PSMA PET/CT Imaging
Undoubtedly, PSMA PET/CT has been one of the most exciting areas of prostate cancer research in recent years. Professor Declan Murphy and colleagues at Peter MacCallum Cancer Centre have been at the forefront of this research and are world leaders in this area.
Leadership in PSMA PET Imaging
Professor Murphy and colleagues have attracted grants worth many millions of dollars to investigate PSMA and have published many important papers as a result. Both within clinical trials and in routine prostate cancer practice, Professor Murphy has extensive experience in the use of PSMA PET/CT for diagnosis and staging of prostate cancer, and continues to publish many papers on this topic. Within the multidisciplinary GU Oncology team which he leads at Peter Mac, he also has extensive experience using PSMA-based therapies such as 177Lutetium-PSMA as a therapy for advanced prostate cancer. He continues to lead and participate in many clinical trials involving PSMA PET/CT for imaging as well as for therapy.
proPSMA trial establishes superiority of PSMA PET/CT
The Lancet 2020
In March 2020, the results of the proPSMA trial were published in the Lancet. This prospective multicentre trial of 300 men was led by Professor Michael Hofman from Peter Mac, with Professor Declan Murphy as senior author. In brief, we demonstrated that PSMA PET/CT was significantly more accurate when compared with conventional scans, and had additional benefits of less radiation for patients, less uncertain results, and more impact in helping clinicians advise patients about best treatment options. This is a practice-changing paper which has received much attention around the world.
Infographic summarises the #proPSMA trial
The PRIMARY Trial
We are conducting a prospective trial comparing PSMA PET/CT with mpMRI in men undergoing prostate biopsy for the first time. Contact Professor Murphy for more details
FAQs
What is a PSMA PET/CT scan?
This scan is called PSMA PET/CT (“prostate specific membrane antigen positron emission tomography/computed tomography”) (“PSMA PET/CT” for short).
This is a full body scan which helps determine if prostate cancer might have spread beyond the prostate.
PSMA is present on the surface of prostate cancer cells. A radioactive substance which binds to PSMA is injected into a vein. This travels around the body and is taken into prostate cancer cells. The patient then undergoes a PET/CT scan. The PET scan lights up areas where PSMA is present at high levels, indicating the presence of prostate cancer cells. The CT scan produces detailed images of the body’s organs and structures. The combination produces whole body three-dimensional imaging enabling visualisation of prostate cancer. The technology can identify tumour deposits as small as 3-4mm in size.
What happens during a PSMA scan?
The PSMA PET scan includes the following procedures performed in a single visit:
● The patient has a needle inserted into a hand or arm vein, and a small amount of a radioactive substance called PSMA (68Ga-PSMA-11) is injected.
● This is followed by a wait of around 1 hour, during which time it is possible to walk around can leave the imaging department. During this time, the PSMA travels through the blood stream and is taken up by any prostate cancer. It has a small amount of radioactivity which is detected by the scanner.
● The patient is positioned on the bed of the scanner to get PET and CT pictures of the body from thighs to head. The total time in the scanner is around 20 minutes.
● A doctor will check the scan to make sure that the pictures are satisfactory. Occasionally, the doctor will request an additional scan to obtain better pictures. The entire visit takes around 90 minutes.
What are the risks associated with a PSMA scan?
IThe PSMA radiotracer that is given does not have any known adverse effects. In the proPSMA study, no adverse effects were reported.
It does result in exposure to a small amount of radiation. As part of everyday living, everyone is exposed to naturally occurring background radiation. This can be measured and the average dose is around 2 millisievert (mSv) each year. The proPSMA study showed that the average dose from a PSMA PET/CT scan was 8 mSv. This was half the dose of current imaging with CT and a bone scan. At this dose level, no harmful effects of radiation have been demonstrated.
There are only minor risks associated with the scan. As with other scans:
● it involves an injection which may cause some discomfort or bruising. Sometimes, the blood vessel may swell, or blood may clot in the blood vessel, or the spot from which blood is taken could become inflamed. Rarely, there could be a minor infection or bleeding. If this happens, it can be easily treated.
● and lying in the scanner can cause claustrophobia (anxiety), occurring in about 5% of patients. If you have experienced this before, you should tell the technologist or nurse who is in the room. The scan can be stopped if needed.
How does it differ from a conventional CT or bone scan?
The standard scanning performed for patients with aggressive prostate cancer are two scans - a bone scan and a CT (Computed Tomography) scan.
The bone scan is good for looking at tumour spread to bones, whereas the CT scan is better for looking at tumour spread to lymph nodes and other organs. A bone scan highlights any areas of bone that are damaged and reacting to a tumour deposit. However, it is not specific for prostate cancer as many other causes of bone injury, for example fractures, also appear on these scans. To obtain a bone scan, the process is similar to a PSMA PET scan. A needle is inserted into a vein, and a radioactive substance that is taken up by bone is injected. This is followed by a 2-4 hour wait and then a scan which takes around 45 minute. The entire visit takes around 5 hours.
The CT scan provides detailed pictures of tissues but it is also not specific for prostate cancer. Tumours generally need be larger than 1 to 1.5cm to be identified on a standard CT scan. To obtain a CT scan, you are positioned on the scanner bed. A needle is inserted and a dye is injected to highlight blood vessels. This makes it easier for the radiologist to interpret the images. The scan itself takes less than 5 minutes.
Could all prostate cancer patients benefit from a PSMA scan?
Not at present. For now, we can say that newly-diagnosed patients with quite aggressive cancer, who are being considered for surgery or radiotherapy, should have a PSMA PET/CT instead of conventional scans such as CT and bone scan. Also, patients who have previously had surgery or radiotherapy for prostate cancer, but who are suspected of having recurrence of their cancer, may benefit from having a PSMA PET/CT as it is more likely to detect any recurrence. Studies are ongoing to determine the value of PSMA PET/CT in patients with earlier and later stages of prostate cancer.
Where can I obtain a PSMA PET/CT scan and how much does it cost?
At present, the availability of PSMA PET/CT is quite variable around the world. In some countries such as Australia and Germany, there is a lot of experience and availability, whereas in countries such as the UK and the USA, there is much less access. This is due to different regulations around radioactive substances in different countries. The scan is not yet approved by the Food and Drug Administration (FDA) in the USA.
Also, costs vary considerably depending on local regulatory and reimbursement. Hopefully the proPSMA trial will lead to improved availability and reimbursement around the world. Prostate cancer specialists can advise on local availability.
At Peter Mac, we have extensive experience using PSMA PET/CT since 2014, and continue to run many studies in this area.