Dynamic changes of circulating tumour DNA in surgical lung cancer patients: protocol for a prospective observational study

Introduction Circulating tumour DNA (ctDNA) has potential applications in cancer management. Most previous studies about ctDNA focused on advanced stage cancer patients. We have completed a clinical prospective study (NCT02645318) and showed the feasibility and clinical application of ctDNA detection in early stage non-small cell lung cancer (NSCLC) patients. The aim of this study is to investigate the elimination rate of ctDNA level after surgery. This is the first prospective study to evaluate the perioperative dynamic changes of ctDNA in surgical lung cancer patients. Methods and analysis This is a prospective observational study to determine the elimination rate of circulating tumour DNA after surgery. Consecutive patients with suspected lung cancer who undergo curative-intent lung resection will be enrolled. 10 mL blood samples are taken by intravenous puncture. Plasma samples are obtained before surgery (time A) and at a series of scheduled time-points (2 min to 72 hours, time B to F) after tumour resection. DNA is prepared from 4 mL of purified plasma. A multiplex assay based on circulating single-molecule amplification and resequencing technology (cSMART) is used to simultaneously detect and quantitate hot spot EGFR, KRAS, BRAF, ERBB2, PIK3CA, TP53, ALK, RET and MET plasma DNA variants. Positive plasma mutations are validated in tumour tissue and normal lung tissue by targeted sequencing. Ethics and dissemination Ethical approval has been obtained from the Peking University People’s Hospital Medical Ethics Committee (2016PHB156-01). Results will be disseminated through presentations at scientific meetings and publications in peer-reviewed journals. Trial registration number NCT02965391; Pre-results.