Detection of oncogenic mutations in resected bronchial margins by next-generation sequencing indicates early relapse in stage IA lung adenocarcinoma patients

Stage I non-small cell lung cancer (NSCLC) patients experience a relatively high rate of recurrence, ranging from about 30-35%. We hypothesized that this elevated risk of recurrence is due to the presence of tumor cells at bronchial margins which was undetected by conventional light microscopy.Patients with clinical stage IA (T1N0M0) NSCLC were enrolled in this study,which included 8 early-relapse(ER) and 6 no-relapse(NR) patients. Primary tumor, bronchial margin,and normal lung tissues were collected and sent to a central site for targeted next-generation sequencing analysis. All of the patients were lung adenocarcinoma. Gene mutations were identified in all tumor tissue samples (100%).Oncogenic mutations were identified in 87.5%(7/8) bronchial margins of early relapse patients,whereas only 16.7%(1/6) no-relapse (NR) patient of marginal tissue had identified gene mutation.Additionally, concordance between primary tumor and bronchial margins was relatively high, with 4 of 8 (50%) ER patients having at least one identical mutation. Moreover, according to the gene mutation status in marginal tissue, 87.5% (7/8) of patients with at least one gene mutation in the bronchial margins had local recurrence or metastasis,whereas only 16.7% (1/6) of patients without any mutation detected had signs of relapse,the recurrence rate was significantly higher than that of the negative mutation margin group ((p (log-rank) = 0.023). The existence of oncogenic mutations in bronchial margins may represent occult residual tumor and elevated risk of recurrence in early stage NSCLC patients.Thus,assessing molecular status in bronchial margins may help identify patients who might benefit from extensive surgery or adjuvant treatment.