Fat graft on radiation skin (photo)

Hi there. I have history of sinus cancer and due to my cancer surgery , I have a sunken face. I did a few session of fat graft and usually it do have a significant results. But unfortunately, I do not see any noticeable result for my last session when I compare the pics taken before and after my last surgery. The plastic surgeon told me maybe my skin will not take in fat graft anymore since the last time I did not have any noticeable results.