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Gamma Knife surgery–induced meningioma

Report of two cases and review of the literature

Jason Sheehan, Chun PO Yen and Ladislau Steiner

✓Gamma Knife surgery (GKS) is a minimally invasive neurosurgical technique. During the past 30 years, radiosurgery has been performed for a number of intracranial disorders with a generally low incidence of side effects. Although radiation-induced neoplasia following radiotherapy is well documented, there are few reports of this complication following radiosurgery.

The authors are engaged in an ongoing project in which they are studying the delayed adverse effects of radiosurgical changes in 2500 patients with arteriovenous malformations (AVMs) treated within a 30-year period. The cases of 1333 patients treated by the senior author (L.S.) have been reviewed thus far. A subset of 288 patients in this group underwent neuroimaging and participated in clinical follow up for at least 10 years.

The authors report two cases of radiosurgically induced neoplasia. In both cases the patient was treated with GKS for an AVM. Longer than 10 years after GKS, each of the patients was found to have an incidental, uniformly enhancing, dura-based mass lesion near the site of the AVM. These lesions displayed the imaging characteristics of a meningioma. Because in both cases the lesion has displayed no evidence of a mass effect, they continue to be followed using serial neuroimaging. These are the fifth and sixth cases meeting the criteria for radiation-induced neoplasms defined by Cahan, et al., in 1998.

Although radiosurgery is generally considered quite safe, the incidence of radiation-induced neoplasms is not known. These cases and the few others detailed in the literature emphasize the need for long-term neurosurgical follow-up review in patients after radiosurgery.

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Douglas Kondziolka

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Claire Olson, Chun-Po Yen, David Schlesinger and Jason Sheehan

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.

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Bruce E. Pollock

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Chun Po Yen, Jason Sheehan, Greg Patterson and Ladislau Steiner

Object

The authors review imaging and clinical outcomes in patients with metastatic brainstem tumors treated using Gamma Knife surgery (GKS).

Methods

Between March 1989 and March 2005, 53 patients (24 men and 29 women) with metastatic brainstem lesions underwent GKS. The metastatic deposits were located in the midbrain in eight patients, the pons in 42, and the medulla oblongata in three. Lung cancer was the most common primary malignancy, followed by breast cancer, melanoma, and renal cell carcinoma. The mean volume of the metastatic deposits at the time of treatment was 2.8 cm3 (range 0.05–21 cm3). The prescription doses varied from 9 to 25 Gy (mean 17.6 Gy).

Imaging follow-up studies were not completed in 16 patients, because of the short-term survival in 11 and patient refusal in five. Of the remaining 37 patients, who underwent an imaging follow-up evaluation at a mean of 9.8 months (range 1–25 months), the tumors disappeared in seven, shrank in 22, remained unchanged in three, and grew in five. All but one of 18 patients with asymptomatic brainstem deposits remained free of symptoms. In 35 patients with symptomatic brainstem deposits, neurological symptoms improved in 21, remained stable in 11, and worsened in three. At the time of this study, 10 patients were alive, and their survival ranged from 3 to 52 months after treatment. Thirty-four patients died of extracranial disease, three of the progressing metastatic brainstem lesion, and six of additional progressing intracranial deposits in other parts of the brain. The overall median survival period was 11 months after GKS. In terms of survival, the absence of active extracranial disease was the only favorable prognostic factor. Neither previous whole-brain radiation therapy nor a single brainstem metastasis was statistically related to the duration of survival.

Conclusions

Compared with allowing a metastatic brainstem lesion to take its natural course, GKS prolongs survival. The risks associated with such treatment are low. The severity of systemic diseases largely determines the prognosis of metastases to the brainstem.

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Chun Po Yen, Jason Sheehan, Greg Patterson and Ladislau Steiner

Object

Although considered benign tumors, neurocytomas have various biological behaviors, histological patterns, and clinical courses. In the last 15 years, fractionated radiotherapy and radiosurgery in addition to microsurgery have been used in their management. In this study, the authors present their experience using Gamma Knife surgery (GKS) in the treatment of these tumors.

