(I treat patients at a cancer center, but opinions are my own and not those of my employer.)

I fully encourage any patient who wants another opinion to get one. Definitely really good advice to seek one out before you start on your treatment plan, if it can be done without undue delay. I think of planning cancer treatment like lining up to take off for a flight: some plans even if imperfect are more dangerous to alter than continue if they've already been put in motion. There are--rarely, thankfully--times where we don't end up concurring at all in the diagnosis or treatment, and this is all best sorted out before the first treatment.

But a second opinion isn't a waste just because it agrees with the initial plan. In my experience, that's actually the most common outcome, and I think it's a really good thing if a second opinion can give deserved reassurance that your original team is doing everything by the book. For many common cancers, there's consensus as to the most appropriate first-line treatment because there's peer-reviewed evidence and agreement on how to apply that evidence. When all of it points towards an effective treatment, down to a standardized dose and schedule, and it's a really good thing!

There's some subtlety that arises when there isn't a clear consensus as to which of (say) two reasonable approaches used by different comprehensive cancer centers is best. If you look at guidelines, both of those approaches would be listed as appropriate, but patients might be recommended one plan at center A and a different one at center B.

What it can come down to is that center A delivering treatment A demonstrates comparable results to center B delivering treatment B. In that scenario, if a patient lives down the street from center A and travels hundreds of miles to see me for a second opinion at center B, I would almost always agree with getting treatment A at center A. Not because I'm trying to manage what center A would think of me, but because I'd truly believe it's in that specific patient's best interest. First, all else being equal, I'd have no grounds to think that traveling hundreds of miles to get treatment B at center B would be better than staying local. Second, in general, I'd strongly doubt that getting treatment B at center A (which wouldn't be the plan they'd have the most experience with) would be superior to getting treatment A at center A.

And, yes, I absolutely have recommended when appropriate for patients to transfer care to our center, and I have also recommended when appropriate for patients to leave our center to go elsewhere (for example, for a particularly promising clinical trial option). I've seen every one of my colleagues do the same without hesitation.

This is all just from one person's perspective, of course. I know patients and families can come from different and totally valid vantage points. But to sum it up, please don't worry about managing your doctors' emotions about getting a second opinion, and find a place where you can be confident that the folks giving you their second opinion likewise aren't thinking about managing your doctors' emotions. Hopefully, they'll earn your trust that a concurring opinion means they really do think your original team has laid out the plan that's best for you.