Early data on efficacy, safety of PSMA-linked lutetium-177

There has been a good deal of optimism about the potential efficacy and safety of the radioisotope-labeled product known as prostate-specific membrane antigen-linked lutetium-177 (177Lu-PSMA) in the treatment of very late stage prostate cancer.

A newly published paper by a German research group (Baum et al.) in the Journal of Nuclear Medicine has now provided us with some initial data from a relatively small Phase II clinical trial.

Baum et al. set out to assess the efficacy and safety of a specific, injectable form of 177Lu-PSMA in men with metastatic castration-resistant prostate cancer (mCRPC). The trial enrolled 56 such patients, all of whom were given 177Lu-PSMA as treatment after initial patient selection based on the use of 68Ga-PSMA PET/CT scans. The same scans — along with other tests — were also used to re-evaluate the patients post-treatment with 177Lu-PSMA.

Here is what the authors report:

  • 177Lu-PSMA was more highly absorbed by prostate cancer tumors (median tumor dose, 3.3 mGy/MBq) as compared to normal organs and tissues.
  • Among the normal tissues and organs, the parotid glands received higher doses of 177Lu-PSMA (1.3 mGy/MBq) than the kidneys (0.8 mGy/MBq).
  • There was a small, statistically significant reduction in erythrocyte and leukocyte counts.
  • No acute adverse events were observed or reported.
  • Two patients were reported to have mild reversible xerostomia (dryness of the mouth), but no other long-term side effects were observed or reported.
  • Severity of prostate cancer-related pain was significantly reduced in 2/6 patients (33 percent) who had such pain.
  • 45/56 patients (80.3 percent) had a decrease in their PSA level.
  • 25 patients were followed for ≥ 6 months after two cycles of treatment with 177Lu-PSMA, and of those patients
    • Molecular response evaluation with 68Ga-PSMA PET/CT scans showed that
      • 14/25 (56 percent) had a partial remission
      • 2/25 (8 percent had stable disease
      • 9/25 (36 percent) had progressive disease
    • Contrast-enhanced CT scans showed that
      • 5/25 (20 percent) had a partial remission
      • 13/25 (52 percent had stable disease
      • 7/25 (28 percent) had progressive disease
  • Median progression-free survival was 13.7 months.
  • Median overall survival was not reached at 28 months of follow-up.

What this abstract does not tell us, unfortunately, is how many prior treatments these patients had received (if any) before they were initially treated with 177Lu-PSMA. This information is presumably in the full text of this paper, and we will see if we can obtain a copy of the full article from the authors or the publisher.

4 Responses

  1. How does median overall survival of > 28 months compare with other metastatic castration-resistant prostate cancer conditions?

  2. Dear Tarhoosier:

    That is precisely the point being made in the last paragraph of the commentary above. Since we don’t know the state of progression of these patients or what other therapies they had previously received, we don’t know how to compare apples to apples.

  3. European guidelines report overall survival in metastatic CRPC to be <19 months

  4. What is the results when prostate removed and 14 years later the PSA is 44 ng/ml and going up fast, because it is growing on another part of my body. What treatment do you prefer to be safe?

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