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Published on: April 11, 2016
Clinical importance of the range of detectable variants between the Oncomine Dx target test and a conventional
Tadashi Sakaguchi1, Akemi Iketani2, Seiya Esumi3
1Department of Respiratory Medicine, Matsusaka Municipal Hospital, 1550, Tonomachi, Matsusaka, Mie, 515-0073, Japan. mchsakaguchi@city-hosp.matsusaka.mie.jp.
Abstract:
Although we have experienced some cases with discordant results between the Oncomine Dx target test (ODxTT) and conventional single gene tests for detecting EGFR alterations, the clinical efficacy of EGFR-TKIs in these discordant cases remains little known. We retrospectively reviewed consecutive patients with non-small-cell lung cancer whose FFPE samples were simultaneously submitted for the ODxTT, and a PNA-LNA PCR clamp test. We evaluated the clinical efficacy of EGFR-TKIs in patients with discordant results between the two tests, focusing on the common EGFR mutations. Among 444 successful results, 10 patients had discordant results for common EGFR mutations (9 Ex 19 deletion and 1 Ex 21 L858R mutation), and all of these were detected only by the PNA-LNA PCR clamp test. Among six discordant cases treated with EGFR-TKI, the mutations detected in 3 patients were not included in the list of detectable variants that are reportable by the ODxTT, while the mutations detected in the other 3 patients were included in the list. For all three discordant cases harboring the mutations not reportable by the ODxTT, good clinical responses were demonstrated. However, among the other three discordant cases harboring the mutations reportable by the ODxTT, only one patient had a clinical response with short duration. Among the discordant cases for common EGFR mutations between the ODxTT and the conventional single gene test, there are a certain number of suitable patients responsive to EGFR-TKIs, especially when the cause of the discordant results comes from the difference in the range of detectable variants that are reportable between the tests.
Insights
Discordant EGFR mutation test results in non-small cell lung cancer patients showed that the PNA-LNA PCR clamp test detected mutations missed by the Oncomine Dx test. Some patients with these missed mutations responded well to EGFR-TKIs.
Area of Science:
- Oncology
- Molecular Diagnostics
- Genetics
Background:
- Discordant results between Oncomine Dx Target Test (ODxTT) and single gene tests for EGFR alterations are known.
- The clinical efficacy of EGFR-TKIs in these discordant cases is not well understood.
Purpose of the Study:
- To evaluate the clinical efficacy of EGFR-TKIs in non-small cell lung cancer (NSCLC) patients with discordant EGFR mutation test results.
- To focus on common EGFR mutations detected by ODxTT and PNA-LNA PCR clamp test.
Main Methods:
- Retrospective review of NSCLC patients with FFPE samples tested simultaneously by ODxTT and PNA-LNA PCR clamp test.
- Evaluation of clinical efficacy of EGFR-TKIs in patients with discordant results for common EGFR mutations.
Main Results:
- Out of 444 successful results, 10 patients had discordant results for common EGFR mutations (9 Ex19del, 1 L858R), all detected only by PNA-LNA.
- Among 6 treated discordant cases, 3 had mutations not reportable by ODxTT, showing good clinical response.
- The other 3 had ODxTT-reportable mutations, with only one showing a short-duration response.
Conclusions:
- A subset of NSCLC patients with discordant EGFR mutation test results are suitable for EGFR-TKIs.
- Discordance due to differences in detectable variants between tests is a key factor in identifying responsive patients.
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