Long-Term Outcome of Unilateral Acoustic Neuromas With or Without Hearing Loss: Over 10 Years and Beyond After Gamma Knife Radiosurgery.

BACKGROUND: Since the long-term outcomes of 162 patients who underwent gamma knife radiosurgery (GKS) as an initial or adjuvant treatment for acoustic neuromas (ANs) with unilateral hearing loss were first reported in 1998, there has been no report of a comprehensive analysis of what has changed in GKS practice. METHODS: We performed a retrospective study of the long-term outcomes of 106 patients with unilateral sporadic ANs who underwent GKS as an initial treatment. The mean patient age was 50 years, and the mean initial tumor volume was 3.68 cm3 (range, 0.10-23.30 cm3). The median marginal tumor dose was 12.5 Gy (range, 8.0-15.0 Gy) and the median follow-up duration was 153 months (range, 120-216 months). RESULTS: The tumor volume increased in 11 patients (10.4%), remained stationary in 27 (25.5%), and decreased in 68 patients (64.2%). The actuarial 3, 5, 10, and 15-year tumor control rates were 95.3 ± 2.1%, 94.3 ± 2.2%, 87.7 ± 3.2%, and 86.6 ± 3.3%, respectively. The 10-year actuarial tumor control rate was significantly lower in the patients with tumor volumes of ≥ 8 cm3 (P = 0.010). The rate of maintaining the same Gardner-Robertson scale grade was 28.6%, and that of serviceable hearing was 46.4%. The rates of newly developed facial and trigeminal neuropathy were 2.8% and 4.7%, respectively. The patients who received marginal doses of less than 12 Gy revealed higher tumor control failure rates (P = 0.129) and newly occurred facial or trigeminal neuropathy rates (P = 0.040 and 0.313, respectively). CONCLUSION: GKS as an initial treatment for ANs could be helpful in terms of tumor control, the preservation of serviceable hearing, and the prevention of cranial neuropathy. It is recommended to perform GKS as soon as possible not only for tumor control in unilateral ANs with hearing loss but also for hearing preservation in those without hearing loss.

Optimal mask fixation method for frameless radiosurgery with Leksell Gamma Knife IconTM.

The Leksell Gamma Knife (LGK) IconTM is used for mask-based and frame-based fixation. The mask fixation provides a noninvasive method. However, an optimal mask fixation method is yet to be established. We evaluated the characteristics of three mask fixation methods (Plain, Folded, and Wide) for the LGK IconTM . Force-sensitive resistor sensors were attached to the forehead, supraorbital, zygoma, mandible, and occipital bone of the phantom, and digital humidity and temperature sensors were attached to both temporal lobes. Cone-beam computed tomography (CBCT) and high-definition motion management (HDMM) for each mask fixation method were used to evaluate the phantom motion during the initial application. Subsequently, the mask was removed and reapplied on the second (1st reapplication) and third days (2nd reapplication). In the initial application, forces acting on most portions of the phantom were stabilized within 1.5 h. The largest force acted on the occipital bone for the Plain and Wide methods and on the mandible for the Folded method. The temperature rapidly approaches the initial temperature, whereas the humidity gradually approached the initial humidity in all fixation methods. The Folded method exhibited a significantly lower translation along the Y-axis of the Leksell coordinate system, and rotations along all axes were under 0.5°. The HDMM values remained at 0.1 mm for all fixation methods. In the reapplications, the force acting on the occipital bone was significantly greater than that during the initial application for all mask fixation methods; the temperature and humidity remained unchanged. All mask fixation methods in the 1st reapplication were not significantly different from those in the 2nd reapplication. The Folded method is recommended as an optimal mask fixation for patients who require tight fixation; the Wide method can be considered if patient comfort is a priority.

Single-Session versus Multisession Gamma Knife Radiosurgery for Large Brain Metastases from Non-Small Cell Lung Cancer: A Retrospective Analysis.

