Uncle has cancer and going into dementia?

could this mean he is dying? my aunt called and said he has started acting really out of character, said hes been really grouchy and unsociable and has said some pretty mean things. I was just wondering if this means he may be dying. he has lung cancer that has metastasized into the other lung, the rib cage, 4 lymphnodes in his neck, and the drs suspect it may be in his stomach too.