PET Scans for Prostate Cancer

What is a PET scan?

The PET (Positron Emission Tomography) scan for prostate cancer is usually used when a patient’s PSA level starts to rise following the first line treatment such as radiotherapy or surgery. The scan can indicate the success of treatment or non-removal of cancer. To identify, locate and measure the development of cancer, further assessments are usually required.

When identifying trace amounts of metastases (cancer spreading beyond its original location), PET scans provide more insight than traditional bone scans. They identify metastatic disease and associated microscopic changes in the soft tissue, bones and lymph nodes using radio-tracers, which cancer cells use up far more quickly than healthy cells.

Because cancerous cells typically consume glucose/sugar faster than normal cells they appear brighter in scans and become far more detectable and recognisable during the highly-detailed scan. You may have an imaging method known as the PSMA PET scan that’s used to dictate treatments whilst being more predictive of a patient’s response to treatment.

PET Scan of Prostate
Credit: Getty Images Ltd.

What are PSMA (Prostate-Specific Membrane Antigen) PET scans?

The PSMA (Prostate-Specific Membrane Antigen) PET scan locates and measures the development of cancer on a biological level; by applying radio-tracers such as choline. These scans are proven to be particularly successful in prostate cancer cases. PET scans outperform CT or MRI scans, which are limited to identifying cancer by detecting any changes in size.

Ongoing research¹ shows that PET scans can identify prostate cancer patients who may benefit from Salvage Radiation Treatment (SRT). A patients response to SRT can be predicted accurately using PSMA PET scans. Negative or fossa-confined PSMA patients respond to best to SRT , while those with distant disease or cancerous nodes respond poorly. Negative PSMA PET scans can predict a positive patients response to SRT treatment.

¹The Australian Journal of Nuclear Medicine, PET Scans, December 2017

What do these scans involve?

Patients having a PET scan don’t usually stay in hospital overnight, but may be asked to fast from up to 6 hours prior (drinking water is permissible) and to avoid any strenuous activity from up to 24 hours prior. Due to the time-sensitive nature of the radio-tracers used, good timekeeping is critical in avoiding cancelled appointments.

Although hospital gowns are usually required, patients can sometimes wear their own loose-fitting clothing; no jewelry or metal components including zips or buttons are permissible. With enough notice, hospital staff can usually help the patient with any anxiety or claustrophobia, by offering reassurance and administering a mild sedative if needed.

Patients are required to lie still and silent on a table for around half an hour during the PET scanner. Patients are aided with a headrest and strap. A small amount of radioactive glucose/sugar (radio-tracer) is then injected into the patient’s bloodstream before the scan to identify areas of built-up glucose/sugar.

Patients typically go home on the same day as the side-effects are minimal (some may encounter mild discomfort from having to keep still for the half hour scan duration). Scan results will be sent to your relevant healthcare professional for further analysis and won’t be made available on the day.

PET scan risks

Understandably, most people are reluctant to have radioactive elements injected into their system. However, when put into context, this trace amount of radiation is (approximately) equivalent to the radiation we’re typically exposed to from the sun over a 36 month period.

Also, these radio-tracers diminish in radioactivity and usually exit the body naturally within hours; this can be sped-up with simple fluid intake. Simple precautionary measures such as avoiding extended contact with infants, young children or pregnant women for hours after being scanned is advisable.

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