Gallium-68 PSMA vs. fluorine-18 fluciclovine PET/CT scans


According to a presentation given yesterday at the ASCO meeting here in Chicago, PET/CT scanning with 68Ga-PSMA-11 is more accurate than 18F-fluciclovine PET/CT at detecting recurrent prostate cancer in men with early biochemical recurrence following radical prostatectomy.

The abstract of the presentation by Dr. Calais can be found here, and there is also a report on this presentation on the Renal & Urology News web site.

Basically, Calais and his colleagues carried out a prospective, single-center, single-arm, head-to-head Phase III study of paired 18F-fluciclovine (FACBC) and 68Ga-PSMA-11 (PSMA) PET/CT scans for localizing early biochemical recurrence (BCR) of prostate cancer in men who had previously undergone a radical prostatectomy.

The trial enrolled 50 consecutive patients with BCR and PSA levels ranging from ≥ 0.2 to ≤ 2.0 ng/ml who had not had any salvage therapy at the time they were scanned. All 50 patients were given both an FACBC PET/CT scan and a PSMA PET/CT scan within 15 days.

The results of the PET/CT scans were all interpreted by three independent, blinded, expert readers who were not involved in study design and data acquisition. PET/CT scans were considered to be positive if any region was rated as positive. Detection rates per-patient and per-region served as primary study endpoint.

Here are the core study findings:

  • Average (median) time interval between the two scans was 6 days (range, 1 to 15 days).
  • Average (median) PSA level at the time of imaging was 0.50 ng/ml (range 0.2 to 2.0 ng/ml).
  • Per-patient detection rates were
    • 26 percent for FACBC PET/CT
    • 56 percent for PSMA PET/CT
    • This difference was statistically significant (p = 0.003)
  • Per-region detection rates were
    • 8 percent for FACBC PET/CT for pelvic nodes
    • 30 percent for PSMA PET/CT for pelvic lymph nodes
    • 0 percent for FACBC PET/CT for extra-pelvic lymph nodes
    • 16 percent for PSMA PET/CT for extra-pelvic lymph nodes
    • These differences were again statistically significant
  • Reader agreement for PSMA PET/CT image interpretations was significantly higher than for FACBC PET/CT (0.67 vs 0.20; p = 0.015).

Calais et al. concude that

In patients with BCR and low serum PSA levels after RP, PSMA PET/CT demonstrates higher detection rates and superior reader agreement when compared with FACBC PET/CT. Therefore, PSMA PET/CT should be the imaging modality of choice in patients with early BCR.

Unfortunately, of course, as yet, 68Ga-PSMA-11 PET/CT scans are not yet approved by the FDA here in American, nor are they available outside of a research setting. However, we assume that these new data will be used by the developers to seek such an approval in the near future. And then we will all have top see whether the cost is one that payers are willing to cover.

 

11 Responses

  1. Reader agreement for PSMA PET/CT image interpretations was significantly higher than for FACBC PET/CT (0.67 vs 0.20; p = 0.015).

    Anybody else more concerned about the reader DIS-agreements?

  2. Typo????
    0 percent for FACBC PET/CT for extra-pelvic lymph nodes
    16 percent for FABC PET/CT for extra-pelvic lymph nodes

  3. Reblogged this on Dan's Journey through Prostate Cancer and commented:

    “Interesting results. Now if the FDA would only approve the GA68 PSMA PET scan but, even if they do, it’s still pretty iffy on detecting cancer with my PSA level hanging out in the 0.10-0.13 range.”

  4. Dear Michael:

    Even highly skilled uroradiologists can beleive that they can “see” or “not see” different things on PET/CT scans. And that probability increases when the scan data are less definitive (which is what this study’s data are telling us about the FACBC data.

    Being an “expert” does not make one “perfect”. It is easy to find specific types of PET scan om which three different “experts” could express different opinions. You need to appreciate that these are not “disagreements” at all. They are differences of opinion. We don’t necessarily know who is right and who is wrong all the time. The interpretation of radiologic images of all types is part science, part skill and experience, and part art. And even if we can “train” AI systems to read such scans, the “skill” of the AI systems will depend on the combination of the skill, experience, and art of the team that developed the AI program!

  5. Rich:

    Thank you. You are correct. See revision above.

    Mike

  6. What I have concluded in my research of a variety of reports are the following order of the currently most effective imaging processes over all others:

    (1) PSMA radiotracer 18F-DCFPyL
    (2) 68Ga-PSMA-11 PET/CT
    (3) 18F-FACBC (radiotracer fluciclovine) (a.k.a. Axumin) PET/CT

    Regarding cost, an NCBI report states: “Because it is a fairly new technique (not yet included in the main oncology guidelines), 68Ga-PSMA PET/CT is restricted to a few diagnostic imaging centers and has a relatively high cost.

    18F-FACBC/fluciclovine/Axumin, on the other hand, has now been approved by the FDA and is covered by Medicare.

  7. Bone metastasis detection for gallium-68 PSMA vs. fluorine-18 fluciclovine PET/CT (Axumin) scans?

    Both of these scans can pick up bone metastases per previous studies. I’m curious if anyone knows why no comparative data on bone metastasis were included in this study( and also how these scans compare to a modern scan designed for bone metastasis – the Na18F PET/CT scan. I’m also curious why soft tissue sites of metastasis other than lymph nodes were not addressed. Whatever the answers, I’m glad this worthy study was done.

    My impression is that this study builds on previous evidence that the 68Ga PSMA scan is superior to Axumin for nodal metastasis detection.

  8. For the sake of clarification for some readers, this study considers “Axumin” vs 68Ga-PSMA. Axumin is not the same as the 18F-DCFPyl PSMA scan.

  9. With regard to Chick Maack’s comment above about the relative effectiveness of three different types of PET/CT imaging agent, we need to also bear in mind that only one of these agents is as yet approved by the FDA in the USA and is covered by Medicare. The situation in other countries is very different.

    In addition, Chuck’s opinion is just that — one man’s opinion. We have no evidence from any head-to-head trials (yet) that confirm the superiority of the 18F-DCFPyL PSMA radiotracer over the other two.

  10. Dear Jim:

    If you look at the trial summary on the ClinicalTrials.gov web site, you will see that a breakdown of where the various metastases occurred is a secondary endpoint of this study. This would suggest that these data are still to come.

    With respect to the Na18F PET/CT scan, an earlier study in Europe has compared this scan to the 68Ga PSMA scan, and concluded that patients should be given both scans. Try telling that to most payers!

  11. Sitemaster — Thanks very much for your post of 6/5 11:50. The link is quite interesting.

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