3465 - PSMA-PET Guided Metastasis-Directed Therapy

02:30pm - 03:45pm PT

Hall F

Screen: 28

POSTER

Presenter(s)

Elitza Koutleva, MD, MBA - University of North Carolina at Chapel Hill, Chapel Hill, NC

E. Koutleva¹, A. C. Williams², X. Tan³, M. Rosenberg², A. Wijetunga⁴, M. C. Repka⁴, and S. Sud⁴; ¹University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, ²University of North Carolina, Chapel Hill, NC, ³Gillings School of Global public health, University of North Carolina, Chapel Hill, NC, ⁴Department of Radiation Oncology, University of North Carolina, Chapel Hill, NC

Purpose/Objective(s): Molecular imaging including prostate-specific membrane antigen positron-emission tomography (PSMA-PET) facilitates earlier detection of limited metastatic disease. There is a critical gap in understanding the role of molecular versus conventional imaging in guiding treatment including general classification of oligometastatic disease as well as the role of metastasis directed therapy (MDT) using stereotactic body radiation therapy (SBRT) or external beam radiation therapy (EBRT) to limited avid sites of disease. This study aimed to evaluate whether molecular imaging-guided MDT improves biochemical disease control in a retrospective cohort.

Materials/Methods: We identified 25 patients at a National Cancer Institute-Designated Cancer Center who underwent PSMA-PET guided MDT with SBRT or EBRT between 2022-2024 for oligorecurrent or oligopersistent/oligoprogressive prostate cancer defined as = 5 total or persistently/progressing avid disease sites, respectively. Clinical characteristics were abstracted from the electronic medical record. Biochemical response was defined as a reduction in the absolute value of prostate-specific antigen (PSA) within 6 months of completion vs. start of MDT. A paired two sample t-test was used to compare pre- and post-SBRT PSA values.

Results: All patients underwent PSMA-PET with the Piflufolastat F-18 radiotracer. Of these, 19/25 had oligorecurrent disease and 6/25 had oligopersistent or oligoprogressive disease. The most common type of systemic therapy at time of SBRT consisted of leuprolide acetate or relugolix (18/25) with or without intensification (17/25). 13 patients were on ADT at baseline and 12 patients initiated concurrently with SBRT.

The majority of patients (23/25, 92%) experienced a post MDT decrease in PSA or maintained an undetectable PSA level. Patients who underwent PSMA-PET guided MDT had a significant reduction in PSA following MDT when compared to baseline (mean baseline 6.01 vs. mean post-treatment 1.67, p=0.04). Median baseline and post-SBRT PSA values among all patients was 2.98 (interquartile range of 4.49) and 0.06 (interquartile range of 1.18), respectively. Among patients who were on ADT prior to MDT, the mean baseline vs. post treatment PSA was 7.20 vs. 2.40 and among patients who initiated ADT concurrently with SBRT, the mean baseline vs. post treatment PSA was 4.72 vs. 0.86.

Conclusion: The majority of patients experienced a decrease in PSA level following PSMA-PET guided MDT. These findings support the ability of PSMA-PET to identify lesions driving biochemical progression and suggest further exploration of molecular imaging guided MDT as a consolidation or salvage strategy to enhance disease control among patients with a low burden of PSMA-PET avid disease on systemic therapy.