Could a doctor refuse a patient's wishes?

In what sense?: You've asked a very broad question here, and i'm not sure what you're getting at. If a patient were depressed, suicidal, and requested to be put to death, doctors would likely refuse these wishes. They would see that the patient is ill and needs help. Doctors are certainly known to listen to patients when going over treatment options for cancer, etc. If i'm missing your point, please re-ask.

Sometimes: Doctors mostly operate to assist the patient with things that will improve their health and well being. Patients sometimes have opinions based upon recommendations of their friends, or their readings on the internet, which would not be beneficial. The reason to go to a physician is to get an informed opinion and if a physician refuses the wishes of a patient, it is probably for good reason.