Objectives: Recent advances in target therapies have prolonged overall survival (OS) for patients with epidermal growth factor receptor (EGFR)-mutant lung cancer. The impact of EGFR mutations on stereotactic radiosurgery (SRS) for brain metastases (BM) has yet to be determined. The present study sought to evaluate the efficacy and limitations of SRS, administered with EGFR-tyrosine kinase inhibitors (TKI), for BM from EGFR-mutant lung adenocarcinoma.
Materials and methods: This retrospective observational study analyzed data from patients with BM arising from EGFR-mutant lung adenocarcinoma who received upfront Gamma Knife SRS between December 2010 and April 2016. OS and distant and local intracranial disease control rates were calculated. The prognostic factors for each event were also determined.
Results: One hundred thirty-three consecutive patients (47 males/86 females) were eligible. The median age was 69 years, and the median Karnofsky performance status (KPS) was 90. Sixty-six patients (50%) had no history of EGFR-TKI use at the time of SRS. EGFR-TKI were administered to 85% of EGFR-TKI naïve patients after SRS. One- and 2-year OS rates were 74% and 52%, respectively. One- and 2-year distant BM recurrence rates (per patient) after SRS were 34% and 53%, respectively. One- and 2-year rates of local tumor control (per lesion) were 97% and 95%, respectively. Multivariate proportional hazards analyses showed that being EGFR-TKI naïve was associated with longer OS (HR: 0.42, P < 0.001), a lower distant intracranial recurrence rate (HR: 0.61, P = 0.037) and a higher local tumor control rate (HR: 0.28, P = 0.001).
Conclusions: The present study demonstrated the upfront SRS strategy to offer a minimally invasive and effective treatment option for EGFR-mutant lung adenocarcinoma patients with limited BM. EGFR-TKI naïve patients were found to be a distinct subgroup for which a longer survival time and durable intracranial disease control can be expected.
Keywords: Brain metastases; Epidermal growth factor receptor; Lung adenocarcinoma; Stereotactic radiosurgery; Tyrosine kinase inhibitor.
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