Smoking and obesity raise the risk, and diets rich in fruits and vegetables lower it, researchers find

Smoking, obesity, and physical activity are risk factors for renal cell carcinoma (RCC) incidence and mortality, a study found.

In addition, men and women whose diets are rich in fruits and vegetables had lower RCC mortality rates, but not lower incidence rates. Higher family income and living in an urban area were associated with lower RCC mortality rates in both sexes.

The study findings, which appear in Urology (2008; published online ahead of print), also showed that RCC incidence rates are higher among men, but not women, in places having more urologists.

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A team led by Janet Colli, MD, assistant professor of urology at the University of Alabama in Birmingham where the study was conducted, reviewed data from the Alabama Statewide Cancer Registry and the National Program of Cancer Registries Cancer Surveillance to determine RCC incidence rates for states across the United States in 2003-2004. RCC mortality rates for states during the years 2000-2003 were obtained from one of the National Center for Health Statistics’ databases.

The researchers analyzed these data together with age-adjusted data for the percentage of Americans in each state who were current smokers, obese, physically inactive, hypertensive, diabetic, or individuals who consumed a diet high in fruits and vegetables or drank large amounts of alcohol in 2003-2005. These data came from the Behavioral Risk Factor Surveillance System.

Although a diet high in fruits and vegetables correlated with lower RCC mortality, it did not correlate with lower RCC incidence. Dr. Colli said that these findings suggest that this type of diet may protect against RCC progression, but not development.

Regarding the positive correlation between urologist prevalence and RCC incidence rates in men, Dr. Colli told Renal & Urology News: “Urologists treat males more often than females; hence renal cell carcinoma is more likely to be detected in males incidental to testing or treatment for other urologic disorders.”

She and her colleagues speculated why higher family income and urbanization were associated with lower RCC mortality. “Renal cell carcinoma cases are probably detected and treated at an earlier stage among affluent people because of their greater access to urologic care than people with lower incomes,” they wrote. “Hospitals and health-care facilities are more likely to be located in urban areas. People in urban areas travel a shorter distance to receive urologic care than do people residing in rural locations.” RCC is probably detected and treated earlier in urban areas, which would explain the decreased risk of RCC mortality associated with urbanization observed in the study.