Cancer always has a cause, or causes. It doesn’t “just happen”. It used to be a rare disease. Now it is an epidemic. We are surrounded by things created by humans that cause cancer. We shouldn’t be surprised that cancer touches all our lives. We should be surprised that more people aren’t getting angry and doing something to stop it.
Here is a link to a conservative list of things that are known to cause cancer, and things that probably cause cancer from the American Cancer Society: http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/GeneralInformationaboutCarcinogens/known-and-probable-human-carcinogens