99mTc-HDP bone scintigraphy and 18F-sodiumfluoride PET/CT in primary staging of patients with prostate cancer

The Impact of Positron Emission Tomography Imaging and Tumor Molecular Profiling on Risk Stratification, Treatment Choice, and Oncological Outcomes of Patients with Primary or Relapsed Prostate Cancer: An International Collaborative Review of the Existing Literature

CONTEXT

The clinical introduction of next-generation imaging methods and molecular biomarkers ("radiogenomics") has revolutionized the field of prostate cancer (PCa). While the clinical validity of these tests has thoroughly been vetted, their clinical utility remains a matter of investigation.

OBJECTIVE

To systematically review the evidence to date on the impact of positron emission tomography (PET) imaging and tissue-based prognostic biomarkers, including Decipher, Prolaris, and Oncotype Dx, on the risk stratification, treatment choice, and oncological outcomes of men with newly diagnosed PCa or those with biochemical failure (BCF).

EVIDENCE ACQUISITION

We performed a quantitative systematic review of the literature using the MEDLINE, EMBASE, and Web of Science databases (2010-2022) following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement guidelines. The validated Quality Assessment of Diagnostic Accuracy Studies 2 scoring system was used to assess the risk of bias.

EVIDENCE SYNTHESIS

A total of 148 studies (130 on PET and 18 on biomarkers) were included. In the primary PCa setting, prostate-specific membrane antigen (PSMA) PET imaging was not useful in improving T staging, moderately useful in improving N staging, but consistently useful in improving M staging in patients with National Comprehensive Cancer Network (NCCN) unfavorable intermediate- to very-high-risk PCa. Its use led to a management change in 20-30% of patients. However, the effect of these treatment changes on survival outcomes was not clear. Similarly, biomarkers in the pretherapy primary PCa setting increased and decreased the risk, respectively, in 7-30% and 32-36% of NCCN low-risk and 31-65% and 4-15% of NCCN favorable intermediate-risk patients being considered for active surveillance. A change in management was noted in up to 65% of patients, with the change being in line with the molecular risk-based reclassification, but again, the impact of these changes on survival outcomes remained unclear. Notably, in the postsurgical primary PCa setting, biomarker-guided adjuvant radiation therapy (RT) was associated with improved oncological control: Δ↓ 2-yr BCF by 22% (level 2b). In the BCF setting, the data were more mature. PSMA PET was consistently useful in improving disease localization-Δ↑ detection for T, N, and M staging was 13-32%, 19-58%, and 9-29%, respectively. Between 29% and 73% of patients had a change in management. Most importantly, these management changes were associated with improved survival outcomes in three trials: Δ↑ 4-yr disease-free survival by 24.3%, Δ↑ 6-mo metastasis-free survival (MFS) by 46.7%, and Δ↑ androgen deprivation therapy-free survival by 8 mo in patients who received PET-concordant RT (level 1b-2b). Biomarker testing in these patients also appeared to be helpful in risk stratifying and guiding the use of early salvage RT (sRT) and concomitant hormonal therapy. Patients with high-genomic-risk scores benefitted from treatment intensification: Δ↑ 8-yr MFS by 20% with the use of early sRT and Δ↑ 12-yr MFS by 11.2% with the use of hormonal therapy alongside early sRT, while low-genomic-risk score patients did equally well with initial conservative management (level 3).

CONCLUSIONS

Both PSMA PET imaging and tumor molecular profiling provide actionable information in the management of men with primary PCa and those with BCF. Emerging data suggest that radiogenomics-guided treatments translate into direct survival benefits for patients, however, additional prospective data are awaited.

PATIENT SUMMARY

In this review, we evaluated the utility of prostate-specific membrane antigen positron emission tomography and tumor molecular profiling in guiding the care of men with prostate cancer (PCa). We found that these tests augmented risk stratification, altered management, and improved cancer control in men with a new diagnosis of PCa or for those experiencing a relapse.

