PSMA PET Scan-Guided LDR Brachytherapy Can Control Localized Prostate Cancer Recurrence

New research by Cleveland Clinic physicians shows that using a PSMA PET scan to guide placement of low-dose-rate brachytherapy seeds offers an effective way to treat local recurrence of prostate cancer, with far less toxicity than other approaches.

PSMA PET scan technology is capable of catching recurrences much earlier, before metastases grow. This allows them to be controlled effectively with LDR brachytherapy, avoiding the need for treatments that have a higher burden of side effects, like surgery or beam radiation, says first author Dr. Jay Ciezki, MD, radiation oncologist at Cleveland Clinic. “This is now an option for patients who have local recurrences that appears to be as good if not better than other treatment options, and the toxicity is massively lower,” he says.

The data was presented at the ASTRO Annual Meeting.

For the study, researchers followed patients whose prostate cancer came back after completing treatment. They used PSMA PET scans to identify the precise locations of recurrences within the prostate, then implanted low-dose-rate brachytherapy seeds inside the tumors. Researchers found that 79% of patients who were treated with this approach were cancer-free at the time of follow-up. Side effects were “not zero, but darn close,” Dr. Ciezki says.

New treatment opportunities with PSMA pet scanning

The PSMA PET scan is an advanced imaging technique that involves attaching a radioactive tracer to prostate-specific membrane antigens (PSMA) to light up cancer cells with extreme precision. This makes it capable of pinpointing tiny metastases and finding them much earlier than an MRI or traditional PET scan.

At these early stages, LDR brachytherapy is more appropriate than beam radiation. LDR brachytherapy causes far less radiation scatter than high-energy beam radiation, typically spreading 50% of the dose around one-half inch away from the target site. In contrast, high-energy beam radiation can spread 50% of the dose as far as the patient’s hips.

“To treat something that’s essentially a tiny dot on the PET scan with SBRT would be overkill and fraught with side effects,” says Dr. Ciezki.

He noted that none of the patients in the study reported more than a one-grade increase in toxicity.

Next, Dr. Ciezki hopes to study whether the location of recurrence within the prostate matters for treatment selection and outcome. More research is needed to understand how better to use PSMA PET imaging to guide treatment decisions and improve outcomes for patients, he added.

“It’s such an exciting time to be treating people with prostate cancer,” he says. “This has opened up a whole new avenue.”