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Role of Diet in Cancer Prevention and Control (Oral Session 16)

(OR16-02-25) A High-Fiber Plant-Based Intervention in Precursor Plasma Cell Disorders Improves Dietary Quality and Microbiome

Monday, June 2, 2025
4:12 PM – 4:24 PM ET
Location: S230 CD
Objectives: Multiple myeloma (MM) is often preceded by precursor plasma cell disorders, monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Elevated body mass index (BMI), poor dietary quality, and microbiome dysbiosis are risk factors for development of MGUS/SMM and MM progression.

Methods: We conducted a single-arm pilot trial providing a high fiber plant-based dietary (HFPBD) intervention for 12 weeks and behavioral counseling for 24 weeks in 20 patients with MGUS/SMM and BMI ≥25 (NCT04920084). Patients were asked to keep weekly food logs for accountability, with 3-day food records clarified prior to dietitian visits. All food records were analyzed using ASA24. Dietary adherence was calculated as the percentage of kcal from minimally processed plant foods out of total kcal consumed. Dietary quality was assessed from HEI scores and fiber intake. The primary endpoint was feasibility measured by dietary adherence and BMI reduction. Secondary and exploratory endpoints included dietary quality and microbiome.

Results: The HFPBD was safe, feasible, and improved diet quality and microbiome. Median dietary adherence increased from baseline (BL) (20%) to week 12 (W12) (91%; p≤0.0001). Median BMI decreased from BL (34.3kg/m2) to W12 (-6.6%; p≤0.0001). Median dietary fiber increased from BL (12.3 g/1000kcal/day) to W12 (24 g/1000kcal/day; p≤0.01). Median HEI-2020 score increased from BL (61.4) to W12 (80; p< 0.0001). Median fecal microbiome α-diversity by 16S increased from BL (6.18) to W12 (8.42; p=0.021). Relative abundance of butyrate producers (RABP) increased from BL (median 0.03) to W12 (0.08; p=0.015). α-diversity was correlated negatively with BMI (p < 0.001), positively with fiber (p=0.004), HEI-2020 score (p=0.017), and dietary adherence (p=0.001). Fiber intake (p=0.014), HEI-2020 scores (p=0.006), and dietary adherence (p=0.002) were positively correlated with higher RABP. Consistent findings were seen at W24 and W52.

Conclusions: This is the first interventional clinical trial to show that a HFPBD can improve dietary quality and microbiome with potential to delay progression of MGUS/SMM to MM. To our knowledge there has been no similar dietary intervention in blood cancers.

Funding Sources: NIH/NCI Cancer Center Support Grant; Paul Calabresi K12 Award; the Allen Foundation Inc; Paula and Rodger Riney Foundation