Association between selected dietary scores and the risk of urothelial cell carcinoma: A prospective cohort study

Studies investigating the association of food and nutrient consumption with the risk of urothelial cell carcinoma (UCC) have produced mixed results. We used three common dietary scores, the Mediterranean Diet Score (MDS), the Alternate Healthy Eating Index 2010 (AHEI-2010) and the Dietary Inflammatory Index (DII) to assess the evidence of an association between diet and the risk of UCC. Over a median follow-up time of 21.3 years, 379 incident UCC cases were diagnosed. Dietary scores were calculated using data from a 121-item food frequency questionnaire administered at baseline. We used Cox models to compute hazard ratios (HR) for the association between dietary scores (per one standard deviation) and UCC risk. In order to reflect overall adherence to a healthy diet, a metascore was constructed by summing the quintiles of each of the three scores. None of the dietary scores was associated with the risk of UCC overall. A healthier diet was found to be inversely associated with the risk of invasive (MDS: HR = 0.86, 95% CI: 0.74-1.00, metascore: HR = 0.84, 95% CI: 0.71-0.98), but not superficial disease (heterogeneity between subtypes p = 0.04 and p = 0.03, respectively). Results were consistent but weaker for the DII and the AHEI-2010. We found some evidence of effect modification by smoking, in particular for the metascore (Current: HR = 0.77, 95% CI: 0.58-1.01, Former: HR = 0.77, 95% CI: 0.64-0.92, Never: HR = 1.01, 95% CI: 0.81-1.26, p for heterogeneity = 0.05). A healthy diet may be protective against the risk of invasive, but not superficial, UCC. Promoting healthy dietary habits may help lower the risk of invasive UCC, especially for current and former smokers.