Anything that increase hyperplasia will increase the risk of cancer because with the addition of new cells the chance of those cells being cancerous is increased but this is not a direct cause of IGF-1, just an increase in random chance. But IGF-1 doesn''t directly cause cancer in any way and if there is existing cancer cells then increased IGF-1 woud equate to more growth. This is also the case with anything that helps growth as Ray said. So if you have cancer, don't use it. If not, it won't directy cause cancer like tobacco and a host of other things that have a more direct impact.