Published: 1.10.2021
Writer: Otto Ettala

According to the current recommendations for the treatment of prostate cancer, feasible spread examination methods include whole-body computed tomography (CT) and bone scan, although it is known that their sensitivity in detecting metastases is poor.

Research has been underway for years to find a good alternative to replace these traditional spread examination methods. Of the numerous options, the most promising is PSMA-PET, that is, positron emission tomography based on prostate-specific membrane antigen. For PSMA-PET, a radioactive tracer is used that binds to the PSMA molecules existing on the cell membranes of normal prostate cells and prostate cancer cells. The distribution of the tracer in the body is visualized by means of a PET camera that detects positron radiation, and the image is usually combined with a whole-body CT. Previously, we have reported that PSMA-PET is a clearly more sensitive imaging method than the traditional spread examinations.

PSMA-PET imaging might increase inequality

Although it is a promising method, there are several challenges related to the use of PSMA-PET for cancer spread examinations. First, PET cameras are expensive and not available in all units providing prostate cancer therapy. Second, the interpretation of PSMA-PET images is not entirely unambiguous.  Assessing PSMA uptakes in bone is particularly difficult and it is not possible to say with certainty if they are metastases or not.   

PSMA-PET imaging may, within a few years, replace the traditional spread examination methods as part of the treatment guidelines for prostate cancer. If so, the risk is that men with a diagnosed prostate cancer will be placed in an unequal position, because not every man with a diagnosis will have the opportunity to undergo a PSMA-PET scan. Another concern is that we do not know exactly which PSMA uptakes should be interpreted as metastases and which ones as benign.

Accessibility is an advantage of PSMA-SPECT imaging

Our research team is initiating a study to explore the feasibility of PSMA-SPECT imaging as a tool to examine the spread of prostate cancer. The PSMA-SPECT is based on the same idea as PSMA-PET: a radioactive tracer is bound to the PSMA molecule. In SPECT (single-photon emission computed tomography) studies, however, instead of using a PET camera, the distribution of the radiotracer in the body is measured by means of a gamma camera, which is being used for traditional bone scan imaging. An advantage here is that a gamma camera can be found in practically any prostate cancer treatment unit.

We are also attempting to investigate the accuracy of the various PSMA imaging methods in detecting metastases. Our plan is to take biopsies from those PSMA uptakes in bone that remain unclear, so that we can determine if they are metastases or benign changes.

The funding granted by the Sakari Alhopuro Foundation will enable us to implement the research to the planned extent. If PSMA-SPECT proved to be, at least, as good a method as PSMA-PET, the result would have a significant impact on the development of prostate cancer spread examinations and, thereby, on reducing inequality among prostate cancer patients.

 

 

 

Otto Ettala, MD, PhD, is working as a Specialist in Urology at Turku University Hospital and a Clinical Lecturer of Surgery at the University of Turku. With his thesis on the risk factors of erectile dysfunction, he earned his PhD in 2015 from the University of Turku. At present, his research team is primarily focused on exploring the imaging of cancer, especially prostate cancer.

 

 

 

 

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