Isolated Nodal Recurrence After Definitive Stereotactic Ablative Radiation Therapy for Non-Small Cell Lung Cancer

Purpose: Stereotactic ablative radiation therapy (SABR) results in high rates of primary tumor control for early-stage non-small cell lung cancer (NSCLC). For patients with isolated hilar or mediastinal nodal recurrence (INR) after SABR, the optimal salvage treatment strategy is unclear. The purpose of this study was to determine the rate of INR after SABR for early-stage NSCLC and to describe patterns of care and treatment outcomes after salvage therapy.

Methods and materials: This retrospective cohort study included 342 patients with stage T1-3N0M0 NSCLC treated with definitive SABR from 2003 to 2018. We evaluated the incidence of INR and baseline factors between patients who did and did not experience INR. Among patients who experienced INR, we described treatment patterns and outcomes including overall survival (OS) and progression free survival (PFS) from the time of nodal failure using the Kaplan-Meier method.

Results: With a median follow-up of 3.3 years, the 3-year INR rate was 10.6% (95% CI, 6.6%-13.4%). Among the 34 patients experiencing INR, the 3-year rates of OS and PFS were 39.3% (24.4%-63.3%) and 26.7% (14.1%-0.3%), respectively. The 34 patients with INR were treated with radiation therapy alone (26.7%), concurrent chemoradiation therapy (43.3%), chemotherapy alone (13.3%), or observation (16.7%). Patients treated with concurrent chemoradiation therapy had the best survival outcomes, with a 3-year OS and PFS of 81.5% (61.1%-100.0%) and 63.9% (40.7%-100.0%), respectively. Of the patients treated with salvage radiation therapy or concurrent chemoradiation therapy, 14.3% experienced grade 3 toxic effects, and no patients had grade ≥4 toxic effects.

Conclusions: In this study, INR occurred in approximately 10% of patients treated with SABR for early-stage NSCLC. The highest rates of OS and PFS among patients with INR were observed in those treated with salvage chemoradiation therapy.