I can see the Vitamin C doing only good for your father. Sometimes by the time the person gets to the point of using vitamin C intravenously the person's immune system has suffered alot of damage from the cancer, radiation and chemo already...this might be the explaination for your fathers health getting worse for that time. I'm glad you all had the courage to continue on with the vitamin c therapy.
There is also sodium bicarbonate therapy that can be used for cancer. Intravenous Hydrogen Peroxide has been proven to bring people back to health from stage 4 cancer. The Gerson therapy can be complimentary to any cancer therapy. There are many more options that can compliment these therapies.