Most preparations of chewing tobacco are smoke or fire cured. The process still introduces many of the byproducts that are created during the combustion of dried organic material.

The most prominent example of chewing tobacco that isn't smoke cured would be Scandinavian-style snus. There's pretty compelling evidence that snus is not associated with oral cancer[1], or at the very least the risk is substantially lower than traditional chewing tobacco.

[1] https://onlinelibrary.wiley.com/doi/full/10.1046/j.1360-0443...

Unless nicotine gum has a similar association, it's probably the same generic cause.

That may be carcinogenic in another way. It's my impression that nasally ingested dry snuff tobacco is not as strongly associated with cancer as smoked or chewed tobacco. That said, it's hard for me to trust anything I read suggesting that, since I can't rule out the possibility that the tobacco industry has corrupted anything I might read suggesting it.

https://en.wikipedia.org/wiki/Snuff_(tobacco)#Health