Performance of the novel ¹⁸F-labeled prostate-specific membrane antigen-ligand PSMA-7 for PET/CT in prostate cancer patients

Objectives: We evaluated the sensitivity of the novel ¹⁸F-labeled PSMA-ligand ¹⁸F-PSMA-7 for PET/CT imaging of prostate cancer patients.

Methods: In this IRB-approved study, our initial experience in 10 patients demonstrated that the sensitivity of ¹⁸F-PSMA-7 was at least equivalent to ⁶⁸Ga-PSMA-11. Both PSMA-tracers were administered less than 3 weeks apart. Next, we examined 124 consecutive patients with biochemical recurrence (BCR), therapy monitoring of metastases or staging of prostate cancer using ¹⁸F-PSMA-7 PET/CT. Out of these 124 patients, 49 were referred for therapy monitoring while under androgen deprivation therapy (ADT). Further, 51 patients had been scanned with other PSMA-tracers in the previous two years (39x ⁶⁸Ga-PSMA-11, 13x ¹⁸F-DCFPyL, 8x ¹⁷⁷Lu-PSMA-617).

Results: No drug-related adverse events occurred. In patients with BCR after prostatectomy, who presented with PSA levels of 0.17 ng/mL or higher, and in patients with BCR after radiotherapy, who exhibited a PSA increase of at least 2 ng/mL, the sensitivity to detect any PSMA-positive lesion was 83.0% (44/53 patients). Patients, who were referred for ¹⁸F-PSMA-7 PET/CT imaging for therapy monitoring, revealed PSMA-positivity of their metastases in 100% without ADT (6/6 patients), and in 87.8% with ADT (43/49 patients). In the initial staging, the primary tumor was PSMA-positive in all patients (7/7 patients). Comparing ⁶⁸Ga-PSMA-11 or ¹⁸F-DCFPyL to ¹⁸F-PSMA-7 in the follow-up exams, the PSMA accumulation was concordantly positive in the culprit lesion in 44/47 patients or concordantly negative in 4/4 patients. In the pilot study of 10 patients, who were examined with both PSMA-tracers, 6 patients exhibited at least one PSMA-positive suspicious lesion detected by ⁶⁸Ga-PSMA-11 or ¹⁸F-PSMA-7 PET/CT, respectively. In 4 of these 6 patients, we detected at least one additional PSMA-positive lesion using ¹⁸F-PSMA-7, compared to the corresponding ⁶⁸Ga-PSMA-11 PET scan. Conclusion: The radiopharmaceutical ¹⁸F-PSMA-7 tracer was safe. We found that ¹⁸F-PSMA-7 was not inferior, when directly compared with ⁶⁸Ga-PSMA-11 in the pilot study. Moreover, we detected additional PSMA-avid lesions using ¹⁸F-PSMA-7 in oligo-metastasized patients with BCR and low PSA levels. In the subsequent larger cohort, we described PSMA-positive lesions in 83.0% of our BCR patients by ¹⁸F-PSMA-7 PET/CT and confirmed an at least equivalent sensitivity of ¹⁸F-PSMA-7 to other PSMA-ligands used at the same institution: In our previous studies in BCR cohorts we had reported a sensitivity of 74.2% for ¹⁸F-DCFPyL and 79.1% for ⁶⁸Ga-PSMA-11, respectively. We recommend ¹⁸F-PSMA-7 for prospective trials. Research support: none