can pet results show false positive for bone mets

traceyoconnell

my tumor markers were a little elevated and a pet scan showed multiple lesions. I am awaiting biopsy results. I did not know there were restrictions other than no food 6 hours prior. I ate the day before exercised the night before and morning of. Just curious if that could show extra activity?

Lula73

I'm not an expert by any means, but I was told that the PET scan shows areas of increased glucose uptake (hypermetabolic activity)which can signify cancer and/or mets. Biopsy still needed to confirm.

pajim

tracey, with PETscans it's usually it's "no exercise for 24 hours before". The reason is that the radioactive sugar is picked up by fast-growing cells. And muscles repairing themselves are faster-growing than normal.

That said, if they've spotted problems in the bone, that may be a different matter. I don't know if bone marrow can get excited by exercise or not.

I never had a biopsy but my cancer was obvious (broke one of my vertebrae). Your biopsy will tell the tale.

Nkb

I was told no exercise or anything that could increase my heart rate for 48 hours before PET and super low carb diet for 24 hours before PET (basically greens, protein and yogurt) and then fasting except for plain water for 6 hours before PET. The scan is done with glucose markers.

zarovka

I believe that the risks are 1) that carbs would interfere with uptake of the radioactive glucose and therefore reduce the sensitivity (false negative not a false positive and 2) exercise and other factors can increase is uptake by brown fat (false positive). Brown fat that lights up can make the pet scan hard to read but would not likely cause a false positive on a bone met. They can tell fat from bone. Little harder to tell fat from lymph nodes etc.

What does cause a false positive with bones are fractures. I fell off my bike in July and, apparently, fractured my rib cage in several places. I reviewed my last pet scan with the radiologist yesterday. My rib cage lights up like a christmas tree, but most of them are not mets but fractures. There is one bright spot that is a new met. It's pretty easy to tell the difference when you are looking at the scan. It's very helpful to sit down with the radiologist and look at the scans and understand the judgement calls they make.

I am glad you are getting a biopsy. It's the only way to get the full picture.

>Z<