My husband was on sutent for 23 months then it stopped working. he then tried afinitor which while it kept the tumor from increasing caused very severe side effects and he had to be taken off. it was at that time that we investigated the stereotactic radiosurgery (cyberknife) and proceeded. we live in Canada and there are only 3 locations that have this equipment. we had to pay ourselves for Phoenix as the locations in Canada said they didn't have experience in radiating mid chest tumors.
at the time of the cyberknife radiation my husband was not on any drugs... he still is drug free as his mediastinal tumor was the one causing all the problems. some small lesions and a couple of small tumors are still in the area but not growing.
i don't think that it is necessary to stop the drug while having the radiation but that is determined by the radiation oncologist. i suggest that you talk to your oncologist and even if he is not too keen, investigate on your own. it worked for us and the tumor is dying. your case sounds much like ours.
keep me informed.