For patients starting Pluvicto, do you have patients stop their ARPI?

While the VISION trial allowed for concomitant use, it was only about half (53%) in the Lu-177-PSMA arm, and 2/3 (68%) of those on the standard of care arm - Garje et al., PMID 36693228. And the PSMAfore trial did not, as noted above by @Dr. First Last

The bigger question is, will you continue the ARPI they were on when they progress, and just add Pluvicto? Why continue a drug that was not working without more data, and why use a new drug now if we don't know if it will be better than using that ...

From the PSMAfore trial, ARPI was not allowed concurrently with Pluvicto. Notably, these were patients with prior exposure to at least one ARPI (inclusion was "eligible for a change in ARPI")

Permitted and prohibited concomitant treatments:
Androgen deprivation therapy was continued, and concomitant supportive care was permitted, including bone health agents. Prohibited concomitant treatments were investigational drugs, biological products, chemotherapy, immunotherapy, PARP inhibitors, systemic ra...

In patients who start Pluvicto after multifocal progression on an ARPI, I favor discontinuing the ARPI. Concomitant ARPIs can add significant toxicity and, in these situations, may not offer additional clinical benefit. Retrospective data from Mayo showed that after adjusting for baseline clinical differences, continuation of an ARPI did not improve PSA50 or OS rates.

There is some variability in what the seminal trials allowed. For example, the PSMAfore trial did not allow continuation of ARPIs ...