Abstract
Next-generation sequencing (NGS)-based cancer panel tests are actively being applied in the clinic for precision oncology. Given the importance of NGS panel tests in the palliative clinical setting, it is critical to understand success rates, factors responsible for test failures, and the incidence of clinically meaningful genetic alterations. We performed NGS cancer panel test with tumors from the stomach (n = 234), colorectum (n = 196), and rare tumors (n = 105) from 535 recurrent or metastatic cancer patients for 1 year. Sequencing was successful in 483 (95.3%) archival tumor samples to find single nucleotide variant (SNV), copy number alteration (CNA), and fusion. NGS testing was unsuccessful in 52 (9.7%) specimens due to inadequate tissue (n = 28), low tumor volume (n = 19), and poor quality of nucleic acid (n = 5). According to the Tier system, variants were classified as Tier IA, 0.8%; IIC, 10.3%; IID, 2.0%; III, 66.7% for gastric: Tier IA, 3.6%; IIC, 11.6% for colorectal: Tier IA, 1.6%; IIC, 13.5%; IID, 0.5%; III, 70.8% for melanoma, and Tier IA, 9.1%; IIC, 1.8%; IID, 1.0%; III, 66.4% for GIST. In total, 30.8% of 483 sequenced cases harbored clinically meaningful variants. In Tier IA, KRAS and ERBB2 were the most commonly altered genes. Interestingly, we identified CD274 (PD-L1) amplification, PTPN11 (SHP2) SNV, TPM3-NTRK1 fusion, and FGFR3-TACC3 fusion as a rare (<2%) alteration having therapeutic targets. In conclusion, although small biopsy samples constitute half of cases, informative NGS results were successfully reported in >90% of archival tissue samples, and 30.8% of them harbored clinically meaningful variants.