18F-Flotufolastat Positron Emission Tomography in African American Patients With Suspected Prostate Cancer Recurrence: Findings From the Phase 3 SPOTLIGHT Study

Purpose

Although African American (AA) patients are disproportionately affected by prostate cancer, they are often underrepresented in oncology clinical trials. The SPOTLIGHT study (NCT04186845) assessed the novel diagnostic positron emission tomography radiopharmaceutical, ¹⁸F-flotufolastat (¹⁸F-rhPSMA-7.3), in patients with recurrent prostate cancer. The proportion of AA patients enrolled in SPOTLIGHT (17%) was greater than typically enrolled in oncology trials (8.5%) and was representative of the US population (14%). This post hoc analysis of SPOTLIGHT evaluates the diagnostic performance of ¹⁸F-flotufolastat in AA patients.

Methods and Materials

Patients underwent positron emission tomography/computed tomography 50 to 70 minutes after intravenous administration of 296 MBq ¹⁸F-flotufolastat. Three blinded readers evaluated all images, with the majority read (agreement of ≥2 readers) result reported here. Standard of truth (SoT) was established with histopathology or correlative imaging. Data from AA patients were evaluated to determine the ¹⁸F-flotufolastat overall detection rate (DR), positive predictive value (PPV), and verified DR (VDR). VDR (SoT-verified) is equivalent to DR × PPV.

Results

In total, 61 of 366 (17%) patients were AAs. Although baseline characteristics were broadly similar, fewer AA patients (56%) had undergone prostatectomy than non-AA patients (82%). The patient-level DR was 93% (57/61) in AA patients, increasing from 67% at prostate-specific antigen <0.5 ng/mL to 100% at prostate-specific antigen ≥10 ng/mL. Patient-level DR was marginally lower in all other patients (87%, 264/305). However, when stratifying by prior treatment, DRs were similar across ethnic groups in postprostatectomy patients, but in patients with intact prostates, AA patients had higher prostate DR than non-AA patients. SoT-verification (predominantly with conventional imaging [79%]) gave a VDR of 64% and PPV of 68% in AA patients, versus 55% and 64%, respectively, in all other patients.

Conclusions

¹⁸F-Flotufolastat DRs were marginally higher in AA patients than in all other patients enrolled in SPOTLIGHT. High VDR and PPV were also achieved in AA patients from across all participating centers, indicating the broad applicability of newly US Food and Drug Administration–approved ¹⁸F-flotufolastat to the US population as a whole.