Significance of metabolic tumor volume and total lesion uptake measured using Ga-68 labelled prostate-specific membrane antigen PET/CT in primary staging of prostate cancer

A Comprehensive Systematic Review and Meta-analysis of the Role of Prostate-specific Membrane Antigen Positron Emission Tomography for Prostate Cancer Diagnosis and Primary Staging before Definitive Treatment

BACKGROUND AND OBJECTIVE

Positron emission tomography (PET) with prostate-specific membrane antigen (PSMA) in the diagnosis and primary staging of patients with prostate cancer (PCa) has an established role, but recent summative evidence on its actual diagnostic and staging value is still missing. We aimed to collect and analyze published studies reporting the accuracy of PSMA PET for the diagnosis of clinically significant prostate cancer (csPCa) and detection of distant metastases at primary staging before definitive treatment.

METHODS

We performed a systematic review of the literature, by searching the PubMed/MEDLINE, Cochrane library's CENTRAL, EMBASE, and Scopus databases, from inception to April 2024. Two coprimary outcomes were assessed: first, to evaluate the sensitivity, specificity, positive (PPV) and negative (NPV) predictive values of PSMA PET in detecting intraprostatic csPCa on a per-patient level, and second, to assess the positivity rates of metastatic disease in the primary staging, prior to definitive therapy. As a secondary outcome, the diagnostic accuracy of PET PSMA for the detection of lymph nodal invasion (LNI) was tested in a per-patient-level analysis of studies where pelvic lymph node dissection (PLND) was available as the reference standard. Positivity and detection rates were pooled using random-effect models. Preplanned subgroup analyses tested the diagnostic accuracy of PET PSMA across different study cohorts. Variation in PPV and NPV over csPCa and LNI prevalence was evaluated.

KEY FINDINGS AND LIMITATIONS

In total, 12 and 99 studies, with a total of 1533 and 18 649 participants, respectively, were included in the quantitative synthesis for intraprostatic diagnosis and staging. For intraprostatic disease, the sensitivity, specificity, PPV, and NPV of PSMA PET for csPCa were 82% (95% confidence interval [CI] 73-90%), 67% (95% CI 46-85%), 77% (95% CI 63-88%), and 73% (95% CI 56-87%), respectively. At a bivariate analysis, the diagnostic accuracy of PSMA PET estimated through a summary receiver operating characteristic curve-derived area under the curve was 84%, increasing up to 88% when combined with magnetic resonance imaging (MRI). On staging level, PSMA PET results were positive outside the prostate in 23% of the patients, with substantial variation in positivity rates between high-risk (31%) and intermediate-risk (12%) subcohorts. When using PLND as the reference standard (51 studies, 7713 patients), the sensitivity, specificity, PPV, and NPV of PSMA PET were, respectively, 54%, 94%, 77%, and 86%. With higher csPCa and LNI prevalence, a similar increase in PPV and a decrease in NPV were observed.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The current updated systematic review and meta-analysis provides updated evidence on the diagnostic and staging accuracy of PSMA PET in PCa. We reported good accuracy of PSMA PET to discriminate csPCa, particularly when added to MRI, but NPV alone is insufficient to omit a biopsy. Regarding staging, PSMA PET cannot be used alone to determine the need for lymph node dissection (LND) and should be combined with additional clinical information within predictive tools. As such, further research should develop and validate models that incorporate PSMA PET to reliably inform biopsy or LND.

Impact of intraprostatic PSMA maximum standardised uptake value following prostatectomy: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis to assess the relationship between intraprostatic maximum standardised uptake value (SUVmax) of the dominant prostatic lesion as measured on preoperative prostate-specific membrane antigen (PSMA) positron emission tomography (PET) with radical prostatectomy International Society of Urological Pathology (ISUP) Grade Group, pathological tumour (pT) staging, and biochemical recurrence (BCR).

METHODS

Prostate-specific membrane antigen PET may offer non-invasive assessment of histopathological and oncological outcomes before definitive treatment. SUVmax of the dominant lesion has been explored as a prognostic biomarker. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, we performed reviews of digital libraries and databases and retrieved studies reporting SUVmax quantified on PSMA PET computed tomography or magnetic resonance imaging and subsequent radical prostatectomy ISUP Grade Group, pT stage, and BCR. Quality assessment was performed using Quality Assessment of Diagnostic Accuracy Studies-2 and Prediction model Risk of Bias Assessment tools. Random effects meta-analysis and meta-regression by ISUP Grade Group and pT2 vs pT3/4 stage was performed. This study was registered on the International Prospective Register of Systematic Reviews (PROSPERO: CRD42023408170).

