Teresa, I know what you are going through. Its a tough thing to deal with. Once the cancer has touched the brain, your going to see your father act very differently forwards everything. Talk to people who aren't there, remember things that he forgot to do 40 years ago, and many other things. Im 21 years old and watched my mother go through it. It was very hard to me. I sometimes got overwhelmed I just wanted to breakdown and just give up. I learned that she cant help it nor can your father, so my advice to you is to just be easy on him. Be easy on yourself. It will get very stressful but trust me you will get though it. My thoughts and prayers are with you and your father. Good luck with everything and wish you both the best.
Oh btw, I do believe they have found a cure for cancer, but due to greedy people and a messed up government we have, we are still "working" on it. I find it very hard to believe with all the cancer research centers and money that was funded for them that we only have treatments for certain types of cancer. It may work, it may not work, all depends how your body reacts to the treatment.
Anyways I don't want to get deeper into this so just stay strong and hope everything works out for the best.