Letter to the Editor – “Intratumoral Fusobacterium nucleatum associates with advanced-stage colorectal cancer and poor prognosis in a Chinese cohort”

The recent study by Justesen et al^[1], reported an interesting association between anaerobic bacteremia and subsequent diagnosis of colorectal cancer (CRC), identifying microbial taxa such as Bacteroides spp. and Clostridium spp. as potential markers of malignancy. While these findings reinforce the role of the gut microbiome in CRC pathogenesis, microbial detection in blood likely reflects advanced disease with systemic translocation rather than early or causative involvement. In contrast, microbial colonization within tumor tissue may provide a more proximal and biologically relevant indicator of neoplastic progression. Accordingly, we investigated intra-tumoral Fusobacterium nucleatum (F. nucleatum) in a rigorously characterized East-Asian cohort, thereby bridging a critical geographic gap and testing whether the organism’s reported prognostic value is conserved across divergent genetic, dietary, and environmental landscapes. In addition, to ensure transparency and reporting integrity in scientific communication, this manuscript adheres to the TITAN 2025 guideline for artificial intelligence disclosure in biomedical research, although no AI tools were utilized in the study design, analysis, or manuscript preparation^[2].

We analyzed 312 consecutive CRC resections from two Shanghai tertiary centers (January 2016–December 2022); patients with prior malignancy or incomplete pathology were excluded. A priori power analysis (α = 0.05) confirmed 80 % power to detect a hazard ratio ≥1.70 for progression-free survival (PFS). FFPE-derived DNA showed high integrity (median DIN 7.1; 260/280 ≥ 1.8). F. nucleatum was quantified by nusG-targeted qPCR, whose analytical limit of detection was 10 fg DNA, with 100 % specificity against 20 gut commensals; negative and no-template controls were included in each run. Statistical analyses were performed in R 4.3.2 (survival, logistf). Multivariable models employed backward stepwise selection (entry P < 0.10); proportional-hazards assumptions were verified with Schoenfeld residuals, variance-inflation factors were <2.0, and multiplicity was controlled at a 10 % false-discovery rate.

HIGHLIGHTS

• Intratumoral Fusobacterium nucleatum is associated with advanced-stage colorectal cancer, metastasis, and reduced progression-free survival in Chinese patients.

• F. nucleatum positivity increases the odds of advanced-stage disease by 5.78-fold (95% CI, 2.99–11.18).

• Findings provide population-specific evidence from a non-Western cohort, expanding the global applicability of CRC microbiome research.

• Supports the integration of microbial biomarkers into colorectal cancer screening, prognostication, and therapeutic strategies.

Kaplan–Meier curves demonstrated significantly shorter PFS for F. nucleatum-positive patients (Fig. 1A; log-rank p < 0.001). After adjustment for age, sex, tumor grade, microsatellite-instability status, adjuvant therapy and tumor location, F. nucleatum positivity remained an independent predictor of inferior PFS (adjusted HR = 2.14; 95 % CI 1.41–3.26; P < 0.001). The proportion of stage IV and stage III disease was higher in the positive group (35% and 30%) than in the negative group (25 % and 20 %; P < 0.001; Figure 1C). Firth-penalized multivariable logistic regression – including age, sex, body-mass index, tumor grade, MSI status, tumor size and location – confirmed independence (adjusted OR = 5.78; 95 % CI 2.99–11.18; P < 0.001; Figure 1B). Subgroup analyses by age (61–75 y, OR = 1.07; 95 % CI 0.81–1.25) and proximal location (OR = 0.78; 95 % CI 0.38–1.62) were non-significant, and no interaction was detected. Tumor size (5.4 cm vs 4.9 cm, P = 0.14) and poor differentiation (36% vs 24%, P = 0.10) did not reach significance. Metastasis was markedly more frequent in positive tumors (30% vs 7%, P < 0.001; Figure 1F).

Figure 1.

Association of Fusobacterium nucleatum with colorectal cancer (CRC) Progression. (A) Kaplan–Meier survival analysis comparing progression-free probability between F. Nucleatum-positive and -negative CRC patients (blue: negative; red: positive); significance assessed using the log-rank test. (B) Odds ratios (ORs) with 95% confidence intervals for association between F. Nucleatum positivity and advanced-stage disease (stage III/IV), presented overall and by subgroups (gender, age, tumor location, tumor size). (C) Distribution of CRC stages (I–IV) by F. Nucleatum status, showing a higher frequency of stage III/IV in the positive group (P = 0.00). (D) In the comparison of tumor size (cm) by F. Nucleatum status, the mean size was greater in positive cases, though not statistically significant (P = 0.14). (E) Tumor grade distribution stratified by F. Nucleatum status; poorly differentiated tumors were more common in the positive group (P = 0.10). (F) Proportion of metastatic disease by F. Nucleatum status, demonstrating a significantly higher metastatic burden in positive cases (P = 0.00). All panels use consistent color coding (blue: F. Nucleatum-negative; red: F. Nucleatum-positive). Statistical significance was assessed using appropriate tests for each comparison.

F. nucleatum promotes tumor growth via β-catenin activation^[3], immune modulation^[4], and autophagy induction^[5], and interacts with TP53/APC driver mutations and the tumor micro-environment^[6,7]. Residual confounding by antibiotic exposure, dietary fiber intake and baseline microbial diversity is acknowledged^[8], whereas, our cross-sectional design precludes causal inference. Nevertheless, the preservation of F. nucleatum’s prognostic signal across two centers with distinct catchment populations strengthens the microbe’s clinical relevance.

Intra-tumor F. nucleatum detection in biopsy or resection material could refine risk stratification, and combining fecal F. nucleatum assays with fecal immunochemical testing may enhance non-invasive screening. These applications remain hypothesis-generating; recent pathology-lab pilots integrating microbial qPCR into routine workflows endorse feasibility and warrant prospective evaluation. In summary, our findings support intra-tumoral F. nucleatum as a reproducible and clinically relevant biomarker of advanced disease, reduced progression-free survival, and metastatic burden in Chinese colorectal cancer patients, thereby reinforcing and extending prior observations from Western cohorts and highlighting its potential relevance in future microbiome-informed prognostic and therapeutic strategies

Ethical approval

This study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of the First Affiliated Hospital of Naval Medical University, Shanghai, China (Approval No. NMU-2022-IRB-157).

Consent

Written informed consent was obtained from all participants or their legal guardians prior to enrollment. All procedures involving human participants adhered to institutional and national research committee ethical standards and applicable regulatory guidelines.

Sources of funding

None.

Author contributions

Y.S., F.Y., and W.W. contributed to the conception and design of the study, data acquisition, and initial interpretation. Y.S. and F.Y. conducted the data analysis and drafted the manuscript. W.W. assisted in statistical analysis and literature review. X.L. supervised the overall project, provided critical revisions, and finalized the manuscript for submission. All authors reviewed and approved the final version of the manuscript.

Conflicts of interest disclosure

None to declare.

Guarantor

Xu Li is the corresponding author and has the full responsibility for this integrity of data.

Research registration unique identifying number

None.

Data availability statement

Data used in this study, can be requested from corresponding author on reasonable request.