Assessing efficacy and safety of stereotactic body radiation therapy for oligometastatic non-small cell lung cancer with epidermal growth factor receptor (EGFR) wild type.

Background: Stereotactic body radiation therapy (SBRT) is an emerging therapy for oligometastatic cancer. The aim of this study was to investigate the efficacy and safety of high-dose radiotherapy for primary and oligometastatic lesions in epidermal growth factor receptor (EGFR) wild-type non-small cell lung cancer (NSCLC).

Methods: A total of 40 EGFR wild-type oligometastatic NSCLC patients (defined as ≤5 metastases) treated with SBRT in our department between 2009 and 2016 were analyzed retrospectively. SBRT was delivered to the lesions with a median biologically effective dose at alpha/beta 10 (BED10) value of 102.7 Gy (range, 94.5-113.5 Gy). Primary endpoints including progression-free survival (PFS) and overall survival (OS) were estimated with the Kaplan-Meier method. Factors potentially affecting OS and PFS were evaluated by univariate and multivariate Cox-regression analyses.

Results: After a median follow-up of 39 months, the median OS observed in this study was 40 months (95% CI: 32.562-47.438 months). One-, 2-, and 3-year OS rates were 100.0%, 72.5%, and 62.5% respectively. Twenty-nine patients (72.5%) succumbed to tumor burden and median PFS was 13 months (range, 10.687-15.313 months). One-, 2-, and 3-year PFS rates were 65.0%, 10.0%, and 0% respectively. Multivariate analysis suggested Eastern Cooperative Oncology Group performance status (ECOG PS) <2 and high-dose radiation regimens were independent prognostic factors of longer OS (P<0.001 and 0.049, respectively), and patients receiving radiotherapy with BED10 ≥100 Gy showed a better PFS than those undergoing low dose (P=0.047). There were no patients of CTCAE v 5.0 grade 4-5 toxicity or treatment-related deaths. Grade 3 toxicity occurred in 2 (5.0%) patients and 36 (90.0%) patients experienced grade 1-2 adverse reactions.

Conclusions: The current study suggested systemic chemotherapy combined with SBRT for pulmonary and metastatic lesions was feasible and tolerable to improve outcomes of EGFR wild-type oligometastatic NSCLC patients.