Stereotactic Body Radiation Therapy With Simultaneous Integrated Boost in Patients With Spinal Metastases.

Stereotactic body radiation therapy in patients with spine metastases maximizes local tumor control and preserves neurologic function. A novel approach could be the use of stereotactic body radiation therapy with simultaneous integrated boost delivering modality. The aim of the present study is to report our experience in the treatment of spine metastases using a frameless radiosurgery system delivering stereotactic body radiation therapy-simultaneous integrated boost technique. The primary endpoints were the pain control and the time to local progression; the secondary ones were the overall survival and toxicity. A total of 20 patients with spine metastases and 22 metastatic sites were treated in our center with stereotactic body radiation therapy-simultaneous integrated boost between December 2007 and July 2018. Stereotactic body radiation therapy-simultaneous integrated boost treatments were delivered doses of 8 to 10 Gy in 1 fraction to isodose line of 50%. The median follow-up was 35 months (range: 12-110). The median time to local progression for all patients was not reached and the actuarial 1-, 2-, and 3-years local free progression rate was 86.36%. In 17 of 20 patients, a complete pain remission was observed and 3 of 20 patients had a partial pain remission (complete pain remission + partial pain remission: 100%). The median overall survival was 38 months (range 12-83). None of the patients experienced neither radiation adverse events (grade 1-4) nor reported pain flair reaction. None of the patients included in our series experienced vertebral compression fracture. Spine radiosurgery with stereotactic body radiation therapy-simultaneous integrated boost is safe. The use of this modality in spine metastases patients provides an excellent local control.

CyberKnife beam output factor measurements: A multi-site and multi-detector study.

PURPOSE: New promising detectors are available for measuring small field size output factors (OFs). This study focused on a multicenter evaluation of two new generation detectors for OF measurements on CyberKnife systems. METHODS: PTW-60019 microDiamond and W1 plastic scintillation detector (PSD) were used to measure OFs on eight CyberKnife units of various generations for 5-60mm fixed cones. MicroDiamond and PSD OF were compared to routinely used silicon diodes data corrected applying published Monte Carlo (MC) factors. PSD data were corrected for Cerenkov Light Ratio (CLR). The uncertainties related to CLR determination were estimated. RESULTS: Considering OF values averaged over all centers, the differences between MC corrected diode and the other two detectors were within 1.5%. MicroDiamond exhibited an over-response of 1.3% at 7.5mm and a trend inversion at 5mm with a difference of 0.2%. This behavior was consistent among the different units. OFs measured by PSD slightly under-responded compared to MC corrected diode for the smaller cones and the differences were within 1%. The observed CLR variability was 2.5% and the related variation in OF values was 1.9%. CONCLUSION: This study indicates that CyberKnife microDiamond OF require corrections below 2%. The results are enhanced by the consistency observed among different units. Scintillator shows a good agreement to MC corrected diode but CLR determination remains critical requiring further investigations. The results emphasized the value of a multi-center validation over a single center approach.

CyberKnife multisession stereotactic radiosurgery and hypofractionated stereotactic radiotherapy for perioptic meningiomas: intermediate-term results and radiobiological considerations.

Single fraction radiosurgery is conventionally precluded for lesions lying <2-3 mm of the anterior visual pathway because of the radiosensitivity of the optic nerve. We analyzed a series of 64 patients with "perioptic" meningiomas treated by CyberKnife multisession radiosurgery and hypofractionated stereotactic radiotherapy (hSRT). Between July 2007-May 2010, patients were treated using conventional multisession Cyberknife schemes (2-5 fractions) and results were retrospectively analyzed. A radiobiological model was then developed to estimate the best tumor control probability (TCP)/ normal tissue complication probability (NTCP) for these lesions. Resulting dose/fraction schemes were applied to patients treated between May 2010 and July 2014. Data were prospectively collected Twenty-five patients were included in the retrospective part of the study. Median tumor volume was 4.95 cc; median dose was 23.0 Gy and median number of fraction was 5 (range 2-5). No patient had visual deterioration at mean follow-up of 60 ± 12 months. Tumor control was achieved in all cases. Thirty-nine patients were treated according the radiobiology model and results prospectively analyzed. Median tumor volume was 7.5 cc, median dose 25.0 Gy and mean number of fraction 5 (range 3-15). No patient had visual deterioration or tumor progression at mean follow-up of 17 ± 10 months. Conventional multisession CyberKnife treatments (2-5 fractions) provided satisfactory results. Nonetheless, our estimation of TCP suggests the use of higher doses to grant long-term disease control. To achieve higher equivalent doses without significantly increasing the NTCP, we suggest the use of a greater number of fractions, moving to hSRT, in tumors in which the encasement of optic nerves is presumed.

Efficacy and toxicity of CyberKnife re-irradiation and "dose dense" temozolomide for recurrent gliomas.

BACKGROUND: Stereotactic radiosurgery (SRS) can be a useful adjunct to the treatment of recurrent glioblastoma multiforme (GBM). Its combination with chemotherapy is attractive for the possible radiosensitization effect and cytotoxicity on tumor cells in distant areas. The aim of this study was to evaluate the efficacy and toxicity of CyberKnife SRS alone and combined with a "dose-dense" administration of temozolomide (TMZ) for recurrent GBM. METHODS: Between July 2007 and July 2010, 23 patients underwent CyberKnife SRS. In 12 patients irradiation was combined with TMZ at 75 mg/m(2)/day for 21 days every 28 days. The median prescription dose in this group was 20 Gy (mean 20.7 ± 4 Gy) with a median number of fractions of 2. The median dose for the 11 patients who underwent SRS alone was 20 Gy (mean 19.9 ± 4.4 Gy; p = NS). RESULTS: The median survival was 12 months for patients who underwent SRS/TMZ and 7 months for those who received SRS alone (p < 0.01). The 6-month progression-free survival (PFS) of the SRS/TMZ group was 66.7% vs. 18% for those who underwent SRS alone (p = 0.03). The median time to progression (TTP) was 7 months for patients who underwent SRS/TMZ and 4 months for those who underwent SRS alone (p = 0.01). Corticosteroid dependency was developed by most patients; radionecrosis was evident in one patient (4.3%) receiving TMZ. Grade 3 hematological toxicity was recorded in >40% of patients receiving chemotherapy. CONCLUSIONS: The results suggest that Cyberknife re-treatments are relatively safe using selected dose/fraction schemes. The combination with TMZ improved patients' outcomes with OS and 6-month PFS that favorably compares with alternative treatments, but the incidence of major adverse effects was >40%. Further studies are warranted.

