Background/Objectives: Medulloblastoma is the most common malignant brain tumor in children. In recent decades, the therapeutic landscape has undergone significant changes, with stereotactic radiosurgery (SRS) emerging as a promising treatment for recurrent cases. Our study provides a comprehensive analysis of the long-term efficacy and safety of SRS in recurrent medulloblastomas across both pediatric and adult patients at a single institution. Methods: We retrospectively reviewed the clinical and radiological records of patients who underwent CyberKnife SRS for recurrent cranial medulloblastomas at our institution between 1998 and 2023. Follow-up data were available for 15 medulloblastomas in 10 patients. The cohort comprised eight pediatric patients (ages 3-18) and two adult patients (ages 19-75). The median age at the time of SRS was 13 years, the median tumor volume accounted for 1.9 cc, the median biologically equivalent dose (BED) was 126 Gy, and the single-fraction equivalent dose (SFED) was 18 Gy. The SRS was administered at 75% of the median isodose line. Results: Following a median follow-up of 39 months (range: 6-78), 53.3% of the medulloblastomas progressed, 13.3% regressed, and 33.3% remained stable. The 3-year local tumor control (LTC) rate for all medulloblastomas was 65%, with lower rates observed in the adult cohort (50%) and higher rates in pediatric patients (67%). The 3-year overall survival (OS) rate was 70%, with significantly higher rates in pediatric patients (75%) compared to adult patients (50%). The 3-year progression-free survival (PFS) rate was 58.3%, with higher rates in pediatric patients (60%) compared to adult patients (50%). Two pediatric patients developed radiation-induced edema, while two adult patients experienced radiation necrosis at the latest follow-up, with both adult patients passing away. Conclusions: Our study provides a complex perspective on the efficacy and safety of CyberKnife SRS in treating recurrent cranial medulloblastomas across pediatric and adult populations. The rarity of adverse radiation events (AREs) underscores the safety profile of SRS, reinforcing its role in enhancing treatment outcomes. The intricacies of symptomatic outcomes, intertwined with factors such as age, tumor location, and prior surgeries, emphasize the need for personalized treatment approaches. Our findings underscore the imperative for ongoing research and the development of more refined treatment strategies for recurrent medulloblastomas. Given the observed disparities in treatment outcomes, a more meticulous tailoring of treatment approaches becomes crucial.

BACKGROUND: White epidermoid cysts (WECs) are a rare type of epidermoid cyst with atypical radiological features. The epidemiological aspects and mechanisms of their onset remain unknown. Herein, the authors report a unique case of WEC transformation from a typical epidermoid cyst after stereotactic radiosurgery (SRS), confirmed by radiological and pathological findings.
METHODS: The case involved a 78-year-old man with a history of 2 surgeries for a left cerebellopontine angle typical epidermoid cyst 23 years earlier and SRS using the CyberKnife for recurrent trigeminal neuralgia (TN) 14 years earlier. The tumor with high intensity on T1-weighted imaging, low intensity on T2-weighted imaging, without restriction on diffusion-weighted imaging had gradually enlarged after SRS. Therefore, a salvage surgery was performed via a left suboccipital craniotomy, and the intraoperative findings showed a cyst with a brown, viscous liquid component, consistent with those of WECs. Histopathologically, keratin calcification and hemorrhage were identified, leading to a diagnosis of WEC. The postoperative course was uneventful, and the TN resolved. No tumor recurrence was recorded at 2 years postoperatively.
CONCLUSIONS: To the best of the authors\' knowledge, this is the first world case of WEC transformation from a typical epidermoid cyst after SRS, confirmed by radiological and pathological findings. Radiation effects could have been involved in this transformation.

UNASSIGNED: The aim of this study was to evaluate local tumor control and complication development rates of fractionated CyberKnife radiosurgery (CRS) in patients with choroidal melanoma.
UNASSIGNED: A total of 29 patients with choroidal melanoma were treated with fractionated CRS at Ankara Oncology Research and Training Hospital, Department of Radiotherapy between May 2009 and December 2013. Patients were treated with CRS if the initial height of the choroidal melanoma was ≥ 6 mm, or juxtapapillary and/or juxtamacular tumors with a height of >2.5 mm. Ophthalmic examinations were performed at baseline and at months 3, 6, 9 and 15 after radiotherapy. Assessment of visual acuity and measurement of tumor base dimension and height using A-scan and B-scan echography were done at each visit.
UNASSIGNED: The mean age was 56 (27-75) years. Tumor was located on choroid in 23 and on ciliochoroid in 6 patients. 86.2% of all melanomas were classified as medium sized and 23.8% as large sized. A median total dose of 5000 cGy was applied. Median tumor height decreased from 7.5 mm at baseline to 4.4 mm at the last follow-up visit (p < 0.001). Median visual acuity decreased from 0.4 at baseline to hand motion (p < 0.001). One patient had been lost to the metastatic disease and one patient had been treated with enucleation due to recurrent tumor growth.
UNASSIGNED: CRS is an effective and reliable local treatment modality in uveal melanoma.

