Pet Scan and Bronchogenic Ca

Had Brachy therapy and Laser for Bronchogenic Ca yet Pet Scan shows nothing.  I have been under impression that it is one of the most accurate test and yet it is negative. Does not even show scar tissue.  Could you please explain.. Thank You

[HeinrikMD]

Hi,

The PET scan detects functional changes. Actively dividing cells (typical of cancer) tend to take up the sugar carrying the radioactive marker. Scar tissue during periods of active inflammation (swelling) would show uptake of the PET marker as well. After this period of swelling, the scar tends to become unremarkable on the PET.

IF the tumor was readily accessible to brachytherapy (and this was definitive/curative treatment), the absence of any findings on PET may indicate cure.

Since the PET detects differences in uptake of the radioactive marker - if the area is extensively inflamed - then there would be no definite area that would stand out - hence, the PET in this case becomes inconclusive.

Another issue to consider is that there are overlaps with uptake levels of the radioactive marker, such that normal surrounding tissue and cancer tissue is not clearly delineated. If you had a PET before and after treatment ,  you could discuss the scenarios above with your doctor and get more substantive answers.