It is natural for people to want to know the why someone got cancer and what caused it. As many have eluded to in this thread it could be a multitude of things and possibly a combination of these things.
There is not always a black and white answer. The human body repairs and replicates billions of cells every day and does an incredible job at it. The error margin in normal cell replacement has an error margin of less tha 0.0000000000000000001 % (these zeros are not arbitrary I did the math.)Most of these errors do not lead to anything more than unnoticeable inconspicous changes between neighboring cells. On occasion an error can cause a catastophic change in the cell and lead to a process of events that eventually cause malignant cancer.
Your bodies immune system eliminates and or destroys millions of rougue (potentially cancer cells) every day...wow. Every once in a while one gets through. To say that this process is 99% successful would be catastrophic. If a 99% sucess rate were acceptable that would mean that every single day over 300 planes would crash, over three hundred thousand cars would be in accidents and more than one million pedestrians would be injured in car accidents!! So your body is more than a hundred million times more efficient than 99%.
If you can find out the why and what and eliminate it that is wonderful but, if after asking and looking you come up lacking just remember on rare occasions bad things happen to good people.
Just my 5 cents worth.
Cheers,
Mike