Comparison of 68Ga-PSMA PET/CT and multiparametric MRI for staging of high-risk prostate cancer68Ga-PSMA PET and MRI in prostate cancer

Optimizing PSMA scintigraphy for resource limited settings - a retrospective comparative study

BACKGROUND

PSMA PET/CT is the most sensitive molecular imaging modality for prostate cancer (PCa), yet much of the developing world has little or no access to PET/CT. [99mTc]Tc-PSMA scintigraphy (PS) is a cheaper and more accessible gamma camera-based alternative. However, many resource-constrained departments have only a single camera without tomographic or hybrid imaging functionality, and camera time is frequently in high demand. Simplifying imaging protocols by limiting the field of view (FOV) and omitting SPECT/CT or even SPECT may provide a partial solution. The aim was thus to determine the adequacy of PS planar-only and/or SPECT-only imaging protocols with a limited FOV.

METHODS

The scans of 95 patients with histologically proven PCa who underwent PS with full-body planar and multi-FOV SPECT/CT were reviewed. The detection rates for uptake in the prostate gland/bed and in metastases were compared on planar, SPECT, and SPECT/CT. The agreement between modalities was calculated for the detection of metastases and for staging. The impact of imaging a limited FOV was determined.

RESULTS

Pathological prostatic uptake was seen in all cases on SPECT/CT (excluding two post-prostatectomy patients), 90.3% of cases on SPECT, and 15.1% on planar images (p < 0.001). Eleven (11.7%) patients had seminal vesicle involvement on SPECT/CT, which was undetectable/indistinguishable on planar images and SPECT. The agreement between modalities was moderate to good (κ = 0.41 to 0.61) for the detection of nodal metastases, with detection rates that did not differ significantly (SPECT/CT = 11.6%, SPECT = 8.4%, planar = 5.3%). Detection rates for bone metastases were 14.7% (SPECT/CT) and 11.6% (SPECT and planar). Agreement between modalities for the detection of bone metastases was good (κ = 0.73 to 0.77). Three (3.1%) patients had visceral metastases on SPECT/CT, two of which were detected on SPECT and planar. There was good agreement between modalities for the TNM staging of patients (κ = 0.70 to 0.88). No metastatic lesions were missed on the limited FOV images.

CONCLUSION

When PS scintigraphy is performed, SPECT/CT is recommended. However, the lack of SPECT/CT capabilities should not preclude the use of PS in the presence of limited resources, as both planar and SPECT imaging are adequate and will correctly stage most PCa patients. Furthermore, time-based optimisations are achievable by limiting the FOV to exclude the distal lower limbs.

Current role of PSMA-PET imaging in the clinical management of prostate cancer

Despite the developments of the last few years, metastatic castration-resistant prostate cancer (PC) remains a deadly disease. Until recently, almost all guidelines recommended magnetic resonance imaging (MRI) or computed tomography (CT) for the initial staging and local/systematic recurrence. Positron emission tomography/computed tomography (PET/CT) with prostate-specific membrane antigen (PSMA) at the present stage, emerged as a promising diagnostic imaging tool for PC. PSMA PET/CT alone or in combination with multiparametric magnetic resonance imaging (mpMRI) can improve the detection of clinically significant PC, especially for Prostate Imaging Reporting & Data System (PI-RADS) = 3 lesions. In addition, PSMA PET/CT is more accurate than CT and bone scan for intermediate to high-risk disease at the initial staging. Contrariwise, a negative PET is not useful for surgeons to avoid a pelvic nodal dissection. PET-PSMA imaging is appropriate for prostate-specific antigen (PSA) persistence or PSA rise from undetectable level after radical prostatectomy or for PSA rise above nadir after definitive radiotherapy. Also, it is recommended for patients fit for curative salvage treatment. It should be noted that in patients, candidates for radionuclide therapy with Lutetium-177 (117Lu), a PSMA strong expression from PET/CT at baseline is considered necessary. This review summarizes the evolution of PSMA PET/CT and its current role in the management of PC.

Can the Gleason score be predicted in patients with prostate cancer? A dynamic contrast-enhanced MRI, (68)Ga-PSMA PET/CT, PSA, and PSA-density comparison study

PURPOSE

The present study aims to evaluate whether perfusion parameters in prostate magnetic resonance imaging (MRI), (68)Ga-prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT), prostate-specific antigen (PSA), and PSA density can be used to predict the lesion grade in patients with prostate cancer (PCa).

METHODS

The study included a total of 137 PCa cases in which 12-quadrant transrectal ultrasound-guided prostate biopsy (TRUSBx) was performed, the Gleason score (GS) was determined, and pre-biopsy multiparametric prostate MRI and (68)Ga-PSMA PET/CT examinations were undertaken. The patient population was evaluated in three groups according to the GS: (1) low risk; (2) intermediate risk; (3) high risk. The PSA, PSA density, pre-TRUSBx (68)Ga-PSMA PET/CT maximum standardized uptake value (SUVmax), perfusion MRI parameters [maximum enhancement, maximum relative enhancement, T0 (s), time to peak (s), wash-in rate (s-1), and wash-out rate (s-1)] were retrospectively evaluated.

RESULTS

There was no significant difference between the three groups in relation to the PSA, PSA density, and (68)Ga-PSMA PET/CT SUVmax (P > 0.05). However, the values of maximum enhancement, maximum relative enhancement (%), T0 (s), time to peak (s), wash-in rate (s-1), and wash-out rate (s-1) significantly differed among the groups. A moderate positive correlation was found among the prostate volume, PSA (r = 0.490), and (68)Ga-PSMA SUVmax (r = 0.322) in the patients. The wash-out rate (s-1) and wash-in rate (s-1) had the best diagnostic test performance (area under the curve: 89.1% and 78.4%, respectively).

CONCLUSION

No significant correlation was found between the (68)Ga-PSMA PET/CT SUVmax and the GS. The wash-out rate was more successful in estimating the pretreatment GS than the (68)Ga-PSMA PET/CT SUVmax.

Application of targeted diagnosis of PSMA in the modality shift of prostate cancer diagnosis: a review

Prostate cancer (PCa) is a serious threat to the health of men all over the world. The progression of PCa varies greatly among different individuals. In clinical practice, some patients often progress to advanced PCa. Therefore, accurate imaging for diagnosis and staging of PCa is particularly important for clinical management of patients. Conventional imaging examinations such as MRI and CT cannot accurately diagnose the pathological stages of advanced PCa, especially metastatic lymph node (LN) stages. As a result, developing an accurate molecular targeted diagnosis is crucial for advanced PCa. Prostate specific membrane antigen (PSMA) is of great value in the diagnosis of PCa because of its specific expression in PCa. At present, researchers have developed positron emission tomography (PET) targeting PSMA. A large number of studies have confirmed that it not only has a higher tumor detection rate, but also has a higher diagnostic efficacy in the pathological stage of advanced PCa compared with traditional imaging methods. This review summarizes recent studies on PSMA targeted PET in PCa diagnosis, analyzes its value in PCa diagnosis in detail, and provides new ideas for urological clinicians in PCa diagnosis and clinical management.

