3 June 2021

Novel imaging technique ‘lights up’ prostate cancer

Clinical Prostate cancer

A study demonstrating higher accuracy using a new imaging technique for prostate cancer is one of two winners of this year’s Clinical Trial of the Year Award. 

The study examined an imaging technique called Prostate Specific Membrane Antigen (PSMA) PET/CT, which can detect small tumour sites that may not be picked up with conventional imaging.

“It’s an imaging technique where we inject a tiny dose of a radioactive substance that binds to this receptor that’s present on prostate cancer cells,” said the study’s chief investigator Professor Michael Hofman.

This radioactive substance shows up on the whole-body PET scan, which provides three dimensional images that localise tumours as small as two or three milimetres, he said. 

Conventional scans like CT scans and bone scans are “quite non-specific” by comparison. 

“A radiologist needs to look through those scans very carefully; they don’t highlight the areas of prostate cancer specifically,” said Professor Hofman.

“But on this new scan, the areas of prostate cancer light up very brightly. We can be sure it’s prostate cancer rather than something else.”

Professor Hofman is the director of the Prostate Cancer Theranostics and Imaging Centre of Excellence at the Peter MacCallum Cancer Centre and led the RCT that showed the greater accuracy of the PSMA PET/CT technique and won the Australian Clinical Trials Alliance 2021 Trial of the Year Award in May. 

In the trial, published in The Lancet in March 2020, 300 men with newly diagnosed prostate cancer underwent PSMA PET/CT imaging. 

The trial team found that PSMA PET/CT had an accuracy of 92% compared to 65% accuracy achieved with conventional imaging. 

The results of this study are now being included in national and international clinical guidelines, and Ga-68 PSMA has also been approved by the US FDA.

Men with prostate cancer often undergo surgery or external beam radiotherapy in an attempt to cure their disease.

“They’re both big procedures and if the tumour has already spread beyond the prostate gland, then those treatments will ultimately be futile,” said Professor Hofman.

“Ordinarily, in this group, around 50% of men who have those curative intent, treatments end up recurring down the track. So, the hope here is that with more accurate imaging, that we’ll be able to tailor management more appropriately at baseline.”

The RCT showed that PSMA PET/CT was associated with a 30% management change, whereas conventional imaging resulted in a 15% management change. 

“So, we hope that those changes will ultimately improve the patient’s outcome downstream, such as survival or quality of life,” said Professor Hofman.

“It’s difficult to show that in an imaging trial, because we’re not treating the patient, we are just staging the extent of disease. 

“And the survival of men with prostate cancer in this early stage is often quite long. So, we do need longer follow up to tease that out. We actually are continuing to follow up the PSMA PET/CT cohort so we will have some more data over time.”

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