• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.243-248
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• 2023

This study aims to analyze the secondary carcinogenesis rate caused by exposure of organs at risk of damage using a glass dosimeter during radiosurgery in vestibular schwannoma disease. Using a pediatric phantom of human tissue equivalent material, the volume of the tumor was set to a total of three volumes: 0.506 cm³, 1.008 cm³, and 2.032 cm³, and a radiosurgery plan was established with an average dose of 18.4 ± 3.4 Gy. After mounting the human body phantom on the table of surgical equipment, glass dosimeters were placed on the right eye, left eye, thyroid gland, thymus, right lung, and left lung to measure the exposure dose, respectively. In this study, the incidence of secondary cancer due to exposure to damaged organs during gamma knife radiosurgery in vestibular schwannoma disease with the largest tumor volume of 2.032 cm³ was measured with a glass dosimeter. This study studies the risk of secondary radiation exposure dose that can occur during stereotactic radiosurgery, and it is considered that it will be used as basic data in the field of radiation damage related to the stochastic effect of radiation in the future.

• Journal of Korean Neurosurgical Society
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• v.58 no.4
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• pp.379-384
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• 2015

Objective : To investigate the risks and pattern of evolution of peritumoral brain edema (PTE) after stereotactic radiosurgery (SRS) for asymptomatic intracranial meningiomas. Methods : A retrospective study was conducted on 320 patients (median age 56 years, range 24-87 years) who underwent primary Gamma Knife radiosurgery for asymptomatic meningiomas between 1998 and 2012. The median tumor volume was 2.7 cc (range 0.2-10.5 cc) and the median follow-up was 48 months (range 24-168 months). Volumetric data sets for tumors and PTE on serial MRIs were analyzed. The edema index (EI) was defined as the ratio of the volume of PTE including tumor to the tumor volume, and the relative edema indices (rEIs) were calculated from serial EIs normalized against the baseline EI. Risk factors for PTE were analyzed using logistic regression. Results : Newly developed or increased PTE was noted in 49 patients (15.3%), among whom it was symptomatic in 28 patients (8.8%). Tumor volume larger than 4.2 cc (p<0.001), hemispheric tumor location (p=0.005), and pre-treatment PTE (p<0.001) were associated with an increased risk of PTE. rEI reached its maximum value at 11 months after SRS and decreased thereafter, and symptoms resolved within 24 months in most patients (85.7%). Conclusion : Caution should be exercised in decision-making on SRS for asymptomatic meningiomas of large volume (>4.2 cc), of hemispheric location, or with pre-treatment PTE. PTE usually develops within months, reaches its maximum degree until a year, and resolves within 2 years after SRS.

• Journal of Korean Neurosurgical Society
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• v.41 no.6
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• pp.359-366
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• 2007

Trigeminal neuralgia is a condition associated with severe episodic lancinating facial pain subject to remissions and relapses. Trigeminal neuralgia is often associated with blood vessel cross compression of the root entry zone or more rarely with demyelinating diseases and occasionally with direct compression by neoplasms of the posterior fossa. If initial medical management fails to control pain or is associated with unacceptable side effects, a variety of surgical procedures offer the hope for long-lasting pain relief or even cure. For patients who are healthy without significant medical co-morbidities, direct microsurgical vascular decompression [MVD] offers treatment that is often definitive. Other surgical options are effective for elderly patients not suitable for MVD. Percutaneous retrogasserian glycerol rhizotomy is a minimally invasive technique that is based on anatomic definition of the trigeminal cistern followed by injection of anhydrous glycerol to produce a weak neurolytic effect on the post-ganglionic fibers. Other percutaneous management strategies include radiofrequency rhizotomy and balloon compression. More recently, stereotactic radiosurgery has been used as a truly minimally invasive strategy. It also is anatomically based using high resolution MRI to define the retrogasserian target. Radiosurgery provides effective symptomatic relief in the vast majority of patients, especially those who have never had prior surgical procedures. For younger patients, we recommend microvascular decompression. For patients with severe exacerbations of their pain and who need rapid response to treatment, we suggest glycerol rhizotomy. For other patients, gamma knife radiosurgery represents an effective management strategy with excellent preservation of existing facial sensation.