PURPOSE: To evaluate the efficacy of Gamma Knife radiosurgery (GKS) in patients with large brain metastases by comparing single-session radiosurgery (S-GKS) and multisession radiosurgery (M-GKS), we retrospectively analyzed the clinical outcomes of patients who underwent GKS for brain metastases from non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Between January 2010 and December 2016, 66 patients with 74 lesions ≥10 cm3 from large brain metastases from only NSCLC were included. Fifty-five patients with 60 lesions were treated with S-GKS; 11 patients with 14 lesions were treated with M-GKS. Median doses were 16 Gy (range, 11-18 Gy) for the S-GKS group and 8 Gy (range, 7-10 Gy) in three fractions for the M-GKS group. RESULTS: With a mean follow-up period of 13.1 months (range, 1.3-76.4 months), the median survival duration was 21.1 months for all patients. Median tumor volume was 14.3 cm3 (range, 10.0-58.3 cm3). The local control rate was 77.0% and the progression-free survival rate was 73.6% at the last follow-up. There were no significant between-group differences in terms of local control rate (p = 0.10). Compared with S-GKS, M-GKS did not differ significantly in radiation-induced complications (38.1 vs. 45.4%, p =0.83). While 8 patients who underwent S-GKS experienced major complications of grade ≥3, no toxicity was observed in patients treated with M-GKS. CONCLUSIONS: M-GKS may be an effective alternative for large brain metastases from NSCLC. Specifically, severe radiation-induced toxicity (≥grade 3) did not occur in M-GKS for large-volume metastases. Although the long-term effects and results from larger samples remain unclear, M-GKS may be a suitable palliative treatment for preserving neurological function.

Frameless Fractionated Gamma Knife Radiosurgery with ICON™ for Large Metastatic Brain Tumors.

BACKGROUND: Recently, a new generation of gamma knife radiosurgery (GKRS) equipped with a frameless immobilization system has encouraged the use of fractionated GKRS as an increasingly favorable treatment option. We investigated the preliminary outcome of efficacy and toxicity associated with frameless fractionated gamma knife radiosurgery (FF GKRS) for the treatment of large metastatic brain tumors. METHODS: Fifteen patients with 17 lesions were treated using FF GKRS and included in this study, because of the large tumor size of more than 10 cm3. FF GKRS was performed based on a thermoplastic mask system for 3 to 5 consecutive days. RESULTS: The mean duration of clinical follow-up was 12 months (range, 4-24), and the local control rate was 100%. Tumor volume decreased in 13 lesions (76.5%), and remained stable in 4 lesions (23.5%). One patient was classified as new lesion development because of the occurrence of leptomeningeal seeding regardless of the tumor volume change. Compared with the initial volume at the time of FF GKRS, tumor volume change at the last follow-up was 62.32% ± 29.80%. Cumulative survival rate at 12 months was 93.3% ± 6.4%. One patient died during the follow-up period because of the progression of the primary disease. No patient showed radiation necrosis on the follow-up images. CONCLUSION: Daily FF GKRS by gamma knife ICON™ revealed satisfactory tumor control rate and low morbidity, despite the short follow-up period. Further prospective studies and a longer follow-up of a large cohort of patients diagnosed with brain metastases are required to elucidate the effect of FF GKRS in brain metastases.

Optimal strategy of gamma knife radiosurgery for craniopharyngiomas.

