I'm sorry to hear your dad has cancer. I'm glad it's curable! I never had chemotherapy, when I had cancer, but I did have radiotherapy after my op. I feel it is fair to warn you that it can make the person feel weak and tired on a short term basis. There are two other 'side effects' that I have to deal with: -
1. It can leave the person feeling depressed for quite some time after, so you will need to keep his spirits up, and
2. My cancer was in the stomach area and the therapy I had, can leave you with problems eating 'acidic' foods and drinks e.g.: - Tomatoes, peppers, certain spices, citrus fruits, apples and pineapples and fruit juices. It can cause diarrhea and severe stomach pains. Even a slice of lemon in a glass of water can cause me severe stomach pains within 30-40 minutes of drinking it. I was up at the hospital for a post op check-up this afternoon & the Dr. told me this would be a permanent problem for me, so I'll have to adjust my diet. So, this side effect can be a long term problem. It may depend on the type of radiotherapy too! There is the low dosage radiotherapy, which involves a short term hospital stay and there is the high dosage kind, (I had this type) which involves a series of appointments as an out-patient for high doses of radiation for a very short time.
Make sure your doctors keep your family well informed, because knowledge is power and will help your dad cope with it better. I hope he makes a full recovery, Chester!
My post-op check-up went

BTW!