A Cleveland Clinic study suggests that PSMA-PET scans can help doctors precisely target recurrent prostate cancer with low-dose-rate (LDR) brachytherapy, potentially offering effective treatment with fewer side effects.
Researchers at Cleveland Clinic have reported that PSMA-PET-guided low-dose-rate (LDR) brachytherapy can effectively treat prostate cancer that returns locally after earlier treatment.
The study analyzed 105 patients whose recurrent prostate cancer was identified using prostate-specific membrane antigen (PSMA) PET scans. Doctors then used the scans to locate the cancer precisely and implanted radioactive seeds directly into the recurrent tumors.
The findings were presented on September 28 at the American Society for Radiation Oncology (ASTRO) meeting in Boston. The researchers said the approach could provide an alternative to higher-dose stereotactic body radiotherapy (SBRT) for selected patients.
Targeted treatment
The LDR brachytherapy procedure used iodine-125 seeds, with a prescribed dose of 144 Gy. Doctors generally used a 0.5-cm treatment margin, but avoided adding a margin near sensitive structures such as the bladder, urethra and rectum.
At a median follow-up of 22.3 months, 83 patients, or 79%, had no evidence of disease. One patient died from prostate cancer, according to the study results.
The researchers also assessed treatment-related side effects. While complications were not completely absent, the study team reported that toxicity was very low.
“To treat something that’s essentially a tiny dot on the PET scan with SBRT would be overkill and fraught with side effects,” said study lead Jay Ciezki, MD, of Cleveland Clinic.
He added that the side effects from the LDR procedure were “not zero, but darn close.”
Why it matters
LDR brachytherapy delivers radiation directly to the tumor and causes less radiation scatter than high-energy beam radiation. According to the researchers, about 50% of the radiation dose typically spreads only around half an inch from the treatment target, while high-energy beam radiation can spread much farther.
The researchers will next study whether the exact location of cancer recurrence within the prostate affects treatment outcomes. They also plan to explore how PSMA-PET imaging can be better used to guide treatment decisions.
“This is now an option for patients who have local recurrences that appears to be as good if not better than other treatment options,” Ciezki said.
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