OBJECT: To analyze the outcomes of gamma knife radiosurgery (GKS) for craniopharyngiomas and elucidate the optimal strategy. METHODS: Between 1998 and 2016, 35 patients underwent GKS for the treatment of 40 recurrent or residual craniopharyngiomas. Among 40 GKSs, 22 procedures were single-session GKSs and 18 procedures were fractionated GKSs. In cases of single-session GKS, the median marginal dose was 15 Gy (range 10-20 Gy). In cases of fractionated GKS, the median marginal dose was 6 Gy (range 5-7.5 Gy) of three fractions. The radiation dose was calculated to the biologic equivalent dose (BED) using α/ß ratios of 10 and 2. RESULT: The location of the tumor, the distance between the optic nerve and tumor (> 10 mm), BED 10 (> 35 Gy), and BED2 (> 80 Gy) were statistically significant with overall response rate (P = 0.008, 0.02, 0.03, and 0.002, respectively). There was a statistically significant difference in progression-free survival according to the distance between the optic nerve and tumor (> 10 mm) and the location of tumor (P = 0.03 and 0.03, respectively). Multivariate logistic regression analysis showed the hypothalamus group had an odds ratio of 0.04 compared with the suprasellar group for tumor progression. The group with BED2 > 80 Gy had an odds ratio of 0.049 compared with the group with BED2 < 80 Gy. CONCLUSION: A sufficient dose is required for treating craniopharyngiomas using single-session and fractionated GKS. The outcomes of GKS can be predicted according to the location of tumor, the distance between the optic nerve and tumor and BED value.

A Retrospective Analysis of the Outcomes of Dural Arteriovenous Fistulas Treated with Gamma Knife Radiosurgery: A Single-Institution Experience.

BACKGROUND: Gamma knife radiosurgery (GKRS) has recently been used as a treatment modality for dural arteriovenous fistula (DAVF). OBJECTIVE: To retrospectively analyze the outcomes of GKRS for DAVF at a single institute. METHODS: Between 1998 and 2016, a total of 20 patients underwent GKRS for DAVF. After excluding 4 patients with > 12 months of follow-up, 16 patients were enrolled in this study. Twelve patients had undergone embolization prior to GKRS. The most common location was the cavernous sinus (CS). The median clinical and radiological follow-up durations were 87.5 (range 24-186) months and 44.5 (range 14-174) months. RESULTS: Ten (62.5%) of the 16 DAVFs were obliterated; 8 were confirmed on angiography. Five cases resulted in small, residual DAVFs, and one case remained unchanged. The obliteration rate of GKRS for CS DAVF was significantly higher than that for non-CS DAVF (100 vs. 40%; p = 0.034). Fifteen out of 16 patients (94%) had a favorable outcome, and the remaining patient had an unfavorable outcome. Hemorrhage after GKRS occurred in only 1 patient, who presented with seizure. CONCLUSIONS: GKRS is a safe and effective treatment modality for DAVF in combination with a traditional treatment option such as endovascular embolization or microsurgery.

Assessment of the accuracy and stability of frameless gamma knife radiosurgery.

The aim of this study was to assess the accuracy and stability of frameless gamma knife radiosurgery (GKRS). The accuracies of the radiation isocenter and patient couch movement were evaluated by film dosimetry with a half-year cycle. Radiation isocenter assessment with a diode detector and cone-beam computed tomography (CBCT) image accuracy tests were performed daily with a vendor-provided tool for one and a half years after installation. CBCT image quality was examined twice a month with a phantom. The accuracy of image coregistration using CBCT images was studied using magnetic resonance (MR) and computed tomography (CT) images of another phantom. The overall positional accuracy was measured in whole procedure tests using film dosimetry with an anthropomorphic phantom. The positional errors of the radiation isocenter at the center and at an extreme position were both less than 0.1 mm. The three-dimensional deviation of the CBCT coordinate system was stable for one and a half years (mean 0.04 ± 0.02 mm). Image coregistration revealed a difference of 0.2 ± 0.1 mm between CT and CBCT images and a deviation of 0.4 ± 0.2 mm between MR and CBCT images. The whole procedure test of the positional accuracy of the mask-based irradiation revealed an accuracy of 0.5 ± 0.6 mm. The radiation isocenter accuracy, patient couch movement accuracy, and Gamma Knife Icon CBCT accuracy were all approximately 0.1 mm and were stable for one and a half years. The coordinate system assigned to MR images through coregistration was more accurate than the system defined by fiducial markers. Possible patient motion during irradiation should be considered when evaluating the overall accuracy of frameless GKRS.

