Understanding Genetic Cancer Risk Might Not Help Smokers Kick the Habit
DURHAM, N.C. -- If smokers knew that they were genetically susceptible to smoking-related cancers, would this knowledge help them stop smoking? New research from Duke University Medical Center shows that in an older, inner-city African-American population the answer is mixed. Smokers who knew they were genetically susceptible to smoking-related cancers were no more likely to quit smoking than those who found out they were not susceptible.
However, this lack of responsiveness to knowledge of genetic susceptibility is not completely a bad thing, said Colleen McBride, Ph.D., study leader and director of the Cancer Prevention, Detection and Control Program at Duke Comprehensive Cancer Center.
"We were concerned that telling smokers that they were not genetically susceptible might undermine their motivation to quit smoking and that was not the case. Unfortunately, being susceptible wasn't strong enough to motivate them to quit either," McBride said.
The study published in the July 2002 issue of Cancer Epidemiology, Biomarkers and Prevention examined 557 African-American smokers with low incomes from an inner-city community health clinic.
"We chose this group to test our intervention because quit rates are lowest among those with a low income," said McBride. "And, African-Americans bear a much greater health burden of smoking than whites. We know that many smokers quit because they are afraid of the health risks. We thought if we personalized that risk for people in our study, that it might convince them to quit smoking."
The researchers randomized the smokers into two groups. The first group of 185 participants received counseling about smoking cessation, a self-help smoking cessation guide and nicotine replacement therapy as appropriate. The second group of 372, received the counseling, guide and nicotine replacement therapy, but also agreed to take a blood test for a gene (GSTM1) that is linked to increased risk for lung cancer. Case studies have shown that individuals with lung cancer are more likely to be missing the GSTM1 than matched controls, and it has been estimated that 35 percent of African Americans may be missing the GSTM1.
GSTM1 is responsible for creating an enzyme involved in detoxifying a number of environmental carcinogens, including those found in cigarette smoke. The researchers likened the enzyme to detergent: if a person lacks the gene, it is as if their body does not have the detergent it needs to clean itself of cancer-causing agents.
"It's a fine line we are walking," McBride said. "If we tell someone that they don't have the enzyme, we aren't saying that if the person smokes he or she will definitely get cancer. Inversely, if we tell someone they do have the enzyme, we aren't saying that person can smoke all they want and never get cancer. We wanted to make sure in our counseling that these points were emphasized."
The participants in the study averaged smoking 15 cigarettes per day, and 59 percent reported attempting to quit in the last year. Sixty-eight percent reported that they believed they would eventually acquire lung cancer if they did not stop smoking, while only 9 percent thought they would still be at-risk for lung cancer if they stopped smoking. Most participants, with an average age of 44, were already experiencing adverse health effects from their smoking.
This high level of concern about cancer and poor health related to years of smoking might be key to why this group didn't respond as well to the knowledge that they might lack a gene that could protect them from cancer, said McBride.
"This group was already afraid of what smoking can and is doing to their health," she said. "Knowledge that they don't have this gene just reinforced what they already knew. Perhaps the next step is to study a younger, healthier group and see what the long-term impact would be."
McBride also said that about 50 percent of the smokers did not understand the feedback of information on their genetic susceptibility; and multiple telephone counseling sessions did not seem to help. She said that future studies should attempt to make results more comprehensible to the public.
"We've just begun to touch on how to communicate genetic make up and health risks to the public," said McBride. "It's difficult to explain the risks to a well-educated person, but it's our responsibility to communicate risk to all patients so they can understand how it impacts their health and take necessary precautions."
The study was funded in part by the National Cancer Institute. Co-authors include Gerold Bepler, H.P. Lee Moffit Cancer Center and Research Institute; Isaac M. Lipkus and Pauline Lyna, Duke Comprehensive Cancer Center; Greg Samsa and Santanu Datta, Duke University Medical Center; Jennifer Albright, University of North Carolina at Chapel Hill; and Barbara K. Rimer, Duke University Medical Center and National Cancer Institute.