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.

Difficulties in Defining Oligometastatic Prostate Cancer: Implications for Clinical Trial Accrual and Community Practice Adoption of Metastasis-Directed Therapy Approaches

BACKGROUND

Metastasis-directed therapy is widely utilized for oligometastatic prostate cancer patients, but standard imaging does not always identify metastases definitively and, even with PSMA PET, there may be equivocal findings. Not all clinicians have access to detailed imaging review, particularly outside of academic cancer centers, and PET scan access is also limited. We sought to understand how imaging interpretation impacted recruitment to a clinical trial for oligometastatic prostate cancer.

METHODS

IRB approval was obtained to review medical records from all patients screened for the institutional IRB-approved clinical trial for men with oligometastatic prostate cancer involving androgen deprivation plus stereotactic radiation to all metastatic sites, as well as radium223 (NCT03361735). Clinical trial inclusion required at least one bone metastatic lesion and no more than five total sites of metastasis, including soft tissue sites. Tumor board discussion records were reviewed, along with results from additional radiology studies ordered or confirmatory biopsies performed. Clinical characteristics such as PSA level and Gleason score were studied for association with likelihood of oligometastatic disease confirmation.

RESULTS

At the time of data analysis, 18 subjects were deemed eligible and 20 were not eligible. The most common reasons for ineligibility were no confirmed bone metastasis in 16 patients (59%) and too many metastatic sites in 3 (11%). The median PSA of eligible subjects was 3.28 (range 0.4-45.5), whereas the median PSA of those found to be ineligible was 10.45 (range 3.7-26.3) when there were too many metastases identified, and 2.7 (range 0.2-34.5) when metastases were unconfirmed. PET imaging (PSMA or fluciclovine PET) increased the number of metastases, while MRI resulted in downstaging to non-metastatic disease.

CONCLUSIONS

This research suggests that additional imaging (i.e., at least two independent imaging modalities of a possible metastatic lesion) or tumor board adjudication of imaging findings may be critical to correctly identify patients appropriate for enrollment in oligometastatic protocols. This should be considered as trials of metastasis-directed therapy for oligometastatic prostate cancer accrue and results are translated to broader oncology practice.

[18F] Sodium Fluoride Dose Reduction Enabled by Digital Photon Counting PET/CT for Evaluation of Osteoblastic Activity

The aim of the study was to assess the quality and reproducibility of reducing the injected [¹⁸F] sodium fluoride ([¹⁸F]NaF) dose while maintaining diagnostic imaging quality in bone imaging in a preclinical skeletal model using digital photon counting PET (dPET) detector technology. Beagles (n = 9) were administered three different [¹⁸F]NaF doses: 111 MBq (n = 5), 20 MBq (n = 5), and 1.9 MBq (n = 9). Imaging started ≃45 min post-injection for ≃30 min total acquisition time. Images were reconstructed using Time-of-Flight, ultra-high definition (voxel size of 1 × 1 × 1 mm³), with 3 iterations and 3 subsets. Point spread function was modeled and Gaussian filtering was applied. Skeleton qualitative and quantitative molecular image assessment was performed. The overall diagnostic quality of all images scored excellent (61%) and acceptable (39%) by all the reviewers. [¹⁸F]NaF SUV_mean showed no statistically significant differences among the three doses in any of the region of interest assessed. This study demonstrated that a 60-fold [¹⁸F]NaF dose reduction was not significantly different from the highest dose, and it had not significant effect on overall image quality and quantitative accuracy. In the future, ultra-low dose [¹⁸F]NaF dPET/CT imaging may significantly decrease PET radiation exposure to preclinical subjects and personnel.

