Background: Multiple primary lung cancers (MPLC) are reported to occur in 0.2-20 % of all primary lung cancer cases. MPLC are considered to harbor various genetic profiling patterns among the tumors even within the same individuals, though they developed from the same occupational and environmental exposure. In this study, we performed paired mutational analyses to clarify genetic mutations in MPLC and its relationship with environmental factors.

Materials and methods: We obtained 38 surgical specimens from 17 patients who were pathologically diagnosed as MPLC and underwent surgery at Osaka City University Hospital between October 2007 and March 2019. In addition to the clinicopathological features, the patients' age, sex, smoking history, body mass index, radiologic features and surgical procedures were reviewed. Four of the 17 MPLC patients had metachronous lesions, whereas 13 patients only had synchronous lesions. For genetic profiling of MPLC patients, the extracted DNAs were deep-sequenced on Ion S5 sequencer (Thermo Fisher) for somatic mutations in 409 cancer-associated genes (Ion AmpliSeq Comprehensive Cancer Panel). The study was approved by institutional review board of Osaka City University Hospital and written informed consent was obtained from all of the patients. For statistically analyses, we assumed genetic mutations occurred by chance and calculated the frequency of concomitant mutations in multiple tumors within the same individuals based on a previous study (JME study; Kawaguchi T et al, J Clin Oncol 2016). Comparing the assumed frequency of mutations with the actual data, statistically analyses whether mutations would occur concomitantly or randomly were performed using an exact test.

Results: Deep sequencing was successfully performed in all of the specimens with the mean coverage of 823. Results from comprehensive genetic analyses suggested that the mutation profiles differed among the tumors within the same individuals, whereas EGFR, KRAS, TP53, and PARP1 mutations were concomitantly detected in multiple tumors within the same individuals. In this study, the frequency of EGFR mutations was significantly higher in never or light -smokers and females. The occurrence of concomitant EGFR or KRAS mutations in multiple tumors within the same individuals was significantly more frequent than expected by chance (EGFR, P = .0023; KRAS, P = .0049), suggesting environmental factors play more role in EGFR and KRAS mutations than the other mutations including TP53 which occurred more randomly in individual tumors. Concomitant EGFR or KRAS mutations were particularly prominent in never or light-smokers and males.

Conclusions: Results from our MPLC study confirmed that the development of EGFR or KRAS-mutated tumors were strongly related to environmental factors such as sex and smoking history, and suggested that the other mutations may occur randomly.

Citation Format: Motohiro Izumi, Jun Oyanagi, Kenji Sawa, Mitsuru Fukui, Koichi Ogawa, Yoshiya Matsumoto, Yoko Tani, Tomohiro Suzumura, Tetsuya Watanabe, Hiroyasu Kaneda, Shigeki Mitsuoka, Kazuhisa Asai, Tatsuo Kimura, Nobuyuki Yamamoto, Tomoya Kawaguchi, Yasuhiro Koh. Mutational landscape of multiple primary lung cancers and its correlation with environmental factors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2333.