EVIDENCE SYNTHESIS

After removing duplicates, 23 studies were included for review. Pooled SUVmax (95% confidence interval [CI]) increased monotonically with advancing ISUP Grade Group, with ISUP 1: 5.8 (95% CI 3.9-7.7), through to ISUP 5: 17.3 (95% CI 13.1-21.5). For pT2 disease, pooled SUVmax: 9.7 (95% CI 7.8-11.5) increasing to 13.8 (95% CI 10.9-16.7) for pT3/4 disease. Substantial inconsistency was noted (I2 >50%) for all subgroups. This was not attenuated by restricting analysis only to studies using [68Ga]Ga-PSMA-11. Narrative synthesis of six papers reporting BCR showed increasing SUVmax was associated with reduced time to BCR.

CONCLUSION

Preoperative intraprostatic PSMA SUVmax increases monotonically with higher ISUP Grade Group and pathological tumour stage. Higher SUVmax is associated with reduced BCR-free survival. However, the use of single SUVmax thresholds for clinical decision making is not recommended as variability between studies is high.

A systematic review and meta-analysis to evaluate the diagnostic accuracy of PSMA PET/CT in the initial staging of prostate cancer

BACKGROUND

Positron Emission Tomography-Computed Tomography using Prostate-Specific Membrane Antigen (PSMA PET/CT) is notable for its superior sensitivity and specificity in detecting recurrent PCa and is under investigation for its potential in pre-treatment staging. Despite its established efficacy in nodal and metastasis staging in trial setting, its role in primary staging awaits fuller validation due to limited evidence on oncologic outcomes. This systematic review and meta-analysis aims to appraise the diagnostic accuracy of PSMA PET/CT compared to CI for comprehensive PCa staging.

METHODS

Medline, Scopus and Web of science databases were searched till March 2023. Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines were followed to identify eligible studies. Primary outcomes were specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV) of PSMA PET/CT for local, nodal and metastatic staging in PCa patients. Due to the unavailability of data, a meta-analysis was feasible only for detection of seminal vesicles invasion (SVI) and LNI.

RESULTS

A total of 49 studies, comprising 3876 patients, were included. Of these, 6 investigated accuracy of PSMA PET/CT in detection of SVI. Pooled sensitivity, specificity, PPV and NPV were 42.29% (95%CI: 29.85-55.78%), 87.59% (95%CI: 77.10%-93.67%), 93.39% (95%CI: 74.95%-98.52%) and 86.60% (95%CI: 58.83%-96.69%), respectively. Heterogeneity analysis revealed significant variability for PPV and NPV. 18 studies investigated PSMA PET/CT accuracy in detection of LNI. Aggregate sensitivity, specificity, PPV and NPV were 43.63% (95%CI: 34.19-53.56%), 85.55% (95%CI: 75.95%-91.74%), 67.47% (95%CI: 52.42%-79.6%) and 83.61% (95%CI: 79.19%-87.24%). No significant heterogeneity was found between studies.

CONCLUSIONS

The present systematic review and meta-analysis highlights PSMA PET-CT effectiveness in detecting SVI and its good accuracy in LNI compared to CI. Nonetheless, it also reveals a lack of high-quality research on its performance in clinical T staging, extraprostatic extension and distant metastasis evaluation, emphasizing the need for further rigorous studies.

Exploring the Correlation Between Multiparameters Detected in Primary Prostate Cancer using F‑18 PSMA‑1007 PET/MRI and their Potential for Predicting Metastasis

Purpose

Prostate-specific membrane antigen (PSMA) Positron emission tomography/magnetic resonance imaging (PET/MRI) surpasses conventional MRI (cMRI) in prostate cancer (PCa) evaluation. Our objective is to evaluate correlation of quantitative parameters in PCa using Fluorine-18 (F-18) PSMA-1007 PET/MRI and their potential for predicting metastases.

Methods

This retrospective study included 51 PCa patients. Apparent diffusion coefficient (ADC), maximum standardized uptake value (SUVmax), PSMA total lesion uptake (PSMA-TLU), and PSMA total volume (PSMA-TV) were calculated in primary tumor. Correlation of ADC with other parameters was analyzed. Receiver Operating Characteristic curve analysis was conducted to determine optimal cut-off values for predicting metastases.

Results

ADC inversely correlated with SUVmax, PSMA-TLU, and PSMA-TV (p < 0.0001, < 0.0001, 0.0050, respectively). Lower ADC was associated with metastatic disease (p < 0.001). SUVmax, PSMA-TLU, PSMA-TV, SUVmax/ADC, PSMA-TLU/ADC, and PSMA-TV/ADC were higher in patients with metastases (p = 0.033 to < 0.001). PSMA-TLU/ADC and PSMA-TV/ADC best predicted metastases (sensitivity: 73.91% and 82.61%; specificity: 89.29% and 71.43%). PSMA-TLU, PSMA-TV, PSMA-TLU/ADC, and PSMA-TV/ADC were higher in patients with lymph node metastasis (p = 0.001 to 0.005). PSMA-TLU/ADC and PSMA-TV/ADC best predicted lymph node metastasis (sensitivity: 77.78% and 100%; specificity: 89.29% and 71.43%). SUVmax and SUVmax/ADC were higher in bone metastasis cases (p = 0.045), but their predictive value for bone metastasis was limited (Area under the curve (AUC): 0.634 and 0.652).