Comparing the Detection Performance Between Multiparametric Magnetic Resonance Imaging and Prostate-Specific Membrane Antigen PET/CT in Patients With Localized Prostate Cancer: A Systematic Review and Meta-analysis

PURPOSE

Multiparametric MRI (mpMRI) has been promoted as an auxiliary diagnostic tool for prostate biopsy. However, prostate-specific membrane antigen (PSMA) including 68 Ga-PSMA-11, 18 F-DCFPyL, and 18 F-PSMA-1007 applied PET/CT imaging was an emerging diagnostic tool in prostate cancer patients for staging or posttreatment follow-up, even early detecting. Many studies have used PSMA PET for comparison with mpMRI to test the diagnostic ability for early prostate cancer. Unfortunately, these studies have shown conflicting results. This meta-analysis aimed to compare the differences in diagnostic performance between PSMA PET and mpMRI for detecting and T staging localized prostatic tumors.

METHODS

This meta-analysis involved a systematic literature search of PubMed/MEDLINE and Cochrane Library databases. The pooling sensitivity and specificity of PSMA and mpMRI verified by pathological analysis were calculated and used to compare the differences between the 2 imaging tools.

RESULTS

Overall, 39 studies were included (3630 patients in total) from 2016 to 2022 in the current meta-analysis and found that the pooling sensitivity values for localized prostatic tumors and T staging T3a and T3b of PSMA PET were 0.84 (95% confidence interval [CI], 0.83-0.86), 0.61 (95% CI, 0.39-0.79), and 0.62 (95% CI, 0.46-0.76), respectively, whereas those of mpMRI were found to be 0.84 (95% 0.78-0.89), 0.67 (95% CI, 0.52-0.80), and 0.60 (95% CI, 0.45-0.73), respectively, without significant differences ( P > 0.05). However, in a subgroup analysis of radiotracer, the pooling sensitivity of 18 F-DCFPyL PET was higher than mpMRI (relative risk, 1.10; 95% CI, 1.03-1.17; P < 0.01).

CONCLUSIONS

This meta-analysis found that whereas 18 F-DCFPyL PET was superior to mpMRI at detecting localized prostatic tumors, the detection performance of PSMA PET for localized prostatic tumors and T staging was comparable to that of mpMRI.

Preoperative evaluation of prostate cancer by 68Ga-PMSA positron emission tomography/computed tomography: comparison with magnetic resonance imaging and with histopathological findings

Objective

To evaluate the accuracy of preoperative positron emission tomography/computed tomography with 68Ga-labeled prostate-specific membrane antigen (68Ga-PSMA PET/CT) for staging prostate cancer and compare it with magnetic resonance imaging (MRI) using histopathology of surgical specimens as the gold standard.

Materials and Methods

In this retrospective study, 65 patients with prostate cancer were analyzed.

Results

The accuracy of 68Ga-PSMA PET/CT for tumor detection was 95%, and that of MRI was 91%. There was no difference between 68Ga-PSMA PET/CT and MRI regarding localization of the lesion. The sensitivity of 68Ga-PSMA PET/CT for detecting extraprostatic extension was quite low (14%). For detection of seminal vesicle invasion, 68Ga-PSMA PET/CT showed a sensitivity of 57% and accuracy of 91%. There was a moderate correlation between the maximum standardized uptake value (SUVmax) and the serum level of prostate-specific antigen (p < 0.01; ρ = 0.368) and between the SUVmax and the International Society of Urological Pathology (ISUP) grade (p < 0.01; ρ = 0.513).

Conclusion

68Ga-PSMA PET/CT is a promising tool for detecting and evaluating the primary tumor, which can alter the staging and management of the disease.

Peering through the PSMA PET Lens: The Role of the European Association of Urology Biochemical Recurrence Risk Groups after Radical Prostatectomy

(1) Background: The European Association of Urology (EAU) biochemical recurrence (BCR) risk grouping relies on data from historical cohorts that used conventional imaging techniques. In the era of PSMA PET/CT, we compared the patterns of positivity in the two risk groups and provided insight into positivity predictive factors. (2) Methods: Data from 1185 patients who underwent ⁶⁸Ga-PSMA-11PET/CT for BCR was analyzed, out of which 435 patients treated initially treated by radical prostatectomy were included in the final analysis. (3) Results: A significantly higher rate of positivity in the BCR high-risk group was observed (59% vs. 36%, p < 0.001). BCR low-risk group demonstrated more local (26% vs. 6%, p < 0.001) and oligometastatic (100% vs. 81%, p < 0.001) recurrences. The BCR risk group and PSA level at the time of PSMA PET/CT were independent predictive factors of positivity. (4) Conclusions: This study confirms that the EAU BCR risk groups have different rates of PSMA PET/CT positivity. Even with a lower rate in the BCR low-risk group, oligometastatic disease was 100% in those with distant metastases. Given the presence of discordant positivity and risk classification, integrating PSMA PET/CT positivity predictors into risk calculators for BCR might improve patient classification for subsequent treatment options. Future prospective studies are still needed to validate the above findings and assumptions.

ACR Appropriateness Criteria® Pretreatment Detection, Surveillance, and Staging of Prostate Cancer: 2022 Update

Prostate cancer is second leading cause of death from malignancy after lung cancer in American men. The primary goal during pretreatment evaluation of prostate cancer is disease detection, localization, establishing disease extent (both local and distant), and evaluating aggressiveness, which are the driving factors of patient outcomes such as recurrence and survival. Prostate cancer is typically diagnosed after the recognizing elevated serum prostate-specific antigen level or abnormal digital rectal examination. Tissue diagnosis is obtained by transrectal ultrasound-guided biopsy or MRI-targeted biopsy, commonly with multiparametric MRI without or with intravenous contrast, which has recently been established as standard of care for detecting, localizing, and assessing local extent of prostate cancer. Although bone scintigraphy and CT are still typically used to detect bone and nodal metastases in patients with intermediate- or high-risk prostate cancer, novel advanced imaging modalities including prostatespecific membrane antigen PET/CT and whole-body MRI are being more frequently utilized for this purpose with improved detection rates. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Imaging Recommendations for Diagnosis, Staging, and Management of Prostate Cancer

The Prostate Carcinoma Guidelines Panel have formulated these guidelines to assist medical professionals in the evidence-based management of prostate cancer. These have been formulated by a panel consisting of Indian multidisciplinary group of radiologists, uro-oncologists, urologists, radiation oncologists, medical oncologists, and pathologists. These recommendations present the best evidence available to the clinicians; however, using these recommendations will not always result in the best outcome. They aid in decision making for individual patients; however, these will never replace clinical expertise when making treatment decisions. Taking personal values and preferences or individual circumstances of patients into account is necessary for final treatment decision. Guidelines are not mandatory and should not to be referred as a legal standard of care.

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.

Feasibility of biology-guided radiotherapy using PSMA-PET to boost to dominant intraprostatic tumour

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Biology-guided radiation therapy (BGRT) uses PET imaging for online image guidance.

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PSMA PET uptake is abundant in the dominant intraprostatic lesion (DIL).

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BgRT boost to PSMA-avid subvolume in the prostate region may be feasible.

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Suitable targets for BgRT were identified in the ProPSMA clinical trial.

Background

Methods

Results

Conclusions

The Continuum of Metastatic Prostate Cancer: Interpreting PSMA PET Findings in Recurrent Prostate Cancer

Conventional imaging has been the standard imaging modality for assessing prostate cancer recurrence and is utilized to determine treatment response to therapy. Molecular imaging with PSMA PET-CT has proven to be more accurate, sensitive, and specific at identifying pelvic or distant metastatic disease, resulting in earlier diagnosis of advanced disease. Since advanced disease may not be seen on conventional imaging, due to its lower sensitivity, but can be identified by molecular imaging, this reveals that metastatic prostate cancer occurs on a continuum from negative PSMA PET-CT and negative conventional imaging to positive PSMA PET-CT and positive conventional imaging. Understanding this continuum, the accuracy of these modalities, and treatment related outcomes based on imaging, will allow the clinician to counsel patients on management. This review will highlight the differences in conventional and molecular imaging in prostate cancer and how PSMA PET-CT can be used for the management of prostate cancer patients in different clinical scenarios, while providing cautionary notes for overtreatment.

