Logically, eating a vegetarian diet and drinking various teas will help reduce the risk of cancers or even destroy cancers. This happens for the same reason why eczema can be cured with a few days at a warm beach or with mangosteen (http://eczemafix.blogspot.com).
The reason is this. The cancer cells are stressed with a complex environment. If they do not die they have to change in a way that would make them survive this stress - ie become normal.