That particular scare story is decades old, unsubstantiated and not much more than urban legend.

Marijuana smoke does contain mutagenic/carcinogenic substances - but you don't need to smoke as much to get an effect as with tobacco, so the risk is less. But the study I linked to is not about carcinogenic tars, it's about nicotine. That particular risk is not shared with marijuana, and it's just as severe for vaping, gum or patches.