The Effects of Storage Time of Colorectal Cancer Tissue on the Detection of K-ras Gene.

Background: The storage times of formalin-fixed paraffin embedded (FFPE) colorectal cancer (CRC) tissues can differ. In this study we investigated the effects of storage time of CRC tissue on K-ras detection. Methods: Forty fresh tissues and 120 FFPE CRC tissues were selected for this study. The storage time of the FFPE samples was 1 to 2 years, 2 to 5 years, and 5 to 10 years with 40 samples in each group. DNA was extracted from these samples and exon 1 of K-ras was sequenced. Results: The concentration or quantity of DNA extracted from the fresh tissues and FFPE tissues did not change. The K-ras detection rate in fresh tissues, tissues stored for 1 to 2 years, tissues stored for 2 to 5 years, and tissues stored for 5 to 10 years was 100%, 92.5%, 87.5%, and 77.5%, respectively. Conclusions: When the storage time was prolonged, the K-ras detection rate of CRC tissue decreased. [ABSTRACT FROM AUTHOR]