Low-dose Gamma Knife Radiosurgery Research Articles

Preplanned Partial Surgical Removal Followed by Low-Dose Gamma Knife Radiosurgery for Large Vestibular Schwannomas.

The present study evaluated outcomes after preplanned partial surgical removal of a large vestibular schwannoma (VS) followed by low-dose Gamma Knife surgery (GKS). Between January 2000 and May 2015, 47 patients with a unilateral VS (median maximum diameter 32mm) underwent preplanned partial tumor removal at our clinic. GKS for a residual lesion was done within a median time interval of 3months. The median prescription dose was 12 Gy. The median length of subsequent follow-up was 74months. The actuarial tumor growth control rates without a need for additional management at 3, 5, and 15years after GKS were 92%, 86%, and 86%, respectively. At the time of the last follow-up, the function of the ipsilateral facial nerve corresponded to House-Brackmann gradeI in 92% of patients. Significant improvement of ipsilateral hearing was noted in two patients after partial tumor removal and in one after GKS. Among 16 patients who presented with ipsilateral serviceable hearing, it was preserved immediately after surgery in 81% of cases and at the time of the last follow-up in 44%. Salvage surgical treatment was required in 9% of patients. Preplanned partial surgical removal followed by low-dose GKS provides a high level of functional preservation in patients with a large VS.

Staged Gamma Knife Radiosurgery for Large Skull Base Meningiomas.

Purpose: The authors have been treating skull base meningiomas using relatively low-dose gamma knife radiosurgery (GKS, ≤ 12 Gy) with acceptable tumor growth control and low morbidity. In the present study, volume-staged, low-dose GKS was performed for large skull base meningiomas with a maximum diameter > 4 cm. In this article, a treatment strategy for volume-staged GKS and results for large skull base meningiomas are described.Methods: Data from 27 patients with large skull base meningiomas histopathologically diagnosed as WHO grade I or diagnosed by imaging, who underwent volume-staged GKS between March 1995 and September 2018, were reviewed. Among these patients, 24 were followed-up for > six months. The tumor was located in the parasellar region in nine patients, cavernous sinus region in four, petroclival region in four, petrocavernous sinus region in four, cerebellopontine angle region in two, and in the tent in one. The mean tumor diameters ranged from 31 to 47.8 mm (median 39.4 mm), with tumor volumes between 14.7 and 49.5 cm3 (median 27.5 cm3).Results: The prescribed radiation dose was 8-12 Gy (median 10 Gy). The treatment interval between the first and second GKS was three to nine months (median 5.5 months). The median duration of follow-up after the first GKS was 84 months (range 6-204 months). Tumor volume decreased in nine (37.5%) patients, remained stable in nine (37.5%), and increased (local failure) in six (25%). The actuarial progression-free local control rate was 88% at three years, 78% at five years, 70% at 10 years, and 70% at 15 years. Neurological status improved in three (12.5%) patients, was unchanged in 16 (66.5%), and deteriorated in five (21%). Permanent radiation injury occurred in one (4%) patient.Conclusion: Volume-staged GKS demonstrated the usefulness for large skull meningiomas > 4 cm in diameter, over a long-term follow-up period.

Chordoid Glioma: A Neoplasm Found in the Anterior Part of the Third Ventricle

Chordoid glioma is a rare low-grade tumor that originates almost exclusively in the anterior part of the third ventricle. The diagnosis and treatment of the tumor remain controversial. In this article, the authors present a novel case of chordoid glioma of the third ventricle. The patient was treated with less invasive microsurgery followed by low-dose gamma knife radiosurgery. Magnetic resonance imaging revealed a decrease in tumor size and necrosis in the central region of the tumor, without significant complications at follow-up 14 months later. Based on these findings, the authors suggest that less invasive microsurgical resection followed by low-dose gamma knife radiosurgery is safe and effective for the treatment of chordoid glioma of the third ventricle.

Long-term outcome after two-stage low-dose Gamma Knife radiosurgery for large recurrent petroclival meningioma

Long-term outcome after two-stage low-dose Gamma Knife radiosurgery for large recurrent petroclival meningioma

Hearing Preservation after Low-dose Gamma Knife Radiosurgery of Vestibular Schwannomas.