Pilot study of the diagnostic utility of 89 Zr-df-IAB2M and 68 Ga-PSMA-11 PET imaging and multiparametric MRI in localized prostate cancer

BACKGROUND

Accurate diagnosis of localized prostate cancer (PCa) is limited by inadequacy of multiparametric (mp) MRI to fully identify and differentiate localized malignant tissue from benign pathologies. Prostate-specific membrane antigen (PSMA) represents an excellent target for molecular imaging. IAB2M, an 85-kD minibody derived from a de-immunized monoclonal antibody directed at the extracellular domain of human PSMA (huJ591), and PSMA-11, a small molecule ligand have been previously tested as probes for visualization of recurrent/metastatic PCa with PET/CT. This pilot, non-randomized trial studied their diagnostic utility in patients (pts) with localized PCa.

METHODS

Pts planned for radical prostatectomy (RP) were enrolled and underwent mpMRI and PET/CT imaging with ⁸⁹ Zr-df-IAB2M and/or ⁶⁸ Ga-PSMA-PET/CT. Image results were read by a radiologist blinded to clinical information and pathology results, mapped and compared to corresponding histopathology findings from all lesions, both clinically significant and nonsignificant. The detection rates of all three imaging modalities were measured and correlated.

RESULTS

20 pts with median age of 64.5 (46-79) years and PSA level of 7.5 (1.6-36.56) ng/ml were enrolled. 19 pts underwent RP and were imaged pre-operatively with ⁸⁹ Zr-Df-IAB2M PET/CT and mpMRI. Nine of those were imaged using ⁶⁸ Ga-PSMA-11 as well. Out of 48 intraprostatic lesions verified on surgical pathology, IAB2M PET/CT was able to detect 36 (75%). A similar proportion of pathologically confirmed, clinically significant lesions (22/29, 76%) was detected. IAB2M PET/CT was also able to identify 14/19 (74%) extraprostatic lesions. The performance of mpMRI was inferior, with 24/48 detectable lesions (50%) and 18/29 clinically significant intraprostatic lesions (62%). Compared to the current standard (mpMRI), IAB2M PET/CT had a sensitivity of 88%, specificity 38%, positive predictive value 58%, and accuracy 63%. In 9 pts who underwent Ga-PSMA-11 as well, the latter yielded a detection rate of 70% (14/20), which was also seen in clinically significant lesions (10/14, 71%). Ga-PSMA-11 PET/CT also detected 4/6 (67%) extraprostatic lesions.

CONCLUSIONS

In this pilot study, the performance of ⁸⁹ Zr-df-IAB2M was superior to mpMRI and similar to ⁶⁸ Ga-PSMA-11 PET/CT. The higher detection rate of PSMA-PET supports its use as a diagnostic tool with consequent management change implications in men with localized PCa.

[18F]-Fluciclovine PET/CT for preoperative nodal staging in high-risk primary prostate cancer: final results of a prospective trial

PURPOSE

The conventional imaging flowchart for prostate cancer (PCa) staging may fail in correctly detecting lymph node metastases (LNM). Pelvic lymph node dissection (PLND) represents the only reliable method, although invasive. A new amino acid PET compound, [18F]-fluciclovine, was recently authorized in suspected PCa recurrence but not yet included in the standard staging work-up of primary PCa. A prospective monocentric study was designed to evaluate [18F]-fluciclovine PET/CT diagnostic performance for preoperative LN staging in primary high-risk PCa.

METHODS

Consecutive patients (pts) with biopsy-proven PCa, standard staging (including [11C]choline PET/CT), eligible for PLND, were enrolled to undergo an investigational [18F]-fluciclovine PET/CT. Nodal uptake higher than surrounding background was reported by at least two readers (blinded to [11C]choline) using a visual 5-point scale (1-2 probably negative; 4-5 probably positive; 3 equivocal); SUVmax, target-to-background (aorta-A; bone marrow-BM) ratios (TBRs), were also calculated. PET results were validated with PLND. [18F]-fluciclovine PET/CT performance using visual score and semi-quantitative indexes was analyzed both per patient and per LN anatomical region, compared to conventional [11C]choline and clinical predictive factors (to note that diagnostic performance of [18F]-fluciclovine was explored for LNM but not examined for intrapelvic or extrapelvic M1 lesions).

RESULTS

Overall, 94 pts underwent [18F]-fluciclovine PET/CT; 72/94 (77%) high-risk pts were included in the final analyses (22 pts excluded: 8 limited PLND; 3 intermediate-risk; 2 treated with radiotherapy; 4 found to be M1; 5 neoadjuvant hormonal therapy). Median LNM risk by Briganti nomogram was 19%. LNM confirmed on histology was 25% (18/72 pts). Overall, 1671 LN were retrieved; 45/1671 (3%) LNM detected. Per pt, median no. of removed LN was 22 (mean 23 ± 10; range 8-51), of LNM was 2 (mean 3 ± 2; range 1-10). Median LNM size was 5 mm (mean 5 ± 2.5; range 2-10). On patient-based analyses (n = 72), diagnostic performance for LNM resulted significant with [18F]-fluciclovine (AUC 0.66, p 0.04; 50% sensitivity, 81% specificity, 47% PPV, 83% NPV, 74% accuracy), but not with [11C]choline (AUC 0.60, p 0.2; 50%, 70%, 36%, 81%, and 65% respectively). Briganti nomogram (OR = 1.03, p = 0.04) and [18F]-fluciclovine visual score (≥ 4) (OR = 4.27, p = 0.02) resulted independent predictors of LNM at multivariable analyses. On region-based semi-quantitative analyses (n = 576), PET/CT performed better using TBR parameters (TBR-A similar to TBR-BM; TBR-A fluciclovine AUC 0.61, p 0.35, vs choline AUC 0.57 p 0.54; TBR-BM fluciclovine AUC 0.61, p 0.36, vs choline AUC 0.58, p 0.52) rather than using absolute LN SUVmax (fluciclovine AUC 0.51, p 0.91, vs choline AUC 0.51, p 0.94). However, in all cases, diagnostic performance was not statistically significant for LNM detection, although slightly in favor of the experimental tracer [18F]-fluciclovine for each parameter. On the contrary, visual interpretation significantly outperformed PET semi-quantitative parameters (choline and fluciclovine: AUC 0.65 and 0.64 respectively; p 0.03) and represents an independent predictive factor of LNM with both tracers, in particular [18F]-fluciclovine (OR = 8.70, p 0.002, vs OR = 3.98, p = 0.03).

CONCLUSION

In high-risk primary PCa, [18F]-fluciclovine demonstrates some advantages compared with [11C]choline but sensitivity for metastatic LN detection is still inadequate compared to PLND. Visual (combined morphological and functional), compared to semi-quantitative assessment, is promising but relies mainly on readers' experience rather than on unquestionable LN avidity.

TRIAL REGISTRATION

EudraCT number: 2014-003,165-15.