• Journal of Korean Neurosurgical Society
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• v.60 no.6
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• pp.667-675
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• 2017

Objective : Total resection without consecutive postoperative whole brain radiation therapy is indicated for patients with a single or two sites of brain metastasis, with close follow-up by serial magnetic resonance imaging (MRI). In this study, we explored the effectiveness, usefulness, and safety of this follow-up regimen. Methods : From January 2006 to December 2015, a total of 109 patients (76 males, 33 females) underwent tumor resection as the first treatment for brain metastases (97 patients with single metastases, 12 with two metastases). The mean age was 59.8 years (range 27-80). The location of the 121 tumors in the 109 patients was supratentorial (n=98) and in the cerebellum (n=23). The origin of the primary cancers was lung (n=45), breast (n=17), gastrointestinal tract (n=18), hepatobiliary system (n=8), kidney (n=7), others (n=11), and unknown origin (n=3). The 121 tumors were totally resected. Follow-up involved regular clinical and MRI assessments. Recurrence-free survival (RFS) and overall survival (OS) after tumor resection were analyzed by Kaplan-Meier methods based on clinical prognostic factors. Results : During the follow-up, MRI scans were done for 85 patients (78%) with 97 tumors. Fifty-six of the 97 tumors showed no recurrence without adjuvant local treatment, representing a numerical tumor recurrence-free rate of 57.7%. Mean and median RFS was 13.6 and 5.3 months, respectively. Kaplan-Meier analysis revealed the cerebellar location of the tumor as the only statistically significant prognostic factor related to RFS (p=0.020). Mean and median OS was 15.2 and 8.1 months, respectively. There were no significant prognostic factors related to OS. The survival rate at one year was 8.2% (9 of 109). Conclusion : With close and regular clinical and image follow-up, initial postoperative observation without prompt postoperative radiation therapy can be applied in patients of brain metastasi(e)s when both the tumor(s) are completely resected.

• Journal of Korean Neurosurgical Society
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• v.54 no.2
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• pp.107-111
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• 2013

Objective : We investigated the effectiveness of stereotactic gamma knife Radiosurgery (GKR) for radioresistant brain metastases with the impact upon histology. Methods : Between April 2004 and May 2011, a total of 23 patients underwent GKR for 67 metastatic brain tumors from 12 renal cell cancers, 5 sarcomas and 6 melanomas. The mean age was 56 years (range, 18 to 79 years). Most of the patients were classified as the Radiation Therapy Oncology Group recursive partitioning analysis class II (91.3%). The synchronous metastasis was found in 6 patients (26.1%) and metachronous metastasis in 17 patients (73.9%). We analyzed the local control rate, intracranial progression-free survival (PFS) and overall survival (OS). Results : The mean tumor volume for GKR was 2.24 cc and the mean prescription dose was 19.4 Gy (range, 10 to 24) to the tumor margin. Out of metachronous metastases, the median duration to intracranial metastasis was 3.3 years in renal cell cancer (RCC), 2.4 years in melanoma and 1.1 years in sarcoma (p=0.012). The total local control rate was 89.6% during the mean 12.4 months follow-up. The six-month and one-year local control rate was 90.2% and 83% respectively. Depending on the pathology, the control rate of RCC was 95.7%, sarcoma 91.3% and melanoma 80.5% during the follow-up. The common cause of local failure was the tumor bleeding in melanoma. The median PFS and OS were 5.2 and 8.4 months in RCC patients, 6.5 and 9.8 months in sarcoma, and 3.8 and 5.1 months in melanoma. Conclusion : The GKR can be one of the effective management options for the intracranial metastatic tumors from the radioresistant tumors. The melanoma showed a poor local control rate compared to other pathologies because of the hemorrhage.

• Journal of Korean Neurosurgical Society
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• v.63 no.3
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• pp.397-405
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• 2020

