BM-14A PARADIGM SHIFT IN DETERMINING BRAIN METASTASIS TREATMENT: DOES NUMBER REALLY MATTER?

BACKGROUND: Local treatment including stereotactic radiosurgery (SRS) or surgical resection is indicated for patients with 1-3 brain metastases (mets). Whole brain radiation therapy (WBRT) is indicated for patients with 4+ brain mets. WBRT aims to treat local disease and prevent distal recurrence; however, WBRT may impair quality of life (QOL) through post treatment cognitive deficits. For patients who have 4+ mets, SRS may be an appropriate alternative to WBRT without impacting overall survival (OS) and QOL. We analyzed how survival outcome is affected by the number of mets and total volume of mets for patients treated with surgery and SRS. METHODS: We retrospectively analyzed pre-treatment brain MRIs and survival data of 48 patients with brain mets from primary melanoma (N = 13) or lung cancer (N = 35). Patients had an average of 2.5 mets (range 1-17). Treatment included resection of the largest met followed by SRS to the tumor bed and remaining mets. Univariate cox proportional hazard analysis was performed for volume of mets and number of mets. Iterative log-rank analysis was utilized to determine if there was a threshold for number of mets or volume that significantly dichotomized OS and progression-free survival (PFS). RESULTS: Univariate cox proportional hazard analysis revealed that volume (p < 0.05) was significant for OS but not number of mets (p = 0.27). Contrary to the current treatment paradigm, there was not a single threshold for number of mets that clearly dichotomized OS for patients; however, a threshold of 1 met optimally dichotomized PFS (p = 0.007). Univariate analysis revealed that number of mets (p = 0.02) was significant for PFS but volume (p = 0.26) was not. OS was significantly shorter for the 4 patients who had 40 cm3 or more total brain met volume (p = 0.002). CONCLUSION: The number of mets did not impact OS for patients treated with SRS, however, volume may affect OS.