Are prostate PET scans (axumin, PSMA, etc.) still useful for patients on androgen suppression therapy?
The detection rate with this radioisotope is a function of PSA level with sensitivity improving with increased level of PSA. I don't think androgen ablation by itself would affect detection rate unless disease is under control with the therapy
This is good review article in PRO comparing sensitivity and specificity of these newer scans. These scans are changing paradigm in managing patients with rising PSA after RP as are able to detect disease with much lower threshold than conventional scan
The effect of ADT on PSMA expression, which would impact PSMA PET imaging, is a complicated and evolving topic, currently under investigation. It seems that ADT initially increases PSMA expression. But later, ADT decreases PSMA expression (please see some references below), and PSMA may be increased during castration resistance.
Hope et al. "68Ga-PSMA-11 PET Imaging of Response to Androgen Receptor Inhibition: First Human Experience." J Nucl Med (2017) 58(1):81-84.
Writght et al. "Upregulation of prostate-specific membrane antigen after androgen-deprivation therapy." Urology (1996) 48(2):326-34.
The performance of Axumin scans is likely affected by ADT. Below, you can learn about the relationship between the LAT1 transporter and Fluciclovine, and the regulatory effects of androgen suppression. As such, it’s probably unreliable after ADT has been started.
http://www.blueearthdiagnostics.com/technology/amino-acid/
As initial or relapse staging, ADT likely suppresses uptake of tracers and will lead to false negative staging scans. On the other hand, if patients become castrate resistant, there may be a change in the inhibitory effect that ADT has on tumor uptake of tracer.
There is a nice review last year in European Journal of Nuclear Medicine: