I'm afraid I spoke too soon the other day when I wrote that Dad's version of cancer fortunately comes without much pain, and that therefore we would probably never have to touch the morphine supply in the refrigerator.
Yesterday, he started rubbing his scalp more frequently in the spot where the tumor is located. We asked if it hurt, and while—in his current mental state—he does not reply to any question with something so simple as a "yes," that appeared to be the gist of his response.