Variable dose interplay effects across radiosurgical apparatus in treating multiple brain metastases

PURPOSE: Normal brain tissue doses have been shown to be strongly apparatus dependent for multi-target stereotactic radiosurgery. In this study, we investigated whether inter-target dose interplay effects across contemporary radiosurgical treatment platforms are responsible for such an observation. METHODS: For the study, subsets ([Formula: see text] and 12) of a total of 12 targets were planned at six institutions. Treatment platforms included the (1) Gamma Knife Perfexion (PFX), (2) CyberKnife, (3) Novalis linear accelerator equipped with a 3.0-mm multi-leaf collimator (MLC), and the (4) Varian Truebeam flattening-filter-free (FFF) linear accelerator also equipped with a 2.5 mm MLC. Identical dose–volume constraints for the targets and critical structures were applied for each apparatus. All treatment plans were developed at individual centers, and the results were centrally analyzed. RESULTS: We found that dose–volume constraints were satisfied by each apparatus with some differences noted in certain structures such as the lens. The peripheral normal brain tissue doses were lowest for the PFX and highest for TrueBeam FFF and CyberKnife treatment plans. Comparing the volumes of normal brain receiving 12 Gy, TrueBeam FFF, Novalis, and CyberKnife were 180–290 % higher than PFX. The mean volume of normal brain-per target receiving 4-Gy increased by approximately 3.0 cc per target for TrueBeam, 2.7 cc per target for CyberKnife, 2.0 cc per target for Novalis, and 0.82 cc per target for PFX. The beam-on time was shortest with the TrueBeam FFF (e.g., 6–9 min at a machine output rate of 1,200 MU/min) and longest for the PFX (e.g., 50–150 mins at a machine output rate of 350 cGy/min). CONCLUSION: The volumes of normal brain receiving 4 and 12 Gy were higher, and increased more swiftly per target, for Linac-based SRS platforms than for PFX. Treatment times were shortest with TrueBeam FFF

Factors influencing prostate cancer patterns of care: An analysis of treatment variation using the SEER database

Purpose: The aim of this study is to describe the trends and factors that influence the initial treatment of men with localized prostate cancer (PC) in the United States between 2004 and 2014. Methods and materials: The National Cancer Institute's Surveillance, Epidemiology and End Results database was used to identify patients with primary prostate adenocarcinoma between 2004 and 2014. Patients were staged in accordance with the American Joint Committee on Cancer 7th edition criteria and stratified according to the National Comprehensive Cancer Network guidelines risk group classification. Descriptive statistics describing treatment patterns by year of diagnosis, age, risk group, insurance status, and region were performed. Results: A total of 460,311 male patients were identified with sufficient information to be categorized into National Comprehensive Cancer Network risk groups. Overall, 30.9% of patients had low-risk disease, 38.1% were intermediate risk, 20.2% were high risk, 4.4% were very high risk, 1.6% were node-positive, and 4.7% had metastatic disease. During the study period, there was a 60% decrease in brachytherapy monotherapy utilization for patients with PC, and no definitive treatment increased from 20.3% in 2004 to 26.3% in 2014. There were regional treatment variations and discrepancies in treatment by age. Radical prostatectomy was performed on a greater proportion of insured patients than patients with Medicaid or those who were uninsured, but radiation therapy and no definitive treatment was administered to a greater proportion of uninsured and Medicaid patients. Conclusions: PC treatment shows declining trends in brachytherapy utilization, increases in conservative management, and stability of surgical procedures over time. There is wide variation by geographical region, age, and insurance status

Delineating the Subarachnoid Space in the Adult Lumbosacral Spine Using Computed Tomographic Myelography: An Aid for Clinical Target Volume Delineation in Craniospinal Irradiation

Purpose: Our aim was to characterize the patterns of cerebrospinal fluid (CSF) extension in the lumbosacral spine using computed tomography (CT) myelograms to provide an evidence base for clinical target volume (CTV) definition in adults receiving craniospinal irradiation. Methods and Materials: This was a retrospective analysis of diagnostic CT lumbar myelograms performed in 30 patients between the ages of 22 and 50. Lateral extension of CSF beyond the thecal sac was measured along each lumbar and sacral nerve root to the nearest millimeter, as was the distance of inferior extension of CSF beyond the caudal end of the thecal sac. Each patient's lateral and inferior CSF extensions were mapped onto a standardized CT data set to create a model target volume in the lumbosacral spine that would contain the aggregate observed CSF distributions from the analyzed CT myelograms. The median extension distances, interquartile ranges, and 90th percentile for distance at each level were calculated. Results: The median lateral extension of CSF along nerve roots beyond the thecal sac—as measured perpendicular to the longitudinal axis—increased from 0 mm (interquartile range [IQR], 0-4 mm) at L1 to 8 mm (IQR, 6-12 mm) at S1 and 0 mm (IQR, 0-0 mm) at S4. The 90th percentile ranged from 5 to 14 mm laterally, with a pattern partially extending into the S1 and S2 sacral foramen. Median CSF extension inferior to the caudal sac was 5 mm (IQR, 2-8 mm), with 90% of patients within 12 mm. An atlas was generated to guide CTV delineation for highly conformal radiation techniques. Conclusion: These results provide information on patterns of CSF extension in the lumbosacral spine of adults and can serve as a model for CTV guidelines that balance comprehensive coverage of the CSF compartment while minimizing the dose to nontarget tissues