Ruptured de novo Aneurysm following Gamma Knife Surgery for Arteriovenous Malformation: Case Report.

Stereotactic radiosurgery is a well-known treatment tool for arteriovenous malformations (AVMs). The method has high validity and minimal invasiveness, but late-onset problems involving tumor formation and vasculopathy induced by radiation have been reported. We present a rare case of a radiation-induced ruptured de novo aneurysm following Gamma Knife surgery (GKS) for an AVM. A 17-year-old, right-handed male underwent GKS for AVM at the left parietal lobe. After 3 years, a follow-up angiogram showed a residual AVM at the angular gyrus. Then, a 2nd GKS was performed for the residual lesion. Six years after the 1st GKS, the AVM disappeared on the angiogram. Seven years later, he suffered a sudden onset of headache. A left carotid angiogram revealed a ruptured aneurysm at the M2-M3 junction of the middle cerebral artery parietal branch. Coil embolization was performed, and the aneurysm was occluded. The patient was discharged without any neurologic deficits.

Gamma Knife Radiosurgery for Petroclival Meningioma: Long-Term Outcome and Failure Pattern.

Total removal of petroclival meningioma is difficult, and aggressive extirpation is often associated with significant surgical morbidity and mortality. The aim of this study was to evaluate the long-term outcome and failure pattern of treatment with Gamma Knife radiosurgery (GKRS) in patients with petroclival meningiomas. Eighty-nine consecutive patients with petroclival meningiomas underwent GKRS between 1998 and 2013. Fifty-eight patients received GKRS as a primary treatment and 31 patients underwent GKRS as a secondary treatment after microsurgery. The mean tumor volume was 6.7 cm3 (range, 0.5-46.3 cm3) and the mean marginal dose was 13.2 Gy (range, 8-17 Gy). At the last radiological follow-up, tumor volume was decreased in 50 patients (56.2%), stationary in 34 patients (38.2%), and increased in 5 patients (5.6%). The actuarial progression-free survival after GKRS was 94.7% at 5 years and 88.9% at 10 years. Favorable cranial nerve outcomes were found in 81 patients (91%). A regrowth pattern was present in all 4 patients of the primary treatment group, whereas cyst formation (3 patients) and regrowth (1 patient) were observed in the secondary treatment group. GKRS is an effective and reasonable option as a primary or secondary treatment for petroclival meningioma. Further studies of failure patterns after GKRS for petroclival meningioma are mandatory.

Radiation-induced osteosarcoma after Gamma Knife surgery for vestibular schwannoma: a case report and literature review.

We present a rare case of radiation-induced osteosarcoma following Gamma Knife® surgery (GKS) for a vestibular schwannoma (VS). A 49-year-old female with sporadic VS underwent GKS. Serial follow-up imaging showed that the tumor size decreased. Six years after GKS, magnetic resonance imaging demonstrated regrowth of the tumor. The tumor was removed via the retrosigmoid approach. Interestingly, the final pathology report confirmed osteosarcoma arising in schwannoma with direct transition (osteosarcoma component: 90 %, schwannoma component: 10 %). The osteosarcoma was considered to be a radiation-induced malignancy. The possibility of this rare complication should be explained to the patient before GKS, and the patient should be screened periodically after GKS.

Gamma Knife Surgery for Recurrent or Residual Supratentorial Primitive Neuroectodermal Tumors.

