Smoking May Account For Link Between Serum Total Carotenoid Levels And Bladder Cancer Risk
Bladder cancer risk appears to be inversely related to serum total carotenoids, although cigarette smoking, a strong risk factor for bladder cancer, may account for this inverse association, new research suggests
It is uncertain whether the intake of micronutrients is protective against bladder cancer; furthermore, previous studies investigating the effects of serum vitamin levels on bladder cancer risk have produced equivocal results.
To evaluate this issue further, Abraham M. Y. Nomura, MD, with the Japan-Hawaii Cancer Study, Kuakini Medical Center, Honolulu, United States, and colleagues examined a cohort of 9,345 Japanese-American men from 1971 to 1977.
Upon examination, blood specimens were obtained and serum was frozen. Among the participants, 111 new cases of bladder cancer were identified over a surveillance period of more than 20 years.
The stored serum and that of 111 age-matched controls were then tested for levels of certain micronutrients, including lutein, zeaxanthin, anhydrolutein, alpha-cryptoxanthin, beta-cryptoxanthin, lycopene, dihydrolycopene, alpha-carotene, beta-carotene, total carotenoids, retinol, alpha-tocopherol, beta-tocopherol, gamma-tocopherol, delta-tocopherol and total tocopherols.
Statistically significant inverse linear trends in bladder cancer risk were found for alpha-carotene (p <0.01), beta-carotene (p = 0.03), lutein plus zeaxanthin (p = 0.03), beta-cryptoxanthin (p = 0.04) and total carotenoids (p = 0.02). However, after adjustment for pack-years of cigarette smoking, none of the inverse trends remained significant.
"Retinol, and total and individual tocopherols had no effect on bladder cancer risk with or without adjustment for cigarette smoking," Dr. Nomura and colleagues note. "Tocopherol values were also adjusted for time since the last meal to control for variations in postprandial tocopherol levels but the results did not change," they add.
According to the researchers, their findings suggest that cigarette smoking, which is a strong risk factor for bladder cancer, may account for the inverse association with individual and total carotenoids.