Molecular adequacy of image-guided rebiopsies for molecular retesting in advanced non-small cell lung cancer: a single centre experience.

INTRODUCTION: In the era of biomarker-driven systemic therapy for advanced non-small cell lung cancer (NSCLC), the role of routine repeated biopsies for decision-making, outside EGFR mutant disease, remains unproven. We report our centre's experience of safety and adequacy for molecular retesting of tumour material obtained from image-guided lung rebiopsies in NSCLC. METHODS: We performed a retrospective case-note analysis of patients undergoing image-guided lung rebiopsies at a single cancer centre between 2011-14. The primary objective was the pathological success rate. Secondary and exploratory objectives were technical success rate, histological concordance, molecular adequacy, genotypes identified and complication rate. RESULTS: 103 patients underwent transthoracic image-guided procedures. 66 rebiopsies in NSCLC were identified and analysed. Pathological success rate was 87.1%. A high histological discordance rate was observed (12/52 evaluable cases, 23.1%). Pre-test molecular adequacy as determined by the lung pathologist was 78.8% (52/66). 51 out of 52 adequate samples were sent for molecular analysis with a total of 209 genes analysed including EGFR, ALK, KRAS, BRAF, DDR2, NRAS, ROS1 and RET. Post-genotyping molecular adequacy was 87.1% (182/209). 20 new potentially actionable mutations were identified, with 13/66 (19.7%) patients commencing new targeted treatment as a result. Overall, rebiopsies informed clinical decision-making in 63.6%. Rates of complications were pneumothorax 15%, pneumothorax requiring chest drain 3% and haemoptysis 8%. CONCLUSION: We validate the pathological and molecular adequacy rates of rebiopsies and demonstrate clinical utility in routine decision-making