1222 - A Prospective Single-Arm Study of POSLUMA PET in Very Low Prostate-Specific Antigen Recurrence Following Prostatectomy
Presenter(s)
T. Walburn1, P. Heidari2, N. Mercaldo3, J. S. Hogan1, A. D. Choudhury4, P. L. Lee1, P. L. Nguyen1, P. J. Saylor5, A. V. DAmico1, D. M. Dahl6, M. T. King1, K. Salari6, J. F. McIntyre1, I. Gnanou1, J. V. Mendoza1, R. Perry1, H. Jacene7, S. A. Esfahani2, J. E. Leeman1, and J. A. Efstathiou1; 1Department of Radiation Oncology, Mass General Brigham, Harvard Medical School, Boston, MA, 2Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Mass General Brigham, Harvard Medical School, Boston, MA, 3Department of Radiology, Mass General Brigham, Harvard Medical School, Boston, MA, 4Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 5Department of Medical Oncology, Mass General Brigham, Harvard Medical School, Boston, MA, 6Department of Urology, Mass General Brigham, Harvard Medical School, Boston, MA, 7Department of Radiology, Brigham and Women’s Hospital / Department of Imaging, Dana-Farber Cancer Institute, Boston, MA
Purpose/Objective(s):
Initiating treatment at low prostate-specific antigen (PSA) levels improves outcomes following radical prostatectomy; however, localizing recurrent disease at very low PSA remains challenging. This prospective study evaluated the patient-level detection rate of flotufolastat F 18 (POSLUMA), a prostate-specific membrane antigen (PSMA) positron emission tomography (PET) tracer in men with biochemical recurrence and PSA =0.20 ng/mL following radical prostatectomy.Materials/Methods:
This was a prospective, single-arm study enrolling males with detectable PSA =0.20 ng/mL concerning for biochemical recurrence following radical prostatectomy. All participants underwent flotufolastat F 18 PET/CT imaging. Images were reviewed by local readers and verified by consensus of three independent, experienced reviewers. The primary endpoint was patient-level detection rate, defined as the proportion of patients with at least one PET-positive lesion (uptake =blood pool if lesion <1 cm, uptake =bone marrow if lesion =1 cm) consistent with prostate cancer recurrence. Detection rates and their corresponding exact binomial confidence intervals (CI) were calculated. Fisher’s Exact tests were used to quantify the association between lesion detection and PSA level (<0.1 vs =0.1), post-operative risk group based on surgical pathology, pathologic Gleason score, and immediately detectable PSA after surgery. All analyses were performed using R 4.5.2.Results:
A total of 50 patients were enrolled; 49 underwent PSMA PET imaging. The overall patient-level detection rate by experienced independent reviewers was 49.0% (n=24, 95%CI [34.4-63.7]). The overall patient-level detection rate by local readers was 24.5% (n=12, 95%CI [ 13.3-38.9]). There was insufficient evidence of associations between detection rates and the following variables: PSA subgroup (p=1.00), post-operative risk group (p=0.788), Gleason score (p=0.257), or immediately detectable post-operative PSA (p=0.754).Conclusion:
In this prospective study of men with biochemical recurrence and very low PSA levels following prostatectomy, flotufolastat F 18 PSMA PET demonstrated a detection rate of 49% by consensus of experienced reviewers and 24.5% by local readers. This discrepancy likely reflects differences in interpretation criteria; independent reviewers were required to provide dichotomous “positive” or “negative” assessments for study purposes, whereas local readers were able to classify findings as indeterminate for routine clinical practice, which likely contributed to the lower “positive” interpretations reported by the latter. Overall, these findings provide prospective data for real-world detection rates of recurrent prostate cancer at low PSA using flotufolastat F 18 PET imaging and support its use in this cohort of patients.