Comprehensive germline and somatic DDR genomic profiles of Chinese patients with multiple primary lung cancer.

e20019 Background: The number of multiple primary lung cancer (MPLC) patients has rapidly increased in recent years. Disruption of the DNA damage repair (DDR) gene is related to cancer risk, progression, and treatment selection. However, the characteristics and significance of DDR alterations remain undefined in MPLC. Methods: A total of 133 Chinese MPLC patients with 308 lesions were enrolled and 784 single-focus lung cancer (SFLC) patients were analyzed as a control in the present study. Genetic testing was performed by utilizing the next-generation sequencing (NGS) of 808 cancer-related genes including 276 DDR genes. The patients were divided into 3 groups: DDR-germline (germline variants, N = 11), DDR-somatic group (somatic variants, N = 98), and the non-DDR group (no DDR variants, N = 24). Results: The overall DDR variants were identified in 82.0% (109/133) of the patients, and a total of 283 variants were found, with almost all being somatic (254/283). The most commonly germline alterations were found in RAD50 (1.5%), WRN (1.5%) and BRCA2 (0.8%), while in the somatic mutations, TP53 (26.3%) showed the highest frequency. DDR-somatic group was more likely to have alterations in TP53, LRP1B, ERBB2 and MYC compared with DDR-germline group. Taken non-DDR group as reference, mutations in TP53 (P<0.05), ALK and PIK3CA were more common in DDR-germline group, but EGFR, RBM10, TP53, LRP1B, TERT and MYC (all P<0.05) in DDR-somatic group. Furthermore, the DDR-somatic group exhibits the highest median tumor mutational burden (6.56) compared with 3.55 (P<0.01) in DDR-germline and 3.69 (P<0.01) in non-DDR group. In addition, the copy number variation (CNV) was statistically different among the three groups (P<0.001). The proportion of copy number gain patients in DDR-somatic group is the highest (28.3%) compared with 12.0% in DDR-germline group and 10.9% in non-DDR group (P<0.01). DDR-somatic MPLC and SFLC patients possessed distinct somatic genomic characteristics, especially with significantly different prevalence in TP53, RBM10, KRAS, BRAF, and ALK (all P<0.05). Moreover, we also found notable differences in the prevalence of TP53 and CNV (both P<0.05) between DDR-germline MPLC and SFLC patients. Conclusions: MPLC patients exhibit a distinctive DDR mutations landscape. The differences in the mutation profile between the DDR-germline and DDR-somatic groups and the distinct actionable genes may indicate the different target-therapy choices for MPLC patients.