# BLOSSOM Dietary Habits and 1-Year Intravesical Recurrence in High-Risk Non-Muscle-Invasive Bladder Cancer Treated with BCG

## TL;DR

This study explores how diet might affect bladder cancer recurrence after BCG treatment, finding possible links to leafy greens and certain minerals, but results need confirmation in larger studies.

## Contribution

The study is the first to explore dietary associations with bladder cancer recurrence after BCG therapy using detailed dietary recalls and statistical adjustments.

## Key findings

- Higher intake of leafy green vegetables showed a nominal inverse association with recurrence.
- Energy-adjusted zinc and magnesium intakes were nominally linked to lower recurrence risk.
- The cohort had low adherence to a Mediterranean-style diet and many participants were overweight.

## Abstract

Non-muscle-invasive bladder cancer can recur after standard intravesical Bacillus Calmette–Guérin (BCG) therapy, leading to repeated cystoscopies and procedures. Because urinary metabolites from foods may influence inflammation and immune responses, we prospectively recorded diets in BCG-naïve patients with high-risk disease. Using repeated interviewer-administered 24 h dietary recalls during the first year of BCG treatment and follow-up, we examined whether food groups, specific foods, or nutrients were linked to recurrence within 1 year. In this small cohort, higher intakes of leafy green vegetables and selected minerals showed nominal inverse associations with recurrence in exploratory analyses, but the findings require confirmation in larger studies. Because the cohort was small, the results are intended to inform hypotheses for future research rather than to provide definitive evidence for clinical practice. Many participants were overweight and had low adherence to a Mediterranean-style dietary pattern, highlighting a potential supportive-care gap.

Evidence on modifiable post-diagnosis factors influencing outcomes after intravesical Bacillus Calmette–Guérin (BCG) therapy for high-risk non-muscle-invasive bladder cancer (NMIBC) is limited. In this exploratory, feasibility-focused prospective multicenter cohort (March 2023–November 2024), BCG-naïve patients completed repeated interviewer-administered 24 h dietary recalls; prespecified food groups, selected foods, and nutrients were screened for associations with 1-year intravesical recurrence using Firth’s penalized logistic regression adjusted a priori for age, sex, and total energy intake, with false discovery rate control within each exposure family. Forty-six patients were enrolled; 41 had evaluable recurrence status, including 8 recurrences (19.5%). Participants were predominantly overweight (mean body mass index (BMI) 28.4 kg/m2) and had low adherence to a Mediterranean dietary pattern (median Mediterranean Adequacy Index 2.25). No dietary exposure met the within-family false discovery rate threshold; the smallest q-value was 0.361. Nominal inverse associations were observed for leafy green vegetables (OR per 1 SD 0.385; 95% CI 0.101–0.972) and for energy-adjusted zinc (OR 0.280; 95% CI 0.069–0.802) and magnesium intakes (OR 0.260; 95% CI 0.045–0.872), but these did not remain significant after FDR adjustment. These exploratory signals warrant replication in larger, biomarker-informed cohorts incorporating dietary biomarkers and immune profiling during BCG. Given the limited sample size and low number of recurrence events, these findings are strictly hypothesis-generating and should not be interpreted as evidence of definitive protective or risk dietary factors.