Insurance Denial

I was diagnosed with Stage 4 prostate cancer that metatisized to the bones. After 18 treatments of chemo my Doctor wanted a petscsn done but because he just put prostate cancer the insurance company refused to approve it. When we called health-first they stated that if the doctor would have put that it metastisized to the bone instaed of just prostate cancer it would have been approved. I told this to my doctor and he said it wouldn't make a difference. That I was in partial remission and he probably would put me on pills to help fight the cancer in the bones but no signs of the cancer being active shows. Meanwhile I had to see another doctor for something else and he took x-rays of my body and they showed up black. He looked at me and said, after telling him what I was told by the oncologist, that if it were him I'd go get a second opinion because from what I see your full of cancer. So what do I do now, call my doctor a liar regarding the petscan. However, I was told from someone in the health field that chemo makes the x-rays show up black. Anyway, I am seeing another oncologist in March. I have no faith in the doctors in florida or the ones that belong to health-first.