Two prominent USC cancer researchers believe that a recent, highly-publicized study of bladder cancer is provocative, but leaves some key questions unanswered.
In an editorial that accompanies the study in the May 6 issue of the New England Journal of Medicine, Peter Jones, director of USC/Norris Comprehensive Cancer Center, and Ronald Ross, professor of preventive medicine, observed that the study’s basic premise is powerful.
“Strategies to prevent the most prevalent cancers in the West are remarkably straightforward in principle,” they wrote. “To prevent lung cancer, quit smoking; to prevent breast cancer, maintain your ideal body weight and exercise; and to prevent skin cancer, stay out of the sun. Now comes a seemingly simple way to reduce the risk of bladder cancer, which is the fourth most common cancer among men in the United States: drink more fluids.”
In a study of 48,000 men, Dominique Michaud of the Harvard School of Public Health and her colleagues showed that those who drank six 8-ounce cups of water per day decreased their risk of bladder cancer by more than half, compared to those who drank less than a cup a day.
The problem, said Jones and Ross, lies in showing just how drinking water decreases the cancer risk.
Some researchers believe that since increasing fluid intake increases the rate of urination, the bladder’s exposure to cancer-causing agents in the urine will be reduced.
However, the USC/Norris researchers said, “despite its many strengths, [Michaud’s] study leaves many empty spaces in the puzzle tying the epidemiology of bladder cancer to the urogenous-contact hypothesis.”
In addition, there is still no “clear molecular framework” that would explain how exposure to the presumed carcinogens would cause the bladder cancer, or how increased urination would prevent it.
Finally, Jones and Ross were concerned that the researchers did not collect data on the sources of the water the study’s subjects consumed.
“The importance of the source of drinking water is illustrated by the situation on the southwestern coast of Taiwan,” they wrote, “where the arsenic in artesian-well water is associated with an incidence of bladder cancer that is 10 times as high as normal. The quality of what you drink may therefore be as important as how much (or little) you imbibe.”