Many Beliefs About Cancer Risks at Odds With Evidence

ATLANTA, July 26 -- Americans are having trouble sifting fact from fiction on the causes of cancer.

So found a survey by the American Cancer Society, a group that expends much effort, apparently often futilely, trying to dispel myths and misunderstandings about malignancies.

Consider that 39% of respondents believed that "living in a polluted city is a greater risk for lung cancer than smoking a pack of cigarettes a day," reported Kevin Stein, Ph.D., of the cancer society, and colleagues, in the July 26 issue of Cancer. Nineteen percent were uncertain.

They survey also found that 68% of the respondents believed that the risk of dying from cancer in the U.S. is increasing, a statement that is clearly false, the researchers said.

Those claiming to be "very informed" about cancer were significantly more likely to have a higher level of misunderstanding that those rating themselves as having lower cancer literacy, found Dr. Stein, and colleagues.

In the phone survey of 957 U.S. adults with no history of cancer there were 12 false statements presented about cancer risks and prevention, all contrary to evidence-based findings. Participants could agree, disagree, or express uncertainty about the truth of each statement.

The false statements, with percent marked "true" and "don't know," included:

• The risk of dying from cancer in the U.S. is increasing. (67.7% true, 9.8% don't know)
• Living in a polluted city is a greater risk for lung cancer than smoking a pack of cigarettes a day. (38.7%, 18.8%)
• Some injuries can cause cancer later in life. (37.2%, 20.9%)
• Electronic devices, like cell phones, can cause cancer in the people who use them. (29.7%, 24.7%)
• What someone does as a young adult has little effect on their chance of getting cancer later in life. (24.8%, 7.1%)
• Long-time smokers cannot reduce their cancer risk by quitting smoking. (16.2%, 5.7%)
• People who smoke low-tar cigarettes have less chance of developing lung cancer than people who smoke regular cigarettes. (14.7%, 10.8%)
• Personal hygiene products, like shampoo and deodorants, can cause cancer. (13.7%, 15.3%)
• Getting a mammogram, or using a special x-ray machine to detect breast cancer, can cause cancer of the breast. (10.2%, 16.1%)
• Getting a base tan or base coat at a tanning salon will provide protection from skin cancer when you go outside in the sun. (8.4%, 13.2%)
• Underwire bras can cause breast cancer. (6.2%, 30.9%)
• You cannot get skin cancer from using a tanning booth. (6.2%, 18.3%)

The sample was weighted to match national parameters for sex, age (35 to 64), education, race, Hispanic origin, and region of the country. Of the respondents, 86.3% had at least a high school education, and 56.2% reported a positive family history of cancer. Most participants said they were very or somewhat informed about cancer.

A consistent finding was that men were more likely to believe statements to be true than did women. Some research indicates that compared with women, men may be less attentive to and less likely to seek medical information and are thus likely to be less informed, the researchers said.

The study's limitations included a question of the degree to which these findings can be considered representative of the U.S. population.

The authors also noted a lack of strong evidence for some of the study statements (the cell phone issue and personal hygiene products statements, for example), which they termed "difficult to evaluate, probably false."

Despite these findings, the researchers said, it is important to recognize that individual beliefs are not always the most influential determinant of health behavior. For example, one of the most powerful predictors of the use of cancer screening is the healthcare provider's recommendation.

Also, the influence of broader socioeconomic issues (tobacco marketing, limited availability of healthful food choices, and safe venues for physical activity in certain neighborhoods) should not be overlooked.