BACKGROUND: Supratentorial primitive neuroectodermal tumors (PNETs) are highly malignant and rare tumors of the central nervous system. OBJECTIVES: The aim of this study was to determine the role of Gamma Knife surgery (GKS) as a salvage treatment option for patients with recurrent or residual supratentorial PNETs. METHODS: Between 1998 and 2014, 11 patients with supratentorial PNETs were retrospectively analyzed. This series consisted of 7 male and 4 female patients. The median age was 17 years. All patients received surgical resection followed by adjuvant therapy. The median time from operation to the first GKS treatment was 72.5 months. The median tumor volume was 17.5 cm3, and the median marginal dose was 11.5 Gy. RESULTS: 15 (65%) of the 23 tumors had been controlled. The actuarial local tumor control rate was 91% at 3 months, 73% at 6 months, and 44% at 12 months. At the time of analysis, 9 (82%) of the patients had died. The median survival time after the first GKS session was 17 months. The median survival time from the initial diagnosis was 65 months. No adverse radiation effect after GKS treatment occurred in any patient. CONCLUSIONS: GKS treatment might be an effective salvage treatment option for recurrent or residual supratentorial PNETs after multimodal treatment.

Hearing Outcomes After Stereotactic Radiosurgery for Vestibular Schwannomas : Mechanism of Hearing Loss and How to Preserve Hearing.

The use of stereotactic radiosurgery (SRS) expanded to include the treatment of vestibular schwannomas (VSs) in 1969; since then, efforts to increase tumour control and to reduce cranial neuropathy have continued. Using the currently recommended marginal dose of 12-13 Gy, long-term reported outcomes after SRS include not only excellent tumour control rates of 92-100 % but also outstanding functional preservation of the trigeminal and facial nerves, with values of 92-100 % and 94-100 %, respectively. Nonetheless, hearing preservation remains in the range of 32-81 %. Previous studies have suggested possible prognostic factors of hearing preservation such as the Gardner-Robertson grade, radiation dose to the cochlea, transient volume expansion (TVE) after SRS, length of irradiated cochlear nerve, marginal dose to the tumour, and age. However, we still do not clearly understand why patients lose their hearing after SRS for VS.Relevant to these considerations, one study recently reported that the auditory brainstem response (ABR) wave V latency and waves I and V interval (IL_I-V) correlated well with intracanalicular pressure values and even with hearing level. The demonstration that ABR values, especially wave V latency and IL_I-V, correlate well with intracanalicular pressure suggests that patients with previously elevated intracanalicular pressure might have an increased chance of hearing loss on development of TVE, which has been recognised as a common phenomenon after SRS or stereotactic radiotherapy (SRT) for intracranial schwannomas.In our experience, the ABR IL_I-V increased during the first 12 months after SRS for VSs in patients who lost their serviceable hearing. The effect of increased ABR IL_I-V on hearing outcome also became significant over time, especially at 12 months after SRS, and was more prominent in patients with poor initial pure-tone average (PTA) and/or ABR values. We hypothesise that patients with considerable intracanalicular pressure at the time of SRS are prone to lose their serviceable hearing due to the added intracanalicular pressure induced by TVE, which usually occurs within the first 12 months after SRS for VSs. Using these findings, we suggested a classification system for the prediction of hearing outcomes after SRS for VSs. This classification system could be useful in the proper selection of management modalities for hearing preservation, especially in patients with only hearing ear schwannoma or neurofibromatosis type 2.Advances in diagnostic tools, treatment modalities, and optimisation of radiosurgical dose have improved clinical outcomes, including tumour control and cranial neuropathies, in patients with VSs. However, the preservation of hearing function still falls short of our expectation. A prediction model for hearing preservation after each treatment modality will guide the proper selection of treatment modalities and permit the appropriate timing of active treatment, which will lead to the preservation of hearing function in patients with VSs.

Evaluation of the degree of arteriovenous shunting in intracranial arteriovenous malformations using pseudo-continuous arterial spin labeling magnetic resonance imaging.

