There are many homeopathic remedies that can be used to help a person stop tobacco or smoking, again depending on their own individuality. Example in Kent Repertory: Stomach - desires - tobacco - there are 15 remedies and these will need to be considered with other symptoms the patient presents. The same for Stomach - desires - smoking - 9 remedies to choose from. The generals, modatities and symptoms need to be taken into consideration so a constitutional can be prescribed.
Consideration of how strong the vital force is in the person needs to be noted as well. The person on Chemo may be in a very week state meaning caution.
There is a remedy to antidote tobacco as well as additional remedies to cope with cravings. As for as just general, refer to the above info.