BY DRS SAMUEL NGUKU AND KHALID MAKHDOMI
Prostate Specific Membrane Antigen (PSMA) PET-CT scan is the latest and most advanced scan available for the evaluation of patients with prostate cancer. It has been available for only a few years in the most advanced centres in the world. It is presently only available in a few centres in Africa, and has not been available in our region until now.
Though MRI and CT scans have been available for long for study of prostate cancer by providing anatomical (structural) information, the PET-CT scan is able to provide vital additional functional or molecular information, which significantly increases the ability or sensitivity of the scan to detect the spread of prostate cancer. This is achieved by injecting a small amount of a radioactive substance that binds to prostate cancer cells in the body.
The site of these cells can then be detected using the PET CT scanner, which detects the radioactivity emitted from the radioactive substance using the PET scan and correlates it with the exact anatomical location provided by the CT scan. Several radioactive substances can be used for this scan.
The radioactive substance that we are using is Fluorine-18 Prostate Specific Membrane Antigen (PSMA) that is produced using a cyclotron and complex radiochemistry procedures. This is the latest and the most accurate and sensitive radioactive substance available for this scan. Its radioactivity decays very quickly and is over within a few hours. Thus it needs to be produced within the vicinity of the institution performing the scan.
Following advancement in our PET CT Scan technology capacity and growth in the expertise of our radiology and laboratory departments, we are now able to produce the radioactive substance required for this scan using our cyclotron and radiochemistry lab, as well as conduct the test, at the Aga Khan University Hospital, Nairobi. This will be a significant development in the management of prostate cancer in the region.
The test
PSMA PET CT scan takes approximately two hours. It involves the injection of a small amount of the radioactive substance (radiotracer) through a vein. The radiotracer is then allowed around one hour to distribute within the body after which the patient is placed in a PET CT scanner and the scan
The PSMA PET CT scan checks for sites of active prostate cancer cells. It is the most sensitive scan to look for spread of prostate cancer within the body, which happens mainly in the bones and lymph nodes. The scan takes approximately 20-30 minutes.
No particular patient preparation is required for this examination.
Advantages
Compared to the presently established methods of imaging prostate cancer such as MRI and bone scan, PSMA PET CT scan has higher sensitivity for identification of sites of prostate cancer spread, be it in the bones or in any other organ such as lymph nodes, liver and lungs. It can be used for this purpose at the initial diagnosis of the disease, during follow-up and when disease recurrence is suspected.
In view of its higher sensitivity, PSMA PET CT scan can identify sites of early prostate cancer spread before they are picked up by conventional imaging modalities. This allows for better treatment options of the disease at a very early stage, which was not possible till now. This is bound to have a major impact on treatment outcome for those with prostate cancer.
Writers are section head, PET CT and section head, nuclear medicine, Aga Khan University Hospital respectively
