Genomic Heterogeneity Of Multifocal Nsclc.

e21595 Background: Distinguishing multiple primary lung cancer (MPLC) and intrapulmonary metastasis (IPM) remains a common diagnostic dilemma but critical for developing a therapeutic strategy. Methods: In this study, we analyse genomic features of 584 tissue samples from 258 NSCLC patients with > 1 surgically-resected tumor. NGS was performed using panels of 1021/59 genes. Results: Among 80 patients with definite diagnosis, 23 patients (46 tumors) were diagnosed with IPM. And 57 patients (145 tumors) were MPLC, consisting of 53 synchronous and 3 metachronous tumor pairs. Among 23 IPM tumor pairs, we identified at least one shared somatic mutation. By contrast, 93%(53/57) MPLC tumor pairs exhibited entirely unique mutation profiles in each tumor. Of 57 MPLCs, 4(7%) had no driver alteration ( EGFR, KRAS, BRAF, ALK, ERBB2, MET Exon 14). 9(16%) had a driver in only one of the tumors. In the remaining 44 MPLCs, 40 had unique driver mutation in each tumor. 50%(20/40) had distinct EGFR mutations, the most common combination was L858R and delins in exon 19. Specifically, 8(20%) patients resided ≥3 unique driver mutations simultaneously. This observation indicated that multiple lesions in the same individual can be driven by distinct molecular events. In contrast, 21 available IPM tumor pairs shared the same driver mutation. Pathogenic germline mutations were also analysed. Two were found in 2 MPLCs, involving PLAB2 and BLM, which were both null variants. While there were no pathogenic germline mutations found in IPMs. Regarding the MSI status, all samples from either MPLCs and IPMs displayed MSS, unexpectedly. To further verify the findings above, the remaining 393 samples with uncertain diagnosis were classified into group M (no shared mutation, 218 samples /97 patients) and I (≥1 shared mutation, 175 samples/81 patients). We find the similarity results among all available patients, driver mutation profiles exhibited completely unique and multiple in group M and fully consistent in group I. Conclusions: Taken together, our analyses indicated that the genomic heterogeneity of multifocal NSCLC may be a potential strategy for differentiating IPM and MPLC. This may hold implications for prioritizing therapeutic strategies.