Yes, that's a real risk. Check out this thread, which /r/Nootropics has wisely kept stickied for a while: https://www.reddit.com/r/Nootropics/comments/pbz9mx/warnings.... It's an anecdotal report of nootropic use not necessarily inducing cancer but potentially making cancer spread much more aggressively.

One definitely shouldn't try nootropics without very thoroughly studying the risks. I sometimes take certain (seemingly) low-risk ones, like racetams combined with choline supplements. (For example, oxiracetam + alpha-GPC.)