Gamma Knife surgery for convexity, parasagittal, and falcine meningiomas

2011 ◽  
Vol 114 (5) ◽  
pp. 1392-1398 ◽  
Author(s):  
Toshinori Hasegawa ◽  
Yoshihisa Kida ◽  
Masayuki Yoshimoto ◽  
Hiroshi Iizuka ◽  
Dai Ishii ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Initial Treatment ◽  
Survival Rates ◽  
Progression Free Survival ◽  
Local Tumor Control ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Tumor Diameter ◽  
Primary Tumors ◽  
Radiation Induced

Object The aim of this study was to evaluate the outcomes in patients with convexity, parasagittal, or falcine meningiomas treated using Gamma Knife surgery (GKS) and to determine management strategy considering a risk of radiation-induced edema. Methods One hundred twelve patients who harbored 125 convexity, parasagittal, or falcine meningiomas were assessed. Forty-six patients underwent GKS as the initial treatment. The median tumor diameter was 25 mm, and median tumor volume was 8 cm3. The median maximum and margin doses were 30 and 16 Gy, respectively. Results The median follow-up period was 72 months. The actuarial 5- and 10-year progression-free survival rates were 78% and 55%, respectively. The actuarial 5- and 10-year local tumor control rates were 87% and 71%, respectively. Of 29 tumors that developed postradiosurgical edema, 7 were symptomatic. The actuarial symptomatic radiation-induced edema rate was 7%. The incidence of this complication was significantly higher in patients who underwent GKS as the initial treatment. Six of 46 patients for whom GKS was the initial treatment had preradiosurgical edema. Of these 6 patients, 4 developed severe panhemispheric edema after GKS (2 patients with parasagittal tumors, 1 with a falx tumor, and 1 with a convexity tumor). Conclusions Gamma Knife surgery is an effective treatment for convexity, parasagittal, and falcine meningiomas as the initial or adjuvant treatment. However, GKS should be restricted to small- to medium-sized tumors, particularly in patients with primary tumors, because radiation-induced edema is more common in convexity, parasagittal, and falcine meningiomas than skull base meningiomas.

scholarly journals Gamma Knife surgery for patients with facial nerve schwannomas: a multiinstitutional retrospective study in Japan

2016 ◽  
Vol 124 (2) ◽  
pp. 403-410 ◽  
Author(s):  
Toshinori Hasegawa ◽  
Takenori Kato ◽  
Yoshihisa Kida ◽  
Motohiro Hayashi ◽  
Takahiko Tsugawa ◽  
...  
Keyword(s):  
Facial Nerve ◽  
Gamma Knife ◽  
Facial Palsy ◽  
Survival Rates ◽  
Progression Free Survival ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Effective Treatment Option ◽  
Safe Alternative

OBJECT The aim of this study was to explore the efficacy and safety of stereotactic radiosurgery for patients with facial nerve schwannomas (FNSs). METHODS This study was a multiinstitutional retrospective analysis of 42 patients with FNSs treated with Gamma Knife surgery (GKS) at 1 of 10 medical centers of the Japan Leksell Gamma Knife Society (JLGK1301). The median age of the patients was 50 years. Twenty-nine patients underwent GKS as the initial treatment, and 13 patients had previously undergone surgery. At the time of the GKS, 33 (79%) patients had some degree of facial palsy, and 21 (50%) did not retain serviceable hearing. Thirty-five (83%) tumors were solid, and 7 (17%) had cystic components. The median tumor volume was 2.5 cm3, and the median prescription dose to the tumor margin was 12 Gy. RESULTS The median follow-up period was 48 months. The last follow-up images showed partial remission in 23 patients and stable tumors in 19 patients. Only 1 patient experienced tumor progression at 60 months, but repeat GKS led to tumor shrinkage. The actuarial 3- and 5-year progression-free survival rates were 100% and 92%, respectively. During the follow-up period, 8 patients presented with newly developed or worsened preexisting facial palsy. The condition was transient in 3 of these patients. At the last clinical follow-up, facial nerve function improved in 8 (19%) patients, remained stable in 29 (69%), and worsened in 5 (12%; House-Brackmann Grade III in 4 patients, Grade IV in 1 patient). With respect to hearing function, 18 (90%) of 20 evaluated patients with a pure tone average of ≤ 50 dB before treatment retained serviceable hearing. CONCLUSIONS GKS is a safe and effective treatment option for patients with either primary or residual FNSs. All patients, including 1 patient who required repeat GKS, achieved good tumor control at the last follow-up. The incidence of newly developed or worsened preexisting facial palsy was 12% at the last clinical follow-up. In addition, the risk of hearing deterioration as an adverse effect of radiation was low. These results suggest that GKS is a safe alternative to resection.

