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(OR09-03-26) Dietary Fiber Intake Correlates With Improved Allo‑HCT Survival and Supports Development of a High‑Fiber Trial

Sunday, July 26, 2026
10:54 AM - 11:06 AM ET
Location: Maryland Ballroom D
Objectives: To determine if fiber intake and intestinal microbiome composition correlate with survival and acute graft‑versus‑host disease (GVHD) risk after allogeneic hematopoietic cell transplantation (allo‑HCT), to define mechanisms in preclinical models, and to design a High‑Fiber clinical intervention.

Methods: In 173 adults undergoing allo‑HCT at Memorial Sloan Kettering Cancer Center, we analized daily dietary intake (day −7 to +30; 37,929 food items; 3,837 patient‑days), fecal microbiota (n=1,230; 16S rRNA) and short‑chain fatty acids (SCFAs; GC‑MS). Associations between dietary intake and overall survival (OS) or acute GVHD were evaluated using multivariable Cox and Fine–Gray models adjusted for antibiotic exposure and clinical covariates. In a murine allo‑HCT model, we compared diets containing 0, 6, or 12% cellulose for effects on GVHD survival, fecal microbiome composition (shotgun, GC-MS), and epithelial homeostasis.

Results: Pre-transplant fiber intake above the cohort median (7.7 g/day) was significantly associated with improved OS (adjusted HR 0.47, p=0.014) and reduced incidence of grade ≥2 acute GVHD (HR 0.48, p=0.032). Insoluble fiber correlated with increased microbial α-diversity (p=0.024), depletion of t Enterococcus, enrichment of Blautia, and higher fecal SCFA concentrations. Patients who developed lower gastrointestinal GVHD had significantly reduced fecal SCFAs versus controls. In mice, a 12% cellulose diet improved GVHD survival (p < 0.05), increased microbial diversity, SCFA producers, cecal butyrate (p=0.038), epithelial barrier function (p=0.002), and higher Treg/Tcon ratios in the lamina propria. Our data informed a precision‑nutrition High-Fiber trial in allo-HCT at City of Hope Los Angeles, that evaluates feasibility, adherence, and safety while incorporating microbiome, metabolome, and immune profiling.

Conclusions: Pre‑transplant dietary fiber intake correlates with improved survival and reduced acute GVHD after allo‑HCT, greater microbiome diversity, higher SCFA production, and depletion of pathogenic taxa. A cellulose‑rich diet in murine allo‑HCT recapitulates these benefits. Together, these findings identify dietary fiber as a modifiable determinant of allo‑HCT outcomes and provide the foundation for an innovative High‑Fiber trial.

Funding Sources: Institutional and shared‑resource funds