Efficacy of gamma knife surgery for control of peritumoral oedema associated with metastatic brain tumours.

OBJECTIVES: To evaluate the efficacy of gamma knife surgery (GKS) for the control of peritumoral oedema associated with metastatic brain tumours.
METHODS: A retrospective study of 280 consecutive metastatic brain tumours-100 from lung cancers, 100 from breast cancers and 80 from renal-cell carcinomas, associated with peritumoral oedema. The peritumoral oedema index was measured as A*B*C, where A (cm) was the maximum diameter of peritumoral oedema on the axial image, B (cm) was the maximum diameter perpendicular to A, and C (cm) was the maximum diameter on the coronal image.
RESULTS: The oedema index of the renal cancer metastases was significantly larger than those of lung and breast cancer metastases (p<0.01). The oedema index of the renal cancer metastases at final imaging was also larger than those of lung (p<0.05) and breast (p<0.01) cancer metastases. The delivered marginal dose (22 Gy or more) was significantly correlated with tumour growth control by multivariate analysis (p = 0.03). Primary site (renal or not renal: p<0.01) and delivered marginal dose (25Gy or more: p = 0.04) were significantly correlated with control of peritumoral oedema by multivariate analysis.
CONCLUSIONS: Brain oedema around metastatic brain tumours from renal-cell carcinomas was more extensive at the time of GKS and at final imaging compared with lung and breast cancer metastases. This paper suggests that the optimal doses for tumour growth control and brain oedema control may differ for metastatic brain tumours from renal-cell carcinomas.