Salvage therapy for prostate cancer after radical prostatectomy

More than 40% of men with intermediate-risk or high-risk prostate cancer will experience a biochemical recurrence after radical prostatectomy. Clinical guidelines for the management of these patients largely focus on the use of salvage radiotherapy with or without systemic therapy. However, not all patients with biochemical recurrence will go on to develop metastases or die from their disease. The optimal pre-salvage therapy investigational workup for patients who experience biochemical recurrence should, therefore, include novel techniques such as PET imaging and genomic analysis of radical prostatectomy specimen tissue, as well as consideration of more traditional clinical variables such as PSA value, PSA kinetics, Gleason score and pathological stage of disease. In patients without metastatic disease, the only known curative intervention is salvage radiotherapy but, given the therapeutic burden of this treatment, importance must be placed on accurate timing of treatment, radiation dose, fractionation and field size. Systemic therapy also has a role in the salvage setting, both concurrently with radiotherapy and as salvage monotherapy.

Diagnostic Performance of [18F]-Labeled PET/CT Tracers for Lymph Node/Bone Metastasis and Biochemical Recurrence Detection in Advanced Prostate Cancer: A Meta-Analysis

PURPOSE

The aim of this study was to explore the diagnostic value of different fluorine-18 (18F)-labeled tracers for lymph node/bone metastasis and biochemical recurrence detection in advanced prostate cancer (PCa).

METHODS

PubMed, Embase, Web of Science, Cochrane databases, and the WHO International Clinical Trial Center were searched. The inclusion criteria were determined based on the Preferred Report Items of the Systematic Review and Meta-Analysis Guidelines. The Quality Assessment of Diagnostic Accuracy Studies-2 was used to assess the quality assessment of the included studies. The quantitative analysis of the included literature was performed on the patient and lesion basis, and the equivocal findings were considered negative or positive results, respectively.

RESULTS

Thirty-seven articles were included. On the patient basis, the pooled sensitivity and specificity of [18F]-labeled tracers were 0.80 (95% confidence interval [CI]: 0.78-0.83) and 0.89 (95% CI: 0.87-0.90) when equivocal results were considered to be positive and 0.80 (95% CI: 0.77-0.82) and 0.87 (95% CI: 0.85-0.89) when equivocal results were considered to be negative. On the lesion basis, the pooled sensitivity and specificity of [18F]-labeled tracers were 0.82 (95% CI: 0.80-0.83) and 0.91 (95% CI: 0.90-0.92) when equivocal lesions were regarded as positive and 0.81 (95% CI: 0.80-0.82) and 0.91 (95% CI: 0.90-0.92) when equivocal lesions were considered to be negative.

CONCLUSION

[18F]-labeled tracers have high diagnostic efficacy for lymph node/bone metastasis and biochemical recurrence in advanced PCa.

Matched-Pair Comparison of 18F-DCFPyL PET/CT and 18F-PSMA-1007 PET/CT in 240 Prostate Cancer Patients: Interreader Agreement and Lesion Detection Rate of Suspected Lesions

Over 20 different prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals for both imaging and therapy have been synthesized. Although variability in biodistribution and affinity for binding to the PSMA receptor is known to exist between different PSMA-targeting radiopharmaceuticals, little is known about the clinical implications of this variability. Therefore, this study analyzed differences in interreader agreement and detection rate between 2 regularly used 18F-labeled PSMA receptor-targeting radiopharmaceuticals: 18F-DCFPyL and 18F-PSMA-1007. Methods: One hundred twenty consecutive patients scanned with 18F-PSMA-1007 were match-paired with 120 patients scanned with 18F-DCFPyL. All 240 PET/CT scans were reviewed by 2 readers and scored according to the criteria of the PSMA Reporting and Data System. Interreader agreement and the detection rate for suspected lesions were scored for different anatomic locations such as the prostate, prostatic fossa, lymph nodes, and bone. Results: Great equality was found between 18F-DCFPyL and 18F-PSMA-1007; however, some clinically relevant and statistically significant differences were observed. 18F-PSMA-1007 detected suspected prostatic or prostatic fossa lesions in a higher proportion of patients and especially in the subcohort scanned for biochemical recurrence. 18F-DCFPyL and 18F-PSMA-1007 showed an equal ability to detect suspected lymph nodes, although interreader agreement for 18F-DCFPyL was higher. 18F-DCFPyL showed fewer equivocal skeletal lesions and higher interreader agreement on skeletal lesions. Most of the equivocal lesions found with 18F-PSMA-1007 at least were determined to be of nonmetastatic origin. Conclusion: Clinically relevant differences, which may account for diagnostic dilemmas, were observed between 18F-DCFPyL and 18F-PSMA-1007. Those findings encourage further studies, as they may have consequences for selection of the proper PSMA-targeting radiopharmaceutical.

