Breast cancer may be likelier to spread to bone with nighttime dim-light exposure. Exposure to dim light at night, which is common in today's lifestyle, may contribute to the spread of breast cancer to the bones, researchers have shown for the first time in an animal study. Source 7z.
Despite this, I still believe that a lot of cancer cases (Including breast cancer) originated from a generational trait of eating specific foods, such as GMOs. Basically if that is true it can lead to more "Likelihood" of certain cancer cells to activate due to sensitivity of the environment.