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ASTRO 2022: PSMA PET/CT and Its Impact on Prostate Cancer Salvage Radiation Therapy Management

By: Julia Fiederlein
Posted: Wednesday, October 26, 2022

Wesley R. Armstrong, BS, of UCLA Nuclear Medicine, Los Angeles, and colleagues conducted the phase III prostate-specific membrane antigen stereotactic radiation therapy (PSMA SRT) trial to compare the success rates of salvage radiation therapy for recurrence of prostate cancer after radical prostatectomy with and without planning based on PSMA PET/CT. The impact of PSMA PET/CT on the treatment plan, which was evaluated as a secondary endpoint, was discussed during the 2022 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 156). The investigators expect that 5-year follow-up will show the impact of such PSMA imaing on biochemical recurrence–free survival.

Patients were randomly assigned to undergo standard salvage radiation therapy with any conventional imaging aside from PSMA PET/CT (n = 90) or to undergo a 68Ga–PSMA-11 PET/CT scan prior to salvage radiation therapy (n = 103). The intended and delivered salvage radiation therapy plans were reported before randomization and after treatment, respectively. Changes in the initial treatment intent after randomization were classified as major (change of androgen-deprivation therapy duration ≥ 3 months, change of standard radiation therapy volumes, target volume delineation beyond standard radiation therapy field, simultaneous integrated boost beyond standard radiation therapy fields, and initiation of advanced systemic therapy) or minor (simultaneous integrated boost within standard radiation therapy fields).

There were minor changes in 0% of patients who underwent conventional imaging and in 7% of those who received PSMA intervention (P = .02). Major changes were reported less frequently with conventional imaging than with PSMA intervention (22% vs. 44%; P = .004); most of the major changes with PSMA intervention were PSMA-related (71%). Higher rates of treatment escalation (69% vs. 41%; P = .048) and lower rates of de-escalation (19% vs. 59%; P = .004) occurred with PSMA intervention. A total of 9% and 1% of the PSMA intervention and conventional imaging groups, respectively, were administered advanced systemic therapy (P = .044).

Disclosure: Mr. Armstrong reported no conflicts of interest.


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