Axumin PET/CT scans change treatment recommendations in recurrent prostate cancer

The value of many cancer-related tests is actually based on whether the results of the particular test change the way that  physicians plan to treat specific patients (hopefully for the better).

On Tuesday this week, Blue Earth Diagnostics issued a media release related to early results from the FALCON trial, which showed that a PET/CT scan using the [18F]fluciclovine (Axumin) radiotracer did indeed change the way that physicians planned to manage men with biochemical recurrence of their prostate cancer. However, we should be clear up front about three things that are specified in the media release:

  • The FALCON trial was carried out in men with “a biochemical recurrence of prostate cancer” after first-line treatment who were being considered for salvage therapy.
  • Here in the USA, Axumin “is indicated for positron emission tomography (PET) imaging in men with suspected prostate cancer recurrence based on elevated blood prostate specific antigen (PSA) levels following prior treatment”.
  • Also here in the USA Axumin “is not currently approved … for treatment planning” in men with a biochemical recurrence of prostate cancer.

The difference is very subtle, but may impact what a clinician or patient needs to tell an insurance provider in terms of why a particular patient needs such a scan. The correct reason to give (at least here in the USA) is: “because I suspect that he has recurrent prostate cancer based on a rising PSA level after prior treatment.”

So, with that caution, here is what was apparently reported by Teoh et al. at the ongoing annual meeting of the American Society for Radiation Oncology (ASTRO):

  • The trial enrolled 85 patients, all of whom had a rising PSA after prior treatment.
  • All 85 patients were initially being considered as good candidates for some form of salvage therapy with curative intent.
  • After having the Axumin PET/CT scan, 52/85 patients (61 percent) had their management plan changed.
  • Of those 52 patients
    • 13 (25 percent) had their management changed from salvage treatment to watchful waiting.
    • 18 (35 percent) had their management changed from salvage treatment to systemic treatment (e.g., androgen deprivation therapy [ADT] or similar)
    • 21 (40 percent) had a modification made to their previously planned radiotherapy field for their salvage radiation therapy.

In  other words, the form of treatment that was recommended to 52/85 patients was changed as a consequence of the Axumin PET/CT scan.

Although this was a small trial in terms of the numbers of patients, this is a pretty striking set of results. However, these results do come with some words of caution.

The patients who were enrolled in this trial all had to meet the following criteria:

  • This had to be the first biochemical recurrence of their prostate cancer after any form of treatment.
  • Either they had to have recurrent prostate cancer based on a PSA level ≥ 2.0 ng/ml above the nadir level after first-line radiotherapy or brachytherapy (the ASTRO Phoenix criterion)
  • Or they had to have a persistently elevated PSA level after a radical prostatectomy (i.e., their PSA had never fallen to an acceptable level, such as < 0.1 ng/ml, post-surgery)
  • Or they had to have two consecutive rises in their PSA level after a radical prostatectomy and a final PSA > 0.1 ng/ml at time of enrollment
  • Or they had to have three consecutive rises in their PSA level after a radical prostatectomy
  • And they also had to have one of either a PSA doubling time of ≤ 15 months or a PSA level ≥ 1.0 ng/mL at time of recruitment

PSA doubling times had to be calculated using the Memorial Sloan-Kettering Cancer Center nomogram.

In other words, a patient whose PSA levels went from 0.05 to 0.07 and 0.09 ng/ml after surgery or from 0.65 to 1.15 to 1.75 after radiation therapy of some type would not have been eligible for this study.

It is worth noting that Blue Earth Diagnostics has also let us know that enrollment in the larger, 220-patient LOCATE study (in men with a rising PSA after initial prostate cancer treatment) was completed earlier than expected, and data from this study can be expected some time next year.

The “New” Prostate Cancer InfoLink is pleased to see that the use of a PET/CT scan in combination with the [18F]fluciclovine (Axumin) radiotracer is able to help to better identify the needs of patients with a rising PSA after first-line therapy. One of the next key questions is going to be whether — at least for men with high-risk prostate cancer — such a scan can give us better insight into how such patients should be treated initially.

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