Five-year survivors from brain metastases treated with stereotactic radiosurgery: Biology, improving treatments, or just plain luck?

Abstract

Improvements in therapies have led to an increasing number of long-term survivors of brain metastases. The present series compares a population of 5-year survivors of brain metastases to a generalized brain metastases population to assess for factors attributable to long-term survival. A single institution retrospective review was performed to identify 5-year survivors of brain metastases who received stereotactic radiosurgery (SRS). Ahistorical control population of 737 patients with brain metastases was used to assess similarities and differences between the long-term survivor population and the general population treated with SRS. A total of 98 patients with brain metastases were found to have survived over 60months. No differences between long-term survivors and controls were identified with regards to the age at first SRS (P=.19), primary cancer distribution (P=.80), and the number of metastases at first SRS (P=.90). Cumulative incidence of neurologic death at 6, 8 and 10years for the long-term survivor cohort was 4.8%, 16%, and 16% respectively. In the historical controls, cumulative incidence of neurologic death reached a plateau at 40% after 4.9years. Asignificant difference in the distribution of burden of disease at the time of the first SRS was found between the 5-year survivors and the control (P=.0049). 58% of 5-year survivors showed no evidence of clinical disease at the last follow-up. Five-year survivors of brain metastases represent a diverse histologic population, suggesting a small population of oligometastatic and indolent cancers exist for each cancer type.