From what I have seen in researching is the body has a method of saving itself; when it is overloaded with toxins it stores them unable to clean them out.
Pathogens find such storehouses a fine spot to set up 'camp' and the body finds itself with a disruption in normal cell production - hence cancer.
When cancer is killed the cells release into the body the toxins and pathogens held there. It is no wonder so many are sick with infections when treatment of cancer is underway.
If this was widely recognized it we would see more surviving. http://jesichashopeathenaeum.com/2017/10/07/the-pandora-effect/