The objective of the retrospective study was to evaluate the factors associated with hearing preservation after low-dose Gamma Knife radiosurgery (GKS) of vestibular schwannomas performed according to the modern standards. From January 2005 to September 2010, 141 consecutive patients underwent such treatment in Tokyo Women’s Medical University. Mean marginal dose was 11.9 Gy (range, 11–12 Gy). The doses for the brain stem, cranial nerves (V, VII, and VIII), and cochlea were kept below 14 Gy, 12 Gy, and 4 Gy, respectively. Out of the total cohort, 102 cases with at least 24 months follow-up were analyzed. Within the median follow-up of 56 months (range, 24–99 months) the crude tumor growth control was 92% (94 cases), whereas its actuarial rate at 5 years was 93%. Out of 49 patients with serviceable hearing on the side of the tumor before GKS, 28 (57%) demonstrated its preservation at the time of the last follow-up. No one evaluated factor, namely Gardner-Robertson hearing class before irradiation, Koos tumor stage, extension of the intrameatal part of the neoplasm up to fundus, nerve of tumor origin, presence of cystic changes in the neoplasm, and cochlea dose demonstrated statistically significant association with preservation of the serviceable hearing after radiosurgery. In conclusion, GKS of vestibular schwannomas performed according to the modern standards of treatment permits to preserve serviceable hearing on the side of the tumor in more than half of the patients. The actual causes of hearing deterioration after radiosurgery remain unclear.

Therapeutic Approach to Chordoid Glioma of the Third Ventricle

Chordoid glioma of the third ventricle is considered to be a benign glial tumor located exclusively in the mid-anterior portion of the third ventricle near the hypothalamus and optic nerves, with the histological features of a chordoma and immuno-labeling for glial fibrillary acidic protein. Unfortunately, the clinical outcome of chordoid glioma has been poor, even in patients receiving gross total or partial removal with or without radiotherapy. Three cases of chordoid glioma of the third ventricle were treated with less invasive microsurgery for pathological diagnosis or partial removal without neuro-endocrinological complication, followed by gamma knife radiosurgery using a lower marginal dose for the optic nerves and hypothalamus. Gamma knife radiosurgery was performed after open biopsy in two patients, and after partial removal in the third patient using a lower marginal dose of 10.5 to 12 Gy. Serial magnetic resonance imaging revealed gradual decrease or at least no change in the tumor size, without significant complication at follow up 70 and 66 months later in two cases. The third patient accidentally died 13 months after gamma knife treatment. We conclude that low dose gamma knife radiosurgery after less invasive microsurgery is both safe and effective for the control of chordoid glioma of the third ventricle over a very long follow-up period.

Combined treatment of invasive giant prolactinoma with surgical excision, low-dose gamma knife radiosurgery, and a dopamine agonist—Report of two cases

Although most prolactinomas are benign, some are invasive or aggressive. The management of invasive giant prolactinomas (IGPs) has been an area of controversy. The present study reports the combined treatment of IGP with surgical excision, low-dose gamma knife radiosurgery (GKRS), and a dopamine agonist. An enhancing mass at the pituitary fossa with suprasellar extension and invasion of the cavernous sinus was identified in two patients. The blood prolactin level was more than 1000 ng/mL in both patients before treatment. Trans-sphenoidal removal of the tumors was done to reduce tumor compression on the optic apparatus. Low-dose GKRS was then used to treat the residual tumor with invasion to the caversinous sinus. The marginal dose was set at 12 and 14 Gy at the 50% and 42% isodose lines, respectively. A dopamine agonist, cabergoline, was used after GKRS. The tumors were markedly reduced and hard to be seen in magnetic resonance images. After a follow-up period of more than 3 years, the blood prolactin level returned to normal in one patient without the use of the dopamine agonist and was nearly normal in the other patient with continuing use of the dopamine agonist. Treatment combining surgical excision, GKRS, and a dopamine agonist may be a good treatment for IGPs. To make sure the remission of the disease, the longer follow-up is needed.

