In The Kite Runner, what's palliative mean?

A palliative is something that eases pain and suffering but doesn't cure it. You can also use the word as an adjective. Palliative care is a type of medical care that strives to alleviate suffering and improve the quality of life for patients with serious, complex, or terminal illness.

In The Kite Runner, Amir helps his father through medical issues:

"As you can see, the cancer's metastasized," [the doctor] said. "He'll have to take steroids to reduce the swelling in his brain and anti-seizure medications. And I'd recommend palliative radiation. Do you know what that means?"
I said I did. I'd become conversant in cancer talk.