Well it is cannot say as reversible I guess. Every day cancer cells build in a human body but since the body's immune system is capable of screening and catching all those cells and destroy them everyone will not get a cancer. Some chemicals cause changes in cells and genetic material which can result in a cancer and those toxins are also removed by body by molecules called antioxidents. Antioxidents are in several forms they are synthesized within the body as well as some well knows substances are there which has antioxident activity like vitamin E, C, A so there is a protective action against cancer but it is not true to say it cures 100%. So it is protective if people take diet which contains lesser amount of chemicals and take fresh fruits an vegetables which contain lot of vitamins. It will boost up the immunity as well.