Diet quality and prognosis in patients with non-muscle invasive bladder cancer: the Be-Well Study

OBJECTIVE: To evaluate whether diet quality around the time of diagnosis is associated with risks of recurrence and progression among individuals with non-muscle invasive bladder cancer (NMIBC). METHODS: We conducted a prospective cohort study within a large integrated healthcare system. A total of 1,143 adults with newly diagnosed primary NMIBC were enrolled between 2015 and 2019. Dietary intake 12 months prior was assessed using food frequency questionnaires. Four diet quality indices were calculated-American Cancer Society guidelines, alternative Healthy Eating Index, 2020 Healthy Eating Index (HEI), Healthy Plant-Based Dietary Index-and then categorized into quartiles (Q). Recurrence and progression were determined through chart review approximately 2 years after diagnosis. Kaplan-Meier curves visualized recurrence-free survival, and multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) were estimated, with analyses stratified by treatment. RESULTS: Among the 1,143 participants, 325 (28.4%) experienced recurrence and 52 (4.5%) had progression over 2 years. Higher diet quality was associated with lower recurrence risk for the HEI (Q4 vs Q1: HR=0.72; 95% CI, 0.52-0.99). In stratified analyses, lower recurrence risk was more pronounced among patients who did not receive intravesical chemotherapy mitomycin C (Q4 vs Q1 HR=0.60; 95% CI, 0.41-0.90). No associations were observed for progression. CONCLUSIONS: Of the four diet quality indices, the highest HEI quartile was associated with lower NMIBC recurrence risk, particularly among patients not treated with mitomycin C. Diet quality may be an important modifiable risk factor in NMIBC survivorship.