Gy prescribed with m-IBB was 34.4 Gy. EUD values for NIBB ranged from 33.9 to 38.2 Gy for prescription doses ranging from 34.0 to 38.5 Gy. CONCLUSIONS: Using EUD calculations to compare APBI techniques and treatment doses, a prescription dose of 36.0 Gy in 10 fractions using NIBB has a comparable biologic equivalent dose to other established brachytherapy techniques.

Nanoparticulate TiO2-promoted PtRu/C catalyst for methanol oxidation: TiO2 nanoparticles promoted PtRu/C catalyst for MOR

To improve the electrocatalytic properties of PtRu/C in methanol electrooxidation, nanoparticulate TiO2-promoted PtRu/C catalysts were prepared by directly mixing TiO2 nanoparticles with PtRu/C. Using cyclic voltammetry, it was found that the addition of 10 wt% TiO2 nanoparticles can effectively improve the electrocatalytic activity and stability of the catalyst during methanol electro-oxidation. The value of the apparent activation energy (Ea) for TiO2-PtRu/C was lower than that for pure PtRu/C at a potential range from 0.45 to 0.60 V. A synergistic effect between PtRu and TiO2 nanoparticles is likely to facilitate the removal of CO-like intermediates from the surface of PtRu catalyst and reduce the poisoning of the PtRu catalysts during methanol electrooxidation. Therefore, we conclude that the direct introduction of TiO2 nanoparticles into PtRu/ C catalysts offers an improved facile method to enhance the electrocatalytic performance of PtRu/C catalyst in methanol electrooxidation.Web of Scienc

SU‐E‐T‐438: Dosimetric Effect of Patient Arm Position in Spinal CyberKnife Robotic Radiosurgery

Purpose: For treatment of spine lesions with robotic CyberKnife (Accuray, Sunnvale, CA) radiosurgery, patients are simulated in the supine position with arms along the torso. Treatments often include lateral beams passing through the arms. Variation in arm position between simulation and delivery could affect delivered doses. The purpose of this work is to evaluate the potential dosimetric effect of patient extremity motion on spinal CyberKnife treatments. Methods: Thirteen patients were selected with spinal lesions between T10 and L4. Prescription doses ranged between 1800 and 4000 cGy, delivered in 1 to 5 fractions. In addition to the treatment plan used as reference standard, a comparison plan was created with the arms contoured and contour density set to zero for each patient. This represented the extreme scenario of the patient moving their arm completely out of the field. Results: Results: The mean difference for the minimum dose to the PTV, the maximum dose to the spinal cord, and dose to 250 cc of spinal cord are 2.4%, 4.8% and 4.5%. PTV coverage in compared plans was changed by 1.4% on average, with the coverage improved, due to less attenuation from the patient arms. As the mean arm dose relative to the prescription dose increased, the impact of removing the arms also increased. Conclusion: The most extreme scenario of extremity motion in CyberKnife spinal radisurgery was investigated. It was found that the dosimetric impact of the arms is small. The difference in PTV coverage was 1.4%, with a difference % in minimum dose to the PTV was 2.4%. Dose differences to critical organs were within 5%. Therefore, any reasonable motion due to set‐up variations and deviation from patient simulation position will be negligible

Stereotactic radiosurgery for large brain metastases

We evaluated patient outcomes following stereotactic radiosurgery (SRS)-treatment of large brain metastasis (3cm) at our institution. SRS is an established treatment for limited brain metastases. However, large tumors pose a challenge for this approach. For this study, 343 patients with 754 total brain metastases were treated with SRS, of which 93 had large tumors. The tumor size was 3-3.5, 3.5-4, and 4cm in 29%, 32%, and 39% of these patients. Surgical resection was performed prior to SRS in 68% of patients, and 53% achieved a gross total resection. The local control of large metastases was inferior compared to smaller tumors, with 1 year local control of 68 versus 86%, respectively (p \u3c 0.001). Among the patients with large metastases, no correlation between local control and surgical resection (p=0.747), or extent of surgery (gross total versus subtotal resection; p=0.120), was identified. Histology (p=0.939), tumor size (3-4 versus \u3e 4cm; p=0.551), and SRS dose (16 versus \u3e 16Gy; p=0.539) also showed no correlation with local failure. The overall survival at 1, 2, and 5years was 46%, 29% and 5%, respectively. Prolonged survival was seen in patients with age \u3c 65years (p=0.009), primary treatment compared with salvage (p=0.077), and controlled primary tumors (p=0.022). Radiation necrosis developed in 10 patients (11.8%). For patients with large brain metastases, SRS is well tolerated and can achieve local central nervous system disease control in the majority of patients, and extended survival in some, though the local control rate is suboptimal. Further strategies to improve the outcomes in this subgroup of patients are needed

Stereotactic radiosurgery for large brain metastases.

We evaluated patient outcomes following stereotactic radiosurgery (SRS)-treatment of large brain metastasis (⩾3 cm) at our institution. SRS is an established treatment for limited brain metastases. However, large tumors pose a challenge for this approach. For this study, 343 patients with 754 total brain metastases were treated with SRS, of which 93 had large tumors. The tumor size was 3-3.5, 3.5-4, and ⩾4 cm in 29%, 32%, and 39% of these patients. Surgical resection was performed prior to SRS in 68% of patients, and 53% achieved a gross total resection. The local control of large metastases was inferior compared to smaller tumors, with 1 year local control of 68 versus 86%, respectively (p4 cm; p=0.551), and SRS dose (⩽16 versus >16 Gy; p=0.539) also showed no correlation with local failure. The overall survival at 1, 2, and 5 years was 46%, 29% and 5%, respectively. Prolonged survival was seen in patients with age <65 years (p=0.009), primary treatment compared with salvage (p=0.077), and controlled primary tumors (p=0.022). Radiation necrosis developed in 10 patients (11.8%). For patients with large brain metastases, SRS is well tolerated and can achieve local central nervous system disease control in the majority of patients, and extended survival in some, though the local control rate is suboptimal. Further strategies to improve the outcomes in this subgroup of patients are needed