Implications of Identifying Additional Cerebral Metastases during Gamma Knife Radiosurgery

Abstract

Introduction. Gamma Knife radiosurgery (GK-SRS) is commonly used to treat cerebral metastases. Although additional intracranial metastases are often found on the day of GK-SRS, the significance of finding them is unknown. Methods. A retrospective review of 133 patients undergoing GK-SRS for cerebral metastases was performed. The change in number of metastases detected between initial referral magnetic resonance imaging (MRI) and subsequent treatment MRI was quantified. Multivariate and Kaplan-Meier analyses were employed to examine the significance of identifying additional lesions. Results. Additional lesions were identified in 41% of patients. An increasing number of metastases on referral MRI (P = 0.001) and the presence of progressive systemic disease (P = 0.003) were predictive of identifying additional metastases. Median survival was 6.9 months for patients with additional metastases, compared to 12.1 months for patients without additional metastases (hazard ratio 1.56, P = 0.021). Conclusions. Identifying additional metastases on the day of GK-SRS may add important prognostic information.

Figure 1

Bar graph demonstrating the relationship between the number of pre-GK-SRS metastases identified and the number of additional metastases (“Delta Mets”) identified at the time of GK-SRS. Error bars are shown.

Figure 2

Bar graph demonstrating the relationship between progressive systemic disease and the number of additional metastases (“Delta Mets”) identified at the time of GK-SRS. Error bars are shown.

Figure 3

Kaplan-Meier plot of overall survival after GK-SRS for all 133 patients, stratified by the number of additional metastases identified at the time of GK-SRS.

Figure 4

Kaplan-Meier plot of overall survival after GK-SRS for all 133 patients, stratified by the presence of progressive systemic disease at the time of GK-SRS.