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Can pet scans give false positive?

Posts: 25
Joined: Aug 2011

My mom had full body PET CT scan ystday - 1yr followup after surgery,chemo and radiation treatments for RC IIIc stage.
It said "Impression: Metabollically active focus along right internal iliac vessels with small nodular soft tissue-this could be the metabolically active lymph node - needs interval followup for stability" and "comments: Interval appearance of lesion along the right internal iliac vessels is of concern for metastatic lymph node. suggest clinical correlation/followup for same" and increased FDG conc. seen in right internal iliac vessels -SUV 6.5

And her CEA was 2.55,2.65,3.05,3.32,3.65 (with <4.3 being normal in the lab here) with 3 months interval.

Showed the scan report to another Onc since our Onc is not available for another 4 days. He said, sometimes pet is more sensitive, with CEA being less than normal - lets wait and see, you can take blood test after 3 months and another pet after 6 months.

Am really concerned as to what this would be and if PET can show something wrong.
Should we wait for 6 months or else what are the alternatives?

Thanks for sharing any useful info on this.

Posts: 72
Joined: Nov 2010

They can show false positives just as easily as they can show false negatives, and are not the be all and end all to detection, progression, etc. Lot of variables that are taken into account, CEA, Scans, etc.

son of hal
Posts: 117
Joined: Mar 2011

Hi Bala- Just to ease your mind a bit, yes PET scans can be less than accurate when determining metastatic changes. When I was first diagnosed with RC II I had a PET as routine staging process. The report showed that I "lit up like a Christmas tree" with several nodes in distant places appearing much larger than normal. They originally believed it may be Lymphoma as well as the RC so they did a biopsy of the furthest and largest in the axila. It was negative for cancer. They waited a few months then did another biopsy of a large node in the groin and that too was nedative. They put on the report, "undetermined cause". Three years later I still have some enlarged nodes on a CAT scan but PETs no longer lite up. My point is while the test seems very "scientific" with the equipment and process, it is not perfect and therefore never a sole, determining factor. Relax for now. Enjoy the holidays and think positive that is just a fluke for now. Worrying about what you cannot control doesn't do anyone any good.
Take care, CJ

Posts: 2215
Joined: Oct 2011

Yes. It happened to me once. That is why my new doctor always does ct scans first then a pet if something shows up as a mass on the ct.

dmj101's picture
Posts: 527
Joined: Nov 2011

yes, the do more often return false postives than patients know..
I for one.. had a false showing bone and spleen and tonsil..
Many thing can contribute to false postives that are good to be aware of a broken or cracked bone that is healing.. . a cold/alergies..

The CEA can also be false..anything below 5 is considered normal.. mine has always been 2 even when I had lots of cancer.. and presently it is undetectable and we are still treating cells in my lungs that we know are colon.

False reading can seem really scary.. just be sure you have a dr interpreting the reality..

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