A High-Fiber Plant-Based Intervention in Precursor Plasma Cell Disorders Improves Dietary Quality and Microbiome

Objectives: Non-muscle invasive bladder cancer (NMIBC) has high rates of recurrence and progression, posing significant clinical challenges and patient burden.We examined the associations of diet quality with risk of cancer recurrence and progression in the Be-Well Study, a prospective cohort study of NMIBC.Methods: We enrolled 1,143 participants diagnosed with new primary NMIBC from 2015-2019 at Kaiser Permanente.Dietary intake was assessed at diagnosis via food frequency questionnaires that captured usual diet over the prior 6 months.Four diet quality indices (DQIs) were calculated: American Cancer Society nutrition guidelines (ACS), alternative Healthy Eating Index (aHEI), 2020 Healthy Eating Index (HEI), and the Healthy Plant-Based Dietary Index (hPDI).Scores were categorized into ascending quartiles with higher scores indicating greater concordance to the DQI, suggestive of higher diet quality.Medical chart reviews were conducted at 24 months post diagnosis for disease recurrence and progression outcomes.Multivariable adjusted hazards ratios (HR) and 95% confidence intervals (CI) were estimated.Analyses were further stratified by treatment type.Results: Of the 1,143 participants, 325 (28.4%) experienced NMIBC recurrence and 52 (4.5%) progression.Higher diet quality was associated with lower risk of recurrence when comparing highest to lowest quartiles for ACS (HR0.67,95% CI 0.46-0.98,P-trend.054)and HEI (HR0.71,95% CI 0.51-0.98,P-trend.09).Associations with progression were stronger but did not achieve statistical significance.In stratified analyses comparing highest to lowest quartiles, the inverse associations between diet quality and recurrence were stronger in patients who did not receive mitomycin C (ACS: HR0.60, 95% CI 0.38-0.96,P-trend.02;HEI: HR0.60, 95% CI 0.41-0.90,P-trend.04)compared with those who did (ACS: HR0.92, 95% CI 0.48-1.78,P-trend.74;HEI: HR1.00, 95% CI 0.57-1.76,P-trend.98).The aHEI and hPDI exhibited weaker associations with both recurrence and progression.Conclusions: Higher diet quality at NMIBC diagnosis was associated with lower recurrence risk, particularly in patients who did not receive mitomycin C.These findings highlight the need for further investigation into the role of diet in NMIBC care and outcomes.