sinus problems question

My husband had stage 4 tonsil cancer back in 2011. he completed chemo and radiation and has been ned since. Recently he has been geeting stuffed up and his sinuses have been draining. He chalked it up to allergies. I finally talked him into going to his ENT. Well the ENT put him on antibiotics - aid his sinuses were really plugged. But he also ordered a cat scan based on his prior hisotry. I called his oncologist and he told me there was very little chance his cancer would come back here based on his treatment. But of course I am anxious and want this cat scan done now! The ENT said there was no rush..Has anyone else experienced metasisis to the sinus area after other head and neck surgeries? He has no lumps, headaches, pain or soreness. Just sounds plugged up. Looking for any advice or knowledge others have.