Priti Patel, CNMT, left, and Terence Wong, MD, PhD, right, meet with a patient before his PSMA PET/CT scan.
A new imaging technique is changing the way aggressive prostate cancer is identified and is making it easier for doctors to design more effective, individualized treatment plans. Duke Health was one of the first centers in the U.S. to offer prostate specific membrane antigen (PSMA) PET/CT imaging following FDA approval of a new radioactive tracer in May 2021. The new technology can identify cancer both in and outside the prostate gland and especially benefits men whose cancer has recurred and are at risk for it spreading to other parts of the body, even after previous treatments.
Beyond a Blood Test
Prostate cancer is typically first detected through a prostate specific antigen (PSA) blood test. Traditionally, elevated PSA levels are followed by a prostate biopsy to confirm or rule out cancer. “The PSA test is a very good marker for the presence of the cancer, but it can't tell you where it is,” said Terence Wong, MD, PhD, a nuclear radiologist at Duke Health. Neither can CT scans or other imaging tests, which can be normal even when prostate cancer is present outside of the prostate gland.
This is a particular concern for men who have just been diagnosed and are at high risk for metastatic cancer or who have already been treated with surgery, radiation, or both and are experiencing a recurrence. “Until now, imaging tests were not sensitive enough to determine if or where the cancer had spread. We needed a new molecular imaging technique,” Dr. Wong said.
Meeting the Need
That need was met when the FDA approved the radioactive tracer 18F-DCFPyL as a molecular imaging marker for prostate cancer. The tracer is injected an hour before imaging and binds to PSMA, a protein on the surface of prostate cancer cells. Cancerous cells are identified as bright spots on the PET scan, and their location is revealed on a CT scan conducted at the same time.
Knowing their exact location can help doctors develop targeted treatment plans -- which may include radiation, chemotherapy, hormone medications, or surgery -- to address each person’s individual needs. “PSMA PET/CT is more sensitive, but most importantly, it is more specific. So if you have a positive test, it's nearly always a true positive,” said Andrew Armstrong, MD, MSc, a medical oncologist at Duke Health. That means doctors can quickly act on information revealed through the scan without having to perform prostate or lymph node biopsies first.
Closer to the Holy Grail
Currently PSMA PET/CT is not intended to be a screening tool. It is for those who have been diagnosed with prostate cancer and who either have a higher chance of it spreading or who have a recurrence and a rising PSA level after initial treatment. “It is for men with suspected metastatic disease in their pelvis -- for instance, in their lymph nodes, or outside of their pelvis in more distant lymph nodes, bones, or organs."
"Our goal is to identify these sites early and to improve cure rates even though they’ve had a relapse, so being able to see the disease is important knowledge,” said Dr. Armstrong. Dr. Wong agreed. “This advancement is much closer to the holy grail of precision and personalized medicine and will have a big impact on patient decision making and treatment options.”