Timing, presentation, and patterns of failure of leptomeningeal disease after surgical resection and radiosurgery for brain metastases: A multi-institutional analysis.

2070Background: Postoperative (post-op) radiosurgery (SRS) has been proposed as a standard of care based on 2 phase III trials, but has been associated with up to 30% risk of leptomeningeal disease (LMD). The specifics of timing, presentation, and patterns of LMD failure have not been well described. Methods: The records of patients (pts) with brain metastases (BM), of which 1 was resected and treated with post-op or pre-op SRS, and who subsequently developed LMD were combined from 7 tertiary care centers. Pts with classically radiosensitive tumors or prior or planned whole brain radiotherapy were excluded. LMD pattern was categorized as either nodular or linear (“sugarcoating”). Results: The study cohort consisted of 147 pts. The most common primary sites were lung (40%), breast (24%), and melanoma (16%), and most pts received post-op SRS (94%). Pts with breast primary were enriched for HER-2 positivity (60%). The majority of resected BM (82%) extended to within 5 mm of the pial surface. Median time from...