Gamma Knife surgery for the treatment of patients with asymptomatic meningiomas

2013 ◽  
Vol 119 (2) ◽  
pp. 487-493 ◽  
Author(s):  
David J. Salvetti ◽  
Tara G. Nagaraja ◽  
Carl Levy ◽  
Zhiyaun Xu ◽  
Jason Sheehan
Keyword(s):  
Gamma Knife ◽  
Symptom Control ◽  
Progression Free Survival ◽  
Lesion Size ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Symptom Development ◽  
Retrospective Case ◽  
Radiation Induced

Object Increasingly, meningiomas are detected incidentally, prior to symptom development. While these lesions are traditionally managed conservatively until symptoms develop or lesion growth occurs, it is conceivable that patients at high risk for symptom development may benefit from earlier intervention prior to the appearance of symptoms. However, little research has been performed to determine whether Gamma Knife surgery (GKS) can alter the rate of symptom development in such patients. Methods A retrospective case study was performed by screening the University of Virginia GKS database for patients treated for asymptomatic meningiomas. From the patient's medical records, pertinent demographic and treatment information was obtained. Yearly follow-up MRI had been performed to assess tumor control and detect signs of radiation-induced injury. Clinical follow-up via neurological examination had been performed to assess symptom development. Results Forty-two patients, 33 females (78.6%) and 9 males (21.4%), with 42 asymptomatic meningiomas were included in the analysis. The median age at GKS was 53 years. The most common lesion location was the cerebral convexities (10 lesions [23.8%]), and the median lesion size was 4.0 ml. The median duration of imaging and clinical follow-ups was 59 and 76 months, respectively. During the follow-up period, 1 tumor (2.4%) increased in size, 2 patients (4.8%) demonstrated symptoms, and 1 patient (2.4%) exhibited possible signs of radiation-induced injury. Thus, actuarial tumor control rates were 100%, 95.7%, and 95.7% for 2, 5, and 10 years, respectively. Actuarial symptom control at 5 and 10 years was 97% and 93.1%, respectively. Overall progression-free survival was 91.1% and 77.8% at 5 and 10 years, respectively. Conclusions Compared with published rates of symptom development in patients with untreated meningiomas, results in this study indicated that patients with asymptomatic lesions may benefit from prophylactic radiosurgery prior to the appearance of symptoms. Additionally, GKS is a treatment option that offers low morbidity.

Radiosurgery for intracranial hemangiopericytomas: outcomes after initial and repeat Gamma Knife surgery

2010 ◽  
Vol 112 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Claire Olson ◽  
Chun-Po Yen ◽  
David Schlesinger ◽  
Jason Sheehan
Keyword(s):  
Survival Rate ◽  
Local Recurrence ◽  
Gamma Knife ◽  
Survival Rates ◽  
Progression Free Survival ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Free Survival ◽  
Fractionated Radiotherapy

Object Intracranial hemangiopericytoma is a rare CNS tumor that exhibits a high incidence of local recurrence and distant metastasis. The purpose of this study was to evaluate the role of Gamma Knife surgery (GKS) in the management of intracranial hemangiopericytomas. Methods In a review of the University of Virginia radiosurgery database between 1989 and 2008, the authors found recurrent or residual hemangiopericytomas after resection in 21 patients in whom radiosurgery was performed to treat 28 discrete tumors. The median age of this population was 47 years (range 31–61 years) at the time of the initial GKS. Prior treatments included embolization (6), transcranial resection (39), transsphenoidal resection (2), and fractionated radiotherapy (8). The mean prescription and maximum radiosurgical doses to the tumors were 17.0 and 40.3 Gy, respectively. Repeat radiosurgery was used to treat 13 tumors. The median follow-up period was 68 months (range 2–138 months). Results At last follow-up, local tumor control was demonstrated in 47.6% of the patients (10 of 21 patients) with hemangiopericytomas. Of the 28 tumors treated, 8 decreased in size on follow-up imaging (28.6%), 5 remained unchanged (17.9%), and 15 ultimately progressed (53.6%). The progression-free survival rates were 90, 60.3, and 28.7% at 1, 3, and 5 years after initial GKS. The progression-free survival rate improved to 95, 71.5, and 71.5% at 1, 3, and 5 years after multiple GKS treatments. The 5-year survival rate after radiosurgery was 81%. Prior fractionated irradiation or radiosurgical prescription dose did not correlate with tumor control. In 4 (19%) of 21 patients extracranial metastases developed. Conclusions Radiosurgery is a reasonable treatment option for recurrent hemangiopericytomas. Long-term close clinical and imaging follow-up is necessary because of the high probability of local recurrence and distant metastases. Repeat radiosurgery may be used to treat new or recurrent hemangiopericytomas over a long follow-up course.

