Stereotactic body radiotherapy for pulmonary oligometastases as an initial metastasis-directed therapy: patterns of relapse and predictive factors for early mortality

Objective: This study aimed to analyze the early mortality rates and patterns of relapse after stereotactic body radiotherapy (SBRT) as an initial metastasis-directed therapy. Methods: Patients with pulmonary oligometastases initially treated with SBRT were included in this retrospective multicenter study. SBRT was performed between 2004 and 2015, and the primary lesion was controlled at the time of SBRT. Multivariate logistic regression was used for early mortality analyses. Results: A total of 720 patients with 793 oligometastatic tumors for whom the median follow-up period was 24.6 months were enrolled. The median overall survival period was 53.2 months. The 90-, 180-, and 360-day mortality rates were 1.1% (8 deaths), 2.4% (17 deaths), and 10.8% (71 deaths), respectively. During follow up, 422 patients relapsed. Over 329 patients had single-site relapse, the most frequent site was the lung in 176; 49 had local failure; and 42 had lymph node metastases. The maximum tumor diameter was significantly related to 90-day mortality. Maximum tumor diameter, biological effective dose, and performance status were significantly related to 180-day mortality, whereas maximum tumor diameter, performance status, and pathology were significantly related to 360-day mortality. Conclusion: Our results showed good survival outcomes and low rates of early mortality after SBRT. The patterns of relapse and factors affecting early mortality were revealed.