Integration of three-dimensional rotational angiography in radiosurgical treatment planning of cerebral arteriovenous malformations.

PURPOSE: Accuracy in delineating the target volume is a major issue for successful stereotactic radiosurgery for arteriovenous malformations. The aim of the present study was to describe a method to integrate three-dimensional (3D) rotational angiography (3DRA) into CyberKnife treatment planning and to investigate its potential advantages compared with computed tomography angiography (CTA) and magnetic resonance angiography. METHODS AND MATERIALS: A total of 20 patients with a diagnosis of cerebral arteriovenous malformation were included in the present study. All patients underwent multislice computed tomography and 3D-volumetric CTA, 3DRA, and 3D magnetic resonance angiography. The contouring of the target and critical volumes was done separately using CTA and thereafter directly using 3DRA. The composite, conjoint, and disjoint volumes were measured. RESULTS: The use of CTA or 3DRA resulted in significant differences in the target and critical volumes. The target volume averaged 3.49 ± 3.01 mL measured using CTA and 3.26 ± 2.93 mL measured using 3DRA, for a difference of 8% (p < .05). The conjoint and disjoint volume analysis showed an 88% volume overlap. The qualitative evaluation showed that the excess volume obtained using CTA was mostly tissue surrounding the nidus and venous structures. The mean contoured venous volume was 0.67 mL measured using CTA and 0.88 mL (range, 0.1-2.7) measured using 3DRA (p < .05). CONCLUSIONS: 3DRA is a volumetric angiographic study that can be integrated into computer-based treatment planning. Although whether 3DRA provides superior accuracy has not yet been proved, its high spatial resolution is attractive and offers a superior 3D view. This allows a better 3D understanding of the target volume and distribution of the radiation doses within the volume. Additional technical efforts to improve the temporal resolution and the development of software tools aimed at improving the performance of 3D contouring are warranted.

Stone-targeted dual-energy CT: a new diagnostic approach to urinary calculosis.

OBJECTIVE: The objective of our study was to assess a stone-targeted low-dose protocol for the detection and characterization of urinary tract stones using a dual-energy CT scanner. SUBJECTS AND METHODS: Thirty-nine patients (20 men, 19 women; age range, 22-87 years; average age, 47 years) with suspected renal colic in which ureteral stones were shown at low-dose unenhanced CT were enrolled in the study. Stone composition could be established in 24 patients, and these patients represent our study population regarding the CT characterization of stones. All examinations were performed with a preliminary low-dose unenhanced CT acquisition of the whole urinary system that was immediately followed by a limited (scanning length, 5 cm) dual-energy acquisition of the region containing the ureteral stone. Stone characterization was assessed using a dual-energy software tool available on the system. Two experienced radiologists who were blinded to the chemical composition of the stones retrospectively reviewed images and analyzed data to determine the composition of the stones. Their results were compared with the biochemical analysis results obtained by stereomicroscopy and infrared spectrometry. RESULTS: Based on in vitro-measured data, our combined protocol reduced dose by up to 50% compared with a full dual-energy acquisition; in addition, the calculated radiation doses of our protocol in patients are comparable to those of low-dose single- and dual-energy protocols. In 24 patients, 24 ureteral stones considered to be responsible for symptoms and detected at low-dose unenhanced CT were also shown at dual-energy CT. Correct chemical composition was obtained by dual-energy analysis in all 24 ureteral calculi regarding the characterization of uric acid (n = 3), calcium salt (n = 18), and combined uric acid-calcium salt (n = 3) stones. CONCLUSION: The use of dual-energy CT attenuation values made it possible to characterize all ureteral calculi, discriminating uric acid stones from calcium salt stones. The increment in radiation exposure due to contemporary scanning with two tubes at different energy levels can be substantially reduced using a limited stone-targeted dual-energy protocol.

Protecting venous structures during radiosurgery for parasagittal meningiomas.

Symptomatic edema is a potential complication of meningioma radiosurgery. Parasagittal meningiomas are at a particular risk for symptomatic edema, suggesting a role for a venous occlusive complication. The authors sought to develop a strategy to optimize CyberKnife stereotactic radiosurgical treatment parameters to reduce the irradiation of the peritumoral venous system. Multislice CT venography with 3D reconstructions was performed and coregistered with thin-section, contrast-enhanced, volumetric MR images. The tumor and critical volumes were contoured on the MR images. Venous anatomical details obtained from the CT venographic study were then exported onto the MR imaging and fused MR imaging-CT study. Target and critical structure volumes and dosimetric parameters obtained with this method were analyzed. The authors found that reducing the irradiation of veins that course along the surface of the meningioma, which may be at risk for radiation-induced occlusion, is feasible in parasagittal meningioma radiosurgery without compromising other treatment parameters including conformality, homogeneity, and target coverage. Long-term follow-up is needed to assess the clinical validity of this treatment strategy.