A five-year retrospective study led by investigators at the UCLA Health Jonsson Comprehensive Cancer Center and published in the Journal of the National Comprehensive Cancer Network shows that prostate-specific membrane antigen (PSMA) PET/CT scans can help doctors target treatment more precisely for men whose prostate cancer returns after surgery, improving long-term outcomes and potentially reducing unnecessary side effects.
Why it matters
Approximately 20% to 40% of men who have surgery for localized prostate cancer will see the cancer return within 10 years, often first detected by a rising PSA blood test. When this happens, doctors typically use radiation therapy, which can slow the cancer's return, reduce the risk of it spreading and improve long-term survival, especially when treatment begins early at very low PSA levels. The challenge is that traditional scans, such as bone scans, CT and MRI, often cannot pinpoint the location of recurrent cancer at low PSA levels. As a result, doctors frequently treat standard areas, such as the prostate bed, and may add radiation to nearby lymph nodes or hormone therapy even when it may not be needed.
A newer imaging tool, PSMA PET/CT, uses a radioactive tracer that binds to prostate-specific membrane antigen, a protein found on most prostate cancer cells. This allows doctors to detect very small clusters of cancer that would otherwise be invisible on standard scans, making it more sensitive than conventional imaging for detecting prostate cancer recurrence and allowing clinicians to see whether the disease is confined to the prostate bed, has spread to nearby lymph nodes, has traveled to other parts of the body, or is not yet visible. By clearly showing the location and extent of recurrent disease, PSMA PET/CT helps doctors tailor treatment to each patient's needs. The information can guide personalized decisions, such as whether to expand radiation to the whole pelvis, deliver higher doses to visible tumors, or add hormone therapy.
What the study did
The study followed 113 men whose PSA levels rose after prostate cancer surgery. All patients underwent PSMA PET/CT scans before receiving radiation therapy, and their outcomes were tracked for a median of five years. Doctors used the scan results to personalize treatment, including decisions about whether to treat the whole pelvis instead of just the prostate bed, add androgen deprivation therapy for patients with cancer in lymph nodes or other distant sites, and deliver higher radiation doses to areas of visible disease.
Researchers tracked long-term outcomes such as cancer recurrence, spread to other parts of the body, and the need for additional treatments. About 60 percent of patients had cancer detected on PSMA PET/CT scans, including many whose disease had already spread beyond the prostate bed to lymph nodes or bones, allowing clinicians to adjust treatment strategies accordingly.
What they found
- Patients with visible cancer in the prostate bed or pelvic lymph nodes benefited most from whole-pelvis radiotherapy, which treats nearby lymph nodes in addition to the prostate bed.
- Patients whose scans showed cancer in lymph nodes or distant sites had better outcomes when androgen deprivation therapy, a type of hormone therapy that suppresses testosterone, was added.
- Patients whose scans showed no visible disease had the best outcomes, suggesting early radiation alone can be effective.
- At five years, nearly all patients were alive and 72% had no distant spread of the disease.
"PSMA PET/CT scans allow us to see exactly where cancer is and tailor treatment accordingly," said Dr. Jeremie Calais , director of the clinical research program in the department of Nuclear Medicine and Theranostics, associate professor at the David Geffen School of Medicine at UCLA and senior author of the study. "Patients can get the therapy they need while avoiding unnecessary side effects, and even those with no visible disease can do very well with standard radiation."
What this means for patients
The findings suggest that more personalized care is possible for men experiencing recurrent prostate cancer. Patients with limited disease may avoid unnecessary hormone therapy, while those with more extensive disease can receive more targeted and effective treatment.
"This research underscores the value of incorporating PSMA PET/CT findings into clinical guidelines when deciding whether to add whole-pelvis radiation or hormone therapy to salvage radiation after prostate surgery," said Dr. John Nikitas , a resident in the department of radiation oncology at UCLA Health, and first author of the study. "We also found that traditional measures such as PSA level were not strongly linked to long-term response, highlighting the importance of imaging-based, rather than PSA-based, decision-making."
About the research team
Other UCLA authors are Clayton Smith, Wesley Armstrong, Vishnu Murthy, Tristan Grogan, Kevyn Clark, Jonathan Moore, Makayla Roberts, Andrea Farolfi, Robert Reiter, Matthew Rettig, John Shen, Luca Valle, Nicholas Nickols, Michael Steinberg, Johannes Czernin and Amar Kishan.