Head-to-Head Comparison of 68Ga-PSMA-11 PET/CT and Multiparametric MRI for Pelvic Lymph Node Staging Prior to Radical Prostatectomy in Patients With Intermediate to High-Risk Prostate Cancer: A Meta-Analysis

PURPOSE

To compare the diagnostic performance of 68Ga-PSMA-11 PET/CT and mpMRI for pelvic lymph node staging prior to radical prostatectomy in prostate cancer (PCa) patients based on per patient data.

METHODS

PubMed and Embase databases were searched until October 2020 for eligible studies evaluating head-to-head comparison of 68Ga-PSMA-PET/CT and mpMRI for the detection of pelvic lymph node metastases (PLNMs) using pelvic lymph node dissection (PLND) as gold standard. The pooled sensitivity, specificity, and area under the summary receiver-operating characteristics curve (AUC) were determined for the two imaging modalities.

RESULTS

Nine studies with 640 patients were included. The pooled sensitivity, specificity, and AUC for 68Ga-PSMA-11 PET/CT vs. mpMRI were 0.71 (95% CI: 0.48-0.86) vs. 0.40 (95% CI: 0.16-0.71), 0.92 (95% CI: 0.88-0.95) vs. 0.92 (95% CI: 0.80-0.97), and 0.92 (95% CI: 0.88-0.95) vs. 0.82 (95% CI: 0.79-0.86), respectively. There was substantial heterogeneity for both imaging modalities, and meta-regression analysis revealed that the number of patients, prevalence of PLNMs, PSA level, reference standard, and risk classification might be the potential causes of heterogeneity.

CONCLUSION

This meta-analysis of head-to-head comparison studies confirms that there is a trend toward a higher sensitivity and diagnostic accuracy of 68Ga-PSMA-11 PET/CT compared to mpMRI for the detection of PLNMs in PCa patients. Nevertheless, according to current guidelines, PLND still needs to be recommended in case of negative results from 68Ga-PSMA-11 PET/CT due to significant risk of malignancy.

Incremental Impact of [68 Ga]Ga-PSMA-11 PET/CT in Primary N and M Staging of Prostate Cancer Prior to Curative-Intent Surgery: a Prospective Clinical Trial in Comparison with mpMRI

Purpose

The main objective of this prospective study was to assess the value of gallium-68 prostate-specific membrane antigen ([⁶⁸ Ga]Ga-PSMA-11) positron emission tomography/computed tomography (PET/CT) in primary N and M staging of intermediate- and high-risk prostate cancer (PCa) patients before planned curative-intent radical prostatectomy (RPE) and extended pelvic lymph node dissection (ePLND). The second objective was to compare the [⁶⁸ Ga]Ga-PSMA-11 PET/CT findings with standard of care pelvic multi-parametric magnetic resonance imaging (mpMRI) in the detection of locoregional lymph node metastases and intraprostatic prostate cancer.

Procedures

A total of 81 patients (mean age: 64.5 years, baseline mean trigger PSA (tPSA) 15.4 ng/ml, ± 15.9) with biopsy proven PCa (24 intermediate- and 57 high risk) scheduled for RPE and ePLND were enrolled in this prospective study. In 52 patients [⁶⁸ Ga]Ga-PSMA-11 PET/CT, pelvic mpMRI, and RPE with ePLND have been performed. Clinical risk stratification and related biomarkers as well as Gleason score (GS) were recorded. The location of the index lesion (IL) was documented systematically for each modality using a standardized segmentation of the prostate in six segments. Distant bone and lymph node metastasis detected by [⁶⁸ Ga]Ga-PSMA-11 PET/CT were documented. [⁶⁸ Ga]Ga-PSMA-11 PET/CT findings were correlated with results of mpMRI and histopathology. A consensus of imaging, clinical and/or follow-up findings were used for determining the distant metastases, which were not verified by histopathology.

Results

In the patient cohort who underwent RPE, [⁶⁸ Ga]Ga-PSMA-11 PET/CT and mpMRI detected the IL in 86.5% and 98.1% of the patients, respectively. The median of the maximum standardized uptake value (SUVmax) in the intraprostatic IL was 12 (range, 4.7–67.8). Intraprostatic IL of the high-risk patients showed significantly higher SUVmax than those in patients with intermediate risk for distant metastases (n = 48; median: 17.84 vs. 8.77; p = 0.02).

In total 729 LN were removed by ePLND in 48 patients. The histopathology verified 26 pelvic lymph node metastases (pLNM) in 20.8% (10/48) of the patients, which have been correctly identified in 60% of the patients on [⁶⁸ Ga]Ga-PSMA-11 PET/CT, and in 50% on mpMRI. All but one pLNM had a maximum diameter below 10 mm.

Bone metastases (BM) and distant LNM (dLNM) were found in 17.3% of the patients on [⁶⁸ Ga]Ga-PSMA-11 PET/CT imaging. 39.0% of the [⁶⁸ Ga]Ga-PSMA-11 PET-positive BM showed no suspicious morphological correlation on CT.

Conclusion

[⁶⁸ Ga]Ga-PSMA-11 PET/CT shows high diagnostic performance for N and M staging of patients with intermediate- and high-risk prostate cancer and seems to be superior to pelvic mpMRI in the detection of locoregional lymph node metastases. A significant correlation was found between SUVmax of the intraprostatic index lesion and risk stratification based on tPSA level and GS. The results of this study emphasize again on the role of metabolic molecular imaging using specific tracers in selected patients, leading to tailored therapy approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11307-021-01650-9.

Pilot study comparing dominant intraprostatic lesion volume using Ga-68 prostate-specific membrane antigen PET-computed tomography and multiparametric MRI

PURPOSE

The standard imaging used for delineation of dominant intraprostatic lesion (DIL) is multiparametric MRI (mpMRI). The use of biologic imaging such as Ga-68 prostate-specific membrane antigen (PSMA) PET-computed tomography (PET-CT) for this purpose is being explored in view of increased sensitivity of this modality and the associated ease of delineation.

MATERIALS AND METHODS

The primary objective of the study was to compare the autogenerated volumes of the DIL in Ga-68 PSMA PET-CT with the standard volume delineated in mpMRI. Twenty patients with biopsy-proven untreated prostatic adenocarcinoma were included. Multiple percentages of the maximum standardized uptake value (%SUVmax) were used to autogenerate DIL volumes in Ga-68 PSMA PET-CT and these volumes were numerically matched with the consensus DIL volume in mpMRI. PSMA tumor volume (PSMA-TV) and total lesion PSMA (TL-PSMA) were also calculated for each lesion.

RESULTS

Median volume of DIL in mpMRI was 4 cm (interquartile range, IQR = 2.5-7.6 cm). The IQR for interobserver variability was 0.5-2.5 cm. Median SUVmax of the DIL was 14.1 (IQR = 10.2-22.3). Median %SUVmax corresponding to mpMRI volume was 41% of SUVmax (IQR = 34-55%). There was a strong negative correlation between MRI volume and %SUVmax (r = -0.829, P < 0.001). There was a significant correlation between TL-PSMA and prostate-specific antigen (r = 0.609, P = 0.004).

CONCLUSIONS

The median DIL volume was 4 cm and median %SUVmax corresponding to MR volume of DIL was 41%. A strong inverse relationship is found between mpMRI-defined DIL volume and the %SUVmax which generates similar volume in Ga-68 PSMA PET-CT. TL-PSMA could be a quantitative biomarker for tumor load and prognosis.

