Abstract

Simple SummaryProstate cancer (PC) is one of the most common malignancies in men. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) hybrid imaging can help improve the diagnosis of recurrent PC, in addition to conventional methods such as computed tomography (CT) or magnetic resonance imaging alone. In order to further evaluate the importance of PSMA hybrid imaging, this study identified prostate-specific antigen (PSA) threshold levels for the detection of PSMA-positive lesions in patients with elevated PSA values after therapy. The thresholds were calculated for two different radiopharmaceuticals, PET/CT with [18F]PSMA-1007 and [68Ga]Ga-PSMA-11, and the results were then compared. In patients who had previously undergone prostatectomy, there was an advantage of PET/CT with [18F]PSMA-1007. Overall, however, the results of both methods were similar. The findings may help improve PC detectability in the future and are likely of considerable interest to clinicians by refining algorithms to help determine the clinical approach for the evaluation and treatment of patients with elevated PSA values after therapy.This study aimed to compare the diagnostic performance of [18F]PSMA-1007 positron emission tomography/computed tomography (PET/CT) (18F-PSMA) and [68Ga]Ga-PSMA-11 PET/CT (68Ga-PSMA) by identifying prostate-specific antigen (PSA) threshold levels for optimal detecting recurrent prostate cancer (PC) and to compare both methods. Retrospectively, the study included 264 patients. The performances of 18F-PSMA and 68Ga-PSMA in relation to the pre-scan PSA were assessed by receiver operating characteristic (ROC) curve. 18F-PSMA showed PC-lesions in 87.5% (112/128 patients), while 68Ga-PSMA identified them in 88.9% (121/136). For 18F-PSMA biochemical recurrent (BCR) patients treated with radical prostatectomy (78/128, patient group: F-RP), a PSA of 1.08 ng/mL was found to be the optimal cut-off level for predicting positive and negative scans (AUC = 0.821; 95%, CI: 0.710–0.932), while for prostatectomized 68Ga-PSMA BCR-patients (89/136, patient group: Ga-RP), the cut-off was 1.84 ng/mL (AUC = 0.588; 95%, CI: 0.410–0.766). In patients with PSA < 1.08 ng/mL (F-RP) 76.3% and <1.84 ng/mL (Ga-RP) 78.6% scans were positive, whereas patients with PSA ≥ 1.08 ng/mL (F-RP) or 1.84 ng/mL (Ga-RP) had positive scan results in 100% and 91.5% (p < 0.001/p = 0.085). The identified PSA thresholds for PSMA-mappable PC lesions in BCR-patients (RP) showed a better separation for 18F-PSMA with regard to the distinguishing of positive and negative PC-lesions compared to 68Ga-PSMA. However, the two PSMA PET/CT tracers gave similar overall findings.

Highlights

  • In Europe and the United States, prostate cancer (PC) is one of the most common solid tumors in men [1,2]

  • The purpose of this study was to evaluate the performance of 18F-prostate-specific membrane antigen (PSMA) and 68GaPSMA scans in patients with biochemical recurrent (BCR) based on calculating the prostate-specific antigen (PSA) threshold levels for the detection of positive lesions on the PSMA positron emission tomography/computed tomography (PET/computed tomography (CT)) and to compare both methods

  • Most 18F-PSMA patients were primarily treated with radical prostatectomy (RP) (F-RP) (84) (Table 1), 78 of whom had a BCR by definition [5]

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Summary

Introduction

In Europe and the United States, prostate cancer (PC) is one of the most common solid tumors in men [1,2]. For patients previously treated with radical prostatectomy (RP) biochemical recurrence (BCR) is defined as a prostate-specific antigen (PSA) > 0.2 ng/mL after RP, which is confirmed in at least two measurements. The early detection of primary PC as well as the detection of PC recurrences and distant metastases have been significantly improved by metabolic imaging methods [6,7]. In patients with suspected PC recurrence after initial intended curative treatment, diagnostic imaging is a challenge for assessing tumor recurrence or distant metastases. Nuclear medicine methods with functional imaging and detection of metabolic activity, such as hybrid positron emission tomography (PET)/CT or PET/MRI (with various radiopharmaceuticals), have been increasingly used to improve the diagnostic sensitivity and accuracy [5,6,8]

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