Prognostic factors for Gamma Knife Radio-surgery in patients with >5 brain metastases

Keywords: brain metastasis, outcome, gamma knife, radiosurgery, lung cancer

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     Gamma-Knife radio-surgery (GK) is one of the mainstays of treatment in patients with brain metastases, especially for 4 or fewer lesions. Currently there is an increasing interest in offering this treatment modality to patients with a more extensive intracranial burden of disease (?5 metastases) as an upfront treatment or in combination with whole brain radiation therapy (WBRT). However, data is lacking specifically related to the outcomes and prognostic factors in this subgroup of patients.
     In this study, prognostic factors contributing to overall survival (OS) of patients with ?5 brain metastases were evaluated.
     Patient median age was 58 and female/male ratio was 94/76.
     An IRB approved retrospective review of 170 patients with >5 brain metastases treated at the Cleveland Clinic GK Center (1997-2010) was performed. Patient demographics, tumor characteristics, treatment related factors as well as outcome of treatment were evaluated. Statistical analysis was performed using Kaplan-Meier survival summaries and Cox proportional hazards regression.>
      The most common primary sites were lung 84(49%) and breast 34(20%). At the time of GK, 70(41%) of the patients had multiple extracranial metastases, and KPS was >90 in 66(39%) of patients. Most of the patients 135(79%) were recursive partitioning analysis (RPA) class II and median graded prognostic index (GPA) was 1.5. Median total intracranial disease volume was 3.25cc(range 0.19-37.19cc) with a tumor volume of ?10cc in 32(19%) of patients. Median number of lesions was 6(range 5-20). Median OS after GK was 6.8 months. At the time of GK, older age, lower KPS, extensive extracranial disease burden, higher RPA class, lower GPA, non-lung primary pathology, and higher total intracranial tumor volume were statistically significant poor prognostic factors using univariate analysis. Multivariate analysis demonstrated lower KPS, multiple extracranial metastases and higher intracranial tumor volume were significant negative prognostic factors.>
     This was a retrospective study.
     In this large series of GK treated patients with >5 brain metastases, OS was significantly improved in patients with higher KPS and without extensive systemic involvement. Further, the total intracranial disease burden was more relevant than the actual number of lesions. 
     This data suggests that GK should be considered an appropriate treatment modality in the management of multiple brain metastases.


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