PSMA Scans and False Positives

[Jeffdanger]

So I saw my MO yesterday to review my ongoing treatment of Xtandi and Lupron. Been 3 months so far with no real side effects except hot flashes. My PSMA scan showed prostate and one met to sacrum. Prostate treated with 28 rounds of EBRT. MO says since sacrum is so close to prostrate it might have been a scattering or reflection and no met at all meaning the cancer was contained in the prostate with no mets. Anyone have any idea of the amount of false positives in this test any any way to verify?

[Tall_Allen]

What was the SUVmax?

[Jeffdanger in reply to Tall_Allen]

Here are the findings:

Study Result

Narrative & Impression

EXAM: PET/CT PSMA PROSTATE IMAGING STUDY

STUDY COMPLETED DATE/TIME: 1/25/2023 4:21 PM.

CLINICAL INDICATION: Malignant neoplasm of prostate

PRIOR STUDIES: No prior PMSA studies have been performed.

CORRELATIVE STUDIES: There are no pertinent prior imaging studies available for comparison.

TECHNIQUE: A low-dose CT scan was performed for attenuation correction and anatomic correlation only. Subsequently, the patient received an IV injection of 9.3 mCi of F18-DCFPyL (PYLARIFY), a prostate-specific membrane antigen. After an initial uptake phase of 60 minutes, positron emission tomography images were obtained from the mid thigh to the vertex of the skull. CT, PET and fused images were reconstructed in transaxial, coronal, and sagittal projections and interpreted from a workstation.

FINDINGS:

*REFERENCE VALUES:

-Descending aorta (blood pool) mean SUV: 1.9 SUV.

-Liver mean SUV: 5.4 SUV.

-Parotid mean SUV: 14.8 SUV.

F18 DCFPyL PET:

Physiologic distribution:

-Normal physiologic distribution of tracer is seen in the salivary and lacrimal glands, blood pool, liver, spleen, pancreas, peripheral ganglia, bone marrow, bowel, kidneys and urinary tract.

Prostate:

-There are 2 subcentimeter foci of the hypermetabolic activity at the prostate gland at the posterior peripheral aspect. The focal metabolic activity around right site demonstrated SUV of 35.1 and left side demonstrated SUV of 10.4.

Lymph nodes nodes:

-There is no discrete focal PyL uptake in lymph nodes to suggest metastatic disease.

Skeleton:

-Focal sclerosis of 1.2 cm with increased radiotracer activity at the sacrum demonstrated SUV of 15.5. Additional CT findings:

-Lung parenchymal evaluation, including for punctate nodules, is limited by low-dose CT and non breathhold technique.

Cholecystectomy.

IMPRESSION:

There are 2 foci of hypermetabolic activity at the prostate gland posteriorly, likely correlate with patient's known neoplastic process.

Metastasis (1.2 cm) identified at the body of the sacrum.

[Tall_Allen in reply to Jeffdanger]

With uptake that high and with a sclerotic CT correlate, it is not likely a false positive.

[Jeffdanger in reply to Tall_Allen]

Thanks for looking and commenting. Interesting thing is I had a lumbar mri and a full body ct scan within a month of this test and neither showed any sclerotic areas on the sacrum.

[LongTimeRunning in reply to Jeffdanger]

Bone and CT scans showed a 2.1 cm lesion on my L2 vertebrae in Jan 2023. My PSMA scan in the following April didn't show anything on L2 (only in pelvis). Bone/CT scans latter in the summer show the L2 lesion sclerosis nearly completely resolving (and the trend continued). The L2 was the biggest lesion from my first scans but the only one that didn't show PSMA activity. A false positive? No clue. It presented via scan progression as if it wasn't, unless it was somehow related to the the heavy (for me) barbell squatting I was doing.

[NanoMRI]

Consider 2nd radiology opinion - I have found them to be critical to my decision making.