Adrenal Cancer

My daughter was diagnosed with adrenal cancer. surgery was performed and thankfully it was fully encapsulated it was 14 cm
so based on these characteristics it was stage 2 the surgeon approached this very agressive he removed the adrenal gland and took a lot of extra tissue once tested the outer portion of the tumor and all of the surrounding tissue was cancer free.
They have started her on Mitotane and steriods. I asked for a pet scan to be performed and was told by the oncoligist that it was premature and it would be done in three months , he feels that because of her surgery and swelling in the area he may get false positives
so he has ordered a cat scan instead and intends on performing the pet scan in three months.
My question is has anyone been told similar things about the pet scan
Im under the impression that the pet scan is the most accurate form of testing for malignant cancer.