Recurrence Patterns and Second Primary Lung Cancers After Stereotactic Body Radiation Therapy for Early-Stage Non-Small-Cell Lung Cancer: Implications for Surveillance

The optimal surveillance regimen remains unclear for patients treated with stereotactic body radiation therapy (SBRT) for early-stage non-small-cell lung cancer (SCLC). We assessed 366 patients with early-stage NSCLC treated with SBRT. In patients with progression after SBRT, 84% of cases occurred within the first 2 years. In patients who experienced second primary lung cancers, 33% of cases occurred after 2 years. Close monitoring beyond 2 years may be necessary in patients treated with SBRT. Background: Patients treated with stereotactic body radiation therapy (SBRT) for early-stage non-small-cell lung cancer (NSCLC) are subject to locoregional and distant recurrence, as well as the formation of second primary lung cancers (SPLCs). The optimal surveillance regimen for patients treated with SBRT for early-stage NSCLC remains unclear; we therefore investigated the posttreatment recurrence patterns and development of SPLCs. Methods: Three hundred sixty-six patients with pathologically proven inoperable early-stage NSCLC treated with SBRT between 2006 and 2013 were assessed. Patients underwent a computed tomographic (CT) scan of the chest every 3 months during years 1 and 2, every 6 months during years 3 and 4, and annually thereafter. Competing risk analysis was used for all time-to-event analyses. Results: With a median follow-up of 23 months, the 2-year cumulative incidence of local, nodal, and distant treatment failures were 12.2%, 16.1%, and 15.5%, respectively. In patients with disease progression after SBRT (n = 108), 84% (n = 91) of cases occurred within the first 2 years. Five percent (n = 19) of patients experienced SPLCs. The median time to development of an SPLC was 16.5 months (range, 6.5-71.1 months), with 33% (n = 6) of these patients experiencing SPLCs after 2 years. None of the never smokers, but 4% of former tobacco smokers and 15% of current tobacco smokers, experienced an SPLC (P = .005). Conclusion: Close monitoring with routine CT scans within the first 2 years after SBRT is effective in detecting early disease progression. In contrast, the risk for the development of an SPLC remains elevated beyond 2 years, particularly in former and current smokers.