Prospective comparison of 18F-PSMA-1007 PET/CT, whole-body MRI and CT in primary nodal staging of unfavourable intermediate- and high-risk prostate cancer

PURPOSE

To prospectively compare 18F-prostate-specific membrane antigen (PSMA)-1007 positron emission tomography (PET)/CT, whole-body magnetic resonance imaging (WBMRI) including diffusion-weighted imaging (DWI) and standard computed tomography (CT), in primary nodal staging of prostate cancer (PCa).

METHODS

Men with newly diagnosed unfavourable intermediate- or high-risk PCa prospectively underwent 18F-PSMA-1007 PET/CT, WBMRI with DWI and contrast-enhanced CT within a median of 8 days. Six readers (two for each modality) independently reported pelvic lymph nodes as malignant, equivocal or benign while blinded to the other imaging modalities. Sensitivity, specificity and accuracy were reported according to optimistic (equivocal lesions interpreted as benign) and pessimistic (equivocal lesions interpreted as malignant) analyses. The reference standard diagnosis was based on multidisciplinary consensus meetings where available histopathology, clinical and follow-up data were used.

RESULTS

Seventy-nine patients completed all the imaging modalities, except for one case of interrupted WBMRI. Thirty-one (39%) patients had pelvic lymph node metastases, which were detected in 27/31 (87%), 14/31 (45%) and 8/31 (26%) patients by 18F-PSMA-1007 PET/CT, WBMRI with DWI and CT, respectively (optimistic analysis). In 8/31 (26%) patients, only 18F-PSMA-1007 PET/CT detected malignant lymph nodes, while the other two imaging modalities were reported as negative. At the patient level, sensitivity and specificity values for 18F-PSMA-1007 PET/CT, WBMRI with DWI and CT in optimistic analysis were 0.87 (95%CI 0.71-0.95) and 0.98 (95%CI 0.89-1.00), 0.37 (95%CI 0.22-0.55) and 0.98 (95%CI 0.89-1.00) and 0.26 (95%CI 0.14-0.43) and 1.00 (95%CI 0.93-1.00), respectively.

CONCLUSION

18F-PSMA-1007 PET/CT showed significantly greater sensitivity in nodal staging of primary PCa than did WBMRI with DWI or CT, while maintaining high specificity.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov ID: NCT03537391.

Is there a utility of adding skeletal imaging to 68-Ga-prostate-specific membrane antigen-PET/computed tomography in initial staging of patients with high-risk prostate cancer?

PURPOSE

Both bone-scan and cross-sectional imaging are indicated in the staging of high-risk prostate cancer (PCa). However, 68Ga-prostate-specific membrane antigen (PSMA)-PET/computed tomography (CT) has proven to be an excellent tracer for detection of skeletal metastases. The aim of this study was to assess if adding skeletal imaging (with 18F-Fluoride-PET/CT) to 68-Ga-PSMA-PET/CT had any impact on high-risk PCa staging.

METHOD

Fifty treatment-naive, histopathologically proven, high-risk (European Association of Urology) PCa patients underwent both 68-Ga-PSMA-PET/CT and 18F-Fluoride-PET/CT for staging.

RESULTS

Fluoride-PET/CT detected significantly a higher number of skeletal metastases/patient than PSMA-PET/CT (median 4.5/patient vs 3.0; Wilcoxan-signed-rank-test, P = 0.060) and there was a significantly higher proportion of only Fluoride-avid than only PSMA-avid lesions (McNemar-test P < 0.001). No significant advantage was seen in patient-wise metrics. Most lesions missed by PSMA-PET/CT were in flat bones (25/33). serum prostate specific antigen (S.PSA) showed positive correlation with both, the number of lesions [r(PSMA)-0.555 (P = 0.006) and r(Fluoride)-0.622 (P = 0.001)] as well as tumor to background ratio (TBR) [[r-0.706 (P < 0.001) and 0.516 (P = 0.010)]. Median TBR was significantly higher in PSMA-PET/CT (22.77 vs 16.30; P < 0.001). All three patients with only Fluoride-avid lesions (also not identified in bone-scan) showed biochemical response with additional therapy.

CONCLUSION

Though, Fluoride-PET/CT detected a higher absolute number of lesions than PSMA-PET/CT, no significant advantage was seen in patient-wise metrics. Fluoride-PET/CT added second-line management in only 3/50 patients, which could have been reduced to 1/50, with more sensitive evaluation of flat bones in PSMA-PET-CT. Therefore, additional skeletal imaging is not needed with 68-Ga-PSMA-PET/CT in initial staging of high-risk PCa.

Recent Development and Future Prospects of Molecular Targeted Therapy in Prostate Cancer

Prostate cancer (PC) is a rapidly increasing ailment worldwide. The previous decade has observed a rapid advancement in PC therapies that was evident from the number of FDA approvals during this phase. Androgen deprivation therapies (ADT) have traditionally remained a mainstay for the management of PCs, but the past decade has experienced the emergence of newer classes of drugs that can be used with or without the administration of ADT. FDA approved poly (ADP-ribose) polymerase inhibitors (PARPi), such as olaparib and rucaparib, after successful clinical trials against gene-mutated metastatic castration-resistant prostate cancer. Furthermore, drugs like apalutamide, darolutamide, and enzalutamide with an androgen-targeted mechanism of action have manifested superior results in non-metastatic castration-resistant prostate cancer (nmCRPC), metastatic castration-sensitive prostate cancer (mCSPC), and metastatic castration-resistant prostate cancer (mCRPC), respectively, with or without previously administered docetaxel. Relugolix, an oral gonadotropin-releasing hormone antagonist, and a combination of abiraterone acetate plus prednisone were also approved by FDA after a successful trial in advanced PC and mCRPC, respectively. This review aims to analyze the FDA-approved agents in PC during the last decade and provide a summary of their clinical trials. It also presents an overview of the ongoing progress of prospective molecules still under trial.

Intracranial Metastasis from Prostate Cancer: Investigation, Incidence, and Imaging Findings in a Large Cohort of Australian Men

Objectives:

Prostate cancer metastasizing to the brain is remarkably uncommon, with the incidence never having been described in the modern setting. The objective of this study was to determine the incidence and imaging pattern of intracranial metastasis from prostate cancer in a large cohort of Australian men with prostate cancer.

Material and Methods:

Retrospective review was undertaken of imaging reports for all known prostate cancer patients, who underwent an imaging examination inclusive of the brain, between July 1, 2014, and July 1, 2020. Once an intracranial lesion was identified, all available imaging and clinical notes were reviewed.

Results:

A total of 5644 imaging examinations which included the brain were identified in 4341 prostate cancer patients. The majority (92.1%) of examinations were 68-Gallium-labeled prostate-specific membrane antigen (⁶⁸Ga-PSMA) positron emission tomography/computed tomography (PET/CT). Eight patients were identified as having an intracranial metastasis from prostate cancer, yielding an incidence of 0.18%. All patients had a Gleason score of 9 (where known), and the majority of patients (5/8) had a non-acinar variant of prostate cancer. At the time of diagnosis of intracranial metastasis, all patients had extensive metastatic disease. Imaging characteristics of the intracranial lesions were highly variable.

Conclusion:

The incidence of intracranial metastasis in prostate cancer patients has never been well-established. In this study, we determined the incidence as being 0.18%. Given the majority of metastasis constituted unexpected findings on routine restaging ⁶⁸Ga-PSMA PET/CT, the incidence determined in our study is arguably the most accurate and clinically relevant described to date.

