The exiled shah of Iran's doctors are "within a day or two" of completing his radiation treatment for cancer and, if things go well medically, could declare him ready to leave the hospital safely by this weekend, medical sources reported yesterday.

One source said the shah "has been up and around and talking about his golf game."

His condition is still "serious," New York Hospital-Cornell Medical Center officials said yesterday, when asked to respond to a banner posted by the demonstrators at the U.S. Embassy in Tehran. The banner read: "Carter is supporting this nasty criminal under the pretext of sick."

According to sketchy public reports, Shah Mohammad Reza Pahlavi has a type of lymph gland cancer that usually is rapidly progressive.

His doctors have not made public and detailed medical reports or evidence for their reported diagnosis of diffuse (meaning disseminated histiocytic lymphoma.)

Such lymphomas generally spread rapidly -- unless they respond to longer treatment than the shah reportedly has had thus far.

The growth in his neck has receded in response to the radiation, it was learned, but his doctors want him to get chemical treatment too, if possible.

Before he leaves New York, his doctors also want to try to remove a gallstone that, according to reports yesterday, has worked its way dangerously into his liver.

This condition makes it dangerous for him to travel, or get further chemical therapy elsewhere.

An attempt to remove the stone could be made "after Thanksgiving," one source said, depending on the state of healing of the area where the shah's gall bladder was removed Oct. 26.

Only the few doctors seeing the shah know what this condition is, and they were not commenting on a timetable.

The doctors, sources said, are expected to try to remove the gallstones either by directing a probe through a tube already in his side or, if this doesn't work, by trying a different kind of probe through a blood vessel. If neither method works -- though they often do -- the shah's doctors have said more extensive and difficult surgery would be needed.