Denosumab Reduces Lesional Fluoride Skeletal Burden on Na[18F]F PET-CT in Patients With Fibrous Dysplasia/McCune-Albright Syndrome

CONTEXT

The correlation between fibrous dysplasia/McCune-Albright syndrome (FD/MAS) skeletal disease burden on Na[18F]F positron emission tomography-computed tomography (PET-CT) and serum bone turnover markers (BTMs) was recently described. The effect of treatment on lesional fluoride burden in FD/MAS is unknown.

OBJECTIVE

To investigate treatment response measurements in patients with FD/MAS who underwent Na[18F]F-PET-CT and treatment with antiresorptives.

METHODS

Observational case series at an academic center of expertise for rare bone diseases. Fifteen consecutive patients were observed with FD/MAS with baseline and follow-up Na[18F]F-PET-CT parameters of healthy bone and FD lesions, BTMs, and pain scores at start of denosumab (n = 8) treatment and non-denosumab patients (n = 7). On Na[18F]F-PET-CT the volumetric measures of FD burden (fluoride tumor volume [FTV]) and "fraction affected skeleton" (FAS) represented the portion of the skeleton affected. This was correlated with BTMs and pain.

RESULTS

Disease activity decreased significantly, with FTV 361 cm3 to 97 cm3 (P = .018) in denosumab-treated patients, but not in non-denosumab patients (P = .249). Serum P1NP and alkaline phosphatase (ALP) decreased significantly: 82 ng/mL vs 55 ng/mL (P = .023) and 119 IU/L vs 84 IU/L (P = .020), respectively. In denosumab-treated patients pain scores improved leading to pain medication reduction. This correlated with lesional uptake, but healthy bone activity did not change. BTMs and FTV correlated positively (P1NP r = 0.730, P < .001; and ALP r = 0.406, P = .006), as did change in BTMs and FTV: P1NP (P = 0.032) and ALP (P = 0.024). FAS strongly correlated with treatment-induced decrease in ALP (P = .027) and P1NP (P = .009).

CONCLUSION

Na[18F]F-PET-CT captured treatment-induced lesional changes which correlated with BTMs and pain reduction. Therefore Na[18F]F-PET-CT can be used as an objective local parameter of response to denosumab treatment in FD/MAS.

A retrospective study on the potential of 99m Tc-HDP imaging before therapy for individualizing treatments with 223 Ra-Cl2 for metastatic castration resistant prostate cancer

PURPOSE

Research on dose-effect correlation is necessary to move toward an individualization of treatments of metastatic castration resistant prostate cancer (mCRPC) with ²²³ Ra-Cl₂ . We first looked for a possible correlation of ^99m Tc-HDP lesion uptake in pretreatment whole-body scans (WBSs) with lesion absorbed dose. Moreover, we looked for a possible correlation of ^99m Tc-HDP lesion uptake in pretreatment WBSs and of lesion absorbed dose with relative change in the ^99m Tc-HDP lesion uptake obtained from pre- and post-treatment WBSs in patients treated for mCRPC with six cycles of ²²³ Ra-Cl₂ .