The Establishment of New Thresholds for PLND-Validated Clinical Nomograms to Predict Non-Regional Lymph Node Metastases: Using 68Ga-PSMA PET/CT as References

Purpose

PLND (pelvic lymph node dissection)-validated nomograms are widely accepted clinical tools to determine the necessity of PLND by predicting the metastasis of lymph nodes (LNMs) in pelvic region. However, these nomograms are in lacking of a threshold to predict the metastasis of extrareolar lymph nodes beyond pelvic region, which is not suitable for PLND. The aim of this study is to evaluate a threshold can be set for current clinical PLND-validated nomograms to predict extrareolar LN metastases beyond pelvic region in high-risk prostate cancer patients, by using ⁶⁸Ga-PSMA PET/CT as a reference to determine LN metastases (LNMs).

Experimental Design

We performed a retrospective analysis of 57 high-risk treatment-naïve PC patients in a large tertiary care hospital in China who underwent ⁶⁸Ga-PSMA-617 PET/CT imaging. LNMs was detected by ⁶⁸Ga-PSMA-617 PET/CT and further determined by imaging follow-up after anti-androgen therapy. The pattern of LN metastatic spread of PC patients were evaluated and analyzed. The impact of ⁶⁸Ga-PSMA PET/CT on clinical decisions based on three clinical PLND-validated nomograms (Briganti, Memorial Sloan Kettering Cancer Center, Winter) were evaluated by a multidisciplinary prostate cancer therapy team. The diagnostic performance and the threshold of these nomograms in predicting extrareolar LNMs metastasis were evaluated via receiver operating characteristic (ROC) curve analysis.

Results

LNMs were observed in 49.1% of the patients by ⁶⁸Ga-PSMA PET/CT, among which 65.5% of LNMs were pelvic-regional and 34.5% of LNMs were observed in extrareolar sites (52.1% of these were located above the diaphragm). The Briganti, MSKCC and Winter nomograms showed that 70.2%-71.9% of the patients in this study need to receive ePLND according to the EAU and NCCN guidelines. The LN staging information obtained from ⁶⁸Ga-PSMA PET/CT would have led to changes of planned management in 70.2% of these patients, including therapy modality changes in 21.1% of the patients, which were mainly due to newly detected non-regional LNMs. The thresholds of nomograms to predict non-regional LNMs were between 64% and 75%. The PC patients with a score >64% in Briganti nomogram, a score >75% in MSKCC nomogram and a score >67% in Winter nomogram were more likely to have non-regional LNMs. The AUCs (Area under curves) of the clinical nomograms (Briganti, MSKCC and Winter) in predicting non-regional LNMs were 0.816, 0.830 and 0.793, respectively.

Conclusions

By using ⁶⁸Ga-PSMA PET/CT as reference of LNM, the PLND-validated clinical nomograms can not only predict regional LNMs, but also predict non-regional LNMs. The additional information from ⁶⁸Ga-PSMA PET/CT may provide added benefit to nomograms-based clinical decision-making in more than two-thirds of patients for reducing unnecessary PLND. We focused on that a threshold can be set for current clinical PLND-validated nomograms to predict extrareolar LN metastases with an AUC accuracy of about 80% after optimizing the simple nomograms which may help to improve the efficiency for PC therapy significantly in clinical practice.

68Ga-PSMA PET/CT for Patients with PSA Relapse after Radical Prostatectomy or External Beam Radiotherapy

The study aimed to summarize clinical characteristics associated with Gallium-68-prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (⁶⁸Ga-PSMA PET/CT) scans as patients were restaged for prostate-specific antigen (PSA) relapse after radical prostatectomy (RP) or external beam radiotherapy (EBRT). Our analyses included multiple cox regression analyses. The study evaluated 95 patients with rising values of PSAs after RP and after EBRT. Sixty 63% of patients had a positive ⁶⁸Ga-PSMA PET/CT scan. Twelve patients (13%) had a positive site in the prostate bed, 29 patients (30%) had a positive site in the regional lymph nodes, and 19 (20%) had positive sites in distant organs. After four years follow-up, 21 patients (22%) died. Using multiple Cox regression analyses, the number of positive sites on the ⁶⁸Ga-PSMA PET/CT scan significantly predicted overall survival (OS) (p = 0.0001), whereas risk score and regional locations of the positive sites were not significant in the multiple Cox regression analyses. Our study indicates that the specific findings of ⁶⁸Ga-PSMA PET/CT scans are important because detailed findings of the scans predict the outcome after salvage treatment of patients with PSA relapse examined with ⁶⁸Ga-PSMA PET/CT scans.

Discrepancy between Multiparametric Magnetic Resonance Imaging and 68Ga Prostate-Specific Membrane Antigen Positron Emission Tomography: A Simultaneous Acquired Positron Emission Tomography-Magnetic Resonance Imaging Case

Conventionally, multiparametric magnetic resonance imaging (mpMRI) incorporating T2-weighted, diffusion-weighted, and dynamic contrast-enhanced sequences is considered the standard for detection and staging of clinically important prostate cancer (PCa).[1] The ⁶⁸gallium (⁶⁸Ga)-labeled positron emission tomography (PET) tracer targeting prostate-specific membrane antigen (PSMA), ⁶⁸Ga-PSMA PET, is a promising tool for detection, localization, and staging carcinoma prostate.[2] Here, we present a case of PCa, showing incongruence between ⁶⁸Ga-PSMA PET and the corresponding mpMRI findings. Moreover, the final histopathology revealed a surprise, which exemplifies the complementary nature of combining ⁶⁸Ga-PSMA PET and mpMRI in the diagnosis and staging of carcinoma prostate.

Histological comparison between predictive value of preoperative 3-T multiparametric MRI and 68 Ga-PSMA PET/CT scan for pathological outcomes at radical prostatectomy and pelvic lymph node dissection for prostate cancer

OBJECTIVE

To evaluate the ability of preoperative multiparametric magnetic resonance imaging (mpMRI) and a gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography (⁶⁸ Ga-PSMA PET/CT) scan to predict pathological outcomes and also identify a group of men with a <5% risk of histological pelvic lymph node metastasis (LNM) at pelvic lymph node dissection (PLND) performed during a robot-assisted laparoscopic radical prostatectomy (RALP) for prostate cancer. We then aimed to compare these results to known risk calculators for LNM, including the Cancer of the Prostate Risk Assessment (CAPRA) score, Memorial Sloan Kettering Cancer Centre (MSKCC) and Briganti nomograms.

PATIENTS AND METHODS

Between July 2014 and September 2019 only men who had both a preoperative mpMRI and staging ⁶⁸ Ga-PSMA PET/CT at our institution followed by a RALP with PLND referred to a single specialist uropathology laboratory were considered for inclusion. The data were collected retrospectively prior to February 2019 and in a prospective manner thereafter. A model was built to allocate probabilities of the men with a negative ⁶⁸ Ga-PSMA PET/CT scan having a <5% risk of histologically LNM at RALP based on the preoperative radiological staging.

