OA 12.08 Genomic Analysis of Non-Small Cell Lung Cancer (NSCLC) Cases with Focal and Non-Focal MET Amplification

MET amplification (METamp) is a known driver and a mechanism of resistance in EGFR-mutated lung cancers treated with targeted therapy. However, development of therapies targeting METamp has been hampered in part due to poor genomic stratification of patients. We investigated the natural distribution of the size of the MET amplicon and associated genomic characteristics. Hybrid-capture based comprehensive genomic profiling (CGP) was performed prospectively on DNA isolated from FFPE samples from NSCLC. Tumor mutational burden (TMB) was calculated from 1.1 Mbp of sequenced DNA and reported as mutations/Mb, as previously described (PMID: 28420421). We identified 545 NSCLC cases with focal, defined as <20 Mbp (n = 457, 84%), or non-focal (n = 88, 16%) amplification of the MET gene using CGP. Within this set, the size of the MET amplicon ranged from 0.095 – 158 Mbp; 25th, 50th and 75th quartiles were 1.63 Mbp, 3.46 Mbp, and 11.66 Mbp, respectively. In cases with focal METamp the median MET copy number was 11, compared to a median of 7 copies for cases with non-focal METamp (P <0.001). Median TMB in cases with focal vs. non-focal METamp was 10.8 and 9.0, respectively (P=0.47). MET exon 14 splice site alterations co-occurred with METamp in 45 cases (8%), of which 80% had focal METamp (median amplicon size of 2.02 Mbp). EGFR mutations co-occurred with METamp in 93 cases (17%) in this dataset, of which 78% had focal METamp (median amplicon size: 3.77 Mbp). In contrast, cases with other co-occurring alterations described in the NSCLC NCCN guidelines (ALK, ROS1 or RET rearrangements, BRAF V600E, or ERBB2 mutations) METamp was more commonly non-focal (3 focal and 6 non-focal cases), with a median amplicon size of 25.5 Mbp. Clinical outcomes will be presented, including a subset of cases in the setting of resistance to EGFR inhibitors. The size of the MET amplicon in MET-amplified NSCLCs is largely variable. Focal amplification is associated with a higher estimate of MET copy number. Neither TMB or co-occurring MET or EGFR mutations significantly correlated with size of the MET amplicon; however, other co-occurring known drivers were associated with non-focal METamp. Additional investigation is warranted to determine the clinical significance of the size of the MET amplicon in NSCLC.