An elevated PSA level in the blood may indicate prostate cancer, but does not yet allow for a definitive diagnosis. Where there is a corresponding suspicion, a tissue sample is therefore usually taken from the prostate. A study by the Medical University of Vienna now shows that a specialised form of imaging – known as PSMA-PET/CT – could provide important additional information even before such a biopsy is carried out. In an analysis of 194 patients, the method detected 91 per cent of clinically relevant prostate cancers. The findings of the research team, led by Marcus Hacker, Head of the Division of Nuclear Medicine at the Department of Biomedical Imaging and Image-guided Therapy, were published in the inaugural issue of the new journal The Lancet Medical Imaging & Theranostics.

PSMA-PET/CT combines two imaging techniques. In positron emission tomography (PET), a small amount of a radioactively labelled substance is administered, which binds specifically to the so-called prostate-specific membrane antigen (PSMA). This protein is particularly abundant on prostate cancer cells. This enables suspicious areas to be visualised. The computed tomography (CT) scan, carried out simultaneously, provides precise images of the body’s structures and enables these areas to be anatomically localised.

High detection rate for clinically relevant prostate cancer
As part of a retrospective analysis of the randomised Phase 3 RAPID trial, the research team led by Holger Einspieler and Sazan Rasul investigated the potential value of PSMA-PET/CT in patients with elevated PSA levels and suspected prostate cancer prior to a biopsy.

Of 77 patients with clinically significant prostate cancer confirmed by tissue examination, 70 were detected by PSMA-PET/CT. This corresponds to a detection rate of 91 per cent. The test’s predictive value was also high in cases where the scan result was normal: in 91 per cent of these cases, no clinically significant tumour was present.

Furthermore, the researchers analysed the subsequent course of the disease. Over a median follow-up period of 35 months, 23 out of 24 patients who went on to develop an aggressive course of the disease had already been identified by PSMA-PET/CT.

Prospects for more targeted diagnosis
The results suggest that PSMA-PET/CT could also play a role in the initial investigation of suspected prostate cancer in future. In particular, a normal scan result could help to better assess which patients actually require a tissue sample. This could potentially avoid unnecessary biopsies. Whether and how the method can be integrated into routine diagnostics must be investigated in further studies.

“Our results show that PSMA-PET/CT may be able to provide valuable information at a very early stage of the diagnostic work-up. The high diagnostic value of a normal result is particularly relevant here. In future, this could help to make better decisions about which patients actually require a biopsy,” says study lead Marcus Hacker.