RESULTS

A total of 233 consecutive men met the inclusion criteria of which 58 men (24.9%) had a LNM identified on PLND histology. The median (range) International Society of Urological Pathology (ISUP) Grade was 5 (1-5) and the median (range) prostate-specific antigen level was 7.4 (1.5-72) ng/mL. The median (range) number of resected lymph nodes was 16 (1-53) and the median (range) number of positive nodes identified on histology was 2 (1-22). Seminal vesicle invasion on mpMRI was more common in node-positive men than in the absence of LNM (31% vs 12%). The maximum standardised uptake value of the primary tumour on ⁶⁸ Ga-PSMA PET/CT was higher in men with LNM (median 9.2 vs 7.2, P = 0.02). Suspected LNM were identified in 42/233 (18.0%) men with ⁶⁸ Ga-PSMA PET/CT compared with 22/233 (9.4%) men with mpMRI (P = 0.023). The positive and negative predictive value for ⁶⁸ Ga-PSMA PET/CT was 66.7% and 84.3% respectively, compared to 59.1% and 78.7% for mpMRI. A predictive model showed only two men (4.2%) with a negative preoperative ⁶⁸ Ga-PSMA PET/CT would be positive for a histological LNM if they are ISUP Grade < 5 and Prostate Imaging-Reporting and Data System (PI-RADS) <5; or ISUP Grade 5 with PI-RADS < 4. An inspection of three additional variables: CAPRA score, MSKCC and Briganti nomograms did not improve the predictive probability for this group. However, of the 61 men with ISUP Grade 4-5 malignancy and also a PI-RADS 5 mpMRI, 20 (32.8%) men had a microscopic LNM despite a negative preoperative ⁶⁸ Ga-PSMA PET/CT.

CONCLUSION

Preoperative ⁶⁸ Ga-PSMA/PET CT was more sensitive in identifying histological pelvic LNM than 3-T mpMRI. Men with a negative ⁶⁸ Ga-PSMA PET/CT have a lower risk of LNM than predicted with CAPRA scores or MSKCC and Briganti nomograms. We identified that the combination of a negative preoperative ⁶⁸ Ga-PSMA PET/CT, ISUP biopsy Grade <5 and PI-RADS <5 prostate mpMRI, or an ISUP Grade 5 with PI-RADS <4 on mpMRI was associated with a <5% risk of a LNM. The addition of CAPRA scores, MSKCC and Briganti nomograms did not improve the predictive probability within this model. Conversely, men with ISUP Grade 4-5 malignancy associated with a PI-RADS 5 prostate mpMRI had a >30% risk of microscopic LNM despite a negative preoperative ⁶⁸ Ga-PSMA PET/CT and this high-risk group would appear suitable for an extended PLND at the time of a radical prostatectomy.

[Prostate-specific membrane antigen (PSMA)-based diagnostics and treatment of prostate cancer]

BACKGROUND

Since their clinical introduction in 2011, PSMA-PET/CT (PSMA: prostate-specific membrane antigen) as well as PSMA therapy of prostate cancer (PC) have spread rapidly worldwide.

OBJECTIVES

To summarize the current knowledge about both PSMA-PET/CT and PSMA therapy of PC.

METHODS

The knowledge derived from the literature as well as the authors' experiences were collected in this review.

RESULTS

PSMA-PET/CT demonstrates a very high sensitivity and specificity for the detection of recurrent PC as well as for the primary staging of intermediate- and high-risk PC. PSMA therapy shows promising results in third-line treatment for patients with castration-resistant, metastatic PC.

CONCLUSIONS

PSMA-PET/CT is meanwhile established as the gold standard for the detection of recurrent PC and is in the process of assuming the same role for primary staging of intermediate- to high-risk PC. PSMA therapy serves as a promising third-line therapy in an increasing number of centers.

Use of gallium-68 prostate-specific membrane antigen positron-emission tomography for detecting lymph node metastases in primary and recurrent prostate cancer and location of recurrence after radical prostatectomy: an overview of the current literature

Objectives

To review the literature to determine the sensitivity and specificity of gallium‐68 prostate‐specific membrane antigen (⁶⁸Ga‐PSMA) positron‐emission tomography (PET) for detecting pelvic lymph node metastases in patients with primary prostate cancer (PCa), and the positive predictive value in patients with biochemical recurrence (BCR) after initial curative treatment, and, in addition, to determine the detection rate and management impact of ⁶⁸Ga‐PSMA PET in patients with BCR after radical prostatectomy (RP).

Materials and Methods

We performed a comprehensive literature search. Search terms used in MEDLINE, EMBASE and Science Direct were ‘(PSMA, ⁶⁸Ga‐PSMA, ⁶⁸Gallium‐PSMA, Ga‐68‐PSMA or prostate‐specific membrane antigen)’ and ‘(histology, lymph node, staging, sensitivity, specificity, positive predictive value, recurrence, recurrent or detection)’. Relevant abstracts were reviewed and full‐text articles obtained where possible. References to and from obtained articles were searched to identify further relevant articles.

Results

Nine retrospective and two prospective studies described the sensitivity and specificity of ⁶⁸Ga‐PSMA PET for detecting pelvic lymph node metastases before initial treatment, which ranged from 33.3% to 100% and 80% to 100%, respectively. In eight retrospective studies, the positive predictive value of ⁶⁸Ga‐PSMA PET in patients with BCR before salvage lymph node dissection ranged from 70% to 100%. The detection rate of ⁶⁸Ga‐PSMA PET in patients with BCR after RP in the PSA subgroups <0.2 ng/mL, 0.2–0.49 ng/mL and 0.5 to <1.0 ng/mL ranged from 11.3% to 50.0%, 20.0% to 72.7% and 25.0% to 87.5%, respectively.

Conclusion

The review results showed that ⁶⁸Ga‐PSMA PET had a high specificity for the detection of pelvic lymph node metastases in primary PCa. Furthermore, ⁶⁸Ga‐PSMA PET had a very high positive predictive value in detecting lymph node metastases in patients with BCR. By contrast, sensitivity was only moderate; therefore, based on the currently available literature, ⁶⁸Ga‐PSMA PET cannot yet replace pelvic lymph node dissection to exclude lymph node metastases. In the salvage phase, ⁶⁸Ga‐PSMA PET had both a high detection rate and impact on radiotherapy planning in early BCR after RP.

Accuracy of standard clinical 3T prostate MRI for pelvic lymph node staging: Comparison to 68Ga-PSMA PET-CT

The aim was to assess the performance of prostate 3T MRI for pelvic lymph node (LN) staging in prostate cancer (PCa), in comparison to ⁶⁸Gallium-prostate specific membrane antigen PET-CT (⁶⁸Ga-PSMA PET-CT) as reference standard for LN detection. 130 patients with PCa underwent non-contrast-enhanced multiparametric prostate 3T MRI and ⁶⁸Ga-PSMA-PET-CT within 180 days at our institution. Overall, 187 LN metastases (n = 43 patients) detected by ⁶⁸Ga-PSMA-PET-CT were characterized by calculating maximum standardized uptake value (SUVmax), area, diameter and anatomical location including iliac, obturator, presacral and inguinal region. MRI achieved an overall sensitivity, specificity, positive and negative predictive value of 81.6% (CI 71.1-88.9%), 98.6% (CI 97.6-99.2%), 73.5% (CI 52.1-87.6%) and 99.5% (CI 98.8-99.8%), respectively. On a region-based analysis, detection rates differed non-significantly (ps > 0.12) in the anatomical regions. On a size-dependent analysis, detection of LN > 10 mm did not differ significantly (ps > 0.09) from LN ≤ 10 mm. In comparison to single T1 sequence evaluation, additional use of the T2 weighted sequences did not improve the overall performance significantly (p > 0.05). 3T prostate MRI represented an accurate tool for the detection of LN compared to ⁶⁸Ga-PSMA-PET-CT. Especially for LN metastases smaller than 10 mm, MRI was less accurate compared to ⁶⁸Ga-PSMA-PET-CT.

