Question re insurance denials and how to deal with them

Hello. I have been newly diagnosed with what is probably mets to the lungs. I'm in the middle of a month long process of testing, ever since I was told I had a nodule in my R upper lobe lung. I was blessed in that we were following up pneumonitis (secondary to radiation in early 2016) w/CT scans and we found this nodule in the lung that had not been there in the previous CT scan, so probably have caught it early. The next step was a needle biopsy which showed the nodule was cancerous but, due to the small amount of tissue, not where in the body was the source, though it has triple negative characteristics that would be consistent w/my previous breast cancer.

My pulmonologist had already ordered a PET scan to be done a week after the needle biopsy, but my insurance company denied coverage for the scan and the hospital cancelled the appointment. Since the needle biopsy came out positive, my oncologist then ordered the PET again since it would be needed to inform the surgeon for my lung surgery, as well as to see if there is more cancer in the lung or anywhere else. The insurance company denied coverage, again, and I told the hospital not to cancel the scan as I would self-pay. You can imagine my feelings toward the insurance company at that point, since I had a definite cancer diagnosis. How could they deny my treating doctors the information needed from the PET? My oncologist did a peer to peer appeal and they continued to deny. I don't know what reason they gave for the denial. I am going to call them myself to continue working on an appeal.

Do any of you have any words of wisdom re this denial and how to handle it? What has been your experience with PET scan denials?

I just got the results from my self-paid PET and it shows that in addition to the 2.3 x 1.6 cm nodule we knew about, there are an additional 2 smaller nodules nearby (1.8 x 1.3 cm and  a 6 mm). There is also an indeterminate 3 mm nodule in the upper lobe of the left lung which the pathologist said is too small to be fully characterized on this PET. So, the information gathered from this PET is key for my surgeon and oncologist--there doesn't appear to be anything suspicious in other areas. I'm glad I went ahead with the self-pay, since surgery is set for next week, but I don't look forward to paying out almost $2,000 that the insurance company should be paying.

Do you have any suggestions as to how to approach the insurance company about this denial?

Thank you for any ideas/advice you may have.