Incidence trends and survival benefit of surgery in solid tumors with synchronous brain-limited metastasis at diagnosis: a population-based cohort study (2010-2022).

[OBJECTIVE] To describe temporal trends and metastatic patterns of brain metastases (BMs) and to assess the associations of primary site surgery (PSS) and metastatic site surgery (MSS) with overall survival (OS) among patients with brain-limited metastases (BLMs) at diagnosis across primary cancer types.

[METHODS] Using SEER-17 (2010-2022), we identified 65,861 patients with BMs at diagnosis among 3,540,748 solid tumors. The analytic cohort included 23,394 patients with BLMs (no extracranial distant metastases) with known PSS/MSS status. Propensity score-based overlap weighting was used to reduce measured confounding in cancer-specific Cox models of OS.

[RESULTS] BMs were identified in 1.9% of solid tumors, with lung cancer accounting for 80.0% of cases. BM counts increased from 4459 (2010) to 5330 (2022), while the overall proportion among solid tumors remained at approximately 2%. BLMs accounted for 35.5% of patients with BMs. Among patients with BLMs, median OS was 7.0 months, and 5-year OS was 9.4%, varying widely by primary site (23-24 months for thyroid/prostate vs. 3 months for pancreatic/liver primaries). PSS was uncommon and declined modestly (8.5% to 7.0%), whereas MSS increased (22.1% to 29.1%). In fully adjusted overlap-weighted models, PSS and MSS were associated with lower mortality for most cancer types; in lung cancer, PSS (HR, 0.52) and MSS (HR, 0.74) were associated with lower mortality, with both associations remaining significant after Benjamini-Hochberg false discovery rate adjustment (adjusted p < .05).

[CONCLUSIONS] Prognosis and surgery-associated survival in BLMs vary by primary site and may help inform cancer-specific multidisciplinary decision-making and the design of future prospective studies.