Purpose:
The value of gross total resection (GTR) in patients with brain metastases (BM) is controversial. Therefore, we analyzed the circumstances under which GTR is crucial for optimal outcome in a large population of patients with BM treated with surgical resection at our institution.

Methods:
The analysis included 539 patients. The extent of resection was rated as complete if no residual contrast-enhancing tumor was detectable on the early postoperative magnet-resonance image (MRI); the tumor size was determined by measuring the volume of the contrast-enhancing areas on the presurgical MRI. Outcome included overall survival (OS) and progression-free survival (PFS).

Results:
GTR was achieved in most patients (82.8%) but was not associated with longer OS and PFS in the entire population (HR: 0.88; p = 0.162 and HR: 0.84; p = 0.319). However, a significant survival benefit of GTR was observed in patients with solitary BM (HR: 0.39; p = 0.0006). Age younger than 65 years (HR: 0.75; p = 0.047), controlled disease status (HR: 0.68; p = 0.033), focal radiotherapy (HR: 0.64, p = 0.044), postsurgical systemic treatment (HR: 0.67; p = 0.038), and no target therapy (HR: 0.75, p = 0.039) were also associated with significant benefit of GTR. Multivariate interaction analysis showed that solitary BM and controlled disease status significantly influenced the impact of GTR in our patient population (p = 0.0001).

Conclusion:
Achieving GTR is highly relevant in patients with solitary BM status, controlled systemic disease, specific postsurgical systemic treatment options, postsurgical focal radiation strategies, and in the population younger than 65 years of age.