Alberta Cancer Foundation

New Technology: Taking Prostate Cancer Imaging to the Next Level

By: Karin Olafson

Prostate cancer is the most common type of cancer in Canadian men. In fact, one in nine men will be diagnosed with prostate cancer at some point during their lifetime. Image by Devrimb, coutesy iStock.

The good news: Screening for prostate cancer has improved considerably over the last 25 years. Now, prostate cancer has one of the highest five-year survival rates at 95 per cent.

Prostate cancer detection has decades of history, according to Dr. Frank Wuest, professor and chair in the Department of Oncology at the University of Alberta. Wuest also holds the Dianne and Irving Kipnes Chair in Radiopharmaceutical Sciences, an endowed research position made possible through a generous donation from the Edmonton-based couple, Dianne and Irving Kipnes.

“In the 1940s and ’50s, the first available test was the prostatic acid phosphatase (PAP) blood test, used to monitor and assess the progression of prostate cancer until the introduction of the PSA test,” says Wuest. In 1993, Canada introduced the prostate-specific antigen (PSA) test, improving outcomes for patients diagnosed with this cancer.

PSA is a protein produced by prostate cells, and small amounts of this protein are detectable in the blood. The PSA test is a simple blood test where the levels of PSA are measured; a high level of PSA in the blood could indicate prostate cancer.

“The PSA test has now largely displaced the PAP test. While the PSA has limitations, there are still benefits,” says Wuest. He explains an elevated PSA result can lead a patient to further testing and result in earlier cancer detection, even before any symptoms develop. However, this test is far from foolproof. For starters, a high PSA level isn’t necessarily indicative of cancer. Only 25 per cent of abnormal PSA tests are due to cancer; high PSA levels can also be due to sexual activity, a urinary tract infection, prostate infection and even bike riding. And this form of testing cannot locate or show what stage the cancer is at, resulting in treatment when it might not have been needed — 42 per cent of diagnosed prostate cancer may never require treatment at all. Treatment can negatively affect the quality of life, sometimes causing incontinence and erectile dysfunction. Additionally, there is the risk of a false-negative result; PSA testing misses roughly 15 per cent of prostate cancers.

In other words, something else is needed to address the shortfalls. A cutting-edge detection option, called functional molecular imaging, has the potential to address these challenges by more effectively distinguishing between aggressive and indolent, or slow-moving, disease. In a nutshell, imaging like a CT scan, MRI or ultrasound takes anatomical pictures of the body. However, functional molecular imaging shows how an organ works at the cellular level by detecting areas of activity in the body, like metabolism or blood flow. Position emission tomography (PET) is a type of functional molecular imaging that uses injectable radioactive substances to detect cancer.

Wuest has researched PET functional molecular imaging technology for about 25 years and says PSMA-PET imaging has the potential to vastly improve how prostate cancer is detected. The PSMA-PET scan works by detecting prostate-specific membrane antigen (PSMA). Unlike PSA, which is secreted into the circulation by the prostate cells, PSMA is a protein stably attached to the surface of prostate cancer cells. Patients are injected with a PSMA-binding radioligand to detect prostate cancer using PET technology. The PSMA radioligand is a radioactive drug specifically used in nuclear medicine diagnosis — which then binds to PSMA on the tumour site.

“The University of Alberta has two cyclotrons. These are particle accelerators which produce short-lived radioactive isotopes — one of the most important ones for PSMA-PET scans is fluorine-18 with a roughly two-hour half-life,” says Wuest. Fluorine-18 is incorporated into a PSMA-binding compound to produce the PSMA radioligand. This is done in a highly specialized radiopharmacy, the Edmonton Radiopharmaceutical Centre, located at the Cross Cancer Institute.

Then, a PET scanner is used to detect the distribution and metabolism of the PSMA radioligand in the body. The PSMA radioligand lights up tumours, which show on the scan as bright spots, pinpointing where the cancer is located.

“PSMA does not circulate in the blood like PSA. It is stuck to the cell,” says Wuest. “This is a huge advantage as it can, therefore, also be used for targeted therapy by using PSMA-binding compounds containing radioactive isotopes which kill tumour cells.”

PET imaging technology can precisely detect and locate prostate cancer, help doctors determine the stage of the cancer, and determine if it has metastasized. It also helps to determine if a patient’s prostate cancer doesn’t require treatment, helping address the issue of overtreatment.

“In my opinion, PSMA-PET is a game-changer in prostate cancer management, which has also stimulated important developments for personalized prostate cancer therapy to improve outcomes,” says Wuest.

Currently, the technology is not Health Canada-approved, and PSMA-PET scans are only available to patients in Alberta through clinical trials. The first patient in Alberta to experience a PSMA-PET scan was in August 2021; it was the result of a highly productive collaboration between Wuest and his colleague Dr. Jonathan Abele from the University of Alberta Hospital. Since then, more than 100 patients have received a PSMA-PET scan. It is estimated that about 2,000 patients per year need this technology in Alberta alone. Wuest and Abele hope that PSMA-PET scan technology will be Health Canada-approved within the next three years.

“More clinical trials have been developed. We will now see larger clinical trials at the Cross Cancer Institute, the University of Alberta Hospital and the Royal Alexandra Hospital with about 800 patients over four years,” says Wuest. “We will also ship the PSMA radioligand to Calgary, as there is currently no cyclotron facility and [researchers and clinicians] are very eager to take advantage of the technology, as well. This will have a huge impact on prostate cancer patient care and improve patient outcomes in Alberta.”