Metastatic Osteosarcoma to the Lungs

Hello.  My sister (mid-40s) was diagnosed with Metastatic Osteosarcoma in October 2017, underwent chemo, had limb salvage surgery in January, did more chemo after, then had surgery on her right lung in mid-May and surgery on her left lung end of May.  We just found out today that she has new spots in her right lower lobe and right middle lobe of her lung. They also found fluid in her pleural cavity.  Doctor ordered a petscan and for the fluid to be checked for cancer cells. We are hoping that petscan will not show any other metastesis and that the fluid will come back free of cancer so they can proceed with the lung surgery.  If not, I believe she has to go through chemo.  Any words of wisdom from anyone?  Please pray for my sister.