METHODS

Eleven patients received six cycles of 55 kBq/kg of ²²³ Ra-Cl₂ separated by 4 weeks. In addition, one patient received concomitant treatment with abiraterone and two patients with enzalutamide. The ^99m Tc-HDP WBSs were acquired before the first cycle and after the sixth cycle of the treatment. For the lesions with the higher ^99m Tc-HDP uptake, the absorbed dose was calculated for the first cycle. Lesion volume was determined from ^99m Tc-HDP SPECT/CT images before the first cycle and ²²³ Ra-Cl₂ activity in the lesions was determined from ²²³ Ra-Cl₂ planar images after the first cycle. The effect of the treatment was evaluated from the relative change of the mean and the maximum counts in the lesions, both estimated from the WBSs acquired before the first cycle and after the sixth cycle.

RESULTS

The absorbed dose was calculated for 30 lesions, with values ranging between 0.4 and 3.8 Gy (mean 1.5 Gy). A significant (P < 0.05) high positive linear correlation was found between the lesion absorbed dose in the first treatment cycle and the mean and maximum counts in the lesions in the WBSs acquired before the first cycle (R = 0.75 and 0.76, respectively). The relative change of the mean and the maximum counts in the lesions in the ^99m Tc-HDP WBSs showed a significant (P < 0.05) high positive logarithmic correlation with the ^99m Tc-HDP mean and maximum counts in the lesions before the first cycle (R = 0.79 and 0.78, respectively). Lastly, a significant (P < 0.05) high positive logarithmic correlation was also found between the relative change of the mean and the maximum counts in the lesions in the ^99m Tc-HDP WBSs and the lesion absorbed dose (R = 0.86 and 0.85, respectively). For this correlation the influence of the administered activity and of the concomitant treatments was not found to be significant (P > 0.05).

CONCLUSIONS

The high correlations found for the ^99m Tc-HDP lesion uptake before the first cycle lesion with the relative change in the ^99m Tc-HDP lesion uptake after the six cycles of ²²³ Ra-Cl₂ , and with the lesion absorbed dose in the first cycle show the potential of pretreatment ^99m Tc-HDP imaging in order to personalize the performance of these treatments.

Comparison of PET/CT and MRI in the Diagnosis of Bone Metastasis in Prostate Cancer Patients: A Network Analysis of Diagnostic Studies

BACKGROUND

Accurate diagnosis of bone metastasis status of prostate cancer (PCa) is becoming increasingly more important in guiding local and systemic treatment. Positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) have increasingly been utilized globally to assess the bone metastases in PCa. Our meta-analysis was a high-volume series in which the utility of PET/CT with different radioligands was compared to MRI with different parameters in this setting.

MATERIALS AND METHODS

Three databases, including Medline, Embase, and Cochrane Library, were searched to retrieve original trials from their inception to August 31, 2019 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. The methodological quality of the included studies was assessed by two independent investigators utilizing Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). A Bayesian network meta-analysis was performed using an arm-based model. Absolute sensitivity and specificity, relative sensitivity and specificity, diagnostic odds ratio (DOR), and superiority index, and their associated 95% confidence intervals (CI) were used to assess the diagnostic value.

RESULTS

Forty-five studies with 2,843 patients and 4,263 lesions were identified. Network meta-analysis reveals that 68Ga-labeled prostate membrane antigen (68Ga-PSMA) PET/CT has the highest superiority index (7.30) with the sensitivity of 0.91 and specificity of 0.99, followed by 18F-NaF, 11C-choline, 18F-choline, 18F-fludeoxyglucose (FDG), and 18F-fluciclovine PET/CT. The use of high magnetic field strength, multisequence, diffusion-weighted imaging (DWI), and more imaging planes will increase the diagnostic value of MRI for the detection of bone metastasis in prostate cancer patients. Where available, 3.0-T high-quality MRI approaches 68Ga-PSMA PET/CT was performed in the detection of bone metastasis on patient-based level (sensitivity, 0.94 vs. 0.91; specificity, 0.94 vs. 0.96; superiority index, 4.43 vs. 4.56).

