Changes in planned disease management after PET/CT in men with biochemically recurrent prostate cancer and low PSA levels

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Published: 16 Feb 2023
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Dr Frédéric Pouliot - Université Laval, Quebec, Canada

Dr Frédéric Pouliot speaks to ecancer at ASCO GU 2023 about a secondary analysis of results from the CONDOR study which looked at changes in planned disease management after PET/CT in men with biochemically recurrent prostate cancer and low PSA levels.

He explains that in this prospective study, physicians had filled in a questionnaire on patient management before and after the PET/CT scan to see if there was a change.

Amongst other findings, Dr Pouliot reports that in patients with a PSA level below 0.5 the management changed in 39% of patients, with the change mostly due to a positive PET scan.

Basically the study we presented is about molecular imaging. In prostate cancer recently there have been a lot of changes in our management with the arrival of a new molecular imaging category of tracer which binds to the PSMA tracer. However, the accuracy of these tracers to detect prostate cancer at very low levels are not that well described. Another very important point for the clinical application of these tracers is how do they change the management of our patients that have prostate cancer. So many years ago the CONDOR study was designed to answer two main questions, first what is the accuracy of PSMA imaging with the DCFPyL, which is one of those tracers, and also to see how does that imaging, PET imaging with DCFPyL, change the management of the patient. 

The CONDOR study is a multicentre prospective study that was done many years ago in centres in Canada and the US and it accrued more than 200 men. All the PET scans that were done in these patients were blinded read. So, basically, the patient, to be included in that study, had to have undergone either radical prostatectomy or radiation therapy for prostate cancer and have PSA recurrence.

What was the methodology?

This is a study that is prospective, multicentre, that was not randomised because it’s single arm. It’s a study that was done in patients that underwent radical prostatectomy or radiation therapy and then that had PSA recurrence after this primary tumour treatment. The patient had to have normal or equivocal imaging and then they would have this investigational molecular imaging modality, the DCFPyL PET scan. The physician had a questionnaire to fill about their management before the imaging and after to see if there was a change in management.

What were the key findings?

The CONDOR study was published already so the key findings were that, first, the accuracy of the DCFPyL was very high at about 85% in terms of positive predictive value. There was a change in management in 62% of patients. However, today what is new, what we presented, is that this imaging modality could change also the management in patients at very low PSA levels. That was a question that was not fully answered and certainly not in a prospective multicentre study with blinded readers.

So what we show is that in the patient that has a change in management and that had a low PSA level, below 0.5, the DCFPyL changed management, in fact, in 39% of patients, so that’s a lot of patients. The change in management was mostly due to a positive PET scan found during the trial. So basically it answers a question that the PSMA PET/CT is useful not only in patients that have a PSA above 1.0 or at higher level of PSA but also at PSAs that are very low and still low enough to get salvage therapies.

How can this impact the future treatment of prostate cancer?

PSMA has been shown clearly to be superior to conventional imaging in many studies but we have to fit it in our clinical practice. One of the key questions we had is can we really use it at low PSA levels, low enough to give radiation therapy to our patients after a radical prostatectomy? It seems that the impact of DCFPyL or PSMA PET/CT is important, very important, at low PSA levels. So there is an indication and a role for this imaging at low PSA levels and that will influence the clinician about the intensification of treatment that they will provide their patient or changing their management.

So the DCFPyL and PSMA PET/CT now are established as a superior modality than conventional imaging. We can use it in recurrent prostate cancer, both after a radical prostatectomy and radiation therapy. Even if we do it at very low PSA levels we might have findings that will change our management and maybe improve patient care.