Abstract B095: Characterizing the composition and diversity of the vaginal microbiome in ovarian cancer

Abstract

Vaginal dysbiosis, Lactobacillus depletion with anaerobic bacterial enrichment, may be relevant to gynecologic cancer risk and prognosis, yet comprehensive microbiome characterization in ovarian cancer (OC) patients, particularly across racial groups, remains limited. We characterized the prevalence, composition, and demographic predictors of vaginal microbiome dysbiosis among racially diverse OC patients. We performed 16S rRNA gene sequencing (V1-V3 region) on self-collected vaginal swabs from 132 OC patients enrolled in the population-based ORCHiD study (83.3% non-Hispanic [NH] white, 16.7% NH-Black). Genus- and amplicon sequence variant (ASV)-level composition was characterized, and Latent Dirichlet Allocation topic modeling identified co-occurring microbial community signatures (“topics”). Beta regression assessed associations between topic proportions and race, age, cancer stage, and histologic subtype, with Benjamini-Hochberg false discovery rate (FDR) correction. Targeted species analyses examined four predominant vaginal Lactobacillus species. Lactobacillus was detected in only 47.7% of patients (mean relative abundance 23.5%). Topic modeling identified seven distinct microbial signatures; a Lactobacillus-dominated topic characterized only 26.8% of patients, while dysbiotic, anaerobe-enriched topics dominated 73.2% of the cohort. An anaerobic dysbiosis signature (Peptoniphilus, Anaerococcus) increased significantly with age (35% higher odds per decade of life, FDR q=0.019). NH-Black patients showed a 5-fold higher prevalence of an Actinomycetaceae-classified ASV (ASV54) compared with NH-white patients (40.9% vs 8.2%, FDR q=0.005), the most robust compositional difference observed. L. crispatus was detected only among NH-white patients (6.4% vs 0%), whereas L. iners was more prevalent among NH-Black patients (22.7% vs 10.0%), though species-level differences did not reach statistical significance after correction. OC patients demonstrate a high burden of vaginal microbiome dysbiosis, with distinct age- and race-associated microbial patterns, including a novel Actinomycetaceae ASV enriched among NH-Black patients. These findings establish a foundation for larger, longitudinal studies to determine whether vaginal microbiome profiles could serve as biomarkers for disease monitoring or as therapeutic targets in OC.Generative AI (Claude, Anthropic) was used to assist in drafting this abstract text from the authors' underlying manuscript and data; all content was reviewed and verified for accuracy by the authors prior to submission. April Deveaux, Oyomoare Osazuwa-Peters, Yeon Ji Kim, Pixu Shi, Drew Neish, Ashwini Joshi, Veronica Duck, Ashliegh Williams, Margaret Gates Kuliszewski, Bin Huang, Kevin Ward, Maria Pisu, Thomas Tucker, Rebecca Previs, Andrew Berchuck, Tomi Akinyemiju. Characterizing the composition and diversity of the vaginal microbiome in ovarian cancer [abstract]. In: Proceedings of the 19th AACR Conference on the Science of Cancer Health Disparities; 2026 Oct 18-21; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2026;35(10 Suppl):Abstract nr B095.