The results of a massive eight year study of 30,000 volunteers by the Loma Linda University (their Adventist Health Study-2) were recently published and it found vegans have a 24% reduced risk of cancers.
In the case of younger vegans, the risk is even less: as much as 40% lower. So the sooner you become fully vegan, the lower your risk will be.
Vegetarians did not fare so well, obviously due to the presence of IGF1 produced by animal proteins such as eggs as well as cheese and other dairy produces. Nevertheless, they still enjoy a reduced risk of 12% over carnivores.