Chances are, you will have to change facilities - that's the way it
usually works.  You can sometimes have 'out of network' benefits, but
these tend to be not so generous & charges are often not discounted at
all as the insurance company has no agreement with them.

I don't know if the doctor is tied to the facility or if the doctor
could remain in network & you'd just have to go somewhere else for
radiation??

I've never seen an insurance that would keep you on past the
termination date of the policy.  I am not an insurance professional but
experienced a lot through my husband's odyssey.

We switched from a PPO to Kaiser just when Socks had been scheduled to
restart chemo.  Based on how well our transition worked, I'd suggest
you obtain the company's group # at the new company in advance (HR can
help).  Then call the new insurance company or provider & explain the
situation.  In our case, we had an appointment for Socks with his new
primary care physician the very day the new insurance went into force.
The primary care guy gave him an immediate referral to oncology & he
didn't miss a beat.  It was actually a very positive experience despite
some initial anxiety.

Best wishes for a seamless transition if your company changes.  Your HR
rep is your friend.  

Fig