Secondhand smoke exposure increases bladder cancer risk

Exposure to secondhand smoke, coupled with genetic traits, increases the risk of bladder cancer for nonsmokers, reported researchers from the University of Minnesota Masonic Cancer Center, Minneapolis.

Jian-Min Yuan, PhD, and Li Tao, MD, conducted a population-based study among participants enrolled in the Shanghai Bladder Cancer Study in Shanghai, China. It included 202 patients (101 women) who were lifelong nonsmokers ages 25 to 74 years at the time of their bladder cancer diagnosis between 1995 and 1998. They were compared with a group of 268 lifelong nonsmokers (130 women) of comparable age and gender.

The team used a questionnaire to interview each study participant about the at-home smoking history of their mothers, fathers, and other family members during the participants’ childhood. In addition, they measured the levels of enzymes cytochrome P450 1A2 and N-acetyltransferase 2 on all study participants.

The study, which was presented at the American Association for Cancer Research annual meeting in Washington, revealed the following:

• Lifelong nonsmokers whose mothers smoked more than 20 cigarettes per day for 10 years had a 3.51-fold increased risk of bladder cancer compared with lifelong nonsmokers who were not exposed to secondhand smoke.
• A similar but weaker association with bladder cancer risk was found for study participants exposed to secondhand smoke from the father or other family members living in the same household.
• Study participants working in an office with coworkers who smoked cigarettes five or more hours per day were at a twofold increased risk for bladder cancer.

"When we combined the interview information with the enzyme level measurements, we found that secondhand smoke was associated with more than twofold increased risk of bladder cancer overall, which is a statistically significant finding," Dr. Yuan said. "These findings further suggest that genetic traits may be a factor in bladder cancer risk for a nonsmoker exposed to secondhand smoke. However, more research needs to be done to determine the role of genetics and secondhand exposure on increased risk."