When it comes to detecting and treating localized, metastatic, or recurrent prostate cancer, precision diagnosis is always a key factor. The PSMA PET/CT scan is a breakthrough imaging technology that improves detection and localization of cancer throughout the body, which can lead to better treatment planning and outcomes. Provision Diagnostic Imaging, located in Knoxville, Tenn., was the first imaging center in East Tennessee to offer this procedure and continues to lead the way as new PSMA PET/CT tools emerge.
What is PSMA?
To understand why the PSMA PET/CT scan is such a valuable diagnostic tool for localized, metastatic or recurrent prostate cancer patients, it helps to understand what “PSMA” is. You’ve probably heard the term “PSA” before, which stands for prostate-specific antigen. PSA is a protein produced by cells of the prostate gland. Your PSA level is detected through a blood test and abnormally high levels can potentially indicate the presence of cancer. A rising PSA level in a previously treated patient can indicate cancer recurrence.
Similarly, prostate-specific membrane antigen (PSMA) is also a protein associated with the presence of prostate cancer. PSMA proteins are found on 95% of prostate cells, but the amount of PSMA is much higher on cancerous cells. Since PSMA is found on the surface of cells, it can be detected through specialized and specific imaging procedures.
Improving PSMA detection
Detecting the presence and localization of PSMA is where the PSMA PET/CT changes the game. Before this technology, physicians would often use other methods like a CT scan or bone scan. However, those procedures may not reveal many of the prostate cancer “hot spots.” For recurrent prostate cancer, it was often difficult to know where exactly the cancer had returned.
Now, with PSMA PET/CT, those “hot spots” can be detected more precisely and potentially sooner, allowing for more successful treatment and outcomes. It works by injecting a radioactive tracer into the body. This tracer is specifically engineered to latch onto PSMA proteins. A PET scan is then performed, which “lights up” areas in which the tracer is found. The results of the PET can be combined with a CT scan, so physicians can see precisely where PSMA is present in the body.
In fact, a study of more than 300 men concluded the PSMA PET/CT was 92% accurate, compared to just 65% accuracy for the standard CT/Bone scan approach.1 The National Cancer Institute reports PSMA PET/CT was “more accurate for both metastases found in lymph nodes in the pelvis and in more distant parts of the body, including bone.” Furthermore, this study also showed that radiation exposure was significantly lower with PSMA PET/CT, compared to the standard approach.
Who should get a PSMA PET/CT scan?
Current guidelines from both the National Comprehensive Cancer Network (NCCN) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) recommend the PSMA PET/CT scan for two subsets of patients:
- Men with confirmed localized prostate cancer where metastatic disease is suspected
- Men previously treated for prostate cancer where disease recurrence is suspected based on rising PSA levels
Since each case is unique, it’s important to be aware of all your diagnostic options and discuss with your physician what’s best for you. Take Terry Douglass, for instance. His PSA increased from 4.2 in 2020 to 5.97 in 2022. The normal standard of care in his case would have been routine follow-ups on the PSA blood test. With no other symptoms or risk factors, there was supposedly nothing to be concerned about.
However, Terry was aware of the PSMA PET/CT scan and discussed it with his physician. After reviewing the specifics of his case, his physician decided to order the scan, which revealed a one centimeter cancerous lesion in his prostate. Terry proceeded with precision treatment of just the lesion and is now free of cancer. He did not experience the often serious short- and long-term side effects associated with more aggressive treatments of the entire prostate.
It’s important to reiterate that ordering a PSMA PET/CT scan without a prior prostate cancer diagnosis is not the current recommendation from the NCCN or SNMMI. Nevertheless, each man should consider what’s best for him and learn as much about his specific situation and options as possible.
The Future of PSMA PET/CT
The first radioactive tracers used in the PSMA PET/CT scan were designed for diagnostic purposes. However, the future of this technology may lie in PSMA’s ability to be used for both diagnostics and therapeutics using a “radiohybrid” PSMA tracer. In other words, the same PSMA tracer that is used to detect the cancer could also be used to treat the cancer. This is known as theranostics, combining therapeutics and diagnostics.
While researchers are still studying the therapeutic capabilities of the radiohybrid tracer, the potential is very promising. First, using a diagnostic radioactive isotope like Flourine-18, the radiohybrid tracer would latch onto cancer cells, revealing their location in the body. Then later, using a therapeutic radioactive isotope like Lutetium-77, the same tracer could be injected, this time latching onto those same cancer cells and attacking them with radiation. Dr. Judson Gash, a Radiologist and Medical Director at Provision Diagnostic Imaging, says the benefits of this “See it, Treat it” approach could make a huge difference for patients.
“It’s an important part of our mission to embrace innovation in cancer diagnostics and treatment,” says Dr. Gash. “That’s why Provision Diagnostic Imaging was the first imaging center in Tennessee to perform a PSMA PET/CT scan using a radiohybrid tracer.”
Between the improved precision in diagnosing prostate cancer and the potential to become part of the treatment plan, it’s clear that the PSMA PET/CT scan is a game-changer when it comes to diagnosis and treatment planning for the best possible outcomes in patients with localized, metastatic, or recurrent prostate cancer.
- Hofman, M. S., Lawrentschuk, N., Francis, R. J., Tang, C., Vela, I., Thomas, P., Rutherford, N., Martin, J. M., Frydenberg, M., Shakher, R., Wong, L. M., Taubman, K., Ting Lee, S., Hsiao, E., Roach, P., Nottage, M., Kirkwood, I., Hayne, D., Link, E., Marusic, P., … proPSMA Study Group Collaborators (2020). Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA): a prospective, randomised, multicentre study. Lancet (London, England), 395(10231), 1208–1216. https://doi.org/10.1016/S0140-6736(20)30314-7