Examining the Formalin Fixation Method for Maintaining High RNA Quality in Surgical Lung Specimens

Multiplex genetic testing is recommended when treating nonsmall cell lung cancer. A certain percentage of test failures in RNA assays owing to poor surgical specimen quality have been documented, and fixation failure is a possible cause. At our institution, sheet-like fixation is performed to reduce fixation time. This study aimed to compare the quality of RNA from resected lung cancer specimens following different fixation methods.

Sheet-like fixation specimens (n = 15), conventional fixation specimens of the same resected lungs (n = 15), and other lung cancer specimens collected for conventional fixation and subjected to multiplex gene-panel testing (n = 22) were retrospectively examined. RNA was extracted from each specimen. RNA quality and quantity were compared, and the success rate of multiplex gene-panel testing was determined.

The DV₂₀₀ value was significantly higher in RNA extracted from sheet-like fixation samples (median 47.5%, interquartile range [IQR]:40.3-51.5) compared with RNA extracted from conventionally fixed samples or conventionally fixed samples of other patient specimens (median 21%, IQR:5.3-29.8 and median 16.3%, IQR:9.5-27.1, respectively). No significant difference was observed in nucleic acid concentration. The multiplex genetic analysis success rate was 95% with conventional methods (one failure); however, it was 100% with the sheet-like fixation method.

Sheet-like fixation preserved RNA extracted from lung cancer specimens, resulting in lesser degradation than with conventional fixation.