As soon as tumour cells grow invasively and form metastases, a tumour is regarded as non-curable. At this stage, therapies should help to prolong life and ensure the best possible quality of life.
There are new hopes for metastatic prostate patients: first publications (see info box on the right) show some excellent results with a therapy using a PSMA ligand that has previously been radioactively labelled. The ligand binds specifically to prostate tumour cells and brings its radioactive radiation directly to the tumour cell. This dies off as a result of the irradiation. Patients could be successfully treated with only a few treatment cycles, which are usually not very stressful for the patients and where there are hardly any side effects. The new test is designed to identify patients who are suitable for this therapy.
After a successful tumour therapy, prostate patients are closely examined with a PSA test. In this way, recurrences should be recognised at an early stage in order to be able to initiate therapies in good time in the event of a re-emergence of the tumour.
Unfortunately, recurrence or metastasis does not lead to increasing PSA values in all patients. Thus, the disease can progress further and the ideal time for the start of a successful therapy elapses.
The new test procedure is intended to be able to monitor this patient group as well as to provide an indication of a starting metastasis process with an increase in the PSMA. These patients can then be treated in time with the new procedure, ideally before the disease has progressed too far.
PSMA stands for Prostate-Specific Membrane Antigen. Prostate carcinoma cells carry PSMA as a recognition enzyme on the surface. Sub-populations of macrophages scan the body for degenerate tumour cells and eliminate them by phagocytosis (absorption of the tumour cell inside the macrophage followed by a digestion process). In a metastasising process PSMA positive cells appear more often, so that the proportion of macrophages that eliminate tumour cells also increases.
The EDIM method is used to determine the proportion of macrophages in which specific PSMA antigens can be detected. For this purpose, antibodies are used which can be used to identify macrophages and to use an antibody which specifically binds to PSMA. Rising values indicate a suspicion of a metastasising process and could possibly benefit from the new therapy.