Agreed, it's whatever you're comfortable with. The best thing you can do is be a strong advocate and if you want something for him, ask for it. Keep in mind however that even with x-rays there can be microscopic mets too small to be picked up on a radiograph. If you really want 100% certainty then a CT scan is the way to go. Costly, but it will pick up things that x-rays can't. However, that test is a double edged sword as Zeus people learned, so you really gotta weigh what you're comfortable knowing, and not knowing, as well as affordability.

Since the thinking is that most dogs with OSA already have micro-mets by the time the cancer is discovered, even if they do have micro-mets but nobody knows for sure, there's no rule that says they will rapidly succumb to the cancer. For example, we didn't do follow up x-rays with Jerry and at 17  months out, that's when two large mets were discovered. Well, those mets couldda been there the whole time, we don't know. What we do know is that he was having a blast all along, and continued to do so, mets or not.

Cancer treatment often feels like a 100% leap of faith, just because there are no guarantees. Follow your heart, live in the Now and you can't go wrong.