Tissue surface area and tumor cell count affect the success rate of the Oncomine Dx Target Test in the analysis of biopsy tissue samples

BACKGROUND: The Oncomine Dx Target Test (ODxTT) is a next‐generation sequencing‐based companion diagnostic test which has been recently developed; however, its analysis success rate could be improved, especially for small samples. The aim of this study was to identify the pathological factors associated with biopsy specimens that affect the analysis success rate of ODxTT. METHODS: We retrospectively investigated 119 cases subjected to ODxTT at Kanagawa Cancer Center. Data pertaining to the results of BRAF V600E mutation analysis in ODxTT and pathological factors based on microscope slides were collected. Pathological factors including tissue surface area, tumor cell count, and tumor content rate were assessed. We constructed receiver operating characteristic curves and determined the optimal cutoff values of each pathological factor. Multivariate logistic analysis was used to identify significant factors. RESULTS: A total of 98 of 119 samples were successfully analyzed (75.6%). The tissue surface area and tumor cell count were significantly higher in the group associated with analysis success (P < 0.001 and P = 0.011, respectively), and their optimal cutoff values were 1.04 mm(2) and 375 cells, respectively. A tissue surface area > 1.04 mm(2) and tumor cell count >375 cells had a positive effect on the analysis success rate of ODxTT (odds ratio [OR] 0.10; 95% confidence interval [CI]: 0.03–0.35; P < 0.001 and OR 0.25; 95% CI: 0.07–0.90; P = 0.033, respectively). CONCLUSIONS: Selecting samples with a tissue surface area > 1.04 mm(2) and a tumor cell count >375 cells might improve the analysis success rate of ODxTT. KEY POINTS: Significant findings of the study: We found that a tissue surface area > 1.04 mm(2) and tumor cell count >375 cells had a positive effect on the analysis success rate of ODxTT in the analysis of biopsy tissue samples. What this study adds: It is sometimes necessary to assess genetic alterations with a small biopsy sample in daily practice. The criteria mentioned above will help to determine which tests should be performed, ODxTT or multiple single‐gene testing.