Multisite stereotactic body radiotherapy for metastatic non-small-cell lung cancer: Delaying the need to start or change systemic therapy?

Objectives: The purpose of this study was to review the clinical outcomes following the use of stereotactic body radiotherapy (SBRT) in patients with metastatic non-small-cell lung cancer (NSCLC) from a large academic institution.

Materials and methods: Metastatic NSCLC patients treated with extracranial SBRT were identified from an institutional database. Treatment indications were: (1) oligometastases, (2) oligoprogression, and (3) local control of dominant tumors. Endpoints included overall survival (OS), progression-free survival (PFS), time to starting/changing systemic therapy (SCST), and local failure (LF). Univariate and multivariable analyses were performed to look for predictive factors.

Results: 108 patients with 165 tumors were treated. SBRT was delivered for oligometastases in 66 patents, for oligoprogression in 20 patients, and for local control in 22 patients. Median OS and PFS for all patients were 27.3 months and 4.4 months, respectively, with treatment indication being the only predictive factor on multivariable analysis (patients with oligometastases having the highest median OS and PFS of 39.3 months and 7.6 months respectively). Cumulative incidence of SCST was only 21.5% at 1 year after SBRT, with larger tumor size and positivity for EGFR/ALK mutation being predictive of higher rates of SCST on multivariable analysis. LF was 15.6% at 1 year, with larger tumor size and exposure to previous systemic therapy being predictive of higher rates of LF on multivariable analysis.

Conclusion: Patients treated with SBRT for oligometastases have better OS and PFS than those treated for oligoprogression or for local control of dominant tumors. Use of SBRT may delay the need for SCST. Larger tumors and previous exposure to systemic therapy were predictive of higher rates of LF.