A new treatment that combines a specialized radioactive drug with focused radiation therapy has been shown to significantly slow the progression of recurrent prostate cancer, giving patients more time before they need hormone therapy.
The results come from the LUNAR trial, a clinical study led by researchers at UCLA Health’s Jonsson Comprehensive Cancer Center, and were presented at the 2025 American Society for Radiation Oncology Annual Meeting in San Francisco.
Prostate cancer is the second most common cancer in men worldwide.
For some patients, the disease comes back years after initial treatment, often in only a few new spots, a stage known as oligorecurrent disease.
Traditionally, these patients are treated with stereotactic body radiotherapy (SBRT), a precise form of radiation that targets visible tumors.
While SBRT can delay progression and postpone the need for hormone therapy, it cannot address microscopic cancer cells that scans do not detect.
To address this challenge, researchers tested a radioligand drug called 177Lu-PNT2002.
The drug targets a protein called PSMA, found on the surface of prostate cancer cells, and delivers radiation directly to them, while sparing healthy tissue.
In the LUNAR trial, 92 men with recurrent prostate cancer were randomly assigned to receive either SBRT alone or two doses of 177Lu-PNT2002 followed by SBRT.
The results were striking. Patients who received the combination therapy went a median of 17.6 months before their cancer progressed, compared with just 7.4 months for those who received SBRT alone.
This translated into a 63 percent reduction in the risk of progression, the need for hormone therapy, or death. On average, men in the combination group also delayed starting hormone therapy by an additional 10 months compared with the SBRT-only group.
“This is the first randomized trial to show that PSMA-targeting radioligand therapy can meaningfully delay progression when added to focused radiation,” said Dr. Amar Kishan, the study’s lead author and executive vice chair of radiation oncology at UCLA.
“It gives patients more time before starting hormonal therapy, which often causes fatigue, bone loss, and other side effects.”
The study also revealed clues about which patients might benefit most.
A stronger immune response after SBRT was linked to better outcomes, and a set of 20 genes related to immune function and DNA repair appeared to predict higher or lower risk of relapse.
Although 64 percent of men in the combination group still experienced progression, the findings establish radioligand therapy as a promising option earlier in the course of the disease. “This is an important proof of principle,” Kishan said.
“It suggests that intervening earlier with targeted therapy can change the course of prostate cancer without adding significant side effects.”
Professor Jeremie Calais, senior author of the study, added that the trial demonstrates the power of combining imaging and therapy.
“This is a great example of how nuclear medicine and radiation oncology can work together to improve outcomes for patients.”
