Feasibility of fecal sample collection for gut microbiome research among Black and Hispanic breast cancer survivors: A pilot study

Background: The gut microbiome is increasingly recognized as a contributor to cancer development, treatment response, and survivorship. Yet few studies have characterized the gut microbiome among racially and ethnically diverse breast cancer (BC) survivors. This pilot study assessed the feasibility of fecal sample collection for microbiome research in Black and Hispanic BC survivors. Methods: We invited women enrolled in the New Jersey Breast Cancer Survivors (NJBCS) study to participate in the microbiome pilot study beginning in Spring 2022. NJBCS participants, identified through the NJ State Cancer Registry, included self-identified Black or Hispanic women with histologically confirmed BC, aged 20-75 years, able to speak and read English or Spanish, with no previous history of cancer except non-melanoma skin cancer. Data collection included in-person home interviews (~18-24 months after BC diagnosis), and women who consented (in English or Spanish) to participate in the microbiome pilot were provided with fecal sample self-collection kits. Samples were mailed by participants to the Columbia Microbiome Core for processing and storage. We used multivariable logistic regression models to examine predictors of providing a fecal sample. Candidate predictors included sociodemographic, lifestyle, and clinical variables: age at diagnosis, time since diagnosis, body mass index, race and ethnicity, place of birth, education, marital status, annual household income, insurance status, physical activity, cigarette smoking, alcohol consumption, tumor stage, cancer treatment, parity, and comorbidities. We used backward elimination to select variables with a statistical significance threshold of P < 0.10. Results: As of July 2025, 358 of 386 eligible women (93%) enrolled in the microbiome, and 292 provided fecal samples (82% response rate), with samples provided in a mean of 20.4 months since diagnosis. The response rate was similar for Black (81%) and Hispanic (83%) participants. Samples arrived at the core a median of 5 days after participant collection. Factors associated with providing a fecal sample included annual household income and endocrine therapy. Higher-income women were somewhat less likely to participate (≥$70,000 vs < $25,000 Odds Ratio (OR): 0.58; 95% Confidence interval (CI): 0.31, 1.07), while women who received endocrine therapy (compared to not) were more likely to provide a sample (OR: 1.97; 95% CI: 1.04, 3.71). Conclusions and Future Directions: This pilot demonstrates high feasibility of fecal sample collection for microbiome research among Black and Hispanic BC survivors. These findings support the feasibility of larger studies to examine whether gut microbiome composition contributes to racial and ethnic differences in BC prognosis and survivorship and lay the groundwork for community-engaged microbiome research to reduce disparities.