When do you think we will see the data from the ProPSMA trial?
We’re currently in the follow-up phase, so all the recruiting is finished. We’re basically looking at the 6- and 12-month reviews since patients have gone on to treatment, and we would expect that data around the time of both the European and American urology meetings in 2020. It’s very likely that data will be presented as an abstract at both the EAU and AUA annual meetings next year.
Let’s talk about PET’s use in oligometastatic disease or biochemical recurrence. First, when do you generally use it? Is there a PSA threshold that practicing urologists might take home if they have access to the scan? Second, what are you doing when you find oligometastatic disease or biochemical recurrence—surgery, radiation therapy, or continuing hormonal therapy?
It’s a very challenging area. The whole problem with the PET PSMA scan is it improves our ability to stage the disease or to restage the disease, but we have no idea whether the interventions we’re studying now have actually changed long-term survival. That remains a challenge for us moving forward.
A number of studies have shown that the PET PSMA results change management. If we look at biochemical-recurrent patients, about 30% to 80% have their management changed as a result of the PSMA scan. Typically what will happen is that instead of there being a presumed local recurrence, we find a pelvic node, an extrapelvic node, a bony metastasis, or sometimes a combination. As such, instead of radiation to the prostate bed, which would normally be standard of care for PSA rise post prostatectomy, we are then faced with the decision whether this should be done, combined with stereotactic ablative radiotherapy to involved nodes, or consider a salvage lymph node dissection, androgen deprivation therapy, or combination of therapies.
I don’t think there’s a belief that we’re going to cure the disease with ablative radiotherapy or salvage node dissections alone because usually the PET PSMA scan underestimates the degree of metastatic spread. However, we have data that we hope to publish soon that will suggest that it at least delays androgen deprivation therapy in about 50% of patients by at least a couple of years. That may at the very least provide the patient some quality of life benefits.
For a young, healthy patient with 20 years life expectancy, do you see a role for surgical removal in a patient with a positive PET scan? Let’s say it’s right at the bifurcation of the aorta and you’ve got one nodal spot that lights up on PET.
It’s clearly another strategy, as is stereotactic ablative radiotherapy, and it’s certainly been done in the U.S. but especially in Europe. Again, the results haven’t been that spectacularly successful because PET PSMA underestimates the amount of metastatic disease that’s present, and the small additional lymph nodes that are present just don’t demonstrate uptake. So you can do an extended node dissection and even a retroperitoneal node dissection, but there may well still be micrometastases in nodes further upstream that you haven’t visualized and hence haven’t been able to tackle.
I think this is an area we have to look at. The role of either radiation or aggressive surgery is very ripe now for clinical trials. But I think the take-home message is, what you see on the PET is probably just the tip of the iceberg, and there’s probably more microscopic disease beyond what is seen. Also, I certainly would not recommend a node pluck to take out the lymph node. You must do a proper node clearance in that area if you’re going to make any impact at all.