My throat has been hoarse for about 3 months and I have very little appetite. What could this be? I have been a heavy smoker and drinker for the last 25 years

Even. Even though your hoarseness could be caused by something as common as gastroesophageal reflux, it is extremely important that you see a doctor as soon as possible for your symptoms. Prolonged hoarseness along with decreased appetite and a history or drinking and smoking could very well be a laryngeal or throat cancer. You should see an otolaryngologist (ear, nose, throat specialist) for a complete laryngeal exam to assess your hoarseness.
Although. Although hoarseness is a very nonspecific symptom in general presenting as a symptom of a list of benign conditions including voice overuse, acid reflux or neurological disorders, the biggest concern with hoarseness is among smokers. The combination of smoking and alcohol is synergistic (they both act together more potently) in promoting cancerous growths of the mouth throat and lungs. Symptoms of long standing hoarseness and decreased appetite in a heavy smoker and drinker warrant a visit to an ear nose and throat doctor because of the high risk of throat cancer.