Would you consider salvage radiation in a recurrent prostate cancer with a positive pelvic node and high inguinal node on PET/Axumin, but negative inguinal biopsy?

I would treat this patient as having oligometastatic disease to the nodes, similar to the more common scenario of finding 1-3 para-aortic nodes beyond a typical pelvic XRT field.

Assuming no prior radiation to these sites, I would try a VMAT plan as long as skin constraints are met for the inguinal skin folds. I'd use one of the SABR-COMET-10 regimens, like 7 Gy x 5 fractions, every other day just like we do for Prostate SBRT with an intact prostate. Keep margins tight, use 10 MV to decrease skin dose, daily CBCT, full bladder etc. If the nodes are very small and constraints are hard to meet, maybe 6 Gy per fraction—better than nothing.

For bowel, bladder, & rectal SBRT constraints—I'd either use an institutional protocol like from UCLA, or r...

I would have a discussion with the radiologist. Not all that lights up on Axumin is prostate cancer. It can depend on CT characteristics. If it was borderline on Axumin and you have a negative biopsy, I would leave him be.

If it's high inguinal and could easily be covered without additional toxicity (say co-planar with your prostate CTV and obturator volumes), then it's not unreasonable to treat with an extension of standard salvage radiation to cover the ipsilateral inguinal region as well, with standard dosing. Would SIB Axumin positive LNs to highest tolerated dose.

This assumes that the pelvic and inguinal LN are on the same side. If they're not, I would be less likely to cover the inguinal LN, especially in the setting of a negative bi...