Father dying of cancer but has perforation of esophageaus and Dr.'s won't perform surgery?

My father is terminal with multiple forms of cancer. Doctors have no grasp on how long he may live. He currently is on a vetilator (but awake) and can communicate via writing, eye movement, head nods, hand signals. He has indicated that he wants any measures taken to continue his life as long as possible. Even if the outcome is painful, uncomfortable, or may only last for a few weeks/days then he'd have otherwise. He would rather die TRYING to live, then live waiting to die. The Dr.s in the HUP (philadelphia hosp. sys) have conviended and decided that because of his overall instability, and overall outcome that they will not perform any surgery to attempt to remedy the perofration he currently has. Some of these same Dr.s wrote articles giving detailed descriptions of what should be done for patients just like my dad. It seems the way the Dr.s communicated to my mom that their main reason for not performing any surgery is that his overall life expentacy is very short; therefore not making it worth the cost/time ect. My dad wants the surgery if for nothing else, to get his dying overwith faster. He doesnt want to live for days/weeks on a ventilator laying in a bed. Do the Dr.s have the right to refuse to perform the surgery. Or are they obligated to do it? His insurance will pay for the surgery so cost is not the issue.