Some tips, he should reduce his breathing see https://normalbreathing.com for example by using the samozdrav comfort device or manual breathing training, this floods the body with oxygen
he should switch to Dr. Johanna Budwigs oil-protein diet, especially the cottage cheese / flaxseed oil mix, this improves cellular breathing. use a winebottle vacuum sealer to keep the flaxseed oil fresh.
Cancer cannot survive in a body flooded with oxygen, therefore combine these two methods for maximum effect.
Incline his bed https://inclinedbedtherapy.com
He should switch to squatting or at least elevate his feet while being on the toilet by using a small foot stool see https://naturesplatform.com , this plays a probably significant role in prostate cancer
get the homeopathic remedies by Dr. Banerji (do an Internet research) for prostate cancer
read Jane McLellands book "how to starve cancer" howtostarvecancer.com
for additional tips see healingcancernaturally.com
All the best for your father!