Figure 9.

Effects of formalin‐fixed paraffin‐embedded (FFPE) block storage duration on RNA quality. The effects of storage duration on quality of RNA extracted from FFPE blocks were examined using FFPE tissue samples from 169 patients with non‐small cell lung cancer. One hundred FFPE block samples were prepared in 2007, and 49 and 20 were prepared in 2012 and 2013, respectively. Using the semiconductor‐based Ion PGM System, amplicon sequencing analyses were performed in 2014 using the Ion AmpliSeq™ RNA Fusion Lung Cancer Research Panel (Thermo Fisher Scientific). In this fusion gene panel, the median total number of reads was 288  838 (range: 157  085−431  332) for the blocks prepared in 2013; 257  516 (range: 149  998−435  890) for blocks prepared in 2012; and 282  887 (range: 4987−562  580) for blocks prepared in 2007. Among the 169 samples, four samples were judged difficult to assess because the total number of reads from blocks prepared in 2007 was ≤20 000. The blocks prepared in 2007 showed fewer reads than those prepared in 2012 or 2013, indicating the effects of sample deterioration over time