Nicotine is not carcinogenic and neither are nicotine products like patches or gum. Nicotine products are distinct from tobacco products, and tobacco contains a lot more than nicotine, and that cocktail is both carcinogenic and more addictive. That's why nicotine products are used for nicotine cessation, they are strictly less harmful and easier to quit. (That doesn't make nicotine safe but it's in an entirely different league than tobacco. Nicotine products almost certainly won't be the reason you die, whereas tobacco products often are.)