RARP 2016. 3+4. GG2. Extensive EPE.
last 2 uPSAs 0.08 & 0.115.
Prostate MRI. FINDINGS: Status post prostatectomy.. There is a new small enhancing nodule in the left superior prostatectomy bed in the region of the left seminal vesicle. This measures approximately 0.9 x 0.4 cm (image 17, series 6 and image 49, series 9).). There are no enlarged or morphologically abnormal lymph nodes. The urinary bladder is unremarkable. No suspicious osseous abnormalities are identified. Stable small postoperative fluid collection in the left external iliac region.
18F-DCFPyL PET/CT OR Gallium 68 PSMA Pet/CT scan 
PSMA PET/CT results
Medicare did not pay for the Pylarify used in PSMA PET/CT Scan
Result of PSMA /PET/CT
Too early after HIFU for PSMA PET/CT Scan?
If confirmed by a PSMA PET/CT (SUV max>10) I don't think you need a biopsy. You may be able to get away with prostate bed RT and no ADT.
Even if not PSMA avid would Bx still provide additional info due to heterogeneity of PCa and it’s been six years?
if only lesion, would focal ablation be a consideration?
No. Micromets in prostate bed are too small to see. Have to treat the entire bed.
A prostate bed focus might possibly represent a local recurrence which would not have the same implication as a metastasis. A local recurrence, theoretically would have a chance of cure, by a local ablative procedure such as surgery or as accepted, radiation therapy. ------- Though, it is not available in the US and still experimental, there is a novel approach, contingent on the solitary focus being PSMA avid, of doing PSMA radioguided surgery - with one of the same advantages that prostatectomy has as an initial curative intent therapy, that if surgery fails, one still has salvage radiotherapy with or without ADT in the toolbox. Admittedly, this is still in its infancy, and has yet to proven. And admittedly testing has been, via conventional imaging detection, on lymph node metastasis with no significant success - but lymph node metastasis is not the same as a presumed local recurrence.
That low T's BCR took 6 years to happen speaks to a relatively indolent relapse, further favoring local recurrence or conceivably oligometastasis over conventional widespread (cows out of the barn) metastases; the latter not considered amenable to directed therapy. Furthermore, even in the widespread de novo metastatic state, albeit only in the low volume subset, cytoreduction of the primary site, shows benefit.
There is no way to ascertain whether cancer cells are only in what you call the "solitary focus." In fact, the treatment area is moving toward widening rather than focal. I'm talking about prostate bed relapse, not regional (pelvic lymph node) metastatic relapse in this case.
prostatecancer.news/2021/05...
On the flip side of pursuing an aggressive approach for curative intent, for a PSA DT of greater than 9 months and time to BCR of 6 years; observation -- kind of akin to active surveillance in the initial diagnosis state, is an accepted approach, as one's prognosis is actually excellent.
Bx only if not PSMA avid. False positives occur in and around prostate due to urinary excretion. If high SUV, that's not a concern.