Yet another new PMSA-linked radioisotope enters clinical trials in prostate cancer

As many readers will be aware, there has been a lot of ongoing research using the gallium-68 (68Ga) radioisotope linked to various forms of prostate-specific membrane antigen (PSMA) in concert with PET scan imaging to identify sites of early recurrence of prostate cancer.

Another new form of radioisotope, copper-64 (64Cu), has recently undergone Phase I clinical testing for similar uses when linked to the PSMA-617 ligand. One of the potential benefits of a 64Cu-PSMA imaging agent is that it is more stable and has a longer half-life than 68Ga. This means that this imaging agent could be made at a central facility and distributed from there to clinical PET scan centers that don’t have the radiochemistry capabilities necessary for the preparation of 68Ga-PSMA imaging agents.

The recent Phase I trial of 64Cu-PSMA was carried out at two nuclear medicine centers (in Vienna, Austria, and Bad Berka, Germany). The study enrolled 29 men who were either highly suspicious for recurrent prostate cancer or were referred for possible surgical or PSMA radioligand therapy planning. PET images of the whole body were performed at 1 hour after injection of the 64Cu-PSMA ligand and additional images of the pelvis were taken at 2 hours after injection.

Results showed that:

  • 23/29 men either had at least one focus of pathological tracer uptake suspicious for primary disease in the prostate lobe or had recurrent disease detected.
  • Among healthy organs, the salivary glands, kidneys, and liver showed the highest radiotracer uptake.
  • Lesions suspicious for prostate cancer were detected with excellent contrast as early as 1 hr post-injection with high detection rates even at low PSA levels.

Clearly more data will be necessary before we will know the full clinical potential of 64Cu-PSMA ligands compared to 68Ga-PSMA and other possible radioligand combinations in association with PET scanning, but what is becoming more and more clear is the potential of these types of imaging agent to accurately detect small amounts of prostate cancer inside and outside the prostate.

7 Responses

  1. That’s great news.

    I wrestled with a rising PSA for 5 years, post-prostatectomy. It would rise and fall in response to testosterone which I began injecting 2 years after my prostatectomy with a PSA of 0.1

    My testosterone dropped from the mid 500s to below 100 post-prostatectomy, with no explanation. I was 51 at the time. My PSA level finally reached 1.5 ng/ml, and categorization from stable disease, watchful waiting to biochemically recurrent, progressive disease.

    I had everything from biopsies to CT scans to MRIs — all inconclusive. I got a choline-C11 PET scan and, sure enough, it showed up.

    I had pelvic salvage radiation with emphasized treatment of the lesions.

    My PSA was at 1.2 ng/ml, prior to radiation, at 6 months off testosterone. After 35 treatments, and 6 months of recovery, my PSA is 0.12 and my disease is stable again. I will resume PSA testing every 6 months.

  2. Does 64Cu-PSMA further reduce the threshold PSMA at which imaging is likely to pick up something?

  3. Dear brodwidr:

    As yet, I have absolutely no idea.

  4. Yes!

    That’s what was so significant for me.

    No other testing identified the source of PSA.

    I had a prostatectomy.

  5. brodwidr,

    I don’t know for sure, but I think the level of PSA at which it can detect cancer has to be very similar to the 68Ga-PSMA-617 PET scan. It is the ligand, PSMA-617, that dictates how sensitive and specific the tracer is, and the same ligand is used for both. The advantage is the longer half-life of 64Cu (12.7 hr) vs. 68Ga (68 minu). This longer half-life means that it doesn’t have to be manufactured using a cyclotron on site; it can be created at a central facility and messengered over to wherever it is needed. The positron energy is similar to that of 18F, so any PET scanner should be able to detect it. Because of the relatively long half-life, I wonder if patients have to stay overnight in the hospital to avoid exposing others to the radioactivity.

  6. thanks.

  7. The test I had required a PSA > 1.

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