Focal amplifi cation and activating point mutation of the MET gene are well-characterized oncogenic drivers that confer susceptibility to targeted MET inhibitors. Recurrent somatic splice site alterations at MET exon 14 ( MET ex14) that result in exon skipping and MET activation have been characterized, but their full diversity and prevalence across tumor types are unknown. Here, we report analysis of tumor genomic profi les from 38,028 patients to identify 221 cases with MET ex14 mutations (0.6%), including 126 distinct sequence variants. MET ex14 mutations are detected most frequently in lung adenocarcinoma (3%), but also frequently in other lung neoplasms (2.3%), brain glioma (0.4%), and tumors of unknown primary origin (0.4%). Further in vitro studies demonstrate sensitivity to MET inhibitors in cells harboring MET ex14 alterations. We also report three new patient cases with MET ex14 alterations in lung or histiocytic sarcoma tumors that showed durable response to two different MET-targeted therapies. The diversity of MET ex14 mutations indicates that diagnostic testing via comprehensive genomic profi ling is necessary for detection in a clinical setting. SIGNIFICANCE:Here we report the identifi cation of diverse exon 14 splice site alterations in MET that result in constitutive activity of this receptor and oncogenic transformation in vitro . Patients whose tumors harbored these alterations derived meaningful clinical benefi t from MET inhibitors. Collectively, these data support the role of MET ex14 alterations as drivers of tumorigenesis, and identify a unique subset of patients likely to derive benefi t from MET inhibitors. Cancer Discov; 5(8);

Therapeutic antibodies blocking programmed death-1 and its ligand (PD-1/PD-L1) induce durable responses in a substantial fraction of melanoma patients. We sought to determine whether the number and/or type of mutations identified using a next generation sequencing (NGS) panel available in the clinic were correlated with response to anti–PD-1 in melanoma. Using archival melanoma samples from anti–PD-1/PD-L1-treated patients, we performed hybrid capture-based NGS on 236–315 genes and T-cell receptor (TCR) sequencing on initial and validation cohorts from two centers. Patients who responded to anti–PD-1/PD-L1 had higher mutational loads in an initial cohort (median 45.6 vs. 3.9 mutations/MB; P = 0.003), and a validation cohort (37.1 vs. 12.8 mutations/MB; P = 0.002) compared to nonresponders. Response rate, progression-free survival, and overall survival was superior in the high, compared to intermediate and low, mutation load groups. Melanomas with NF1 mutations harbored high mutational loads (median 62.7 mutations/MB) and high response rates (74%) whereas BRAF/NRAS/NF1 wild-type melanomas had a lower mutational load. In these archival samples, TCR clonality did not predict response. Mutation numbers in the 315 genes in the NGS platform strongly correlated with those detected by whole exome sequencing in The Cancer Genome Atlas samples, but was not associated with survival. In conclusion, mutational load, as determined by an NGS platform available in the clinic, effectively stratified patients by likelihood of response. This approach may provide a clinically feasible predictor of response to anti–PD-1/PD-L1.

This article has an accompanying continuing medical education activity, also eligible for MOC credit, on page e19 (https://www. gastrojournal.org/cme/home). Learning Objective: Upon completion of this CME activity, successful leaners will be able to identify current clinically relevant genomic alterations in pancreatic ductal adenocarcinoma.

PURPOSE Broad, hybrid capture-based next-generation sequencing (NGS), as a clinical test, uses less tissue to identify more clinically relevant genomic alterations compared to profiling with multiple non-NGS tests. We set out to determine the frequency of such genomic alterations via this approach in tumors where previous extensive non-NGS testing had not yielded a targetable driver alteration. METHODS We enrolled lung adenocarcinoma patients with a ≤15 pack-year smoking history whose tumors previously tested “negative” for alterations in 11 genes (mutations in EGFR, ERBB2, KRAS, NRAS, BRAF, MAP2K1, PIK3CA, and AKT1, and fusions involving ALK, ROS1, and RET) via multiple non-NGS methods. We performed hybridization capture of the coding exons of 287 cancer-related genes and 47 introns of 19 frequently rearranged genes and sequenced these to deep, uniform coverage. RESULTS Actionable genomic alterations with a targeted agent based on NCCN guidelines were identified in 26% (8/31: EGFR G719A, BRAF V600E, SOCS5-ALK, CLIP4-ALK, CD74-ROS1, KIF5B-RET [n=2], CCDC6-RET). 7 of these patients either received or are candidates for targeted therapy. Comprehensive genomic profiling using this method also identified a genomic alteration with a targeted agent available on a clinical trial in an additional 39% (12/31). CONCLUSION Broad, hybrid capture-based NGS identified actionable genomic alterations in 65% (95% CI 48–82%) of tumors from never or light smokers with lung cancers deemed without targetable genomic alterations by earlier extensive non-NGS testing. These findings support first-line profiling of lung adenocarcinomas using this approach as a more comprehensive and efficient strategy compared to non-NGS testing.

Concurrent TMB assessment accurately classifies MSI tumors as TMB-high and simultaneously identifies nearly 3% or CRC as MSS/TMB-high. This subgroup may expand the population of CRC who may benefit from immune checkpoint inhibitor based therapeutic approaches.