Prognostic Impact of Fusobacterium nucleatum Depends on Combined Tumor Location and Microsatellite Instability Status in Stage II/III Colorectal Cancers Treated with Adjuvant Chemotherapy.

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.