Hello mate.
I'm sorry that 8/9 years after your prostatectomy, this area of concern has materialised.
Had your PSA been always been at undetectable levels prior to the rise? If so, what was that undetectable level, and was the rise to 0.395, sudden or gradual.
AI suggests these are potential reasons for the apparent discrepancy between the two scans.
Sensitivity Mismatch (Micro-metastasis): The PET scan may have detected a small cluster of cancer cells that was too small (less than 5-6 mm) to be seen as a nodule or mass on a regular CT scan.
Resolution/Technical Factors: The PET scan is more sensitive for prostate cancer spread, while a CT scan only shows anatomical changes. A tumor might be "active" (high PSMA expression) but still too small for structural imaging.
Response to Therapy (False Negative CT): If treatment (such as ADT/hormone therapy, radiation, or chemotherapy) was initiated between the PET scan and the CT scan, the cancer cells could have died or decreased in size enough that the tumor is no longer visible on the CT, even if the scan was done 6 months later.
Benign/Inflammatory False Positive (PET): PSMA is not exclusively expressed by prostate cancer. Increased PSMA uptake can occur in benign conditions, such as pulmonary infections, pneumonia, or inflammatory lung processes, which may resolve over 6 months.
Injection Artifacts (Rare): Rarely, focal PSMA uptake in the lungs without CT correlation is caused by small, microscopic clots (platelet-rich thrombi) formed at the site of the tracer injection, which then travel to the lungs.
Clinical Implications:
A PET scan is generally considered more accurate in identifying early spread compared to conventional CT scans. However, the absence of a lesion on a later CT scan often leads to "equivocal" or indeterminate results. Follow-up studies are usually needed to determine if the area is truly negative or if the disease has changed.
I hope this helps.
Edited by member 15 Apr 2026 at 03:49
| Reason: Additional text