The oral microbiome and breast cancer and nonmalignant breast disease, and its relationship with the fecal microbiome in the Ghana Breast Health Study Original paper

What was studied?

This study investigated the oral microbiome and breast cancer within a population-based case-control design in Ghana, focusing on how oral microbial diversity and taxa relate to breast cancer and non-malignant breast disease. Because the oral microbiome and breast cancer relationship is poorly understood globally and nearly unstudied in African populations, the researchers assessed whether oral microbial signatures—including diversity metrics, community composition, and specific taxa such as Porphyromonas, Fusobacterium, and Prevotella—were associated with disease status. The study also examined cross-body correlations between oral and fecal microbiomes to understand systemic microbial relationships. The sequencing targeted the 16S rRNA V4 region from both saliva and stool, enabling detailed evaluation of alpha- and beta-diversity, taxa presence, and relative abundance.

Who was studied?

A total of 881 Ghanaian women were included: 369 with breast cancer, 93 with non-malignant breast disease, and 419 population-based controls. Participants were drawn from Accra and Kumasi and represented a broad demographic distribution. Oral microbiome samples were obtained prior to any neoadjuvant therapy, improving validity by avoiding treatment-related microbial disturbances. A subset of 840 women with sufficient sequencing depth contributed to combined oral–fecal microbiome analyses. The participants varied by age, lifestyle factors, reproductive history, antibiotic exposure, and socioeconomic characteristics, and the analysis adjusted for these variables to reduce confounding.

Most important findings

The oral microbiome showed strong, inverse associations with breast cancer and non-malignant breast disease. Lower alpha-diversity—including observed ASVs, Shannon index, and Faith’s PD—was consistently linked to higher odds of disease. For every 10-ASV increase, breast cancer odds decreased by 14%, while non-malignant disease odds decreased by 21%. Beta-diversity differences (Bray–Curtis, Jaccard, unweighted and weighted UniFrac) were significant when comparing cases with controls, confirming broad compositional shifts. Several genera—especially periodontal pathogens—were inversely associated with breast cancer. Porphyromonas presence showed one of the strongest protective associations (OR≈0.02). Relative abundance analyses reinforced these trends: each 1% increase in Porphyromonas or Fusobacterium abundance corresponded to reduced cancer odds. Additionally, the oral microbiome was more tightly linked to the fecal microbiome in breast cancer cases than in controls. Notably, oral Porphyromonas was strongly and inversely correlated with fecal Bacteroides (r = –0.37), a genus previously shown to be positively associated with breast cancer risk in the same population. This suggests coordinated cross-site microbial alterations specific to disease physiology.

Key implications

These findings highlight the oral microbiome as a potentially meaningful biomarker source in breast cancer risk assessment and early detection strategies. The significant inverse relationships between alpha-diversity and breast cancer indicate that reduced oral microbial richness may reflect systemic inflammatory or hormonal environments conducive to tumor development. The strong cross-body correlations between oral and fecal taxa among cases suggest that breast cancer may involve broader microbial network disruptions rather than localized changes. Periodontal pathogens—counterintuitively showing protective associations—underscore the complexity of microbe–host interactions, suggesting mechanisms unrelated to traditional periodontal disease pathways. Future work, especially in prospective designs, should explore microbial contributions to estrogen metabolism, systemic inflammation, and immune modulation, which may connect oral and gut microbial ecosystems to breast tumorigenesis.

Citation

Wu Z, Byrd DA, Wan Y, Ansong D, Clegg-Lamptey JN, Wiafe-Addai B, et al. The oral microbiome and breast cancer and non-malignant breast disease, and its relationship with the fecal microbiome in the Ghana Breast Health Study.Int J Cancer. 2022;151(8):1248-1260. doi:10.1002/ijc.34145