When it comes to diagnosing localized prostate cancer (PCa), there’s the old world and the new world.
Localized PCa means the disease is still contained in the prostate gland at the time of treatment. This knowledge is a crucial key to wise treatment decisions, especially radical treatments aimed at removing or destroying the entire gland. But if PCa has already left the gland, why put a patient through such aggressive treatment that can result in urinary or sexual side effects? In such situations, there is a high probability of recurrence, yet few potentially curative options left.
A common location for early PCa spread is nearby pelvic lymph nodes. In the old diagnostic world, it was very difficult to detect pelvic lymph node involvement, even for patients whose high PSA and high-grade biopsy results raised a suspicion of spread. After a positive biopsy, patients were routinely sent for a CT scan and a bone scan to check for possible metastasis (mets). However, those older standard-of-care imaging methods missed very small mets. No doubt patients were relieved when told their cancer was still contained; they then proceeded to have a radical prostatectomy or a course of radiation to the whole gland, confident that they were rid of PCa. Imagine the shock, dismay, and even sense of betrayal when their PSA began to rise a few years later.
The new world of PSMA imaging
Now, in the new world of diagnosis, there is an imaging technology that leaves conventional CT scanning in its outdated dust. It is called PSMA PET/CT scan, sometimes referred to as the “Best Available Method to See Prostate Cancer Anywhere in the Body.”[i] It relies on Positron Emission Tomography (PET), which involves radioactive tracers (specially generated molecules) that are taken up by cancer cells, and emit small amounts of radioactivity that “light up” on a scan.
Earlier radiotracers did not generally bind with prostate cancer cells. Just within the last few years, however, researchers developed specialized radiohybrid tracers that are formulated to bind with prostate-specific membrane antigen (PSMA), a surface protein particularly abundant on PCa cells much more than on normal prostate cells. When these hybrids adhere to the cancer cells, it’s like shining a spotlight on even very small mets in lymph nodes, bone, and organ tissue. Knowing the location of mets, even early lymph node involvement, makes an enormous difference for treatment planning.
In a new study comparing ordinary CT vs. PSMA-PET formulated with a radiotracer called F-18, the research team demonstrated that the F-18 PSMA-PET scan was “more effective than CT for identifying tumors prior to surgery in patients with advanced prostate cancer.”[ii] The study involved a group of PCa patients who underwent prostatectomy/removal of pelvic lymph nodes, and whose presurgical CT scans and F-18 PSMA-PET results were available for comparison with the actual surgical prostate and node specimens. Side-by-side comparisons of tissue and scan results found that overall imaging accuracy for detecting PCa in lymph nodes was 88% for PSMA-PET vs. 75.9% for CT.
Ongoing refinements in radiohybrids are producing formulations with high bonding power to PCa cells but that also wash out of the body more readily to minimize radiation exposure—even though the radiation itself has a short lifespan.
The good news for PCa patients is that the new world of diagnosis affords them accurate pre-treatment detection of spread. In turn, new therapies such as immunotherapy and PSMA-based treatments that target individual PCa cells anywhere in the body are already in use, or are in clinical trials. As these new clinical methods become available, the day is fast approaching when we can literally design treatment strategies for each unique patient. This will be the ultimate in matching therapy to disease.
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[ii] Morton, Will. “Radiohybrid tracer superior to CT in prostate cancer imaging.”AuntMinnie.com, Jan. 13, 2022. https://www.auntminnie.com/index.aspx?sec=sup&sub=mol&pag=dis&ItemID=134713