Can a PSA bounce be seen shortly after SBRT to prostate cancer oligometastases while on androgen deprivation therapy?  

I would not consider it a "bounce" if it happens shortly after treatment because the timing of a post-treatment bounce is later. If the PSA is higher than pre-treatment baseline soon after metastasis-directed SBRT, then you are likely observing one of two scenarios. First, the pre-treatment baseline...

I have seen a PSA bounce if the PSA is done sooner than 3 months, even while castrate. This is why I do not order a PSA until at least 3 months post any radiation, including to the primary or to metastatic sites. 

Some additional commentary and a clarification on my comment to Dr. @Chaudhary’s answer below: The nuance here is about the target structure and purpose - for intact primary prostate treatment, I agree completely and have also noted these bounces. Literature traditionally describes bounces in...

PSA bounces are more common in SBRT cases. They occur much later than most of us were taught; median of 14 months, i.e., beyond the three-month follow-up time points noted. This is, of course, extrapolated from localized treatment vs oligomets such as an excellent meta-analysis from Germany (Dejonck...

Echoing the excellent points here, I think for a patient with known metastatic disease on ADT with rising PSA 3 months after SBRT is concerning. I have seen bounces for mets directed RT in men who are using SBRT to delay or defer ADT at 3 months, but if testosterone is truly at castrate levels, the...