Wow that is good news for you.
I have a similar yet different situation. Merkel showed up on my forehead, had surgery and at the same time removed 42 lymph nodes in my neck and under chin. Then 30 rounds of radiation. Merkel spread into my bones and was able to do pin point radiation on my sternum, Feemer and Adrenal gland. Waiting for my next PET/CT on April 2. No immunotherapy yet.
I had a liver transplant 2019 so immunotherapy will be a tricky thing to implement considering anti rejection meds.
Good luck to you and stay positive.