The efficacy and limitations of salvage gamma knife surgery (GKS) have not been thoroughly described. This study evaluated the efficacy of GKS for treating brain metastases associated with small-cell lung cancer (SCLC) after whole-brain radiotherapy (WBRT) as the first-line radiation therapy.

Forty-four patients with recurrent or new SCLC-associated brain metastases underwent GKS after receiving WBRT (median age, 62 years; median duration between WBRT and first GKS, 8.8 months). The median Karnofsky performance status (KPS) score was 100 (range, 40-100), and the median number of brain metastases at the first GKS was five. Ten patients who partially or completely responded to chemotherapy received prophylactic cranial irradiation (PCI) for limited disease.

The median prescribed dose and number of lesions treated with the initial GKS were 20.0 Gy and 3.5, respectively, and the tumor control rate was 95.8 % (median follow-up period, 4.0 months). The 6-month new lesion-free survival, functional preservation rates, and overall survival were 50.0 %, 94.7 %, and 5.8 months, respectively. Neurological death occurred in 17.9 % of cases. The poor prognostic factors for new lesion-free survival time and functional preservation were >5 brain metastases and carcinomatous meningitis, respectively. Poor prognostic factors for survival time were KPS <70, >10 brain metastases, diameter of the largest tumor >20 mm, and carcinomatous meningitis. Median overall survival time from brain metastasis diagnosis was 16.9 months.

GKS may be an effective option for controlling SCLC-associated brain metastases after WBRT and for preventing neurological death in patients without carcinomatous meningitis.