Combination of microsurgery and Gamma Knife surgery for the treatment of intracranial chondrosarcomas

2006 ◽  
Vol 105 (Supplement) ◽  
pp. 18-25 ◽  
Author(s):  
Petter Förander ◽  
Tiit Rähn ◽  
Lars Kihlström ◽  
Elfar Ulfarsson ◽  
Tiit Mathiesen
Keyword(s):  
Gamma Knife ◽  
Cranial Nerve ◽  
Residual Tumor ◽  
Local Tumor Control ◽  
Gamma Knife Surgery ◽  
Long Term Results ◽  
Tumor Control ◽  
Low Grade ◽  
Cranial Nerve Palsies ◽  
Tumor Volume Reduction

ObjectIntracranial chondrosarcomas have a high risk of recurrence after surgery. This retrospective study of patients with intracranial chondrosarcoma was conducted to determine the long-term results of microsurgery followed by Gamma Knife surgery (GKS) for residual tumor or recurrence.MethodsThe authors treated nine patients whose median age was 36 years. Seven patients had low-grade chondrosarcomas (LGCSs), whereas mesenchymal chondrosarcomas (MCSs) were diagnosed in two. Radiosurgery was performed in eight patients, whereas one patient declined further surgical intervention and tumor-volume reduction necessary for the GKS.The patients were followed up for 15 to 173 months (median 108 months) after diagnosis and 3 to 166 months (median 88 months) after GKS. Seven patients had residual tumor tissue after microsurgery, and two operations appeared radical. In the two latter cases, tumors recurred after 25 and 45 months. Thus, definite tumor control was not achieved after surgery alone in any patient, whereas the addition of radiosurgery allowed tumor control in all six patients with LGCSs. Two of these patients experienced an initial tumor regrowth after GKS; in both cases the recurrences were outside the prescribed radiation field. The patients underwent repeated GKS, and subsequent tumor control was observed. An MCS was diagnosed in the remaining two patients. Complications after microsurgery included diplopia, facial numbness, and paresis. After GKS, one patient had radiation necrosis, which required microsurgery, and two patients had new cranial nerve palsies.Conclusions Tumor control after microsurgery alone was not achieved in any patient, whereas adjuvant radiosurgery provided local tumor control in six of eight GKS-treated patients. Tumor control was not achieved in the two patients with MCS. Similar to other treatments for intracranial chondrosarcoma, morbidity after micro- and radiosurgical combination therapy was high and included severe cranial nerve palsies.

scholarly journals RADI-06. Gamma knife surgery for brain stem metastases

2021 ◽  
Vol 3 (Supplement_3) ◽  
pp. iii19-iii19
Author(s):  
Choo Heng Tan ◽  
Bengt Karlsson ◽  
Shilin Wang ◽  
John J Y Zhang ◽  
Yvonne Ang ◽  
...  
Keyword(s):  
Survival Time ◽  
Gamma Knife ◽  
Performance Status ◽  
Local Tumor Control ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Cerebral Peduncle ◽  
Complication Rates ◽  
Tumor Control Rate ◽  
Number Of Patients

