Diet and renal cell carcinoma

Abstract: Renal cell carcinoma (RCC) represents 80-85% of all tumors of the kidney and is responsible for about 2% of all cancer deaths in developed countries. Its incidence varies among countries, among migrants, and by socioeconomic status suggesting that environmental factors play a major etiological role. There are many biologically plausible hypotheses that could explain why consumption of plant foods or alcohol might prevent or slow the development of this cancer. However findings from epidemiologic studies, mainly case-control studies, are not consistent. In a population-based prospective cohort of over 60, 000 women, included in the Swedish Mammography Cohort (SMC), we investigated the association between fruit, vegetable and alcohol consumption as well as the major dietary patterns, assessed by self-administered food frequency questionnaire (FFQ), and risk of RCC. We identified 122 incident cases of RCC (ICD-9 diagnosis code 189.0) diagnosed between the return of the questionnaire at baseline (1987-1990) and June 30, 2003, by linkage to the Regional Cancer Registry (paper I). In analyses of alcohol (paper II) and dietary patterns (paper IV) the follow-up was through June 30, 2004. Validity of the FFQbased. dietary patterns identified by factor analysis was estimated by comparing to the patterns based on4x7-day dietary records in 129 women from the SMC cohort; reproducibility was estimated in 212 women by comparing patterns from two FFQs filled in 1 year apart (paper III). In analyses of the association between dietary factors and RCC, we used Cox proportional hazards to estimate the risk as rate ratios (RR) with 95% confidence interval. We observed a non-significant inverse association between combined consumption of fruits and vegetables and RCC risk (multivariate RR = 0.55 (95% Cl, 0.25-1.21 for > 5 servings/day compared to <5-6/week); bananas and root vegetables were significantly inversely associated with RCC risk. Women who drank > 1 servings of alcoholic beverages/week had lower RCC risk than did women who drank <1servings/week (RR = 0.62, 95% Cl, 0.41-0.94); the corresponding estimate for women > 55 years of age was RR = 0.44, 95% Cl 0.22-0.88. We identified three major dietary patterns that we named "Healthy", "Western" and "Drinker". The validity of the three patterns was r(Spearman) =0.59, 0.50 and 0.85 and reproducibility 0.63, 0.68 and 0.73, respectively. Higher Healthy pattern scores were only non-significantly associated with decreased risk of RCC (the highest vs. the lowest tertile was RR=0.81; 95% Cl 0.45-1.48 and among women :S 65 years corresponding estimate RR-0.54; 95% Cl 0.27-1.10). There was a suggestion of an inverse association between the Drinker pattern and RCC risk (RR comparing the second and third with the first tertile, 0.56; 95% Cl, 0.34-0.95; and 0.72; 95% Cl, 0.42-1.22 respectively, (p=0.08 by Wald test); the association was more clear among women< 65 years (p=0.02 by Wald test). In conclusion, our findings from this large population-based prospective cohort study, suggested that high consumption of fruits and vegetables might be associated with reduced risk of RCC. Moderate alcohol consumption may be associated with decreased risk of RCC. We identified three major dietary patterns, and showed that identification of dietary patterns using the FFQ and factor analysis is a reproducible and valid method that can be used in nutritional epidemiology as an alternative approach to dietary assessment. Our data do not provide evidence for a significant inverse association between higher Healthy pattern scores and risk of RCC, but suggest an inverse association with higher Drinker pattern scores.