Patterns of Disease Recurrence after SABR for Early Stage Non-Small-Cell Lung Cancer: Optimizing Follow-Up Schedules for Salvage Therapy.

Introduction: Stereotactic ablative radiotherapy is a guideline-recommended treatment for early stage non-small-cell lung cancer. We report on incidence and salvage of local recurrences (LR) and second primary lung cancers (SPLC) in a large series of patients with long-term follow-up, to generate data for evidence-based follow-up regimens.

Methods: We excluded all patients with double tumors, TNM-stages other than T1-T2N0M0, biologically effective dose less than 100 Gy10 and previous treatment for the index tumor from our institutional database. LR was defined as recurrence in/adjacent to the planning target volume. A diagnosis of SPLC was determined using criteria described by Martini et al.

Results: The 855 patients included had a median follow-up of 52 months. Forty-six patients developed LR after a median of 22 months (range 7-87 months). Actuarial local control rates at 3 and 5 years were 92.4% and 90.9%, respectively. Fifty-four percent had isolated LR and 13% had LR in combination with regional recurrences. Ten patients underwent radical salvage treatment; surgery (N = 6), high-dose radiotherapy (N = 3), or chemoradiation (N = 1). Median overall survival following LR was 13 months, but it was 36 months in patients who underwent radical salvage. A SPLC was diagnosed in 79 patients, after a median interval of 34 months. Actuarial cumulative incidences of SPLC at 3 and 5 years were 11.7% and 16.7%, respectively. Radical salvage for SPLC was performed in 63 patients (80%).

Conclusions: Both the timing of LR and persistent risk of SPLC serve as rationale for long-term follow-up using computed tomography scans in patients fit enough to undergo any radical treatment.