Factors influencing survival after gamma knife radiosurgery for patients with single and multiple brain metastases

Radiosurgery has been reported to yield high local control rates for brain metastases. However, further work is needed to define which subgroups of patients may benefit from this treatment modality.

We reviewed 116 patients who underwent stereotactic radiosurgery for initial management or recurrence of solitary or multiple brain metastases from September 1991 through December 1994 at the University of California, San Francisco. Survival time and time to local-regional failure were calculated using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox proportional hazards model.

Median survival was 40 weeks from radiosurgery. In multivariate analysis, smaller total tumor volume, absence of extracranial metastases, higher Karnofsky score, and age < or = 70 had a positive effect on survival. In patients initially managed for brain metastases, the addition of whole brain radiotherapy to radiosurgery had no significant effect on survival. Although the presence of multiple metastases was associated with a significantly worse survival rate in patients initially managed with radiosurgery in univariate analysis, it was not as a significant factor in multivariate analysis. An analysis of patients within this series treated with radiosurgery who would have been eligible for Patchell's study on the role of surgery in the treatment of solitary brain metastasis revealed a favorable median survival of 70 weeks.

We conclude that radiosurgical treatment of brain metastases results in survival times that compare favorably with the historic experience in patients treated with whole brain radiotherapy alone or with surgical resection. In patients presenting initially with brain metastases, radiosurgery alone may yield survival results equivalent to radiosurgery with whole brain radiotherapy, but intracranial control and quality of life also need to be evaluated. Also, the presence of multiple brain metastases should not be a contraindication for the use of radiosurgery given the good survival achieved with such patients in this series. Each such case should therefore be evaluated based on other factors such as patient's age, Karnofsky score and systemic disease.