In a study of over 64,000 heavy long term smokers researchers found no increased chance of getting lung cancer from cannabis, infact, they found the chances slightly dropped, not to mention THC can control cell division.

And THC doesnt kill brain cells, it's keeps the healthier ones alive for longer, promoting the theory that even smoking cannabis can increase life time.

If you got cancer from smoking weed - you'd be one very unlucky person.