Background: Integration of genotype-based stratification into the lung cancer clinic is essential to implement the personalized medicine for patients with lung adenocarcinoma. Thus we have developed a multiplexed tumor genotyping panel for detecting somatic mutations relevant to molecular targeted therapies for lung cancer. The mutation profile data are communicated to clinicians to assign patients to appropriate therapy and/or clinical trials.

Methods: Multiplexed tumor genotyping panel was developed to assess 23 mutations in 9 genes (EGFR, KRAS, BRAF, PIK3CA, NRAS, MEK1, AKT1, PTEN and HER2), 5 genes amplifications (EGFR, MET, PIK3CA, FGFR1 and FGFR2), and 5 fusion genes (EML4-ALK, CD74-ROS1, SLC34A2-ROS1, KIF5B-RET and CCDC6-RET) using pyrosequencing plus capillary electrophoresis, qRT-PCR, and multiplex RT-PCR, respectively. A written informed consent was obtained upfront from all patients enrolled into this study. Surgically resected tissues, tumor biopsies, pleural effusions and/or pericardial effusions from 280 patients were collected between July 2011 and July 2012 and used for tumor genotyping.

Results: Somatic mutations were detected in 52.9% (148/280) of all patients. The most common mutation detected in this study was EGFR mutation (35.4%, 99) followed by KRAS mutation (10.4%, 29). EGFR L858R (52.5%) and KRAS G12C (44.8%) was the most frequent among EGFR and KRAS mutations, respectively. Other detected mutations were PIK3CA mutation (2.5%), PIK3CA amplification (2.5%), EGFR amplification (2.5%), MET amplification (2.1%), EML4-ALK fusion gene (1.4%), BRAF mutation (1.1%), NRAS mutation (1.1%), HER2 mutation (1.1%), MEK1 mutation (0.7%), AKT1 mutation (0.7%), KIF5B-RET fusion gene (0.4%), CD74-ROS1 fusion gene (0.4%) and FGFR1 amplification (0.4%). EGFR tyrosine kinase inhibitor (EGFR-TKI) was administered to 71.9% (41/57) of previously untreated patients who harbor EGFR activating mutations. Among those treated with EGFR-TKIs, simultaneous mutations in other genes with EGFR mutations were detected in 21.9% (9/41). Response rate of EGFR-TKIs in patients with simultaneous mutations (44.4%) was lower than that in patients with EGFR mutation alone (68.8%), suggesting that additional mutations may play some role in evading oncogenic signaling blockade. EGFR mutations were detected less frequently in smokers than in never-smokers (25.1% vs 60.5%, p<0.0001). Meanwhile, KRAS mutations were detected more frequently in smokers than in never-smokers (13.6% vs 2.5%, p=0.0043), which is consistent with previous reports. The majority of patients with never-smoking history harbored targetable somatic mutations compared to those with smoking history (71.6% vs 45.2%, p<0.0001).

Conclusions: We have established the multiplexed tumor genotyping panel and this should be incorporated into lung cancer clinical practice to facilitate personalized cancer medicine.

Citation Format: Masakuni Serizawa, Yasuhiro Koh, Hirotsugu Kenmotsu, Mitsuhiro Isaka, Akane Naruoka, Junko Suzuki, Masaru Watanabe, Masahiro Endo, Takashi Nakajima, Shoji Takahashi, Yasuhisa Ode, Tateaki Naito, Tetsuhiko Taira, Akira Ono, Toshiaki Takahashi, Nobuyuki Yamamoto. Multiplexed mutational profiling of Japanese lung adenocarcinoma patients for personalized cancer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 37. doi:10.1158/1538-7445.AM2013-37