CONCLUSIONS

68Ga-PSMA PET/CT is recommended for the diagnosis of bone metastasis in prostate cancer patients. Where available, 3.0-T high-quality MRI approaches 68Ga-PSMA PET/CT should be performed in the detection of bone metastasis.

Imaging Fibroblast Activation Protein Alpha Improves Diagnosis of Metastatic Prostate Cancer with Positron Emission Tomography

PURPOSE

Metastatic castration-resistant prostate cancer (mCRPC) is a lethal, heterogeneous disease with few therapeutic strategies that significantly prolong survival. Innovative therapies for mCRPC are needed; however, the development of new therapies relies on accurate imaging to assess metastasis and monitor response. Standard imaging modalities for prostate cancer require improvement and there remains a need for selective and sensitive imaging probes that can be widely used in patients with mCRPC.

EXPERIMENTAL DESIGN

We evaluated the transmembrane protease fibroblast activation protein alpha (FAP) as a targetable cell surface antigen for mCRPC. Genomic and IHC analyses were performed to investigate FAP expression in prostate cancer. Our FAP-targeted antibody imaging probe, [89Zr]Zr-B12 IgG, was evaluated by PET/CT imaging in preclinical prostate cancer models.

RESULTS

Analysis of patient data documented FAP overexpression in metastatic disease across tumor subtypes. PET imaging with [89Zr]Zr-B12 IgG demonstrated high tumor uptake and long-term retention of the probe in the preclinical models examined. FAP-positive stroma tumor uptake of [89Zr]Zr-B12 IgG was 5-fold higher than the isotype control with mean %ID/cc of 34.13 ± 1.99 versus 6.12 ± 2.03 (n = 3/group; P = 0.0006) at 72 hours. Ex vivo biodistribution corroborated these results documenting rapid blood clearance by 24 hours and high tumor uptake of [89Zr]Zr-B12 IgG by 72 hours.

CONCLUSIONS

Our study reveals FAP as a target for imaging the tumor microenvironment of prostate cancer. Validation of [89Zr]Zr-B12 IgG as a selective imaging probe for FAP-expressing tumors presents a new approach for noninvasive PET/CT imaging of mCRPC.

Clinical impact of PSMA PET/CT in primary prostate cancer compared to conventional nodal and distant staging: a retrospective single center study

Background

To evaluate the impact of Gallium-68 [⁶⁸Ga] labeled prostate specific membrane antigen (PSMA) positron emission tomography (PET)/X-ray computed tomography (CT) compared with conventional imaging on staging and clinical management of men evaluated for primary prostate cancer (PCa).

Methods

Men with newly diagnosed biopsy-proven PCa who had been staged with a conventional staging protocol including bone scintigraphy (BS) and additionally underwent [⁶⁸Ga]PSMA PET/CT, were evaluated retrospectively. Imaging findings from BS, magnetic resonance imaging (MRI) and/or CT were categorized regarding locoregional nodal (N) and distant metastasis (M) status as negative, positive or equivocal before and after addition of the information of PET/CT. Also, the imaging-based level of confidence (LoC) in correct assessment of N and M status was scored. Impact of PET/CT on clinical management was evaluated by the percentage of treatment category changes after PET/CT as determined in the multidisciplinary tumour board.

Results

Sixty-four men with intermediate and high-risk PCa were evaluated. With additional information of PET/CT, N status was upstaged in 23%, and downstaged in 9%. M status was upstaged in 13%, and downstaged in 23%. A net increase in LoC of 20% was noted, mainly regarding M status.

Treatment category changed from palliative to curative in 9%, and from curative to palliative in 3%. An undecided treatment plan changed to curative in 14%, as well as to palliative in another 9%. In total, a 36% treatment category change was noted.

High negative predictive value of PET/CT for M status was indicated by 27 patients that underwent robot-assisted radical prostatectomy and reached postoperative biochemical disease-free status or had a likely other site of disease recurrence.

