Whole Brain Dose From Multiple Gamma Knife Sessions For Cns Metastatic Disease: The William Beaumont Hospital Experience

Keywords: brain metastasis, radiotherapy, gamma knife, dose planning, technique

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       Gamma knife (GK) irradiation has become a common treatment option for patients with metastatic CNS disease. This is important in that it is estimated that between 20-40% of all cancer patients will have CNS presentation during their disease course. In the past the finding of CNS metastasis has been met with expectations of short survival, however with more effective chemotherapy and enhanced surgical techniques and the ability to treat local sites that may persist or develop after whole brain irradiation has led to many patients having increased survival. One of the main complaints related to the use of whole brain irradiation has been the negative neuro-cognitive effects it may have. Couple this with use of GK to "boost" poorly responding lesions or for treatment of newly developed lesions and patients may be exposed to possibility of increased whole brain dose above and beyond that given with standard techniques.
     We have retrospectively reviewed our series of patients referred for treatment of CNS metastatic disease and focused on those receiving multiple treatment sessions to calculate the additional whole brain dose that is delivered using GK techniques to determine if total treatment sessions, total treatment sites, lesion location or total treatment volume had any impact on the additional whole brain dose delivered.
     Between 12/06 and 09/09 307 patients were referred to the GK center at William Beaumont Hospital . Of these patients 53 were referred for multiple sessions. The characteristics of these patients were as follows: Total number of lesions treated: 129. Lesion location: Frontal n = 40, Parietal n = 23, Occipital n = 17, Temporal n = 9, Other n = 40
     Treatment of CNS metastatic disease.
     No patient developed radiation induced necrosis of clinical significance
     This is a retrospective study.
     The use of GK , even in multiple sessions and for multiple lesions, does not appear to add substantial additional whole brain dose to patients .
     This is important in that many patients are referred after already receiving traditional whole brain irradiation.


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