Optimal PSA for lesion detection with 68Ga-PSMA-11 PET/CT for BCR after RP and RT

A study that looked at the optimal PSA levels for lesion detection for BCR after primary treatment with RP or RT.

PSA and PSA Kinetics Thresholds for the Presence of 68Ga-PSMA-11 PET/CT-Detectable Lesions in Patients With Biochemical Recurrent Prostate Cancer [2020, Full Text] (Click on "Download PDF" for the Full Text)

"Abstract
68Ga-PSMA-11 positron-emission tomography/computed tomography (PET/CT) is commonly used for restaging recurrent prostate cancer (PC) in European clinical practice. The goal of this study is to determine the optimum time for performing these PET/CT scans in a large cohort of patients by identifying the prostate-specific-antigen (PSA) and PSA kinetics thresholds for detecting and localizing recurrent PC. This retrospective analysis includes 581 patients with biochemical recurrence (BC) by definition. The performance of 68Ga-PSMA-11 PET/CT in relation to the PSA value at the scan time as well as PSA kinetics was assessed by the receiver-operating-characteristic-curve (ROC) generated by plotting sensitivity versus 1-specificity. Malignant prostatic lesions were identified in 77%. For patients that were treated with radical prostatectomy (RP) a PSA value of 1.24 ng/mL was found to be the optimal cutoff level for predicting positive and negative scans, while for patients previously treated with radiotherapy (RT) it was 5.75 ng/mL. In RP-patients with PSA value <1.24 ng/mL, 52% scans were positive, whereas patients with PSA ≥1.24 ng/mL had positive scan results in 87%. RT-patients with PSA <5.75 ng/mL had positive scans in 86% and and for those with PSA ≥5.75 ng/mL 94% had positive scans. This study identifies the PSA and PSA kinetics threshold levels for the presence of 68Ga-PSMA-11 PET/CT-detectable PC-lesions in BC patients."

[Emphasis mine]

Djin

Post Edited (DjinTonic) : 2/13/2020 11:17:11 AM (GMT-7)

akai said...
Does that mean that patients with BC should wait for PSA to rise to a certain minimum level before having a scan?
Is GA68 PSMA scan now available outside of clinical trial in the US?

Thanks,

MP

My understanding is that there are locations where you can pay out-of-pocket for this scan. However, it's not (yet) FDA-approved, so AFAIK, the only way to get it without charge is through a clinical trial. My uro thinks that once it gets approval, more locations will invest in the setup.

How long to wait for the scan is an active topic of research. There is some evidence that for post-RP BCR, the higher the G grade and the great the number and extent of the adverse findings in the path report, the earlier you start SRT the better. However, there is no use irradiating use the prostate fossa if the only sources are pelvic or more distant mets, and the higher the PSA, the better chance of revealing all locations on the scan. If you had extensive positive margines, extraprostatic extension, and/or seminal vesicle invasion, you might make a case that the fossa is a likely source of BCR. Recent papers emphasize that there isn't a one-size fits all answer to the PSA for post-RP SRT. The AUA has not changed it's position that post-RP BCR is a PSA of 0.2 and rising. Some are advocating SRT at as low as 0.03 and rising for high-risk cases, which is adjuvant territory.

Other parameters are the time from primary treatment to the onset of BCR and the velocity of the increase.

Other will have to chime in on post-RT BCR. There is the nadir + 2 guideline.

Post Edited (DjinTonic) : 2/14/2020 11:07:26 AM (GMT-7)

trailguy said...
My team says PSA needs to be 3.0 or more to get the OK for an Axumin F18 PET scan. Did that, got the PET and some nice clear pix.

At what point in your treatments did you have the auxumin scan?

Djin

rcroller said...
I had the Axumin F18 PET scan at a PSA of 1.0 with a doubling time of 6 months to find a previously diagnosed negative biopsied bone met (first identified on an F18 choline pet scan with a PSA of 0.1) to be larger and another new met identified in the pelvis. Biopsies aren’t always accurate and PSA isn’t always a reliable indicator of disease progression. Post Axumin I’m on Eligard and Xtandi and hoping they work. Side effects are occurring but glad these drugs and diagnostic tests are available to us. My RO told me the Axumin is owned by the same company as PSMA so until they make their money back on Axumin it’s unlikely the PSMA will be available in the states, unless you are fortunate enough to have the money to pay out of pocket.

Approval for 68Ga-PSMA has the PSMA-11 is expected this year, 2020. Clinical-trial results have been submitted the past few years. I don't know which company/companies have it, but once there is FDA approval, insurance coverage will follow. The companies involved would be foolish not to want approval and more general use as soon as possible -- it's just a question of time before a new radionuclide will come along with better sensitivity. They can charge whatever the market will bear and shouldn't care whether the patient or the insurance pays for it -- the bank certainly doesn't care.

Axumin (18F) will continue to be useful for (1) men who do not produce PSMA and (2) cases where bladder-invasion are suspected, since 68Ga is eliminated via the kidneys, so the entire bladder lights up on the scan (Axumin is metabolized by the liver).

Djin