Comprehensive analysis of TMB, TNB, and HLA via NGS sequencing in a large cohort of Chinese pan-cancer patients.

2656 Background: Evidence suggests that patients with high tumor mutational burden (TMB) and tumor neoantigen burden (TNB) are more likely to benefit from Immune checkpoint inhibitors (ICIs). Furthermore, loss of heterozygosity (LOH) in human leukocyte antigen (HLA) alleles, particularly HLA class I, impairs neoantigen presentation and contributes to resistance against ICIs. This study provides real-world insights into the distribution of TMB, TNB, and HLA variations within a large cohort of Chinese patients with various cancers. Methods: From 2021 to 2023, we performed a retrospective analysis on 1603 cancer patients, examining genetic mutations and HLA traits using the Med1 CDx DNA-based NGS panel targeting 601 cancer-related genes and HLA class I. TMB was calculated as the average number of coding mutations per megabase of the genome. HLA class I alleles (HLA-A, B and C) were identified and predicted using the OptiType and pVACtools software suites. TNB was defined as the number of high-affinity (IC50 ≤ 50 nM) neoantigens per megabase of the genome. Statistical analyses were performed to explore the relationship between TMB, TNB, and LOH status in critical regions of HLA. Results: This study enrolled participants across 25 cancer types. With 32.56% having non-small cell lung cancer (NSCLC), 11.79% colorectal carcinoma (CRC), and 18.34% unidentified solid tumors. The remaining 37.31% comprised cases of cholangiocarcinoma, hepatocellular carcinoma, pancreatic cancer, etc. High-affinity neoantigen-generating genes such as TP53, EGFR, KRAS, LRP1B, DMD, and FAT1 were identified. Our findings indicate substantial variation in tumor neoantigen burden (TNB) across various cancer types and even among different samples within the same type. Neuroendocrine tumors exhibited the highest TNB at 4 neoantigens/Mb, followed by esophageal cancer (3.3), melanoma and urothelial carcinoma (2.67 each), indicating higher TNB levels in these cancers compared to others. A significant positive correlation was observed between TMB and TNB (p< 0.0001). Analysis revealed no significant TNB differences attributable to age (cutoff at 60 years) or gender. However, individuals aged over 70 years demonstrated a higher TNB of 4 compared to those under 70 with 3.33, highlighting potential age-related differences in TNB. Conclusions: Our analysis highlights significant variation in TNB across cancer types, with the highest TNB found in neuroendocrine tumors and the lowest in gastrointestinal stromal tumors, indicating TNB's value as a biomarker for optimizing ICI therapy. Furthermore, we found that people over 70 years old have higher TNB levels than younger individuals, suggesting a potential for improved ICI efficacy without chemotherapy. The evident strong correlation between Tumor Mutational Burden (TMB) and TNB underlines their crucial role in the success of cancer immunotherapy.