An Analysis Of The Relative Efficacy Of Gamma Knife Radiosurgery And Whole Brain Radiotherapy In Metastatic Disease Of The Brain.

Keywords: brain metastasis, radiotherapy, gamma knife, radiosurgery, outcome

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     The aim of the study was to analyze statistically the factors affecting outcome in all patients treated with radiation for brain metastasis in order to determine the optimal approach to treatment using whole brain radiotherapy (WBRT), gamma knife surgery (GKS) or a combination of both.
     From a total of 272 patients treated between 2004 and 2007 and evaluated prospectively, 172 were available for analysis with 2 year follow up.   Gamma Knife cases included 127 patients with 143 primary treatment sessions and 24 retreatments. The patients were divided into 4 groups. A: WBRT alone, B: WBRT first followed by supplementary GKS, C: GKS alone, D: GKS first with supplementary WBRT. 
     The cases and groups were analyzed with respect to age, sex, number, size, diagnosis, Karnowsky (KPS), BSBM, time to local progression, survival, retreatment. The Kruskal Wallis or Crosstabs tests were used for matching groups. The Kaplan-Meier method using log rank tests was used to assess the difference in survival between groups. Patients treated with surgical removal were excluded.
     Using the Kruskal Wallis test or Crosstabs test, all groups were found to be matched for age (P=0.15), KPS (P=0.79), sex (P=0.09), and diagnosis (P=0.09) but not for BSBM (P=0.016) or size (P=0.004). The cases were distributed as follows: Group A: 38, Group B: 54, Group C: 49, Group D: 1. Of the WBRT alone cases, 7 (15%) required salvage GKS. Of the GKS alone cases, 1 (2%) required salvage WBRT. Of all GKS cases, 15 (12%) required retreatment with GKS, in one patient on five occasions. Retreatment was associated with multiple metastases.  Of the 24 GKS retreatments, 15 were in group C and 9 in group B. Thus 15/49 (31%) of group C and 9/54 (17%) of group B needed retreatment, a bias suggesting WBRT protects against recurrence over the expected life span of the patient. No significant difference in survival after GKS was found between groups of single and multiple metastases (p = 0.236).
     This is a retrospective study.
     Multiple treatments may be required for multiple metastases.  WBRT protects against recurrence, but the chance of a GKS case needing salvage WBRT is very low if repeat GKS is available. 
     Multiple metastases do not have a statistically proven worse prognosis. Combined treatments need to be tailored to the individual patient’s needs.


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