Methods

Between 1989 and 2004, the authors performed GKS in seven patients with a total of nine neurocytomas. Three patients harbored five recurrent tumors after a gross-total resection, three had progression of previous partially resected tumors, and one had undergone a tumor biopsy only. The mean tumor volume at the time of GKS ranged from 1.4 to 19.8 cm3 (mean 6.0 cm3). A mean peripheral dose of 16 Gy was prescribed to the tumor margin with the median isodose configuration of 32.5%.

Results

After a mean follow-up period of 60 months, four of the nine tumors treated disappeared and four shrank significantly. Because of secondary hemorrhage, an accurate tumor volume could not be determined in one. Four patients were asymptomatic during the follow-up period, and the condition of the patient who had residual hemiparesis from a previous transcortical resection of the tumor was stable. Additionally, the patient who experienced tumor hemorrhage required a shunt revision, and another patient died of sepsis due to a shunt infection.

Conclusions

Based on this limited experience, GKS seems to be an appropriate management alternative. It offers control over the tumor with the benefits of minimal invasiveness and low morbidity rates. Recurrence, however, is not unusual following both microsurgery and GKS. Open-ended follow-up imaging is required to detect early recurrence and determine the need for retreatment.

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Jason Sheehan and Chun Po Yen

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Editorial

Arteriovenous malformations

Douglas Kondziolka

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Robert G. Louis Jr., Chun Po Yen, Carrie A. Mohila, James W. Mandell and Jason Sheehan

The authors report the case of a patient with an intraosseous spinal arteriovenous malformation (AVM) presenting as an epidural mass lesion that was causing spinal cord compression. The 59-year-old woman had bilateral numbness, weakness, and hyperreflexia of both legs. Magnetic resonance imaging revealed intermediate T1 signal and hyperintense T2 signal involving the right transverse process, bilateral pedicles, and T-5 spinous process; the lesion's epidural extension was causing severe canal compromise and cord displacement. Coil embolization was performed, and the patient underwent resection, after which preoperative symptoms improved. Histopathological analysis revealed a benign vascular proliferation consistent with an intraosseous spinal AVM. On review of the literature, the authors found this case to be the second intraosseous spinal AVM, and the first in a patient whose clinical presentation was consistent with that of a mass lesion of the bone.

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Jason P. Sheehan, Chun-Po Yen, James Nguyen, Jessica A. Rainey, Kasandra Dassoulas and David J. Schlesinger

Object

Stereotactic radiosurgery has been shown to afford a reasonable chance of local tumor control. However, new brain metastasis can arise following successful local tumor control from radiosurgery. This study evaluates the timing, number, and risk factors for development of subsequent new brain metastasis in a group of patients treated with stereotactic radiosurgery alone.

Methods

One hundred seventeen patients with histologically confirmed metastatic cancer underwent Gamma Knife surgery (GKS) to treat all brain metastases demonstrable on MR imaging. Patients were followed clinically and radiologically at approximately 3-month intervals for a median of 14.4 months (range 0.37–51.8 months). Follow-up MR images were evaluated for evidence of new brain metastasis formation. Statistical analyses were performed to determine the timing, number, and risk factors for development of new brain metastases.

Results

The median time to development of a new brain metastasis was 8.8 months. Patients with 3 or more metastases at the time of initial radiosurgery or those with cancer histologies other than non–small cell lung carcinoma were found to be at increased risk for early formation of new brain metastasis (p < 0.05). The mean number of new metastases per patient was 1.6 (range 0–11). Those with a higher Karnofsky Performance Scale score at the time of initial GKS were significantly more likely to develop a greater number of brain metastases by the last follow-up evaluation.

Conclusions

The timing and number of new brain metastases developing in patients treated with GKS alone is not inconsequential. Those with 3 or more metastases at the time of radiosurgery and those with cancer histology other than non–small cell lung carcinoma were at greater risk of early formation of new brain metastasis. Frequent follow-up evaluations, such as at 3-month intervals, appears appropriate in this patient population, particularly in high-risk patients. When detected early, salvage treatments including repeat radiosurgery can be used to treat new brain metastasis.