Evaluation of appropriate conditions for Oncomine DxTT testing of FFPE specimens for driver gene alterations in non–small cell lung cancer

BACKGROUND: The Oncomine Dx Target Test Multi‐CDx System (ODxTT) is a next‐generation sequencing panel approved as a companion diagnostic for drugs targeted to corresponding gene alterations in non–small cell lung cancer. However, appropriate slide conditions for ODxTT have remained unclear. METHODS: We focused on the production of the number of tumor cells on a formalin‐fixed paraffin‐embedded (FFPE) section and the number of prepared slides, designated the TS value, and determined a TS value of ≥4000 as a target slide condition for ODxTT. We evaluated the impact of this condition on ODxTT testing with tumor specimens found to have a TS of <4000 (n = 23) or a TS of ≥4000 (n = 142). RESULTS: A positive correlation was apparent between the TS value and the concentrations of both DNA and RNA. Among the 142 samples with a TS of ≥4000, a sufficient concentration of DNA or RNA for ODxTT analysis was achieved in 100% and 98% samples, respectively. Among samples explored for driver gene alterations after determination of the target slide condition (TS ≥4000), most (84.9%) had a TS of ≥4000 and were submitted for ODxTT analysis. CONCLUSION: Our findings indicate that a TS of ≥4000 is a feasible and relevant criterion for ODxTT testing, and its adoption should help to improve the success rate of such testing in clinical practice.