A pituitary carcinoma (PC) is a rare neoplasm, accounting for only 0.2% of pituitary tumors, and is defined by the presence of noncontiguous metastatic disease. Its management requires a multimodal approach including surgery, irradiation, and medical therapy. Stereotactic radiosurgery (SRS) by means of the Gamma Knife or CyberKnife may be considered potentially useful in such cases. It has mainly been applied for localized metastases and symptomatic lesions, but it may also be effective in control of aggressive tumor growth at the primary site after sufficient surgical debulking of the lesion. Given the infrequency of PC and their heterogeneous nature with regard to the histopathological type, local extension, and location of metastases, large clinical series have not been compiled to date. While, in such cases, SRS is certainly not curative and does not prevent disease progression, it is quite reasonable to incorporate this treatment option into a multimodal management strategy and apply it judiciously at the treating clinician\'s discretion on a case-by-case basis.

OBJECTIVE: Experience with management of craniopharyngiomas (CPH) was evaluated retrospectively.
METHODS: Between 1981 and 2012, 100 patients underwent removal of a CPH (the main surgical group), and an original tumor grading system was applied to these cases. The mean length of follow-up was 121 months. Additionally, 17 patients underwent removal of a CPH between 2012 and 2017 (the supplementary surgical group), and in 6 of them, CyberKnife radiosurgery was performed on a residual tumor (in 5 cases) or at the time of recurrence (in 1 case).
RESULTS: In the main surgical group, the gross total resection (GTR) rate was 81%. The early and late disease-specific postoperative mortality rates were 0% and 2%, respectively. Tumor recurrence was never noted after GTR. There was a statistically significant increase in the Karnofsky Performance Scale (KPS) score after surgery. The tumor surgical grade was inversely associated with both the pre- and postoperative KPS scores, and was lower in cases operated on via the transnasal transsphenoidal approach, but was unrelated to the GTR rate. In the supplementary surgical group, the GTR rate was 65%. CyberKnife radiosurgery consistently resulted in tumor shrinkage.
CONCLUSIONS: GTR is the preferred management option for CPH. The original surgical grading system developed at Tokyo Women\'s Medical University may be helpful for clinical decision-making. CyberKnife radiosurgery for residual and recurrent CPH is associated with high tumor response rates.

OBJECTIVE: To develop an automated optimization strategy to facilitate collimator design for small-field radiotherapy systems.
METHODS: We developed an objective function that links the dose profile characteristics (FWHM, penumbra, and central dose rate) and the treatment head geometric parameters (collimator thickness/radii, source-to-distal-collimator distance[SDC]) for small-field radiotherapy systems. We performed optimization using a downhill simplex algorithm. We applied this optimization strategy to a linac-based radiosurgery system to determine the optimal geometry of four pencil-beam collimators to produce 5, 10, 15, and 20mm diameter photon beams (from a 6.7MeV, 2.1mmFWHM electron beam). Two different optimizations were performed to prioritize minimum penumbra or maximum central dose rate for each beam size. We compared the optimized geometric parameters and dose distributions to an existing clinical system (CyberKnife).
RESULTS: When minimum penumbra was prioritized, using the same collimator thickness and SDC (40cm) as a CyberKnife system, the optimized collimator upstream and downstream radii agreed with the CyberKnife system within 3-14%, the optimized output factors agreed within 0-8%, and the optimized transverse and percentage depth dose profiles matched those of the CyberKnife with the penumbras agreeing within 2%. However, when maximum dose rate was prioritized, allowing both the collimator thickness and SDC to change, the central dose rate for larger collimator sizes (10, 15, 20mm) could be increased by about 1.5-2 times at the cost of 1.5-2 times larger penumbras. No further improvement in central dose rate for the 5mm beam size could be achieved.
CONCLUSIONS: We developed an automated optimization strategy to design the collimator geometry for small-field radiation therapy systems. Using this strategy, the penumbra-prioritized dose distribution and geometric parameters agree well with the CyberKnife system as an example, suggesting that this system was designed to prioritize sharp penumbra. This represents proof-of-principle that an automated optimization strategy may apply to more complex collimator designs with multiple optimization parameters.

