I have been with the same oncologist for two years. The letter says he is out of network from January 1st. I am halfway through a course of treatment and I do not know if I can change plans or if I even should.
What happens to people in this situation? I do not want to start again with someone new.
First: you are not stuck, and you almost certainly have more time than that letter makes it feel like.
Two things to ask about, in this order.
Continuity of care. Most Advantage plans have a transition provision for someone actively in treatment — often 90 days, sometimes through the end of an episode of care. It is not automatic. Call member services, use the words "continuity of care exception", and ask them to send you the request form. Get the reference number for that call.
Your enrollment options. Depending on the specifics there may be a Special Enrollment Period available to you, which would let you move outside the usual window. Whether one applies depends on details I would not guess at from here.
The thing I would not do is switch plans in a hurry to chase one doctor before checking whether the exception covers you. Ask for the exception first.
Adding one practical thing to Sandra's answer: ask your oncologist's office who handles insurance authorizations. That person deals with this every week and often knows which plans grant exceptions readily.
They are also usually willing to write the letter of medical necessity, which matters more than anything you write yourself.
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