This may not apply at all to the nosebleeds from cancer Tx but thought I'd mention in case it might be something to try. I had frequent nosebleeds from early childhood until I was 20. They would last several hours and left me weak and anemic. My mother took me from doctor to doctor but no one had an answer.Finally at age 20 I found a plastic surgeon who said that the veins in my nose were too close to the surface of the skin and that with even the slightest trauma, like blowing the nose would cause the bleeding. So right in his office, he cauterized the veins and the nosebleeds were a thing of the past. You might check with the doctor or a plastic surgeon to see what they think. I sure hope something can be done to help your Dad.