• Gillianne G Y Lai, Tse Hui Lim, John Lim, Perry J R Liew, Xue Lin Kwang, Rahul Nahar, Zaw Win Aung, Angela Takano, Yin Yeng Lee, Dawn P X Lau, Gek San Tan, Sze Huey Tan, Wan Ling Tan, Mei-Kim Ang, Chee Keong Toh, Bien Soo Tan, Anantham Devanand, Chow Wei Too, Apoorva Gogna, Boon Hean Ong, Tina P T Koh, Ravindran Kanesvaran, Quan Sing Ng, Amit Jain, Tanujaa Rajasekaran, Ju Yuan, Lim Tony Kiat Hon TKH 2 Singapore General Hospital, Singapore., Alvin S T Lim, Axel M Hillmer, Wan Teck Lim, N Gopalakrishna Iyer, Wai Leong Tam, Weiwei Zhai, Eng-Huat Tan, and Tan Daniel S W DSW 1 National Cancer Centre Singapore, Singapore. 3 Genome Institute of Singapore, Singa.
• 1 National Cancer Centre Singapore, Singapore.
• J. Clin. Oncol. 2019 Apr 10; 37 (11): 876-884.

PurposeMesenchymal epithelial transition factor ( MET) activation has been implicated as an oncogenic driver in epidermal growth factor receptor ( EGFR)-mutant non-small-cell lung cancer (NSCLC) and can mediate primary and secondary resistance to EGFR tyrosine kinase inhibitors (TKI). High copy number thresholds have been suggested to enrich for response to MET inhibitors. We examined the clinical relevance of MET copy number gain (CNG) in the setting of treatment-naive metastatic EGFR-mutant-positive NSCLC.Patients And MethodsMET fluorescence in situ hybridization was performed in 200 consecutive patients identified as metastatic treatment-naïve EGFR-mutant-positive. We defined MET-high as CNG greater than or equal to 5, with an additional criterion of MET/centromeric portion of chromosome 7 ratiο greater than or equal to 2 for amplification. Time-to-treatment failure (TTF) to EGFR TKI in patients identified as MET-high and -low was estimated by Kaplan-Meier method and compared using log-rank test. Multiregion single-nucleotide polymorphism array analysis was performed on 13 early-stage resected EGFR-mutant-positive NSCLC across 59 sectors to investigate intratumoral heterogeneity of MET CNG.ResultsFifty-two (26%) of 200 patients in the metastatic cohort were MET-high at diagnosis; 46 (23%) had polysomy and six (3%) had amplification. Median TTF was 12.2 months (95% CI, 5.7 to 22.6 months) versus 13.1 months (95% CI, 10.6 to 15.0 months) for MET-high and -low, respectively ( P = .566), with no significant difference in response rate regardless of copy number thresholds. Loss of MET was observed in three of six patients identified as MET-high who underwent postprogression biopsies, which is consistent with marked intratumoral heterogeneity in MET CNG observed in early-stage tumors. Suboptimal response (TTF, 1.0 to 6.4 months) to EGFR TKI was observed in patients with coexisting MET amplification (five [3.2%] of 154).ConclusionAlthough up to 26% of TKI-naïve EGFR-mutant-positive NSCLC harbor high MET CNG by fluorescence in situ hybridization, this did not significantly affect response to TKI, except in patients identified as MET-amplified. Our data underscore the limitations of adopting arbitrary copy number thresholds and the need for cross-assay validation to define therapeutically tractable MET pathway dysregulation in EGFR-mutant-positive NSCLC.

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