Multi-centre registry trial tests use of PSMA tracer for early detection of prostate cancer

Led by researchers at Lawson Health Research Institute, a multi-centre registry trial is testing the use of a new imaging tracer, called a PSMA tracer, for early detection of recurrent prostate cancer. The registry gives patients access to a new type of imaging and will assess the impact on patient care.

PSMA tracers are used in positron emission tomography (PET) scans to target a protein found in prostate cancer cells called prostate specific membrane antigen (PSMA). Supported by Cancer Care Ontario and McMaster University's Centre for Probe Development and Commercialization (CPDC), the goal of the registry trial is to capture detailed PET images to guide treatment decisions made by patients and their care teams.

The trial is providing valuable insights to research participants like Wayne Smith, a 71-year-old man from Ingersoll, Ontario. When he was diagnosed with prostate cancer in 2013, Wayne made the decision to have his prostate removed. After some time, his prostate specific antigen (PSA) levels began to rise and his doctors were concerned that the cancer was coming back.

A challenge of the standard PSA blood test is that it can indicate a cancer is returning before the location of the tumour can be detected by a bone scan or computed tomography (CT) scan.

"I was told a PET scan was available through research and that it could help locate the disease," says Wayne. He went for the scan earlier this year at St. Joseph's Hospital, part of St. Joseph's Health Care London. "Nothing showed up on the scan, but that was good news; it meant the cancer was microscopically small."

Wayne and his doctors decided on hormone therapy and radiation therapy to eradicate any cancerous cells. He was treated at London Health Sciences Centre's (LHSC) London Regional Cancer Program.

Early evidence suggests that a clear PET scan despite rising PSA levels is likely associated with persistent cancer at the original site. Based on the scan, Wayne was able to do a much shorter round of hormone therapy - six months rather than being on hormone therapy indefinitely.

Dr. Glenn Bauman, Lawson Scientist and Radiation Oncologist at LHSC

Wayne is one of 1,500 Ontario men who will participate in the PSMA-PET Registry Trial. Eligible participants are those with suspected prostate cancer that cannot be detected in conventional bone and CT scans.

Participants have a PET scan using a specific PSMA tracer called 18F-DCFPyL. The tracer is injected and spreads out in the body to find spots of cancer which are then visible on the scan.

"With this trial, men in Ontario can access a promising test that could impact their treatment outcomes," says Dr. Bauman. "The PSMA tracer may be able to locate prostate cancer that was once undiscoverable."

Led by Dr. Bauman along with Drs. Ur Metser and Tony Finelli at University Health Network (UHN), the trial is currently available across five sites in Ontario: London Health Sciences Centre; St. Joseph's Health Care Hamilton; Sunnybrook Health Sciences Centre; Princess Margaret Cancer Centre (UHN); and Thunder Bay Regional Health Sciences Centre. The trial is also expected to open at The Ottawa Hospital this year.

The PSMA tracer is considered an investigational agent in Canada and is currently only available through clinical trials. After studying the accuracy of the tracer in detecting early cancer recurrence, the research team hopes to have enough data to recommend when it could be used in the clinic.

In 2016, Lawson researchers were the first in Canada to use the 18F-DCFPyL PSMA tracer to capture PET images with a patient at St. Joseph's Hospital. The tracer is provided by CanProbe, a joint venture between CPDC and UHN located in Toronto, and was set up with funding from the Movember Foundation.

"We conducted an initial trial that included 20 men with prostate cancer who were having their prostate removed. The goal was to determine how effective the PSMA probe was in detecting disease at the time of initial treatment," explains Dr. Bauman. "We found the PET scan was able to detect spots of cancer in almost all participants, which corresponded to spots of cancer identified in the prostate after it was removed and examined under the microscope."

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