Abstract Introduction Gamma Knife Surgery (GKS) is widely used for treatment of brainstem metastases (BSMs) with or without whole bran radiation therapy (WBRT). We hypothesized that BSMs treated with GKS using lower doses and omitting WBRT result in acceptable tumor control rates and low complication rates. Methods A retrospective single center study was performed to investigate the outcome following GKS of BSMs. All 33 patients with follow-up information treated with GKS for 39 metastases located in the cerebral peduncle, midbrain, pons or medulla oblongata were included in the study. The median treatment dose, defined as the lowest dose to 95% of the tumor volume, was 18 Gy. The tumor control rate as well as the survival time were related to a number of patients, tumor and treatment parameters. Results The local tumor control rate was 100% at one year and 89% at five years, and the overall median survival was 17 months. A good performance status and a treatable extracranial disease were favorably related to survival time. Two complications were observed, one lethal hemorrhage at the day of the treatment and one transient complication three months following GKS, resulting in a 6% complication rate at five years. Four of the 10 patient with symptomatic BSM improved clinically after GKS, while six remained unchanged. Conclusions High local control and a low complication rates can be achieved using GKS for BSMs using lower doses as compared to brain metastases in other locations.

scholarly journals Clinical outcomes of previously untreated patients with unresectable intrahepatic cholangiocarcinoma following proton beam therapy

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Shosei Shimizu ◽  
Toshiyuki Okumura ◽  
Yoshiko Oshiro ◽  
Nobuyoshi Fukumitsu ◽  
Kuniaki Fukuda ◽  
...  
Keyword(s):  
Overall Survival ◽  
Proton Beam ◽  
Intrahepatic Cholangiocarcinoma ◽  
Initial Treatment ◽  
Survival Rates ◽  
Progression Free Survival ◽  
Proton Beam Therapy ◽  
Target Volume ◽  
Tumor Control ◽  
Intraductal Growth

Abstract Background The effectiveness of proton beam therapy (PBT) as initial treatment for patients with unresectable intrahepatic cholangiocarcinoma (ICC) is unclear, particularly as related to ICC histological subtypes. We performed this study to address this gap in knowledge. Methods Thirty-seven patients with unresectable ICC who underwent PBT as their initial treatment were evaluated. Twenty-seven patients had Child-Pugh class A liver function, 11 exhibited jaundice, and 10 had multiple tumors. Nineteen, 7, and 11 tumors were classified as mass forming (MF), periductal infiltrating (PI), and intraductal growth (IG) types, respectively, based on gross appearance in imaging studies. Patients were classified into the curative group (n = 25) and palliative group (n = 12) depending on whether the planning target volume covered all the macroscopic tumors. Results The 1- and 2-year overall survival rates were 60.3, and 41.4%, respectively; the median survival time (MST) was 15 months for all patients. The MSTs for curative and palliative groups were 25 and 7 months, respectively. Curative treatment and adjuvant chemotherapy significantly improved overall survival, while the presence of periductal infiltrating type tumors was a negative prognostic factor. In the curative group, the 1- and 2-year local control rates were 100 and 71.5%, respectively, while the 1-, and 2-year progression-free survival rates were 58.5, and 37.6%, respectively. No severe acute toxicities were observed. Three patients experienced grade 3 biliary tract infection, although it was unclear whether this was radiotherapy-related. Conclusion PBT may yield to improve survival and local tumor control among patients with unresectable ICC.

scholarly journals Gamma Knife surgery for patients with brainstem metastases

2012 ◽  
Vol 117 (Special_Suppl) ◽  
pp. 23-30 ◽  
Author(s):  
Takuya Kawabe ◽  
Masaaki Yamamoto ◽  
Yasunori Sato ◽  
Bierta E. Barfod ◽  
Yoichi Urakawa ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Tumor Volume ◽  
Recursive Partitioning ◽  
Survival Rates ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Karnofsky Performance Scale ◽  
Radical Cure ◽  
Class Iii ◽  
Meningeal Dissemination