Advances in prostate-specific membrane antigen PET of prostate cancer

PURPOSE OF REVIEW

In recent years, a large number of reports have been published on prostate-specific membrane antigen (PSMA)/PET in prostate cancer (PCa). This review highlights advances in PSMA PET in PCa during the past year.

RECENT FINDINGS

PSMA PET/computed tomography (CT) is useful in detection of biochemical recurrence, especially at low prostate-specific antigen (PSA) values. The detection rate of PSMA PET is influenced by PSA level. For primary PCa, PSMA PET/CT shows promise for tumour localization in the prostate, especially in combination with multiparametric MRI (mpMRI). For primary staging, PSMA PET/CT can be used in intermediate and high-risk PCa. Intraoperative PSMA radioligand guidance seems promising for detection of malignant lymph nodes. While the use of PSMA PET/MRI in primary localized disease is limited to high and intermediate-risk patients and localized staging, in the recurrence setting, PET/MRI can be particularly helpful when the lesions are subtle. PSMA PET/CT is superior to choline PET/CT and other conventional imaging modalities.

SUMMARY

Molecular imaging with PSMA PET continues to pave the way for personalized medicine in PCa.However, large prospective clinical studies are still needed to fully evaluate the role of PSMA PET/CT and PET/MRI in the clinical workflow of PCa.

Comparison of percentage free PSA, MRI and GaPSMA PET scan for diagnosing cancer prostate in men with PSA between 4 and 20 ng/ml

Introduction:

We compared the diagnostic accuracy of percentage free prostate-specific antigen (PSA), multiparametric magnetic resonance imaging (mpMRI), and gallium-68 prostate-specific membrane antigen positron emission tomography (Ga-PSMA PET) to detect cancer prostate in men with PSA between 4 and 20 ng/ml in prebiopsy settings.

Materials and Methods:

This prospective study evaluated men with PSA values between 4 and 20 ng/ml, and all patients underwent percentage free PSA estimation, mpMRI, and Ga-PSMA PET scan, followed by cognitive fusion/registration biopsy along with systematic 12-core biopsy to detect cancer prostate. The diagnostic accuracy of percentage free PSA, mpMRI, and Ga-PSMA PET scan was compared with results of cognitive fusion/registration biopsy.

Results:

A total of 15 patients were included, of which 11 had an identifiable lesion on imaging and 9 had malignancy on the final histopathology report. The sensitivity, specificity, positive predictive value, negative predictive value (NPV), and diagnostic accuracy of mpMRI were 62.5%, 71.4%, 71.4%, 62.5%, and 66.6%, respectively, and that of Ga-PSMA PET scan were 88.8%, 66.6%, 80%, 80%, and 80%, respectively. The sensitivity of detection of clinically significant cancers for Ga-PSMA was higher (100%) compared to MRI (33.3%). However, Ga-PSMA also detected a greater number of insignificant lesions as compared to MRI.

Conclusion:

Ga-PSMA PET scan has high NPV and accuracy in predicting presence of cancer and can also be used to direct specific biopsy cores during systematic biopsy.

Multimodal imaging for radiation therapy planning in patients with primary prostate cancer

Implementation of advanced imaging techniques like multiparametric magnetic resonance imaging (mpMRI) or Positron Emission Tomography (PET) in radiation therapy (RT) planning of patients with primary prostate cancer demands several preconditions: accurate staging of the extraprostatic and intraprostatic tumor mass, robust delineation of the intraprostatic gross tumor volume (GTV) and a reproducible characterization of the prostate cancer's biological properties. In the current review we searched for the currently available imaging techniques and we discussed their ability to fulfill these preconditions. We found that current pretreatment imaging was mainly performed with mpMRI and/or Prostate-specific membrane antigen PET imaging. Both techniques offered an accurate detection of the extraprostatic and intraprostatic tumor burden and had a major impact on RT concepts. However, some studies postulated that mpMRI and PSMA PET had complementary information for intraprostatic GTV detection. Moreover, interobserver differences for intraprostatic tumor delineation based on mpMRI were observed. It is currently unclear whether PET based GTV delineation underlies also interobserver heterogeneity. Further research is warranted to answer whether multimodal imaging is able to visualize biological processes related to prostate cancer pathophysiology and radiation resistance.

Evaluation of Tumor Viability for Primary and Bone Metastases in Metastatic Castration-Resistant Prostate Cancer Using Whole-Body Magnetic Resonance Imaging

In contrast to bone scan and computed tomography (CT), which depend on osteoblastic response to detect bone metastasis, whole-body magnetic resonance imaging (WB-MRI) may be able to directly detect viable tumors. A 75-year-old male who had progressive metastatic prostate cancer during primary androgen deprivation therapy was referred to our hospital. Although bone scan and CT showed multiple bone metastases, WB-MRI suggested nonviable bone metastasis and viable tumor of the primary lesion. Prostate needle biopsy demonstrated viable prostate cancer cells from 10 of 12 cores. In contrast, CT-guided needle biopsy from bone metastasis of the lumbar vertebra revealed no malignant cells. Based on these findings, we reasoned that viable tumor cells inducing disease progression may primarily exist in the primary lesions and not in the metastatic lesions, and combined prostate radiotherapy and systemic hormonal therapy resulted in successful clinical response and disease control. The use of WB-MRI to detect viable disease lesions may enable us to design optimal treatment strategies for patients with metastatic castration-resistant prostate cancer.

68Ga-PSMA and 11C-Choline comparison using a tri-modality PET/CT-MRI (3.0 T) system with a dedicated shuttle

Background

The aim of this study was to prospectively compare the detection rate of ⁶⁸Ga-PSMA versus ¹¹C-Choline in men with prostate cancer with biochemical recurrence and to demonstrate the added value of a tri-modality PET/CT-MRI system.

Methods

We analysed 36 patients who underwent both ¹¹C-Choline PET/CT and ⁶⁸Ga-PSMA PET/CT scanning within a time window of 1-2 weeks. Additionally, for the ⁶⁸Ga-PSMA scan, we used a PET/CT-MRI (3.0 T) system with a dedicated shuttle, acquiring MRI images of the pelvis.

Results

Both scans were positive in 18 patients (50%) and negative in 8 patients (22%). Nine patients were positive with ⁶⁸Ga-PSMA alone (25%) and one with ¹¹C-Choline only (3%). The median detected lesion per patient was 2 for ⁶⁸Ga-PSMA (range 0-93) and 1 for ¹¹C-Choline (range 0-57). Tumour to background ratios in all concordant lesions (n = 96) were higher for ⁶⁸Ga-PSMA than for ¹¹C-Choline (110.3 ± 107.8 and 27.5 ± 17.1, mean ± S.D., for each tracer, respectively P = 0.0001). The number of detected lesions per patient was higher for ¹¹C-Choline in those with PSA ≥ 3.3 ng/mL, while the number of detected lesions was independent of PSA levels for ⁶⁸Ga-PSMA using the same PSA cut-off value. Metastatic pelvic lesions were found in 25 patients (69%) with ⁶⁸Ga-PSMA PET/CT, in 18 (50%) with ¹¹C-Choline PET/CT and in 21 (58%) with MRI (3.0 T). MRI was very useful in detecting recurrence in cases classified as indeterminate by means of PET/CT alone at prostate bed.

Conclusions

In patients with prostate cancer with biochemical recurrence ⁶⁸Ga-PSMA detected more lesions per patient than ¹¹C-Choline, regardless of PSA levels. PET/CT-MRI (3.0 T) system is a feasible imaging modality that potentially adds useful relevant information with increased accuracy of diagnosis.