JRSBRT 3.4, p. 281-286

Factors that determine local control with gamma knife radiosurgery: The role of primary histology
Paul J. Black, Brandi R. Page, John T. Lucas, Jr., Ryan T. Hughes, Adrian W. Laxton, Stephen B. Tatter, Michael T. Munley, and Michael D. Chan

Background: Stereotactic radiosurgery for the treatment of brain metastases is commonly delivered without regard to primary cancer histology. This study sought to determine if the primary site of origin for brain metastases affected the propensity for local failure.

Methods: A total of 83 patients with 200 brain metastases were examined retrospectively for predictors of infield failure. Tumor, patient, and treatment characteristics were analyzed including primary tumor histology, radiosurgical dose and age. Cox proportional hazards models, univariate and multivariate analyses were used to identify predictors of local failure.

Results: Freedom from local failure for the entire population was 83% and 65% at 6 and 12 months, respectively. Multivariate analysis revealed that breast cancer brain metastases have a significantly lower risk of local failure than melanoma (HR = 0.31, p< 0.001). Additionally, multivariate analysis revealed that increasing dose lowered risk for local failure (HR = 0.87, p<0.001).

Conclusions: Melanoma histology leads to a higher rate of local failure. Higher prescription dose results in higher incidence of local control.

Keywords: brain metastasis; gamma knife; stereotactic radiosurgery; radiosensitivity; histology; predictive outcomes; breast neoplasms, proportional hazards models; retrospective studies; multivariate analysis; brain neoplasms; melanoma.

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