Conclusions

PSMA PET/CT can cause considerable changes in N and M staging, as well as in management compared to conventional staging. Findings of this study support the replacement of BS and CT by PSMA PET/CT in staging primary PCa.

The Value of 68Ga-PSMA PET/CT Following Equivocal 18F-NaF PET/CT in Prostate Cancer Patients

Background: Inconclusive bone scans are a challenge but there is no consensus about follow-up imaging. We evaluated the use of ⁶⁸gallium-labelled prostate-specific membrane antigen (⁶⁸Ga-PSMA) PET/CT if ¹⁸F-sodium fluoride (¹⁸F-NaF) PET/CT was inconclusive. Methods: This retrospective study included patients with no previously known bone metastases who had one or more equivocal bone lesions on ¹⁸F-NaF PET/CT and underwent additional ⁶⁸Ga-PSMA PET/CT. The bone lesions were deemed as true metastases or not based on follow-up by surveying supplemental imaging modalities and hospital records. A subgroup of patients with “most valid follow-up” was created, which included patients with unmeasurable PSA after prostatectomy or subsequent imaging (additional ¹⁸F-NaF PET/CT, ⁶⁸Ga-PSMA PET/CT, CT, or MRI). Results: Of the 2918 patients referred for ¹⁸F-NaF PET/CT from the department of urology in the inclusion period, 51 (1.7%) were inconclusive regarding bone metastases and underwent additional ⁶⁸Ga-PSMA PET/CT. Thirteen of these patients (25%) were ultimately diagnosed with bone metastases. Patient-based sensitivity, specificity, and accuracy of additional ⁶⁸Ga-PSMA PET/CT were 100%, 95%, and 96%, respectively. In patients with “most valid follow-up”, the same parameters were 100%, 93%, and 94%, respectively. Conclusion: ⁶⁸Ga-PSMA PET/CT is an excellent complementary modality in when ¹⁸F-NaF PET/CT is equivocal.

Development and validation of a prediction model for identifying men with intermediate- or high-risk prostate cancer for whom bone imaging is unnecessary: a nation-wide population-based study

Objective: To develop and validate a nomogram that identifies men for whom bone scan is unnecessary.Material and methods: The study datasets were derived from the National Prostate Cancer Register (NPCR) of Sweden. All men in the NPCR ≤80 years of age who were diagnosed with intermediate- or high-risk prostate cancer and who had pretreatment bone imaging (^99mTc MDP scintigraphy, plain x-ray, computed tomography, magnetic resonance imaging, and/or positron emission tomography fused with computed tomography) were included. Men diagnosed from 2015-2016 formed a development dataset and men diagnosed in 2017 formed a validation dataset. Outcome was metastasis on bone imaging as registered in NPCR. Multivariable logistic regression was used to develop a nomogram.Results: In the development dataset 482/5084 men (10%) had bone metastasis, the corresponding percentage in the validation dataset was 282/2554 (11%). Gleason grade group, clinical T stage, and prostate-specific antigen were included in the final model. Discrimination and calibration were satisfactory in both the development (AUC 0.80, 95% CI 0.78-0.82) and validation dataset (AUC 0.80, 95% CI, 0.77-0.82). Compared with using the EAU guidelines' recommendation for selecting men for imaging, using the nomogram with a cut-off at 4% chance of bone metastasis, would have avoided imaging in 519/2068 men (25%) and miss bone metastasis in 10/519 (2%) men in the validation dataset.Conclusion: By use of our nomogram, bone scans of men with prostate cancer can be avoided in a large proportion of men.

Comparison of PSMA-PET/CT, choline-PET/CT, NaF-PET/CT, MRI, and bone scintigraphy in the diagnosis of bone metastases in patients with prostate cancer: a systematic review and meta-analysis

OBJECTIVE

A systematic review and meta-analysis to compare the diagnostic performance of prostate-specific membrane antigen (PSMA)-PET/CT, choline-PET/CT, Sodium Fluoride (NaF) PET/CT, MRI, and bone scintigraphy (BS) in detecting bone metastases in patients with prostate cancer.

