Optimized Application of 68Ga-Prostate-Specific Membrane Antigen-617 Whole-Body PET/CT and Pelvic PET/MR in Prostate Cancer Initial Diagnosis and Staging

[68Ga]Ga-PSMA-617 PET/MRI for imaging patients suspected of hepatocellular carcinoma

PURPOSE

Radiolabeled probes targeting prostate-specific membrane antigen (PSMA) have been used in prostate cancer. Moreover, PSMA is also overexpressed on neovessels in hepatocellular carcinoma (HCC). This study aimed to preliminarily evaluate the diagnostic effectiveness of [68Ga]Ga-PSMA-617 PET/MRI for HCC.

METHODS

Patients suspected of HCC were prospectively enrolled in this single-center study (NCT05006326, 2021-08-16) to perform [68Ga]Ga-PSMA-617 PET/MRI, along with contrast enhanced CT (ceCT) or ceMRI. The main suspicious intrahepatic lesions were resected and pathologically verified. Visual evaluation of [68Ga]Ga-PSMA-617 PET/MRI images was performed on all lesions. Maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), tumor-to-liver ratio (TLR), tumor-to-blood ratio (TBR), and tumor-to-parotid ratio (TPR) were measured or calculated. The diagnostic efficiency of different modalities was summarized. PSMA expression was evaluated by immunohistochemistry and the correlation of PSMA expression and [68Ga]Ga-PSMA-617 uptake in HCC primary tumors was quantitatively analyzed.

RESULTS

A total of 12 patients (ten men and two women; mean age 58.75 ± 12.08 years) were included. Ten patients were diagnosed with HCC, 2 with intrahepatic cholangiocarcinoma (ICC), and 4 with hemangioma. The SUVmax, TLR, TBR, and TPR of HCC primary tumors were higher than those of ICC and hemangioma. The diagnostic accuracy of [68Ga]Ga-PSMA-617 PET/MRI for primary HCC was 82.4%. When combined with ceCT or ceMRI, the accuracy increased to 88.2%. A moderate correlation was observed between SUVmax and mean PSMA expression in HCC primary tumors (R = 0.788).

CONCLUSION

Utilizing a hybrid PET/MRI system to combine [68Ga]Ga-PSMA-617 PET/MRI with ceMRI is a promising one-stop solution for the accurate diagnosis of HCC.

TRIAL REGISTRATION

NCT05006326. Registered August 16, 2021, https://clinicaltrials.gov/study/NCT05006326 .

The image quality and feasibility of solitary delayed [68 Ga]Ga-PSMA-11 PET/CT using long field-of-view scanning in patients with prostate cancer

BACKGROUND

Previous studies have demonstrated that delayed [68 Ga]Ga-PSMA PET/CT imaging improves lesion detection compared to early [68 Ga]Ga-PSMA PET/CT in patients with prostate cancer. However, the sole use of delayed [68 Ga]Ga-PSMA PET/CT has been limited due to the insufficient number of photons obtained with standard PET/CT scanners. The combination of early and delayed [68 Ga]Ga-PSMA standard PET/CT may be considered, and it is challenging to incorporate into a high-demand clinical setting. Long field-of-view (LFOV) PET/CT scanners have higher sensitivity compared to standard PET/CT. However, it remains unknown whether the image quality of solitary delayed [68 Ga]Ga-PSMA LFOV PET/CT imaging is adequate to satisfy clinical diagnostic requirements. Therefore, the purpose of this study was to evaluate the image quality of delayed [68 Ga]Ga-PSMA LFOV PET/CT and examine the feasibility of utilizing delayed [68 Ga]Ga-PSMA LFOV PET/CT imaging alone in patients with prostate cancer.

METHODS

The study sample consisted of 56 prostate cancer patients who underwent [68 Ga]Ga-PSMA-11 LFOV PET/CT scanning between December 2020 and July 2021. All patients were subjected to early LFOV PET/CT imaging at 1-h post-injection as well as delayed LFOV PET/CT imaging at 3-h post-injection using [68 Ga]Ga-PSMA-11. The image quality and diagnostic efficiency of solitary delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT imaging was analyzed.

RESULTS

The results showed that delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT yielded satisfactory image quality that fulfilled clinical diagnostic benchmarks. Compared to early imaging, delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT demonstrated heightened lesion SUVmax values (11.0 [2.3-193.6] vs. 7.0 [2.0-124.3], P < 0.001) and superior tumor-to-background ratios (3.3 [0.5-62.2] vs. 1.7 [0.3-30.7], P < 0.001). Additionally, delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT detected supplementary lesions in 14 patients (25%) compared to early imaging, resulting in modifications to disease staging and management plans.

CONCLUSIONS

In summary, the findings indicate that the image quality of delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT is satisfactory for meeting clinical diagnostic prerequisites. The use of solitary delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT imaging in prostate cancer simplifies the examination protocol and improves patient compliance, compared to [68 Ga]Ga-PSMA-11 standard PET/CT which necessitates both early and delayed imaging.

Can 18F-PSMA-7Q PET/CT replace prostate biopsy for the diagnosis of prostate cancer?-A single-center retrospective study

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.

Prostate specific membrane antigen positron emission tomography in primary prostate cancer diagnosis: First-line imaging is afoot

Prostate specific membrane antigen positron emission tomography (PSMA PET) is an excellent molecular imaging technique for prostate cancer. Currently, PSMA PET for patients with primary prostate cancer is supplementary to conventional imaging techniques, according to guidelines. This supplementary function of PSMA PET is due to a lack of systematic review of its strengths, limitations, and potential development direction. Thus, we review PSMA ligands, detection, T, N, and M staging, treatment management, and false results of PSMA PET in clinical studies. We also discuss the strengths and challenges of PSMA PET. PSMA PET can greatly increase the detection rate of prostate cancer and accuracy of T/N/M staging, which facilitates more appropriate treatment for primary prostate cancer. Lastly, we propose that PSMA PET could become the first-line imaging modality for primary prostate cancer, and we describe its potential expanded application.