I go to KU Med, and they have always scheduled my PET scans for the day before my next injection.
I started on Sandostatin, then was switched to Lanreotide, and am now back to Sandostatin. It's my understanding these are both slow releasing drugs so I would think they're still working for you. Try not to panic, which is easier said than done... I've been living with metastatic NET since 2007!
Best wishes on your journey!