Long term outcome after 48 Gy stereotactic ablative body radiotherapy for peripheral stage I non-small cell lung cancer

BACKGROUND: To evaluate the outcome of patients treated with stereotactic ablative body radiotherapy (SABR) with curative intent for stage I non-small cell lung cancer (NSCLC) with regard to local, regional and distant tumor control, disease-free survival (DFS), overall survival (OS) and toxicity. METHODS: Data of 300 patients treated with SABR for NSCLC cancer for the period of November 2007 to June 2016 were retrospectively analyzed. Of which, 189 patients had single primary lung lesion and were included in the study. The prescribed dose for the tumor was 48 Gy, given in 12 Gy × 4 fractions for all patients. In 2010, an improved protocol was established in advanced technology for the planning CT, dose calculation and imaging. Cumulative incidence function (CIF) of local, regional, distant or any recurrences were computed using competing risk analysis with death as a competing event. Survivals (DFS and OS) were estimated using the Kaplan-Meier method and Cox proportional regression was used for comparisons. Toxicities were graded according to the common terminology criteria for adverse events version 4.0 (CTCAE v.4). RESULTS: Diagnosis was histologically confirmed in 42% of the patients (N = 80). At 1, 2 and 4 years, the cumulative incidence function (CIF) of local relapses were 8% [4–13%], 15% [10–21%] and 18% [12–25%], the CIF of regional relapses were 4% [2–8%], 10% [6–16%] and 12% [8–19%], the CIF of distant relapses were 9% [5–14%], 15% [11–22%] and 20% [15–28%] and the CIF of any relapses were 14% [10–20%], 28% [22–36%], 34% [27–43%], respectively. After 1, 2 and 4 years, the OS rates were 83% [95% CI: 78–89%] (N = 128), 65% [95% CI: 57–73%] (N = 78) and 37% [95% CI: 29–47%] (N = 53), respectively. The median survival time was 37 months. The DFS after 1, 2 and 4 years reached 75% [95% CI: 68–81%] (N = 114), 49% [95% CI: 42–58%] (N = 60) and 31% [95% CI: 24–41%] (N = 41), respectively. No grade 4 or 5 toxicity was observed. CONCLUSIONS: We observed a long-term local control and survival after SABR for peripheral stage I NSCLC in this large series of patients with the expected low toxicity.