Prostate cancer is a leading cause of cancer death in American men, second only to lung cancer. It’s also the most common cancer diagnosed in men after non-melanoma skin cancer, according to the Centers for Disease Control.
Many men who have prostate cancer die from other causes, because it is often a slow-growing cancer. However, men do die from prostate cancer, and survival depends upon many factors. One important factor is early detection of prostate cancer recurrence, a task that is not always easy.
A new study has found promising results from Positron Emission Tomography (PET) used in conjunction with Computed Tomography (CT) with a new PET tracer chemical. The study was conducted on men who have had their prostate glands removed and who have had biochemical signs of recurrence.
Detecting Prostate Cancer Recurrence in Some Men Is More Challenging
Prostate-specific antigen (PSA) is produced by the prostate, and when levels of PSA are elevated, doctors typically want to rule out prostate cancer. High PSA levels can also indicate an enlarged prostate that isn’t cancerous. At the same time, some men with prostate cancer do not have elevated PSA levels, so more information is needed to make a diagnosis.
PET studies using a radioactive tracer called F-18 fluoromethylcholine (FMC) is sometimes used to attempt to diagnose recurrence of prostate cancer, but it has its limitations. A new tracer, called GA-68 PSMA, has been developed, and a recent study compared these two tracers in men with prostate cancer who had their prostates removed or irradiated.
Ga-68 PSMA Vs. F-18 FMC in PET/CT
An Australian study of 39 prostate cancer patients with varying PSA levels after first-round cancer treatment who were not receiving systemic treatment were evaluated by PET. Each underwent F-18 FMC PET, Ga-68 PSMA PET, and diagnostic CT.
Researchers found that even in men with extremely low PSA levels after treatment of prostate cancer, Ga-68 PSMA could detect possible recurrence sites in half the patients, while F-18 FMC only detected recurrences in 12.5% of patients.
This made a measurable practical difference in treatment because steps could be taken early on in recurrence to manage the disease. What was especially promising about the Ga-68 PSMA PET/CT imaging was that it worked so well in men with very low PSA levels.
German Study Shows Positive Results for Ga-68 PSMA Too
Researchers at University Hospital of Heidelberg in Germany also compared these two tracers in men with prostate cancer relapse, in these cases in men with a range of PSA levels (low, normal, and high). The Ga-68 PSMA scans detected a statistically significantly higher number of lesions. In men whose F-18 FMC scans showed lesions, Ga-68 PSMA scans were also performed. Most of these lesions showed increased uptake of the Ga-68 PSMA tracer, and the tumor-to-background ratio was higher in almost all of the lesions on the Ga-68 PSMA scans. In other words, this study echoes the results obtained in the Australian study.
Another Potential Imaging Agent for Diagnosing Prostate Cancer Recurrence
Traditional medical imaging can only do so much to detect prostate cancer recurrence accurately. Researchers at Memorial Sloan Kettering Cancer Center in New York developed another imaging agent for PET/CT from zirconium-89 combined with a fragment of an antibody. The antibody fragment has anti-PSMA qualities and attaches to an enzyme on the exterior of prostate cancer cells wherever they are in the body. This tracer, called Zr-89 Df-IAB2M, allows for faster imaging than other tracers and has been shown to be safe. The resulting PET/CT scans highlight hot spots of PSMA overexpression indicative of metastasized prostate cancer. Specifically, this tracer detects prostate cancer cells that have metastasized to bone, which is difficult to evaluate using standard medical imaging techniques.
Using Nuclear Medicine to Increase Treatment Options for Prostate Cancer
The Board-certified owner-operators of SteleRAD cover all radiology subspecialties and provide services throughout South Florida, including PET/CT studies like the ones used to detect cancer recurrence. If you would like to know more about the benefits that the radiologists of SteleRAD can offer your hospital, imaging center, or medical practice, we encourage you to call 954-358-5250 or contact us online at any time.