62 male with tyriod cancer

Hello, I have a question regarding thyroid cancer and I would like if someone could advise me on what to do in this situation. Two years ago, my father was diagnosed with Stage 3 Hürthle cell thyroid cancer. After his thyroid gland was removed, he underwent radioiodine therapy, which was successful as his Tg hormone level dropped below 1. A scintigraphy showed clustered spots on his lungs, and one year later, he received radioiodine therapy again (both doses were described as strong). After the second therapy, his Tg level rose from 2.4 to 4.7 within the three months between the therapy and the follow-up. I should mention that his TSH was insufficiently stimulated at the time of the therapy because he was called in for treatment a week earlier (holiday season), so the low-iodine diet did not have its full effect.

Please, please tell me how alarming this situation is. The doctor managing his disease scheduled a follow-up in three months to consider an additional scan based on the Tg level at that time.

I am terrified that my father will die in a year or two and that I won't be able to do anything. Thank you very much in advance. 🙏