Distant urethral metastasis of the castration-resistant prostate cancer (CRPC) is very rare. In this case report, we present a 69-year-old man who was first diagnosed prostate cancer from the sessile papillary tumor in the prostatic urethra which recurred after surgery and androgen deprivation therapy and finally treated with CyberKnife radiosurgery. There has been no recurrence for 50 months. To the best of our knowledge, there is no case of urethral metastasis of the CRPC successfully controlled with CyberKnife radiosurgery in the literature.

A pineal parenchymal tumor of intermediate differentiation (PPID) is a rare entity, and optimal treatment is still unclear. Combined multimodality treatment should be considered in PPID due to high recurrence rates. Gross total resection is the first choice of treatment, however, it may not be feasible in every case due to location. Stereotactic radiosurgery (SRS) can be considered for the treatment of primary and recurrent disease, as it enables us to deliver a high radiation dose to the target while minimizing radiation exposure to normal tissue. In this report, we present a case treated with hypofractionated SRS for recurrent/metastatic PPID after the primary tumor was controlled with the combination of surgery and conventionally fractionated radiotherapy.

Head and neck paragangliomas (HNPs) are rare, usually benign hyper vascularized neuroendocrine tumors that traditionally have been treated by surgery, with or without endovascular embolization, or, more recently stereotactic radiosurgery (SRS). The aim of our study is to determine the clinical and radiographic effectiveness of SRS for treatment of HNPs. A systematic search of electronic databases was performed, and 37 articles reporting 11,174 patients (1144 tumors) with glomus jugulare (GJT: 993, 86.9%), glomus tympanicum (GTT: 94, 8.2%), carotid body tumors (CBTs: 28, 2.4%), and glomus vagale (GVT: 16, 1.4%) treated with SRS definitively or adjuvantly were included. The local control (LC) was estimated from the pooled analysis of the series, and its association with SRS technique as well as demographic and clinical factors was analyzed. The median age was 56 years (44-69 years). With a median clinical and radiological follow-up of 44 months (9-161 months), LC was 94.2%. Majority of the patients (61.0%) underwent Gamma Knife Radiosurgery (GKS), but there was no statistically significant difference in LC depending upon the SRS technique (p = 0.9). Spearmen\'s correlation showed that LC was strongly and negatively correlated with multiple parameters, which included female gender (r = - 0.4, p = 0.001), right-sided tumor (r = - 0.3, p = 0.03), primary SRS (r = - 0.5, p ≤ 0.001), and initial clinical presentation of hearing loss (r = - 0.4, p = 0.001). To achieve a LC ≥ 90%, a median marginal dose (Gy) of 15 (range, 12-30 Gy) was required. The results corroborate that SRS in HNPs is associated with good clinical and radiological outcome.

BACKGROUND: 18F-FDG PET/CT metabolic parameters have been applied as prognostic factors in multi-malignancies. However, the role in locally advanced pancreatic cancer (LAPC) was not confirmed. In this study, we investigated the prognostic value of 18F-FDG PET/CT metabolic parameters in LAPC patients treated with stereotactic body radiation therapy (SBRT).
METHODS: Seventy three LAPC patients who received SBRT therapy and pre-treatment 18F-FDG PET/CT imaging from January 2012 to January 2016 were included in this retrospective study. The study aim was to evaluate the relationship between metabolic parameters with clinical factors, and the value of metabolic parameters in the prognosis of LAPC. The median of parameters was set as the cut-off value for statistical analysis. Univariate survival analysis was performed by the Kaplan Meier method and log-rank test, and multivariate analysis was carried out by a Cox proportional hazards model.
RESULTS: Patients with lymph node metastasis or longer tumor diameters were associated with higher TLG (P < 0.05). Univariate analysis showed MTV, TLG, radiotherapy dose and chemotherapy were significantly associated with disease progression-free survival (PFS) and overall survival (OS) (P < 0.05). Lymph node metastasis and tumor longest diameter were associated with OS. Multivariate analysis demonstrated TLG, radiotherapy dose, and chemotherapy were independent factors of PFS and OS (HR: 2.307, 0.591, 0.572 and 2.145, 0.480, 0.471, P < 0.05).
CONCLUSIONS: TLG was found to be the independent prognostic factor of OS and PFS. Among clinical factors, radiotherapy dose and chemotherapy were independent prognostic factors of OS and PFS.