Abstract
BACKGROUND: This study aimed to investigate the prognostic impact of intratumoral Fusobacterium nucleatum in colorectal cancer (CRC) treated with adjuvant chemotherapy. METHODS: F. nucleatumDNA was quantitatively measured in a total of 593 CRC tissues retrospectively collectedfrom surgically resected specimens of stage III or high-risk stage II CRC patients who had receivedcurative surgery and subsequent oxaliplatin-based adjuvant chemotherapy (either FOLFOXor CAPOX). Each case was classified into one of the three categories: F. nucleatum-high, -low, or -negative. RESULTS: No significant differences in survival were observed between the F.nucleatum-high and -low/negative groups in the 593 CRCs (p = .671). Subgroup analyses accordingto tumor location demonstrated that disease-free survival was significantly better in F.nucleatum-high than in -low/negative patients with non-sigmoid colon cancer (including cecal,ascending, transverse, and descending colon cancers; n = 219; log-rank p = .026). In multivariateanalysis, F. nucleatum was determined to be an independent prognostic factor in non-sigmoidcolon cancers (hazard ratio, 0.42; 95% confidence interval, 0.18 to 0.97; p = .043). Furthermore,the favorable prognostic effect of F. nucleatum-high was observed only in a non-microsatellite instability-high (non-MSI-high) subset of non-sigmoid colon cancers (log-rank p = 0.014), but not ina MSI-high subset (log-rank p = 0.844), suggesting that the combined status of tumor locationand MSI may be a critical factor for different prognostic impacts of F. nucleatum in CRCs treatedwith adjuvant chemotherapy. CONCLUSIONS: Intratumoral F. nucleatum load is a potential prognosticfactor in a non-MSI-high/non-sigmoid/non-rectal cancer subset of stage II/III CRCs treatedwith oxaliplatin-based adjuvant chemotherapy.