Gamma Knife radiosurgery for skull base meningioma: long-term results of low-dose treatment

In this study, the authors evaluate the long-term results after Gamma Knife radiosurgery of cranial base meningiomas. This study is a follow-up to their previously published report on the early results. Between January 1994 and December 2001, the authors treated benign cranial base meningiomas in 108 patients using low-dose Gamma Knife radiosurgery. The tumor volumes ranged from 1.7 to 55.3 cm3 (median 8.1 cm3), and the radiosurgery doses ranged from 8 to 12 Gy (median 12 Gy) to the tumor margin. The mean duration of follow-up was 86.1 months (range 20-144 months). Tumor volume decreased in 50 patients (46%), remained stable in 51 patients (47%), and increased (local failure) in 7 patients (6%). Eleven patients experienced tumor recurrence outside the treatment field. Among these patients, marginal failure was seen in 5 and distant recurrence was seen in 6. Seven patients were thought to have malignant transformation based on histological or radiological characteristics of the lesion. The actuarial progression-free survival rate, including malignant transformation and outside recurrence, was 93% at 5 years and 83% at 10 years. Neurological status improved in 16 patients (15%). Permanent radiation injury occurred in 7 patients (6%). Gamma Knife radiosurgery is a safe and effective treatment for cranial base meningiomas as demonstrated with a long-term follow-up period of > 7 years. Surgeons must be aware of the possibility of treatment failure, defined as local failure, marginal failure, and malignant transformation; however, this may be the natural course of meningiomas and not related to radiosurgery.

Low-Dose Gamma Knife Radiosurgery for Cavernous Sinus Hemangioma: Report of 3 Cases and Literature Review

Optimal management of cavernous sinus hemangiomas remains unclear. Total microsurgical removal of these neoplasms may be extremely difficult due to their rich vascularization. Three cases of cavernous sinus hemangioma treated with low-dose Gamma Knife radiosurgery are presented. Marginal dose varied from 10 to 13 Gy. Treatment planning and radiation dosimetry were done with a goal of conformal and selective coverage of the lesion with 50% prescription isodose line using multiisocenter technique. In all cases significant shrinkage of the neoplasm was marked at 3 months after treatment. Mean volume reduction at 12 months after radiosurgery was 60% (range: 45-75%). In all patients the shrinkage of the neoplasm was accompanied by notable improvement of the preexistent oculomotor nerve palsy. No radiosurgery-related complications were met during follow-up. In conclusion, low-dose Gamma Knife radiosurgery seems to be very effective for management of cavernous sinus hemangiomas, and can be considered as a treatment modality of choice for these lesions.

Gamma knife radiosurgery for acoustic schwannoma: early effects and preservation of hearing.

The effects of relatively low dose gamma knife irradiation on acoustic schwannoma were evaluated. The signal intensity change and tumor shrinkage on magnetic resonance (MR) images, change in hearing, and complications in 28 patients (mean age 47.0 +/- 13.6 yrs) were studied. Three patients had bilateral tumors. Six were already deaf when treated. The maximum tumor diameter was 35 mm. The mean dose delivered to the tumor was 12.1 +/- 1.6 Gy at the periphery, and 25.2 +/- 4.3 Gy at the center. The mean follow-up time was 16 months and the longest 24 months. Lowering of the MR signal intensity in the tumor center appeared after 3 months at earliest but generally after 6 months. Signs of tumor shrinkage appeared within 12 months on average. Cyst in the tumor enlarged rapidly after treatment in two patients. The percentage of hearing preservation was 85% (17/20) at 3 months, 80% (16/20) at 6 months, 72% (13/18) at 9 months, 75% (12/16) at 12 months, 67% (8/12) at 15 months, 60% (6/10) at 18 months, and 50% (2/4) at 24 months. Subtle changes in hearing were detected by speech tone audiometry. Temporary facial numbness and weakness was seen in one patient each. No patient had lower cranial nerve paresis. Relatively low dose gamma knife radiosurgery is effective in suppressing growth of acoustic schwannoma with preservation of hearing.