I disagree with Gary, there is a great deal known about the causes of cancers, particularly the genetic alterations and subsequent mutations that lead up to malignancy. The beginnings of genetic mutation which must occur about four times, passed on to daughter cells and then their progeny, to become a malignancy are generated by a variety of things. The most common are chemicals, radiation, viruses, and inherited genetic defects. In oral cancers the most common cause, chemicals (via tobacco by products under combustion) is seconded by alcohol, which even though a chemical, acts more in synergy to facilitate the access of tobacco carcinogens through to the cells by thinning the cell wall itself, (smoking and drinking are a common combination in our society), and virals, particularly the same virus that causes 95% of cervical cancer, HPV 16 and 18. Most of the lecturers that I have heard and doctors that I speak with blame the majority of the 25% non-tobacco user patients on virals, but there can be other reasons. A very small percentage have an inherited gene p-53 defect, and there may be other environmental factors yet to be identified which will contribute another small percentage. Retrospective inquiry seldom yields satisfaction to cancer patients. If they had a lifestyle habit that caused their malignancy, they fall prey to self-recrimination and beating themselves up, to no good end. If they were virally infected there is no way to tell where in the chain of sexual partners (the most likely transmission of HPV) they could place the blame as it could have been decades before. None of this leads to satisfactory knowledge that can be used to any purpose. The important thing now is the future. Making good decisions about treatment and fighting to beat the disease. Looking for cause yields nothing and does not help treatment. Except for smokers, the rest of us will likely never know for sure........