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Location: Marriott Marquis
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PQA 08 - PQA 08 Genitourinary Cancer, Patient Safety, and Nursing/Supportive Care Poster Q&A

3210 - 18F-Flotufolastat Detection Rates in the Pelvis Region for Patients with Prostate Cancer Recurrence after Radical Prostatectomy and PSA Levels <1 ng/mL: Data from the Phase 3 SPOTLIGHT S

Tuesday, October 1, 2024
2:30 PM – 3:45 PM ET
Location: Hall C

Screen: 14

B. F. Koontz1, B. Lowentritt2, A. Jani3, P. Davis4, A. Chau5, B. Chapin6, and D. M. Schuster7; 1East Carolina University, Greenville, NC, 2Chesapeake Urology Research Associates, Towson, MD, 3Department of Radiation Oncology, Emory University, Atlanta, GA, 4Blue Earth Diagnostics, Inc., Monroe Township, NJ, 5Blue Earth Diagnostics, Oxford, United Kingdom, 6Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, 7Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA

Purpose/Objective(s): Radiohybrid PET radiopharmaceutical 18F-flotufolastat (18F-rhPSMA-7.3) is a novel high affinity PSMA-targeting ligand. Clinical data show it to have lower average urinary excretion than reported for other renally-cleared PSMA-PET-ligands, suggesting potential for improved lesion detection in the pelvis. The SPOTLIGHT study (NCT04186845) evaluated the performance of 18F-flotufolastat in men with suspected prostate cancer recurrence. Here, we report findings from a post-hoc analysis of SPOTLIGHT to determine 18F-flotufolastat detection rates (DR) in the pelvic region (prostate bed and pelvic lymph nodes [PLN]) of patients previously treated with radical prostatectomy (RP) only, and with a baseline (prior to PET) PSA level <1 ng/mL.

Materials/

Methods: The present report analyzed all PSA-recurrent patients previously treated with RP only who had an evaluable scan and a baseline PSA <1 ng/mL. Patients underwent PET 50–70 min after IV administration of 296 MBq 18F-flotufolastat. Scans were evaluated by 3 blinded central readers, with the majority read representing agreement between =2 readers. Patient-level and pelvic region DR (% positivity of all scans) by majority read were determined, stratifying DR according to patients’ baseline PSA.


Results: Of the 389 SPOTLIGHT patients with an evaluable 18F-flotufolastat scan, 168 had previously undergone RP only. Of these, 119 had a baseline PSA <1 ng/mL and were eligible for this analysis. In total, 69% (82/119) of patients with a PSA <1 ng/mL and 67% (57/85) with a PSA <0.5 ng/mL had a positive 18F-flotufolastat scan by majority read.

As shown in Table 1, at PSA <0.5 ng/mL, the prostate bed DR was 25/85 (29%). However, in 20/85 (24%) patients, recurrence was limited to the prostate bed only. PLN DR was 13/85 (15%), with 6/85 (7.1%) showing recurrence only in PLN. At PSA =0.5 – <1 ng/mL, the prostate bed DR increased to 14/34 (41%) with the prostate bed only DR remaining at 8/34 (24%). PLN DR also increased to 13/34 (38%), with 6/34 (18%) showing recurrence only in PLN.



Conclusion: Among this post-RP cohort of patients with PSA levels <1 ng/mL, 69% had 18F-flotufolastat-avid lesions. Approximately one-third of patients had detectable recurrence in the prostate bed, suggesting 18F-flotufolastat may be a useful tool for identification of recurrence adjacent to bladder, thus providing potential to guide curative salvage therapy in men with early biochemical recurrence of prostate cancer.

Abstract 3210 – Table 1

Table 1. Majority read pelvic region DR in patients previously treated with RP only and with PSA <1 ng/mL
PSA, ng/mL Prostate bed DR* Prostate bed ONLY DR PLN DR* PLN ONLY DR
<0.5 29% 25/85 24% 20/85 15% 13/85 7.1% 6/85
=0.5 – <1 41% 14/34 24% 8/34 38% 13/34 18% 6/34
Cumulative (all <1) 33% 39/119 24% 28/119 22% 26/119 10% 12/119
*includes scans that were positive in other regions