Object Because brainstem metastases are not deemed resectable, stereotactic radiosurgery (SRS) is the only treatment modality expected to achieve a radical cure. The authors describe their treatment results, focusing particularly on how long patients can survive without neurological deterioration following SRS for brainstem metastases. Methods This was an institutional review board–approved, retrospective cohort study in which the authors pulled from their database information on 2553 consecutive patients with brain metastases who underwent Gamma Knife surgery (GKS) at the Mito GammaHouse between July 1998 and July 2011. Among the 2553 patients, excluding cases in which there was meningeal dissemination, 200 cases of brainstem metastases (78 women and 122 men with a mean age of 64 years [range 36–86 years]) were identified and analyzed. The most common primary site was the lung (137 patients) followed by the gastrointestinal tract (24 patients), breast (17 patients), kidney (12 patients), and others (10 patients). Among the 200 patients, 15 patients (7.5%) harbored at least 2 tumors in the brainstem: 11 patients had 2 tumors, 2 patients had 3 tumors, and 1 patient each had 4 or 5 tumors. Therefore, a total of 222 tumors were irradiated. These 222 tumors were located in the pons (121 lesions), the midbrain (65 lesions), and the medulla oblongata (36 lesions). The mean and median tumor volumes were 1.3 and 0.2 cm3 (range 0.005–10.7 cm3), and the median peripheral radiation dose was 18.0 Gy (range 12.0–25.0 Gy). Results The overall median survival time (MST) was 6.0 months. Distribution of MSTs across Recursive Partitioning Analysis (RPA) classes showed that the MSTs were 9.4 months in Class I (20 patients), 6.0 months in Class II (171 patients), and 1.9 months in Class III (9 patients). Better Karnofsky Performance Scale score, single metastasis, and well-controlled primary tumor were significant predictive factors for longer survival. The neurological and qualitative survival rates were 90.8% and 89.2%, respectively, at 24 months post-GKS. Better KPS score and smaller tumor volume tended to be associated with prolonged qualitative survival. Follow-up imaging studies were available for 129 patients (64.5%). The tumor control rate was 81.8% at 24 months post-GKS. Smaller tumor volume tended to contribute to tumor control. Conclusions The present results indicate that GKS is effective in the treatment of brainstem metastases, particularly from the viewpoint of maintaining a good neurological condition in the patient.

Long-term tumor control and cranial nerve outcomes following Gamma Knife surgery for larger-volume vestibular schwannomas

2012 ◽  
Vol 116 (3) ◽  
pp. 598-604 ◽  
Author(s):  
Brian D. Milligan ◽  
Bruce E. Pollock ◽  
Robert L. Foote ◽  
Michael J. Link
Keyword(s):  
Posterior Fossa ◽  
Gamma Knife ◽  
Cranial Nerve ◽  
Tumor Volume ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Tumor Diameter ◽  
Tumor Margin ◽  
Median Maximum

Object Gamma Knife surgery (GKS) for vestibular schwannoma (VS) is an accepted treatment for small- to medium-sized tumors, generally smaller than 2.5 cm in the maximum posterior fossa dimension. The purpose of this study was to evaluate the efficacy and toxicity of GKS for larger tumors. Methods Prospectively collected data were analyzed for 22 patients who had undergone GKS for VSs larger than 2.5 cm in the posterior fossa diameter between 1997 and 2006. No patient had symptomatic brainstem compression at the time of GKS. The median treated tumor volume was 9.4 cm3 (range 5.3–19.1 cm3). The median maximum posterior fossa diameter was 2.8 cm (range 2.5–3.8 cm). The median tumor margin dose was 12 Gy (range 12–14 Gy). Serial imaging, audiometry (10 patients with serviceable hearing pre-GKS), and clinical follow-up were available for a median of 66 months (range 26–121 months). Tumor control failure was defined as either a progressive increase in tumor diameter of at least 2 mm in any dimension or a later resection. Results Four patients met the criteria for GKS failure, including 1 patient who demonstrated sarcomatous degeneration more than 7 years after GKS and died 3 months after microsurgical debulking. An enlarging cystic component was the surgical indication in 1 of the 2 patients who required resection, although 27% of tumors (6 lesions) were cystic before GKS. The 3-year actuarial rate of tumor control, freedom from new facial neuropathy, and preservation of functional hearing were 86%, 92%, and 47%, respectively. At 5 years post-GKS, these rates decreased to 82%, 85%, and 28%, respectively. At the most recent follow-up, 91% of tumors were smaller than at the time of GKS and the median maximum posterior fossa diameter reduction was 26%. On multivariate analysis, none of the following factors was associated with GKS failure, new facial weakness, new trigeminal neuropathy, or loss of serviceable hearing: patient age, tumor volume, tumor margin dose, and preoperative cranial nerve dysfunction. Conclusions Single-session radiosurgery is a successful treatment for the majority of patients with larger VSs. Although tumor control rates are lower than those for smaller VSs managed with GKS, the cranial nerve morbidity of GKS is significantly lower than that typically achieved via resection of larger VSs.