Conclusion

F-18 PSMA-1007 PET/MRI may improve diagnostic accuracy for primary PCa lesions by utilizing the inverse relationship between ADC and other parameters. Moreover, a strong correlation between such parameters and presence of metastasis holds prognostic value of this modality.

Utility of PSMA-PET derived volumetric parameters in initial risk stratification and prediction of prostate cancer metastasis - a head-to-head comparison of the radiotracers 18 F-PSMA-1007 and 68 Ga-PSMA-11

OBJECTIVE

This study aimed to explore and compare the utility of baseline 18 F-PSMA-1007 and 68 Ga-PSMA-11 PET/computed tomography (CT) derived volumetric parameters in initial risk stratification and prediction of prostate cancer (PCa) metastasis.

METHODS

Forty treatment-naïve, biopsy-proven intermediate-/high-risk PCa patients were prospectively recruited. Each patient underwent PET/CT with 68 Ga-PSMA-11 and 18 F-PSMA-1007 (within 2 weeks). The maximum and mean standardized uptake values (SUVmax and SUVmean) of primary tumor, prostate PSMA-tumor volume (PSMA-TVp), and prostate total lesion PSMA (TL-PSMAp) were measured.

RESULTS

PSMA-TVp and TL-PSMAp (with both radiotracers) mostly exhibited moderate-to-strong correlation with Gleason score, serum prostate-specific antigen level and clinical tumor stage (Spearman ρ  = 0.361-0.783, P -values ≤0.022). Primary tumor SUVmax values were similar across initial risk categories. PSMA-TVp and TL-PSMAp, however, were significantly higher in high-risk PCa compared to intermediate-risk PCa ( P -values ≤0.001). Receiver operating characteristic (ROC) curve analysis revealed that F-PSMA-TVp, Ga-PSMA-TVp, F-TL-PSMAp, and Ga-TL-PSMAp (optimal cutoff values of 20.9, 23.4, 142.5, and 144.8, respectively) could effectively differentiate high-risk from intermediate-risk PCa [area under the ROC curve (AUCs) 0.859-0.898, P -values <0.001] with high sensitivity (~68.8-75%) and excellent specificity (100%). PSMA-TVp and TL-PSMAp (with both radiotracers) could predict presence of regional and extraregional nodal metastasis (AUCs 0.703-0.801, P -values ≤0.03) with moderate sensitivity (~47.8-70.6%) and excellent specificity (~82.6-94.1%).

CONCLUSION

Our results suggest that baseline PSMA-PET primary tumor volumetric parameters provide a noninvasive, objective, and accurate index for initial risk stratification and can predict presence of regional and extraregional nodal metastasis in PCa patients. Larger studies are warranted to evaluate their incremental role over conventional parameters.

Gene's expression underpinning the divergent predictive value of [18F]F-fluorodeoxyglucose and prostate-specific membrane antigen positron emission tomography in primary prostate cancer: a bioinformatic and experimental study

BACKGROUND

Positron Emission Tomography (PET) imaging with Prostate-Specific Membrane Antigen (PSMA) and Fluorodeoxyglucose (FDG) represent promising biomarkers for risk-stratification of Prostate Cancer (PCa). We verified whether the expression of genes encoding for PSMA and enzymes regulating FDG cellular uptake are independent and additive prognosticators in PCa.

METHODS

mRNA expression of genes involved in glucose metabolism and PSMA regulation obtained from primary PCa specimens were retrieved from open-source databases and analyzed using an integrative bioinformatics approach. Machine Learning (ML) techniques were used to create predictive Progression-Free Survival (PFS) models. Cellular models of primary PCa with different aggressiveness were used to compare [18F]F-PSMA-1007 and [18F]F-FDG uptake kinetics in vitro. Confocal microscopy, immunofluorescence staining, and quantification analyses were performed to assess the intracellular and cellular membrane PSMA expression.

RESULTS

ML analyses identified a predictive functional network involving four glucose metabolism-related genes: ALDOB, CTH, PARP2, and SLC2A4. By contrast, FOLH1 expression (encoding for PSMA) did not provide any additive predictive value to the model. At a cellular level, the increase in proliferation rate and migratory potential by primary PCa cells was associated with enhanced FDG uptake and decreased PSMA retention (paralleled by the preferential intracellular localization).

CONCLUSIONS

The overexpression of a functional network involving four glucose metabolism-related genes identifies a higher risk of disease progression since the earliest phases of PCa, in agreement with the acknowledged prognostic value of FDG PET imaging. By contrast, the prognostic value of PSMA PET imaging is independent of the expression of its encoding gene FOLH1. Instead, it is influenced by the protein docking to the cell membrane, regulating its accessibility to tracer binding.