Early data from the PROPS imaging trial prior to SRT

A recent presentation by Pouliot Frederick, MD, at the annual meeting of the Canadian Urological Association in Halifax, Nova Scotia, provided information on the roles of multiparametric MRI, [18F]choline, and 86Ga-PSMA PET/CT scans in determining the utility and value of salvage radiation therapy (SRT) for patients progressing after first-line surgery. A full report on this presentation is available on the UroToday web site.

Basically, Dr. Frederick provided data based on an early read-out from the ongoing PROPS trial that is being run in Canada, the UK, and Australia. A total of 91 patients had data available for evaluation at the time of the presentation, but the trial appears to have finally enrolled a total of 99 patients.

The fundamental goal of the PROPS trial is to work out what percentage of patients men with negative or equivocal conventional restaging after radical prostatecomy are found to have disease identified outside the prostate bed on other imaging modalities. The patiensts eligible for inclusion in the study are those who were with N0 or Nx at surgery, who had a documented PSA rise to > 0.2 ng/ml and at least one other adverse feature (PSA > 1 ng/ml, Gleason score > 8, PSA doubling time < 10 months), and who had been considered a potential candidates for SRT.

The basic results in the 91 patients evaluated to date, and reported by Fredrick at the meeting, are these:

  • Median patient age at time of imaging was 65 years
  • Median time since RP at time of imaging was 23 months
  • Median patient PSA level at time of imaging was 0.42 ng/ml
  • Median patient PSA doubling time at imaging was 5 months
  • Patient staging data at time of surgery was
    • 34/91 patients (37 percent) had pT2 disease
    • 36/91 patients (40 percent) had pT3a disease
    • 21/91 patients (23 percent) had pT3b disease
    • 27/91 patients (30 percent) had positive surgical margins
    • 60/91 patients (66 percent) had Gleason 6 or 7 disease
    • 29/91 patients (32 percent) had Gleason 8 to 10 disease
  • The diagnostic accuracy of metastasis detection was
    • 47.8 percent sensitivity and 97% specificity for [18F]choline PET/CT scans
    • 66.7 percent sensitivity and 100% specificity for 86Ga-PSMA PET/CT scans
  • Consequent changes in management were seen in
    • 23 percent of patients based on their mpMRI data
    • 46 percent of patients based on their  [18F]choline PET/CT data
  • The type of management was changed
    • From curative to palliative in 14 percent of patients
    • From palliative to curative in 30 percent of patients

In summarizing this talk, Frederick indicated that

  • These imaging techniques can detect lesions at PSA levels for which SRT is still effective in about a third of patients.
  • They can lead to  changes in management in about 50 percent of patients.

However, this is still a small study and has inherent limitations. It doesn’t yet get us close to determining what “the best” type of scan is for a man with a rising PSA after radical prostatectomy so as to be able to come to the best decision about if and how to administer SRT, but it does help to get us closer than we were.

The “missing” scan in this trial is the approved [18F]fluciclovine (Axumin) PET/CT scan, which has also, already, been shown (in the FALCON trial) to change clinicians’ decisions about appropriate treatment — see here.

3 Responses

  1. Sorry, I know only the results from this info. It is an interesting study but I might not get it right. If PSMA PET/CT was more accurate than choline PET/CT, why did only choline PET/CT lead to changes of treatment. Further, the interesting point is not change of treatment from treatment with a palliative intent to treatment with a curative intent — but whether in follow-up the patients gain from the curative treatment targeting deteted sites. Several studies of LNM metastases detected with PSMA PET/CT showed a limited time to PSA recurrence. The question therefore might be the change in treatment — did it change the development of the cancer to the better?

  2. Dear Finn:

    (1) These are early stage data from a small study and should be considered as such.

    (2) Only a small number of patients got 68Ga PSMA PET/CT scans compared to the number given the [18F]choline scans. My assumption ios that it wasn’t enough patients to calculate any change in treatment plan.

    (3) Actually the change in treatment is, in and of itself, very interesting, but you are correct in that, in the long-term, what will be important is the patient’s outcome (i.e., whether the change in teratment was correctly justifiable).

    (4) I think we will all be wiser when there is an actual published paper providing the initial data, as opposed to just a write-up from an oral presentation at a meeting.

  3. After 22 years of ADT following failed surgical removal in 12/1992 and salvage RT between 4/1993 and 5/1993, and recurrence 11/1996, then over all these years usual imaging of CT, MRI, bone scans unable to identify area of continued activity, recently had injection of the radiotracer/isotope fluciclovine (Axumin) by the University of Kansas nuclear radiotherapy department and 18F PET/CT imaging from top of head down to mid thigh. FINALLY, the only activity found was near the area of the anastomosis connection of the urethra to the bladder neck following that surgical removal “26 years ago!” Head, breast, abdomen, pelvis otherwise clear of any metastasis.

    Currently undergoing five treatments of targeted radiation using EDGE radiation equipment with the hope that just possibly I might finally experience eradication of my prostate cancer that though managed and controlled all these years with ADT and most ADT medications including abiraterone and enzalutamide, I had little recourse than to have to learn how to tolerate these drugs for my long-time survival up to now. I shall report results once the five targeted radiation procedures are completed. Until then, prayers appreciated.

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