Objective : We retrospectively evaluated the efficacy of Gamma Knife radiosurgery (GKS) for recurrent nasopharyngeal carcinoma (NPC) in patients who previously underwent radiotherapy, and analyzed the treatment outcomes over 14 years. Methods : Ten patients with recurrent NPC who had previously received radiotherapy underwent stereotactic radiosurgery using a Gamma Knife^® (Elekta Inc, Atlanta, GA, USA) between 2005 and 2018. The median target volume was 8.2 ㎤ (range, 1.7-17.8), and the median radiation dose to the target was 18 Gy (range, 12-30). The median follow-up period was 18 months (range, 6-76 months). Overall and local failure-free survival rates were determined using the Kaplan-Meier method. Results : The NPCs recurred at the primary cancer site in seven patients (70%), as distant brain metastasis in two (20%), and as an extension into brain in one (10%). The recurrent tumors in seven of the 10 patients (70%) were found on the routine follow-up imaging studies. Two patients presented with headache and one with facial pain. Local failure after GKS occurred in five patients (50%) : two of whom died eight and 6 months after GKS, respectively. No adverse radiation effects were noted after GKS. The 1- and 3-year overall survival rates after GKS were 90% and 77%, respectively. The local failure-free survival rates at 6 months, 1 year, and 3 years after GKS were 80%, 48%, and 32%, respectively. The median interval from GKS to local failure was 8 months (range, 6-12). Univariate analysis revealed that using co-registration with positron emission tomography-computed tomography (PET-CT) and magnetic resonance imaging (MRI) was associated with a lower local failure rate of recurrent NPC (p=0.027). Conclusion : GKS is an acceptable salvage treatment option for patients with recurrent NPC who previously received radiation therapy. PET-CT and MRI co-registration for dose planning can help achieve local control of recurrent NPC.

• Journal of Korean Neurosurgical Society
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• v.43 no.6
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• pp.265-269
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• 2008

Objective : Outcome of gamma knife radiosurgery (GKS) in the consecutive 100 cases with cerebral arteriovenous malformations (AVMs) was analyzed. Methods : Data from initial 100 patients treated with GKS in the authors' institute were reviewed retrospectively. Spetzler-Martin grade at diagnosis were I in 18 patients, II in 27, III in 36, IV in 11, and V in 8. Thirty-five patients had experienced previous bleeding, 27 patients presented with seizure, and 31 patients presented with headache. The mean volume of the lesion was $4.3\;cm^3\;(0.1-29.3\;cm^3)$. The median radiation dose delivered to the margin was 20.0Gy (13-32Gy). Mean follow-up period was 37.5 months (5-63 months). Results : Angiographic follow-up was performed in 48 patients at least 2 years after GKS. Sixteen patients were lost in follow up following 2 years from GKS. Twenty-eight of 48 patients (58%) showed complete obliteration and 20 patients (42%) showed partial obliteration. Seven patients presented with post-GKS hemorrhage. Adverse radiation effect (ARE) was observed at follow-up MRI in 25 of 76 patients, and it was symptomatic in 5 patients. Complete obliteration was confirmed in 24 of 31 (77%) patients with volume less than $4\;cm^3$, meanwhile only 4 of 17 (24%) patients with volume of $4\;cm^3$ or more showed complete obliteration. Complete obliteration rate was 67% with 20Gy or higher marginal dose, 63% with 15-20 Gy, and 17% with less than 15Gy. Conclusion : GKS can provide high rates of obliteration with acceptable risk of morbidity in a subgroup of small AVMs. However, overall outcome in whole spectrum of AVMs, in which large proportion of cases have unfavorable characteristics for radiosurgery, is much worse. More effective therapeutic strategy needs to be developed for large AVMs that are difficult to be managed with current available treatment modalities.

• Journal of Korean Neurosurgical Society
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• v.50 no.4
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• pp.299-303
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• 2011

Objective : Brainstem metastases are rarely operable and generally unresponsive to conventional radiation therapy or chemotherapy. Recently, Gamma Knife Radiosurgery (GKRS) was used as feasible treatment option for brainstem metastasis. The present study evaluated our experience of brainstem metastasis which was treated with GKRS. Methods : Between November 1992 and June 2010, 32 patients (23 men and 9 women, mean age 56.1 years, range 39-73) were treated with GKRS for brainstem metastases. There were metastatic lesions in pons in 23, the midbrain in 6, and the medulla oblongata in 3 patients, respectively. The primary tumor site was lung in 21, breast in 3, kidney in 2 and other locations in 6 patients. The mean tumor volume was $1,517mm^3$ (range, 9-6,000), and the mean marginal dose was 15.9 Gy (range, 6-23). Magnetic Resonance Imaging (MRI) was obtained every 2-3 months following GKRS. Follow-up MRI was possible in 24 patients at a mean follow-up duration of 12.0 months (range, 1-45). Kaplan-Meier survival analysis was used to evaluate the prognostic factors. Results : Follow-up MRI showed tumor disappearance in 6, tumor shrinkage in 14, no change in tumor size in 1, and tumor growth in 3 patients, which translated into a local tumor control rate of 87.5% (21 of 24 tumors). The mean progression free survival was 12.2 months (range, 2-45) after GKRS. Nine patients were alive at the completion of the study, and the overall mean survival time after GKRS was 7.7 months (range, 1-22). One patient with metastatic melanoma experienced intratumoral hemorrhage during the follow-up period. Survival was found to be associated with score of more than 70 on Karnofsky performance status and low recursive partitioning analysis class (class 1 or 2), in terms of favorable prognostic factors. Conclusion : GKRS was found to be safe and effective for management of brainstem metastasis. The integral clinical status of patient seems to be important in determining the overall survival time.

