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Purpose The objective of this study was to compare recurrent tumor locations after radiation therapy with pretreatment delineations of high-grade gliomas from magnetic resonance imaging (MRI) and 3,4-dihydroxy-6-[ 18 F]fluoro-l-phenylalanine ( 18 F-FDOPA) positron emission tomography (PET) using contours delineated by multiple observers. Methods and Materials Nineteen patients with newly diagnosed high-grade gliomas underwent computed tomography (CT), gadolinium contrast-enhanced MRI, and 18 F-FDOPA PET/CT. The image sets (CT, MRI, and PET/CT) were registered, and 5 observers contoured gross tumor volumes (GTVs) using MRI and PET. Consensus contours were obtained by simultaneous truth and performance level estimation (STAPLE). Interobserver variability was quantified by the percentage of volume overlap. Recurrent tumor locations after radiation therapy were contoured by each observer using CT or MRI. Consensus recurrence contours were obtained with STAPLE. Results The mean interobserver volume overlap for PET GTVs (42% ± 22%) and MRI GTVs (41% ± 22%) was not significantly different ( P =.67). The mean consensus volume was significantly larger for PET GTVs (58.6 ± 52.4 cm 3 ) than for MRI GTVs (30.8 ± 26.0 cm 3 , P =.003). More than 95% of the consensus recurrence volume was within the 95% isodose surface for 11 of 12 (92%) cases with recurrent tumor imaging. Ten (91%) of these cases extended beyond the PET GTV, and 9 (82%) were contained within a 2-cm margin on the MRI GTV. One recurrence (8%) was located outside the 95% isodose surface. Conclusions High-grade glioma contours obtained with 18 F-FDOPA PET had similar interobserver agreement to volumes obtained with MRI. Although PET-based consensus target volumes were larger than MRI-based volumes, treatment planning using PET-based volumes may not have yielded better treatment outcomes, given that all but 1 recurrence extended beyond the PET GTV and most were contained by a 2-cm margin on the MRI GTV.

To investigate predictive factors in the development of symptomatic radiation injury after treatment with linear accelerator-based stereotactic radiosurgery for intracerebral arteriovenous malformations and relate the findings to the conclusions drawn by Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC).Archived plans for 73 patients who were treated at the British Columbia Cancer Agency were studied. Actuarial estimates of freedom from radiation injury were calculated using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazards models were used for analysis of incidence of radiation injury. Log-rank test was used to search for dosimetric parameters associated with freedom from radiation injury.Symptomatic radiation injury was exhibited by 14 of 73 patients (19.2%). Actuarial rate of symptomatic radiation injury was 23.0% at 4 years. Most patients (78.5%) had mild to moderate deficits according to Common Terminology Criteria for Adverse Events, version 4.0. On univariate analysis, lesion volume and diameter, dose to isocenter, and a V(x) for doses ≥8 Gy showed statistical significance. Only lesion diameter showed statistical significance (p 0.05) in a multivariate model. According to the log-rank test, AVM volumes5 cm(3) and diameters30 mm were significantly associated with the risk of radiation injury (p0.01). The V(12) also showed strong association with the incidence of radiation injury. Actuarial incidence of radiation injury was 16.8% if V(12) was28 cm(3) and 53.2% if28 cm(3) (log-rank test, p = 0.001).This study confirms that the risk of developing symptomatic radiation injury after radiosurgery is related to lesion diameter and volume and irradiated volume. Results suggest a higher tolerance than proposed by QUANTEC. The widely differing findings reported in the literature, however, raise considerable uncertainties.

To evaluate the feasibility of using volumetric modulated arc therapy (VMAT) to deliver whole brain radiotherapy (WBRT) with hippocampal avoidance and a simultaneous integrated boost (SIB) for one to three brain metastases.Ten patients previously treated with stereotactic radiosurgery for one to three brain metastases underwent repeat planning using VMAT. The whole brain prescription dose was 32.25 Gy in 15 fractions, and SIB doses to brain metastases were 63 Gy to lesionsor=2.0 cm and 70.8 Gy to lesions2.0 cm in diameter. The mean dose to the hippocampus was kept at6 Gy(2). Plans were optimized for conformity and target coverage while minimizing hippocampal and ocular doses. Plans were evaluated on target coverage, prescription isodose to target volume ratio, conformity number, homogeneity index, and maximum dose to prescription dose ratio.Ten patients had 18 metastases. Mean values for the brain metastases were as follows: conformity number = 0.73 +/- 0.10, target coverage = 0.98 +/- 0.01, prescription isodose to target volume = 1.34 +/- 0.19, maximum dose to prescription dose ratio = 1.09 +/- 0.02, and homogeneity index = 0.07 +/- 0.02. For the whole brain, the mean target coverage and homogeneity index were 0.960 +/- 0.002 and 0.39 +/- 0.06, respectively. The mean hippocampal dose was 5.23 +/- 0.39 Gy(2). The mean treatment delivery time was 3.6 min (range, 3.3-4.1 min).VMAT was able to achieve adequate whole brain coverage with conformal hippocampal avoidance and radiosurgical quality dose distributions for one to three brain metastases. The mean delivery time was under 4 min.