18F-PSMA-7Q PET/CT for the Diagnosis of Prostate Cancer

Abstract and Introduction

Abstract

Background: Of the currently available prostate-specific membrane antigen (PSMA) positron emission tomography (PET) tracers, although ⁶⁸Ga-PSMA-11 and ¹⁸F-DCFPyL have been approved by the US Food and Drug Administration (FDA), both tracers are excreted rapidly through the urinary tract, resulting in strong accumulation in the bladder and blurring the prostate. ¹⁸F-PSMA-7Q is a novel quinoline-containing PSMA PET tracer developed by our team, which is primarily excreted through the liver. It can reduce the incidence of urine-induced false-positives in the prostate. We aimed to explore the diagnostic efficacy of ¹⁸F-PSMA-7Q PET/computed tomography (CT), and when ¹⁸F-PSMA-7Q PET/CT can be used instead of prostate biopsy to diagnose prostate cancer.

Methods: Patients who underwent ¹⁸F-PSMA-7Q PET/CT for prostate cancer staging or prostate biopsy guidance at our institution between July 2020 and December 2021 were retrospectively enrolled. Molecular imaging PSMA (miPSMA) scores were assigned for intra-prostatic lesions according to the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) criteria, and the diagnostic efficacy of ¹⁸F-PSMA-7Q PET/CT for different miPSMA scores was evaluated using pathological diagnosis as the gold standard.

Results: Of the 125 enrolled patients, 101 had prostate cancer, and 24 had prostatic hyperplasia or prostatitis. miPSMA ≥2 was the optimal diagnostic threshold, and area under curve (AUC) was 0.948, the sensitivity and specificity were 91.1% and 83.0%. The prostate cancer detection rates of ¹⁸F-PSMA-7Q PET/CT were 14.3% (3/21), 60.0% (6/10), 96.7% (58/60), and 100% (34/34) for patients with miPSMA scores of 0, 1, 2, and 3, respectively.There was no significant difference in the detection rate of prostate cancer between groups with miPSMA scores of 2 and 3, but there were significant differences between any other 2 groups.

Conclusions: The prostate cancer detection rate of ¹⁸F-PSMA-7Q PET/CT was high for lesions with greater miPSMA scores of 2 and 3. For patients with a high miPSMA score, particularly those with a miPSMA score of 3, prostate biopsy can be omitted and prostate cancer-related treatment can be considered.

Introduction

Prostate cancer is one of the most common malignancies in older men.^[1] The current gold standard for diagnosing prostate cancer relies on a transrectal ultrasound-guided, systematic twelve-core random biopsy that is blind to the cancer location, and thus, can lead to false-negative prostate cancer diagnoses.^[2] Moreover, prostate biopsies often underestimate the final prostate cancer Gleason score compared to histologic examination after radical prostatectomy.^[3] Repeated biopsy is permitted for patients whose initial biopsy is negative but is still highly suspicious for prostate cancer. However, repeated biopsies are challenging for patients.

In contrast to needle biopsy, imaging is non-invasive. Therefore, accurately identifying men with prostate cancer using imaging rather than (repeat) systematic prostate biopsies is appealing. However, the imaging tools must be accurate.^[4] Presently, the primary reason that conventional imaging examinations [such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI)] have not replaced needle biopsy is that their diagnostic accuracy is too low.

Prostate-specific membrane antigen (PSMA) is a cell-surface glycoprotein with an increased expression in prostate cancer cells.^[5] Due to this unique characteristic, PSMA is an excellent target for binding radiolabeled ligands. As a result, PSMA positron emission tomography (PET) imaging is superior to conventional imaging methods and shows high accuracy about 91% in the diagnosis and staging of prostate cancer.^[6–8] Of the currently available PSMA PET tracers, only ⁶⁸Ga-PSMA-11 and ¹⁸F-DCFPyL are approved by US Food and Drug Administration (FDA) for PET imaging of prostate cancer. However, both tracers are excreted rapidly through the urinary tract, resulting in strong accumulation in the bladder and blurring the prostate. ¹⁸F-PSMA-7Q is a novel quinoline-containing PSMA PET tracer developed by our team, which is mainly excreted through the liver.^[9] Since ¹⁸F-PMA-7Q is rarely excreted in the urine, the incidence of false positives in the prostate may be reduced. However, it remains unknown whether ¹⁸F-PMA-7Q PET can replace prostate biopsies in the diagnosis of prostate cancer. This study is a retrospective analysis to determine whether ¹⁸F-PSMA-7Q PET/CT can replace prostate biopsy for the diagnosis of prostate cancer, and under which circumstances this can be used. We present the following article in accordance with the STARD reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-22-813/rc).