His symptoms could be caused by many different diseases or conditions and the smoking and dipping [don't know what this term means] may just be making it worse.
Try to get a detailed description of all of his symptoms, including when they're at their worst. The most common symptoms associated with cancer are: sudden weight loss, fever, night sweats, rapid pulse, extreme fatigue, inability to fight off infections, pallor [unusual paleness of the skin], petechiea [pinpoint bleeding on the skin due to burst capillaries], reduced blood clotting ability [cuts bleed longer], susceptibility to bruising [bruises easily and bruises last a long time], and unexplained swelling including lumps or bumps.
Here's the government cancer site:
There are many other possibilities such as mononucleosis, strep, staph, oral thrush, etc. or a toxin.
Oral thrush: [url="http://www.nlm.nih.gov/medlineplus/ency/article/000966.htm"]http://www.nlm.nih.gov/medlineplus/ency/article/000966.htm[/url]