Beliefs about the cause of cancer change over time and may predict decisions to use specific treatment including complementary and alternative medicine and IO. Copyright © 2015 John Wiley & Sons, Ltd.

Patients' lay theories about the cause of their cancer may influence patient behavior and adjustment, they have also been found to differ substantially from scientific evidence of cancer risk factors. This report describes beliefs about genetic causes of breast cancer, among 522 recently diagnosed breast cancer survivors participating in an observational study. Patients were asked to respond to an open-ended question about the cause of their cancer. Causes mentioned included family history, genetics, lifestyle, reproductive and environmental factors, often in combination. Of particular interest we found in total, 31% of women described inheritable causes, including family history, genetics, and specific genes. Lay theories about cancer's cause appear to have evolved to include new information about breast cancer genetics including BRCA1/2, epigenetic influence, and other mutations. Other causes seen in prior reports are also described and were used in many cases in combination with genetic explanations. We present evidence that genetics and family history appear to be particularly satisfying answers to questions of cause for many women with breast cancer.These findings have implications for those seeking to educate and counsel breast cancer patients with and without a family history of cancer.