Surgery or stereotactic body radiotherapy for metachronous primary lung cancer? A propensity score matching analysis

Objective: We compared outcomes after surgery or stereotactic body radiotherapy (SBRT) among patients with metachronous primary lung cancer (MPLC). Methods: Patients with MPLC were treated with either surgery (2008–2018) or SBRT (2010–2018). We used propensity score matching (PSM) to reduce bias from various clinicopathological factors. MPLC was defined by the Martini and Melamed criteria. Results: Of 77 patients, 51 underwent surgery and 26 received SBRT. Most median clinicopathological characteristics did not significantly differ between the surgery and SBRT groups (male sex: 67% vs 65%; age: 73 vs 77 years; time after first surgery: 6.2 vs 4.7 years; lobectomy as first procedure: 82% vs 85%; second tumor size: 11 vs 12 mm; clinical stage I: 96% vs 100%; CEA: 2.9 vs 3.0 ng/ml). However, the surgery group had significantly more ipsilateral second tumors (n = 71, 58%, P = 0.003), better performance status (P = 0.03), and preserved lung function (P = 0.02). Surgery, thus, tended to be selected for patients with good physical function and for the MPLC in the contralateral side. Five-year overall survival did not significantly differ between the surgery and SBRT groups, either before PSM (86.5% vs 65.8%, P = 0.24, log-rank) or after PSM (100% vs 84.4%, P = 0.73). Conclusions: Surgery and SBRT for MPLC patients are safe and feasible treatments with similar outcomes. However, this finding should be verified by a random controlled trial with a larger study cohort.