INTRODUCTION: Intracranial arteriovenous malformations (AVMs) display venous signals on arterial spin labeling (ASL) magnetic resonance (MR) imaging due to the presence of arteriovenous shunting. Our aim was to quantitatively correlate AVM signal intensity on ASL with the degree of arteriovenous shunting estimated on digital subtraction angiography (DSA) in AVMs. METHODS: MR imaging including pseudo-continuous ASL at 3 T and DSA were obtained on the same day in 40 patients with intracranial AVMs. Two reviewers assessed the nidus and venous signal intensities on ASL images to determine the presence of arteriovenous shunting. Interobserver agreement on ASL between the reviewers was determined. ASL signal intensity of the AVM lesion was correlated with AVM size and the time difference between normal and AVM venous transit times measured from the DSA images. RESULTS: Interobserver agreement between two reviewers for nidus and venous signal intensities was excellent (κ = 0.80 and 1.0, respectively). Interobserver agreement regarding the presence of arteriovenous shunting was perfect (κ = 1.0). AVM signal intensity showed a positive relationship with the time difference between normal and AVM venous transit times (r = 0.638, P < 0.001). AVM signal intensity also demonstrated a positive relationship with AVM size (r = 0.561, P < 0.001). CONCLUSION: AVM signal intensity on ASL in patients with AVM correlates well with the degree of early vein opacification on DSA, which corresponds to the degree of arteriovenous shunting.

Stereotactic radiosurgery for cavernous sinus hemangiomas.

We performed this retrospective study to analyze the outcome of patients with cavernous sinus hemangioma (CSH) after stereotactic radiosurgery (SRS). We analyzed 19 patients with CSHs who were treated with SRS between 1998 and 2011. The median age of the patients was 50 years (range, 35-73 years), and 16 (84.2%) of the patients were female. SRS was performed as a primary treatment for 18 patients and to treat a residual lesion after surgical resection in one patient. Nine (47.4%) patients had cranial neuropathies in 14 cranial nerves before SRS, whereas five (26.3%) patients were initially asymptomatic. The mean volume of the CSHs was 6.1 ± 7.2 cm(3) (range, 0.3-32.3 cm(3)), and the median marginal dose at the 50% isodose line was 14.5 Gy (range, 11.5-16.0 Gy). The mean follow-up period was 37 months (range, 12-85 months). At the last follow-up, the lesion volume had decreased in all patients. The average tumor volume had decreased to 26% (range, 0-70%) of the initial volume at the last follow-up MRI. The first follow-up MRI, performed 6.1 ± 1.0 months after the SRS, showed that the tumor volume had decreased to 41% (range, 0-88%) of the initial volume. All 14 of the cranial neuropathies observed before SRS had improved, with complete remission in 12 (85.7%) cranial nerves and partial remission in two (14.3%). There were no radiation-induced neuropathies or complications during the follow-up period. SRS appears to be an effective and safe treatment modality for the management of CSHs.

Stereotactic radiosurgery for brain metastases from hepatocellular carcinoma.

The purpose of this study is to investigate the possible role of stereotactic radiosurgery (SRS) in the management of patients with brain metastases from hepatocellular carcinoma (HCC). Thirty-two consecutive patients with 80 brain metastases from HCC were treated with SRS. Twenty-eight (87.5 %) patients were male, and the mean age of the patients was 54 ± 12 years (range 22-73). Twenty-seven (84.4 %) patients were classified as RTOG RPA Class 2. The mean tumor volume was 6.14 ± 11.3 cm(3) (range 0.01-67.3). The mean marginal dose prescribed was 20.1 ± 3.6 Gy (range 10.0-25.0). The median overall survival time after SRS was 11.3 ± 5.8 weeks (95 % CI 0-22.7). A greater total volume of brain metastases (>14 cm(3)) was the only independent prognostic factor (HR = 2.419; 95 % CI 1.040-5.624; p = 0.040). The actuarial control rate of brain metastases was 51.3 % at 4 months after SRS. The prescribed marginal dose (>18 Gy) was significantly related with the actuarial tumor control (HR = 0.254; 95 % CI 0.089-0.725; p = 0.010). The prognosis of patients with brain metastases from HCC is dismal even with the modern technology of radiosurgery. The marginal dose prescribed should be reevaluated to improve upon the current poor local control rates.

Radiosurgery for central neurocytoma: long-term outcome and failure pattern.

