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PurposeWe sought to investigate the tumor control probability (TCP) of vestibular schwannomas after single-fraction stereotactic radiosurgery (SRS) or hypofractionated SRS over 2 to 5 fractions (fSRS).Methods and materialsStudies (PubMed indexed from 1993-2017) were eligible for data extraction if they contained dosimetric details of SRS/fSRS correlated with local tumor control. The rate of tumor control at 5 years (or at 3 years if 5-year data were not available) were collated. Poisson modeling estimated the TCP per equivalent dose in 2 Gy per fraction (EQD2) and in 1, 3, and 5 fractions.ResultsData were extracted from 35 publications containing a total of 5162 patients. TCP modeling was limited by the absence of analyzable data of 12 Gy. Using linear-quadratic-based dose conversion, the 3- to 5-year TCP was estimated at 95% at an EQD2 of 25 Gy, corresponding to 1-, 3-, and 5-fraction doses of 13.8 Gy, 19.2 Gy, and 21.5 Gy, respectively. Single-fraction doses of 10 Gy, 11 Gy, 12 Gy, and 13 Gy predicted a TCP of 85.0%, 88.4%, 91.2%, and 93.5%, respectively. For fSRS, 18 Gy in 3 fractions (EQD2 of 23.0 Gy) and 25 Gy in 5 fractions (EQD2 of 30.2 Gy) corresponded to TCP of 93.6% and 97.2%. Overall, the quality of dosimetric reporting was poor; recommended reporting guidelines are presented.ConclusionsWith current typical SRS doses of 12 Gy in 1 fraction, 18 Gy in 3 fractions, and 25 Gy in 5 fractions, 3- to 5-year TCP exceeds 91%. To improve pooled data analyses to optimize treatment outcomes for patients with vestibular schwannoma, future reports of SRS should include complete dosimetric details with well-defined tumor control and toxicity endpoints.

PurposeDosimetric and clinical predictors of radiation-induced optic nerve/chiasm neuropathy (RION) after single-fraction stereotactic radiosurgery (SRS) or hypofractionated (2-5 fractions) radiosurgery (fSRS) were analyzed from pooled data that were extracted from published reports (PubMed indexed from 1990 to June 2015). This study was undertaken as part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, investigating normal tissue complication probability (NTCP) after hypofractionated radiation.Methods and materialsEligible studies described dose delivered to optic nerve/chiasm and provided crude or actuarial toxicity risks, with visual endpoints (ie, loss of visual acuity, alterations in visual fields, and/or blindness/complete vision loss). Studies of patients with optic nerve sheath tumors, optic nerve gliomas, or ocular/uveal melanoma were excluded to obviate direct tumor effects on visual outcomes, as were studies not specifying causes of vision loss (ie, tumor progression vs RION).ResultsThirty-four studies (1578 patients) were analyzed. Histologies included pituitary adenoma, cavernous sinus meningioma, craniopharyngioma, and malignant skull base tumors. Prior resection (76% of patients) did not correlate with RION risk (P = .66). Prior irradiation (6% of patients) was associated with a crude 10-fold increased RION risk versus no prior radiation therapy. In patients with no prior radiation therapy receiving SRS/fSRS in 1-5 fractions, optic apparatus maximum point doses resulting in

Purpose: To demonstrate that (125)I seeds can be localized in transrectal ultrasound (TRUS) images obtained with a high-resolution probe when the implant is performed with linked seeds and spacers. Adequate seed localization is essential to the implementation of TRUS-based intraoperative dosimetry for prostate brachytherapy. Methods and Materials: Thirteen preplanned peripherally loaded prostate implants were performed using (125)I seeds and spacers linked together in linear arrays that prevent seed migration and maintain precise seed spacing. A set of two-dimensional transverse images spaced at 0.50-cm intervals were obtained with a high-resolution TRUS probe at the conclusion of the procedure with the patient still under anesthesia. The image set extended from 1.0 cm superior to the base to 1.0 cm inferior to the apex. The visible echoes along each needle track were first localized and then compared with the known construction of the implanted array. The first step was to define the distal and proximal ends of each array. The visible echoes were then identified as seeds or spacers from the known sequence of the array. The locations of the seeds that did not produce a visible echo were interpolated from their known position in the array. A CT scan was obtained after implantation for comparison with the TRUS images. Results: On average, 93% (range, 86-99%) of the seeds were visible in the TRUS images. However, it was possible to localize 100% of the seeds in each case, because the locations of the missing seeds could be determined from the known construction of the arrays. Two factors complicated the interpretation of the TRUS images. One was that the spacers also produced echoes. Although weak and diffuse, these echoes could be mistaken for seeds. The other was that the number of echoes along a needle track sometimes exceeded the number of seeds and spacers implanted. This was attributed to the overall length of the array, which was approximately 0.5 cm longer than the center-to-center distance between the first and last seed owing to the finite length of the seeds at the ends of the array. When this occurred, it was necessary to disregard either the most distal or most proximal echo, which produced a 0.5-cm uncertainty in the location of the array in the axial direction. For these reasons, simply localizing the visible echoes in the TRUS images did not guarantee the reliable identification of the seeds. Conclusion: Our results have demonstrated that a high percentage (>85%) of the implanted (125)I seeds can be directly visualized in postimplant TRUS images when the seeds and spacers are linked to preclude seed migration and rotation and when the images are obtained with a high-resolution TRUS probe. Moreover, it is possible to localize 100% of the seeds with the mechanism of linked seeds because the locations of the missing seeds can be determined from the known construction of the arrays. [ABSTRACT FROM AUTHOR]