Consolidative stereotactic ablative radiotherapy (SABR) to intrapulmonary lesions is associated with prolonged progression-free survival and overall survival in oligometastatic NSCLC patients: A prospective phase 2 study.

Objectives: Stereotactic Ablative Radiotherapy (SABR) has shown high rates of local control and prolonged survival in early-stage non-small cell lung cancer (NSCLC), though its role in oligometastatic disease is undefined. This study aimed to evaluate SABR as a local consolidative therapy (LCT) in oligometastatic NSCLC patients.

Methods: In this prospective, single-arm phase 2 trial, we sought to evaluate SABR in patients with stage IV NSCLC, with ≤ five lesions, including the primary tumor. Patients received initial systemic therapy according to international guidelines. Patients without progression after front-line therapy (two months of targeted therapy and ≥ four cycles of chemotherapy) were evaluated by an 18F-FDG-PET/CT to receive consolidative SABR (45-60 Gy in 3-5 fractions) to the primary and all intrapulmonary metastatic sites. The primary endpoint was progression-free survival (PFS); secondary endpoints were overall survival (OS) and toxicity.

Results: A total of 47 patients were included. Mean age was 58.9 years, 59.6 % were female, 87.2 % had adenocarcinoma histology, and the contralateral lung was the main site of metastases in 42.6 %. All patients received systemic front-line therapy, chemotherapy in 61.7 %, and a tyrosine kinase inhibitor (TKI) in 38.3 %. Disease control rate (DCR) and complete metabolic response (CMR) to SABR were 93.6 % and 70.2 %. Median PFS was 34.3 months (95 %CI; 31.1-38.8) for the total cohort; patients with a CMR had a median PFS of 53.9 monthsvs.31.9 months in those without CMR (p = 0.011). Median OS was not reached.Grade 1, 2, and 3 pneumonitis were observed in 79.5 % (31/39), 12.8 % (5/39) and 7.7 % (3/39), respectively. No grade ≥4 toxicities were observed.

Conclusion: The use of SABR as LCT in oligometastatic NSCLC patients was well tolerated and showed favorable results regarding PFS and OS compared with historical data. The benefit was significantly higher in patients who reached a CMR as assessed by 18F-FDG-PET/CT.