Objective: To describe cancer survivors' beliefs about the causes of prostate, colorectal or breast cancers.

Methods: A survey of beliefs about cancer causation was completed by 670 cancer survivors (416 with breast cancer, 165 with prostate cancer and 89 with colorectal cancer) enrolled in a population-based study in Colorado. Categorical analysis was used to describe associations between participant's beliefs about the cause of their cancer type, both in themselves and in others, and personal characteristics, including gender, age, and familial cancer risk.

Results: Cancer survivors most frequently reported genetic factors, smoking, environmental factors (e.g., pollutants or occupation), and psychosocial factors (e.g., stress) as causing their type of cancer. Respondents underestimated the importance of behavioral factors that are known to be associated with increased cancer risk, such as obesity and physical inactivity, while overestimating the importance of stress and environmental pollution.

Conclusions: Cancer survivors' beliefs about what causes cancer are substantially different than those of experts. Because those affected by cancer should be well informed about the causes of cancer, educational efforts are needed, especially regarding the importance of factors that can be modified to reduce cancer risk.