Detection of second primary lung cancers on surveillance imaging following stereotactic ablative radiotherapy for non-small cell lung cancer

Development and detection of second primary lung cancer (SPLC) following stereotactic ablative radiotherapy (SABR) for lung cancer may differ from surgical patients. We analyze 134 patients treated with SABR followed with frequent surveillance imaging. Eighteen patients developed 21 SPLC at a median of 28.5 months, with good survival following definitive treatment of SPLC. INTRODUCTION/BACKGROUND: Second primary lung cancers (SPLC) are common following non-small cell lung cancer (NSCLC) treatment. Development of SPLC following stereotactic ablative radiation therapy (SABR) may differ as compared to surgical cohorts. We report incidence of and outcomes for SPLC detected by surveillance imaging in a cohort of patients treated with SABR. MATERIALS/METHODS: Patients treated with SABR for node-negative NSCLC between February, 2007 to May, 2019 were retrospectively identified. Patient characteristics, frequency of surveillance imaging, development of SPLC, recurrence patterns, and survival were reviewed. Surveillance CT was performed Q3–4 month year 1, Q3–6 month year 2, Q6–12 month year 3–5, and Q12 month thereafter. Actuarial estimates of development of SPLC and overall survival (OS) were generated with competing risk analysis. RESULTS: We identified 134 patients treated with SABR with ≥6 months follow up. Eighteen (13.4%) developed a total of 21 SPLC at a median of 28.5 months (range 3.0–84.7 months) following SABR, 19 (90.5%) biopsy-proven. Twenty (95.2%) SPLC were detected by surveillance imaging. Three patients developed 2 metachronous SPLC. Three and 5 year SPLC estimates were 11.7% and 13.1%. Eighteen (85.7%) SPLC were treated with curative intent. Two and 3 year estimate of OS following detection of SPLC was 79.8% and 54.7%. CONCLUSION: SPLC were more common in our cohort than other published studies. Outcomes following surveillance detected SPLC are similar to those of de novo early stage lung cancers. The high frequency of SPLC in our cohort suggests further studies to refine overall surveillance in very high-risk populations are needed.