Long-term outcomes of Gamma Knife surgery for cavernous sinus meningioma

2007 ◽  
Vol 107 (4) ◽  
pp. 745-751 ◽  
Author(s):  
Toshinori Hasegawa ◽  
Yoshihisa Kida ◽  
Masayuki Yoshimoto ◽  
Joji Koike ◽  
Hiroshi Iizuka ◽  
...  
Keyword(s):  
Tumor Progression ◽  
Gamma Knife ◽  
Cavernous Sinus ◽  
Initial Treatment ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Long Term Outcomes ◽  
The Mean

Object The aim of this study was to evaluate long-term outcomes, including tumor control and neurological function, in patients with cavernous sinus meningiomas treated using Gamma Knife surgery (GKS). Methods One hundred fifteen patients with cavernous sinus meningiomas, excluding atypical or malignant meningiomas, were treated with GKS between 1991 and 2003. Forty-nine patients (43%) underwent GKS as the initial treatment. The mean tumor volume was 14 cm3, and the mean maximum and margin doses applied to the tumor were 27 and 13 Gy, respectively. The median follow-up period was 62 months. During the follow-up, 111 patients were able to be evaluated with neuroimaging. Results The actuarial 5- and 10-year progression-free survival rates were 87 and 73%, respectively. Similarly, the actuarial 5- and 10-year focal tumor control rates were 94 and 92%, respectively. Regarding functional outcomes, 43 patients (46%) experienced some degree of improvement, 40 (43%) remained stable, and 11 (12%) had worse preexisting or newly developed symptoms. Patients who underwent GKS as the initial treatment experienced significant improvement of their symptoms (p = 0.006). Conclusions Gamma Knife surgery is a safe and effective treatment over the long term in selected patients with cavernous sinus meningiomas. Tumor progression is more likely to occur from the lesion margin outside the treatment volume. In small to medium-sized tumors, GKS is an excellent alternative to resection, preserving good neurological function. For relatively large-sized tumors, low-dose radiosurgery (≤ 12 Gy) is acceptable for the prevention of tumor progression.

Gamma Knife surgery for primary central nervous system lymphoma: usefulness as palliative local tumor control

2006 ◽  
Vol 105 (Supplement) ◽  
pp. 133-138 ◽  
Author(s):  
Hiroyuki Kenai ◽  
Masanori Yamashita ◽  
Takaharu Nakamura ◽  
Tomoshige Asano ◽  
Yasutomo Momii ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Central Nervous System ◽  
Nervous System ◽  
Gamma Knife ◽  
Central Nervous System Lymphoma ◽  
Local Tumor Control ◽  
Gamma Knife Surgery ◽  
Tumor Control ◽  
Local Tumor

ObjectAlthough there is no established treatment for primary central nervous system lymphoma (PCNSL), therapeutic protocols involving high-dose methotrexate therapy followed, in some cases, by whole-brain radiotherapy (WBRT) have generally been adopted, and they have yielded relatively favorable results. Gamma Knife surgery (GKS) is a stopgap measure to treat patients with PCNSL. The authors summarize the results of their cases and evaluate the efficacy and usefulness of GKS.MethodsBetween June 1999, and June 2005, 22 patients suffering from PCNSL were treated with GKS at the authors' institution and were followed up for more than 6 months. Some combination of chemotherapy and/or WBRT and/or microsurgery had been performed in 18 of the 22 patients before GKS. The remaining four patients had not undergone any previous treatment. In these patients, the mean tumor volume was 4.14 cm3, and the tumors were treated with a mean margin dose of 16.5 Gy to the 52.8% isodose line. Magnetic resonance imaging demonstrated the disappearance of the GKS-treated lesions; however, new lesions were observed in other regions of the brain in 10 patients and repeated GKS was performed in some cases. No local recurrences were observed an average of 19.4 months after GKS, and good level of quality of life (QOL) was maintained during this period.Conclusions Gamma Knife surgery should be performed only for local tumor control as a stopgap measure in the treatment of PCNSL. It is noninvasive and safe, and its effects occur rapidly. Its use improves prognosis and enhances the patient's quality of life. Gamma Knife surgery should be considered one of the treatment strategies for patients with PCNSLs.

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