The previous post is correct in that IL-2 can produce a durable response, albeit, with very low odds. I believe in the range of 5-20% success from what I read.
I took high dose IL-2 last year at 44 and I was in great shape. Very difficult and strenuous treatment. It did not work for me (although I was able to tolerate 18 courses).
If your dad at his age (75) is in excellent shape and he likes the odds, great, IL-2 worth a try but with caution.
You mentioned you can get Sutent/Nexavar for free, then are able to do the trial if they don't work? Your insurance may operate differently in Poland verses the States.
Since the trial drugs Avastin, Torisel, interferon are a different class of drugs compared to Sutent or Nexavar, he still might be able to do the trial. Check with the study doctor what the exclusions for the trial are.
Also, Pfiser (it may hold true for Nexavar as well), has a program that helps low income individuals obtain Sutent. This may apply to your dad if his insurance company will not pay for it. At his age, there is a good chance he would qualify. Google it in Polish to get into the website, maybe your Oncologist will have a contact number in Poland. I have the number somewhere, but it is in the States. Let me know if you would like it. You can private e-mail me if you wish.
Good luck and God Bless both of you.
Krys