• Journal of Korean Neurosurgical Society
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• v.54 no.5
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• pp.399-404
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• 2013

Objective : The authors conducted a retrospective cohort study to determine prognostic factors and treatment outcomes of brain metastases (BM) from breast cancer (BC) after Gamma Knife radiosurgery (GKS). Methods : Pathologic and clinical features, and outcomes were analyzed in a cohort of 62 patients with BM from BC treated by GKS. The Kaplan- Meier method, the log-rank test, and Cox's proportional hazards model were used to assess prognostic factors. Results : Median survival after GKS was 73.0 weeks (95% confidence interval, 46.0-100.1). HER2+ [hazard ratio (HR) 0.441; p=0.045], Karnofsky performance scale (KPS) ${\geq}70$ (RR 0.416; p=0.050) and systemic chemotherapy after GKS (RR 0.282; p=0.001) were found to be a favorable prognostic factor of overall survival. Actuarial local control (LC) rate were $89.5{\pm}4.5%$ and $70.5{\pm}6.9%$ at 6 and 12 months after GKS, respectively. No prognostic factors were found to affect LC rate. Uni- and multivariate analysis revealed that the distant control (DC) rate was higher in patients with; a small number (${\leq}3$) of metastasis (HR 0.300; p=0.045), no known extracranial metastasis (p=0.013, log-rank test), or the HER2+ subtype (HR 0.267; p=0.027). Additional whole brain radiation therapy and metastasis volume were not found to be significantly associated with LC, DC, or overall survival. Conclusion : The treatment outcomes of patients with newly diagnosed BM from BC treated with GKS could be affected primarily by intrinsic subtype, KPS, and systemic chemotherapy. Therapeutic strategy and prognosis scoring system should be individualized based on considerations of intrinsic subtype in addition to traditionally known parameters related to stereotactic radiosurgery.

• Journal of Korean Neurosurgical Society
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• v.30 no.5
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• pp.567-574
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• 2001

Objective : As for growth hormone(GH) secreting pituitary adenoma, it's remission should be declared on the basis of satisfactory controlling of the tumor, normalization of hormonal level, and symptomatic improvement of the patient. Several modalities of treatment have been applied and administered, and yet, this disease still remains as inveterate one to be fully treated. The purpose of this study is to evaluate the outcome of gamma knife radiosurgery(GKRS) for GH secreting pituitary adenoma, and to identify various factors affecting the outcome of the treatment. Method : A group of 24 out of 35 patients, treated by Leksell gamma knife unit during the period of March of 1992 through October of 1997, had been observed for more than two years. The mean target volume of microadenoma was $449.3mm^3(range 216-880mm^3)$, and that of macroadenoma was $3183.1mm^3(range 1456-13125mm^3)$. The tumor margin was covered with 50% isodose profile, and mean marginal dose was 25.2Gy(range 15-32.4Gy). The mean number of isocenter was 4.3(range 1-6). The exposed dose to the optic apparatus was less than 8Gy. The mean follow-up period was 37.8months(range 24-102months). Result : No patients showed any increase in the tumor volume during the follow-up period. And definite shrinkage of tumor volume(tumor volume reduction rate, TVRR : more than 50%) was obtained in 10 patients(41.7%). Twenty one patients(87.5%) had reduced hormonal level compared than pre-treatment level. Among them, normalization of the hormonal level was achieved in 12 patients(50%). Clinicoendocrinological remission was seen in 3 patients (12.5%). According to the results of statistical analysis, tumor volume(p=0.016),duration of symptoms(p=0.046), initial GH level(p=0.017), and the invasion of cavernous sinus(p=0.036) were significantly favorable to post-radiosurgical outcome. The TVRR was significantly related to post-radiosurgical reduction of serum GH level. Permanent complication was not seen. Conclusion : The authors concluded that GKRS is a safe and effective treatment modality for acromegaly. To otain the better outcome of GKRS in GH secreting pituitary adenoma, more careful and sophisticated treatment-planning is recommended.