Outcomes of Stereotactic Radiosurgery for Brain Metastases in Patients with Small-Cell Lung Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Several randomized studies have established stereotactic radiosurgery (SRS) as a first-line treatment modality for limited brain metastases. However, these trials frequently excluded patients with primary small cell lung cancer (SCLC). Here, we assess clinical outcomes of patients with primary SCLC who have undergone SRS for brain metastases. <h3>Materials/Methods</h3> We identified patients with histologically-proven SCLC who underwent first-time SRS for brain metastases at our institution. Overall survival, local recurrence, and time to distant CNS failure were estimated with the Kaplan-Meier method. Univariate log-rank test and multivariate Cox regression were used to assess the significance of prognostic factors including age, sex, prior whole brain radiation, number of brain metastases, and extracranial disease control status. <h3>Results</h3> Fifty-nine patients (median age 64) with SCLC completed SRS for brain metastases at our institution from July 2007 to December 2021. 88.1% (n=52) of patients received Gamma Knife SRS, whereas the remainder received LINAC-based SRS. 61.0% (n=36) had received prior whole brain or prophylactic cranial irradiation. The median number of treated brain metastases was 2 (range 1-11) with a median tumor diameter of 1.0 cm and a marginal dose of 18 Gy. Median overall survival was 11 months. On multivariate Cox regression, both increased number of brain metastases (HR 1.22; 95% CI 1.02-1.44) and increased age (HR 1.09; 95% CI 1.03-1.16) were associated with poorer overall survival. 11.9% (n=7) of patients experienced local recurrence at a median of 5 months post-SRS (range 2-9 months). The median time to distant CNS failure was 6 months. Multivariate analysis identified extracranial disease control status as the sole significant predictor of distant failure. Log-rank test demonstrated that the patient cohort with uncontrolled extracranial disease had a lower time to distant failure compared to those with stable or well-controlled disease (4 vs. 22 months; p=0.0001). <h3>Conclusion</h3> SRS provides excellent local control of SCLC-associated brain metastases without compromising overall survival. Our institutional data support the rationale for future prospective studies to establish the role of intracranial SRS in this patient population.