Intracranial relapse rates and patterns, and survival trends following post-resection cavity radiosurgery for patients with single intracranial metastases

The objective of this study is to evaluate the patterns of relapse and survival trends in patients with single brain metastases treated with post-operative adjuvant Gamma knife stereotactic radiosurgery (GKS) without whole brain radiotherapy (WBRT). Retrospective analysis of all consecutive patients who underwent GKS to the tumor cavity following resection of solitary brain metastasis was performed at a single institution. Between March 2001 and June 2010, 56 patients underwent GKS to the resection cavity following resection of intracranial metastases; no patient received pre- or post-operative WBRT as an adjuvant (salvage WBRT was permissible). The mean marginal dose was 17.1 Gy (range 14-20 Gy). The mean follow-up period was 24 months (range 3-99 months). Five patients (8.9%) had local recurrence in the immediate vicinity of the resection cavity, qualifying as "local failures", and 21 (37.5%) recurred at distant intracranial sites. Median intracranial recurrence free survival was 13 months. Median overall survival was 20.5 months. Salvage interventions were required in 26 patients, and included repeat radiosurgery in 17 patients, further surgery in two patients, and salvage WBRT in eight (14.3%; two of whom had also been locally salvaged with repeat radiosurgery) patients. As expected, avoidance of WBRT results in a high rate of intracranial failure (26/56 patients, 46%), even in well-selected patients with only single brain metastases. As anticipated, the majority of failures (21, 37.5%) are "distant intracranial", and in this well-selected cohort the local failure rate is low (5/56 patients, <9%). All patients failing intracranially (46%) are potential candidates for salvage therapies, but WBRT as salvage was utilized in only 14.3% of patients. The median intracranial relapse-free was 13 months and overall survival was 20.5 months.