Despite the favorable outcomes of radiosurgery for central neurocytoma (CN), these results are based on case series that included a limited number of patients and short follow-up periods because of the scarcity of CN. Because CN is a benign tumor with an indolent clinical course, long-term follow-up and analysis of failure pattern are required for the establishment of the role of radiosurgery in the management of CN. Twenty consecutive patients (10 patients who received Gamma Knife radiosurgery (GKRS) as a primary treatment and 10 patients who received GKRS as a secondary treatment) with a radiological follow-up period ≥36 months were included in this study. The mean radiological follow-up duration was 100 months (range 43-149 months). The mean tumor volume was 10.4 cm(3) (range 0.4-36.4 cm(3)) and the mean marginal dose was 15.4 Gy (range 9-20 Gy). Local control failure was found in six patients at the last radiological follow-up. Overall actuarial local control rates were 89.5 % at 5 years and 83.1 % at 10 years. The primary GKRS group included two cases with local failure, with cyst formation or local recurrence. In contrast, in the secondary GKRS group, local control failure was found in four cases (including three cases with an "out-of-field recurrence" pattern) and occurred earlier compared with the primary GKRS group. Our study suggests that GKRS could be a primary or secondary treatment option for CN. However, long-term radiological follow-up is mandatory. In particular, more careful consideration during margin delineation and planning procedure is required in the secondary GKRS group.

Transcerebellar biopsy of diffuse pontine gliomas in children: a technical note.

INTRODUCTION: The need for a surgical biopsy for diffuse pontine glioma (DPG) is increasing, and a safer and less invasive procedure is required. METHODS: We describe a transcerebellar stereotactic biopsy procedure that can be safely performed in young children. Four pediatric patients with DPG underwent transcerebellar stereotactic biopsies. RESULTS: All of the patients were diagnosed with gliomas, and one patient had a transient numbness of the lip margin after the procedure. DISCUSSION: Transcerebellar stereotactic biopsy is a relatively safe way to obtain a tissue diagnosis for children with DPG.

A 3-month survival model after Gamma Knife surgery in patients with brain metastasis from lung cancer with Karnofsky performance status ≤ 70.

Gamma Knife surgery (GKS) for brain metastasis (BM) has been generally advocated for patients with a Karnofsky performance status (KPS) scale of ≥ 70. However, some patients with a poor KPS scale of < 70 are recoverable after GKS and show durable survival. A purpose of this study is to devise a 3-month survival prediction model to screen patients with BM with a KPS of ≤ 70 in whom GKS is needed. A retrospective analysis of 67 patients with a KPS scale of 60-70 undergoing GKS for BM of non-small cell lung cancer (NSCLC) from 2016 to 2020 in our institute was performed. Univariate and multivariate logistic regression analyses were performed to investigate factors related to survival for more than 3 months after GKS. The probability (P) prediction model was designed by giving a weight corresponding to the odds ratio of the variables. The overall survival was 9.9 ± 12.7 months (range 0.2-53.2), with a 3-month survival rate of 59.7% (n = 40). In multivariate logistic regression analysis, extracranial disease (ECD) control (p = .033), focal neurological deficit (FND) (p = .014), and cumulative tumor volume (∑ TV) (p = .005) were associated with 3-month survival. The prediction model of 3-month survival (Harrell's C index = 0.767) was devised based on associated factors. In conclusion, GKS for BMs is recommended in selected patients, even if the KPS scale is ≤ 70.

Consistency of dose rates after applying machine-specific reference correction factors for the gamma knife 16 mm collimator field.

