Fusobacterium nucleatum: caution with interpreting historical patient sample cohort

Fusobacterium nucleatum (Fn) was first noted to be associated with colorectal cancer (CRC) in 2012. Since then there have been several publications in retrospective cohorts analyzing the relationship between colorectal tumor fusobacterial abundance, clinical and molecular characteristics and clinical outcomes. The majority of studies, including ‘Prognostic impact of Fusobacterium nucleatum depends on combined tumor location and microsatellite instability status in stage II/III colorectal cancers treated with adjuvant chemotherapy’ by Oh et al. published in Journal of Pathology amd Translational Medicine, utilize quantative polymerase chain reaction for the NusG gene in Fn relative to a control prostaglandin transporter gene (SLCO2A1). Many of these studies utilize formalin-fixed paraffin-embedded (FFPE) tissue that has been stored for up to two decades. Although this enables a long follow-up period for clinical outcomes, recent data from our lab shows that advanced age of sample significantly impairs the ability to detect Fn.