THE "NEW" PROSTATE CANCER INFOLINK

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.

Filed under: Drugs in development, Living with Prostate Cancer, Management, Treatment | Tagged: castration-resistant, Lu-177, lutetium-177, mCRPC, metastatic, PSMA, Treatment |