What is Lutetium-PSMA?
An example of a commonly used beta emitter is the radioactive Lutetium-177 (Lu-177). When this Lu-177 is linked to a substance that specifically binds to PSMA on the tumor cells, the Lu-177 can destroy the cancer cells to which it is bound. This works through single-strand and double-strand DNA damage.
Lutetium-177-PSMA therapy usually consists of 4-6 injections with 4-6 weeks in between. As Lutetium-177 releases gamma radiation, you can visualize the therapy after therapeutic injection with a gamma camera. In most cases the patient will stay in the hospital for 1 night following an injection. However, this can vary according to the local legislation.
To date, studies have shown that 1 in 3 patients do not respond to PSMA therapy.
Several clinical studies have shown a positive effect on overall survival and the progression-free period. About 2 in 3 patients respond to Lutetium-PSMA therapy, ranging from temporary stabilization of disease to disease reduction (based on PSA levels and PSMA PET scans). However, about a third of treated men have progressive disease during treatment. In this group it is better to discontinue therapy. Factors likely to predict whether a patient will not respond to Lutetium-PSMA therapy include:
- Young age (< 65)
- High concentration of g-glutamyl transferase (> 100 U/l)
- Low hemoglobin before start of therapy
- High Gleason score
- High platelet count
- High value C-reactive protein
- Regular need for pain relief
- High value lactate dehydrogenase
The side effects were primarily studied in the group of patients who had finished treatment with a lot of tumor tissue in their body. In this group, the side effects are generally mild . In the studies published to date, most patients had mild dry mouth , which may persist in the long term. Most patients had a decrease in blood cells, but were often unaffected, and spontaneously recovered. About half of the patients had mild transient fatigue. About a third had mild nausea or vomiting in the first 2 days after the injection. 1 in 5 patients had mild dry eyes, which can persist in the long term.
Not enough is known about the side effects in early phases of the disease and the side effects in the long term, so it is wise to only carry out these treatments in a study context.
Rules of Life
Because some radiation is emitted from the body and there is also some Lutetium-PSMA in the urine, short-term living rules apply. If a patient receives PSMA therapy, the treating hospital gives the patient detailed instructions, tailored to the patient’s living conditions.
For more information, you can watch the following video:
A nuclear medicine doctor looks at the distribution of Lu-177-PSMA in the patient’s body using a SPECT scanner.