BACKGROUND: The machine-specific reference (msr) correction factors ( k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ ) were introduced in International Atomic Energy Agency (IAEA) Technical Report Series 483 (TRS-483) for reference dosimetry of small fields. Several correction factor sets exist for a Leksell Gamma Knife (GK) Perfexion or Icon. Nevertheless, experiments have not rigorously validated the correction factors from different studies. PURPOSE: This study aimed to assess the role and accuracy of k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ values in determining the absorbed dose rates to water in the reference dosimetry of Gamma Knife. METHODS: The dose rates in the 16 mm collimator field of a GK were determined following the international code of practices with three ionization chambers: PTW T31010, PTW T31016 (PTW Freiberg GmbH, New York, NY), and Exradin A16 (Standard Imaging, Inc., Middleton, WI). A chamber was placed at the center of a solid water phantom (Elekta AB, Stockholm, Sweden) using a detector-specific insert. The reference point of the ionization chamber was confirmed using cone-beam CT images. Consistency checks were repeated five times at a GK site and performed once at seven GK sites. Correction factors from six simulations reported in previous studies were employed. Variations in the dose rates and relative dose rates before and after applying the k Q m s r , Q 0 f m s r , f r e f $k_{{Q_{msr}},\;{Q_0}}^{{f_{msr}},{f_{ref}}}$ were statistically compared. RESULTS: The standard deviation of the dose rates measured by the three chambers decreased significantly after any correction method was applied (p = 0.000). When the correction factors of all studies were averaged, the standard deviation was reduced significantly more than when any single correction method was applied (p ≤ 0.030), except for the IAEA TRS-483 correction factors (p = 0.148). Before any correction was applied, there were statistically significant differences among the relative dose rates measured by the three chambers (p = 0.000). None of the single correction methods could remove the differences among the ionization chambers (p ≤ 0.038). After TRS-483 correction, the dose rate of Exradin A16 differed from those of the other two chambers (p ≤ 0.025). After the averaged factors were applied, there were no statistically significant differences between any pairs of chambers according to Scheffe's post hoc analyses (p ≥ 0.051); however, PTW T31010 differed from PTW 31016 according to Tukey's HSD analyses (p = 0.040). CONCLUSION: The k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ significantly reduced variations in the dose rates measured by the three ionization chambers. The mean correction factors of the six simulations produced the most consistent results, but this finding was not explicitly proven in the statistical analyses.

Hearing preservation in patients with unilateral vestibular schwannoma who undergo stereotactic radiosurgery: Reinterpretation of the auditory brainstem response.

BACKGROUND: The objective of this study was to identify the prognostic factors for hearing preservation that would allow the more accurate stratification of patients who undergo stereotactic radiosurgery (SRS) for unilateral, sporadic vestibular schwannoma (VS). METHODS: In total, 119 patients with VS who had serviceable hearing underwent SRS as primary treatment. The mean (±standard deviation) patient age was 48 ± 11 years, and the mean (±standard deviation) follow-up duration was 55.2 ± 35.7 months. The median marginal radiotherapy dose was 12.0 grays (Gy), and the mean (±standard deviation) tumor volume was 1.95 ± 2.24 cm(3) . The mean (±standard deviation) pure tone average (PTA) score was 26 ± 12 decibels (dB) (range, 4-50 dB), and the mean (±standard deviation) maximum speech discrimination score was 91 ± 12% (range, 52-100%). The mean (±standard deviation) baseline values for the interlatency (IL) of waves I and III (IL I-III) and the IL of waves I through V (IL I-V) on auditory brainstem response were 2.58 ± 0.60 milliseconds (mS) (range, 1.92-4.30 mS) and 4.80 ± 0.61 mS (range, 3.80-6.40 mS), respectively. RESULTS: In multivariate analysis, the PTA score and IL I-V were significant and independent prognostic factors (hazard ratio, 1.072; 95% confidence interval, 1.046-1.098; P < .001; and hazard ratio, 1.534; 95% confidence interval, 1.008-2.336; P = .046, respectively). By using the PTA score and IL I-V, the patients were classified into 4 groups. The ratios of patients with serviceable hearing after SRS were 89.6%, 64.0%, 25.8%, and 6.7%, respectively, in Groups A through D (P < .001). CONCLUSIONS: The current results indicated that the classification system based on using the PTA score and the IL I-V of the auditory brainstem response may be useful and specific for predicting the rate of hearing preservation in each individual.