Metabolic characteristics of intracranilal metastases, detected by single-voxel proton magnetic resonance spectroscopy, are seemingly not predictive for tumor response to gamma knife radiosurgery

Metabolic characteristics of intracranial metastases, detected with proton magnetic resonance spectroscopy (H-1-MRS) have known associations with clinical predictors of tumor response to radiosurgery. Therefore, it can be suspected that the metabolic profile of the neoplasm by itself might have some prognostic significance for the outcome after irradiation. Twenty-six intracranial metastases, which underwent metabolic evaluation with single-voxel H-1-MRS before gamma knife radiosurgery (GKR) and were followed for at least 3 months after treatment, were selected for retrospective analysis. The tumors most frequently originated from the lungs (9 cases), breast (7 cases), colon and rectum (5 cases). The average volume of the investigated intracranial neoplasm was 5.4 +/- 2.0 mL. The average marginal irradiation dose was 18.6 +/- 2.3 Gy. The mean follow-up after GKR constituted 8.0 +/- 5.5 months. Tumor response to GKR was identified in 13 cases on average 2.2 +/- 1.8 months after treatment. Local recurrence was marked in 10 cases on average 8.7 +/- 4.1 months after treatment. None of the investigated H-1-MRS metabolic parameters of intracranial metastases showed a statistically significant association with the outcome after GKR. The negative results of the present study make doubtful the predictive value of metabolic characteristics of intracranial metastases, detected with single-voxel H-1-MRS, for the outcome after radiosurgery.