I was diagnosed with stage IV metastatic breast cancer by a PET scan on August 31, 2017. Lesions in liver, lymph nodes, parotid gland, and pelivic bones. I was placed on Ibrance/Faslodex therapy for treatment. Progress was followed by monthly cancer antigen tests. The results of the tests showed success in the therapy with levels now lower than when I was first diagnosed. I feel wonderful and healthy. However while 3- month follow-up PET scan showed a decrease in size in the majority of lesions there was a slight increase in size of the original liver lesion. My Dr said this proves the Ibrance was not working and suggested changing me to Afinitor/ Aromasin. Which is the more reliable diagnostic tool? PET scan or blood tests? Should we give the Ibance more time before making a change?