
These are attempts to focus the beam so that the Xrays or Gamma rays are kept tightly to the contours of the tumor, and do less scattering through normal tissue.  It is impossible with this modality to completely spare normal tissue from any exposure to radiation, but it does help preserve tissue.

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<b>Gamma Knife / Stereotactic Radiation  -- Annotated Citations</b>


Stereotact Funct Neurosurg 2000;74(1):37-51 
<b>Gamma knife radiosurgery for the treatment of brain metastases. </b>
Sansur CA, Chin LS, Ames JW, Banegura AT, Aggarwal S, Ballesteros M, Amin P, Simard JM, Eisenberg H. 
Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD 21201-1595, USA. 

One hundred and ninety-three patients with brain metastases from various primary sites received Gamma Knife radiosurgery (GKR) from July 1992 to August ,,, Survival follow-up was available on 173 patients. Whole-brain radiation therapy was also administered to 148 of these patients. The median survival was 13.1 months from initial detection of brain metastases, and 7.5 months from GKR. <b>Univariate and multivariate analyses were performed to determine prognostic factors that influenced survival following GKR. Enhanced survival is observed in patients with radiosensitive tumor types, supratentorial tumor, history of brain tumor resection, controlled primary site, and absent extracranial metastases. Local lesion control was obtained in 82% of the patients according to their last follow-up MRI scan. GKR is an effective means of treating patients with brain metastases.</b> Copyright 2000 S. Karger AG, Basel [permission to use abstract obtained] 
&&url PMID: 11124663  


J Clin Oncol 1990 Apr;8(4):576-82 Comment in: J Clin Oncol. 1990 Apr;8(4):571-3 
<b>The treatment of recurrent brain metastases with stereotactic radiosurgery. </b>
Loeffler JS, Kooy HM, Wen PY, Fine HA, Cheng CW, Mannarino EG, Tsai JS, Alexander E 3rd. 
Neurosurgical Service, Brigham and Women's Hospital, Boston, MA. 

,,, To be eligible for radiosurgery, patients had to have a performance status of greater than or equal to 70% and have no evidence of (or stable) systemic disease. All but one patient had received prior radiotherapy, and were treated with stereotactic radiosurgery at the time of recurrence. Polar lesions were treated only if the patient had undergone and failed previous complete surgical resection (10 patients). Single doses of radiation (900 to 2,500 cGy) were delivered to limited volumes (less than 27 cm3) using a modified 6MV linear accelerator. ,,, With median follow-up of 9 months (range, 1 to 39), all tumors have been controlled in the radiosurgery field. Two patients failed in the immediate margin of the treated volume and were subsequently treated with surgery and implantation of 125I to control the disease. <b>Radiographic response was dramatic and rapid in the patients with adenocarcinoma, while slight reduction and stabilization occurred in those patients with melanoma, renal cell carcinoma, and sarcoma. The majority of patients improved neurologically following treatment, and were able to be withdrawn from corticosteroid therapy. Complications were limited and transient in nature and no cases of symptomatic radiation necrosis occurred in any patient despite previous exposure to radiotherapy. Stereotactic radiosurgery is an effective and relatively safe treatment for recurrent solitary metastases and is an appealing technique for the initial management of deep-seated lesions as a boost to whole brain radiotherapy.</b> 
&&url PMID: 2179476 


Neurochirurgie 1999 Dec;45(5):393-7 
<b>[Radiosurgery for brain metastases]. [Article in French]</b> 
Nataf F. Service de Neurochirurgie, CH Sainte-Anne, 1, rue Cabanis, 75674 Paris Cedex 14, France. 

This article presents the state of art in radiosurgery as a new therapeutic strategy of brain metastases. Radiosurgery of brain metastases is ten years old and we propose to make an update of the literature. X-rays and gamma-rays are commonly used for radiosurgery and does not make a difference for dosimetry and precision. Selected patients for this treatment have usually good Karnofsky status and the mean size of their metastases is about 20 mm. Mean number of metastases treated in the same procedure is 2. Most frequent primary sites are lung and breast, but also kidney and skin (malignant melanoma) which are supposed to be radioresistant and so often untreatable by other techniques. Usual dose administrated ranges between 15 and 25 Grays in center of target with a 80% isodose in peripheral. <b>Results are quite good for local control (80% to 100%) but survival does not seem to be improved (11 months). Radiation complication rate is 4% and sometimes hemorrhagic complications occur (1 to 2%). For local control, quality of life and cost/benefit ratio, there are strong arguments in favor of radiosurgery, especially for radioresistant metastases in spite of the lack of improvement of survival duration. Moreover published studies do not allow any comparison with efficacy of surgery and radiosurgery, whole brain radiosurgery and radiosurgery of the present metastases. Evaluations are still going on in several centers. Their results will allow more precise indications of this technique.</b> 
&&url PMID: 10717588 


Int J Radiat Oncol Biol Phys. 1991 Jun;20(6):1287-95. 
<b>Radiosurgery for solitary brain metastases using the cobalt-60 gamma unit: methods and results in 24 patients.</b>
Coffey RJ, Flickinger JC, Bissonette DJ, Lunsford LD.
Department of Neurosurgery, Mayo Clinic, Rochester, MN 55905.

To define the role of stereotactic radiosurgery in the treatment of metastatic brain tumors we treated 24 consecutive patients ... with the 201-source 60Co gamma unit ...
 All tumors were less than or equal to 3.0 cm in greatest diameter [none were sarcomas]. Twenty patients received a planned combination of 30-40 Gy whole brain fractionated irradiation and a radiosurgical "boost" of 16-20 Gy to the tumor margins; ...During this 23-month period (median follow-up of 7 months) no patient died from progression of a radiosurgically-treated brain metastasis. ... To date, median survival after radiosurgery has been 10 months; 1-year survival was 33.3%. Stereotactic radiosurgery eliminated the surgical and anesthetic risks associated with craniotomy and resection of solitary brain metastases. Radiosurgery also effectively controlled the growth of tumors considered "resistant" to conventional irradiation.  
&&url PMID: 1646195 