Low-dose-rate (LDR) brachytherapy guided by prostate-specific membrane antigen (PSMA) PET scans can effectively treat locally recurrent prostate cancer, Cleveland Clinic physicians have reported.
The researchers analyzed data from 105 patients who underwent PSMA-PET scans to identify the precise locations of recurrences within the prostate, and then implanted low-dose-rate brachytherapy seeds inside the tumors, with findings suggesting the technique may be an effective alternative to higher-dose stereotactic body radiotherapy (SBRT), according to the group.
“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, in a Cleveland Clinic release. The results were presented September 28 at the American Society for Radiation Oncology (ASTRO) meeting in Boston.
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, according to the group.
For the study, the researchers analyzed data on 105 patients, all of who had recurrence identified by PSMA-PET and who then underwent all had focal salvage LDR brachytherapy. A dose of 144 Gy was prescribed with iodine-125. A margin of 0.5 cm was given except when adjacent to bladder, urethra, or rectum, in which case no margin was given with any of those structures. The efficacy was assessed by PSA readings and imaging. Toxicity was also assessed.
At last follow-up (median, 22.3 months) 83 (79%) patients were without evidence of disease, according to the results. One patient died of disease. On univariable analysis of clinical failure after focal salvage the LDR procedure, longer time to local failure (p = 0.0231, HR: 0.981-0.999) and seminal vesicle treatment (p = 0.0272. HR: 1.119-6.536) were significant, the researchers noted.
In addition, side effects were “not zero, but darn close,” Ciezki said.
Next steps will be to study whether the location of recurrence within the prostate matters for treatment selection and outcome and understand how better to use PSMA PET imaging to guide treatment decisions and improve outcomes for patients, Ciezki added.
“This is now an option for patients who have local recurrences that appears to be as good if not better than other treatment options,” he said.
Full data is available here in the ASTRO abstract.
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