METHODS

We searched PubMed and Embase for articles published between January 1990 and September 2018. Two evaluators independently extracted the sensitivity, specificity, the numbers of true and false positives, and true and false negatives. We calculated the pooled sensitivity, specificity, and 95% confidence intervals (CI) for each method. We calculated the tests' diagnostic odds ratios (DOR); drew the summary receiver operating characteristic (SROC) curves; and obtained the areas under the curves (AUC), Q* values, and 95% CIs.

RESULTS

The per-patient pooled sensitivities of PSMA-PET/CT, choline-PET/CT, NaF-PET/CT, MRI, and BS were 0.97, 0.87, 0.96, 0.91, and 0.86, respectively. The pooled specificities were 1.00, 0.99, 0.97, 0.96, and 0.95, respectively. The pooled DOR values were 504.16, 673.67, 242.63, and 114.44, respectively. The AUC were 1.00, 0.99, 0.99, 0.98, and 0.95, respectively. The per-lesion pooled sensitivities of PSMA-PET/CT, choline-PET/CT, NaF-PET/CT, MRI, and bone imaging were 0.88, 0.80, 0.97, 0.81 and 0.68, respectively.

CONCLUSIONS

According to the meta-analysis, PSMA-PET/CT had the highest per-patient sensitivity and specificity in detecting bone metastases with prostate cancer. The sensitivities of NaF-PET/CT and MRI were better than those for choline-PET/CT and BS. The specificity of PSMA-PET/CT was significantly better than BS. Others were similar. For per-lesion, NaF-PET/CT had the highest sensitivity, PSMA-PET/CT had higher sensitivity than choline-PET/CT and MRI, and BS had the lowest sensitivity.

Exploitation of CD133 for the Targeted Imaging of Lethal Prostate Cancer

PURPOSE

Aggressive variant prostate cancer (AVPC) is a nonandrogen receptor-driven form of disease that arises in men in whom standard-of-care therapies have failed. Therapeutic options for AVPC are limited, and the development of novel therapeutics is significantly hindered by the inability to accurately quantify patient response to therapy by imaging. Imaging modalities that accurately and sensitively detect the bone and visceral metastases associated with AVPC do not exist.

EXPERIMENTAL DESIGN

This study investigated the transmembrane protein CD133 as a targetable cell surface antigen in AVPC. We evaluated the expression of CD133 by microarray and IHC analysis. The imaging potential of the CD133-targeted IgG (HA10 IgG) was evaluated in preclinical prostate cancer models using two different imaging modalities: near-infrared and PET imaging.

RESULTS

Evaluation of the patient data demonstrated that CD133 is overexpressed in a specific phenotype of AVPC that is androgen receptor indifferent and neuroendocrine differentiated. In addition, HA10 IgG was selective for CD133-expressing tumors in all preclinical imaging studies. PET imaging with [⁸⁹Zr]Zr-HA10 IgG revealed a mean %ID/g of 24.30 ± 3.19 in CD133-positive metastatic lesions as compared with 11.82 ± 0.57 in CD133-negative lesions after 72 hours (P = 0.0069). Ex vivo biodistribution showed similar trends as signals were increased by nearly 3-fold in CD133-positive tumors (P < 0.0001).

CONCLUSIONS

To our knowledge, this is the first study to define CD133 as a targetable marker of AVPC. Similarly, we have developed a novel imaging agent, which is selective for CD133-expressing tumors, resulting in a noninvasive PET imaging approach to more effectively detect and monitor AVPC.

Robot-assisted Radical Prostatectomy Due to a Primary Carcinoid Prostatic Tumor in a Three-Year-Old Child: A Case Report

We present an extremely rare case of a 3-year-old child with a primary carcinoid tumor of the prostate. A 3-year-old boy presented with failure to thrive, constipation, recurrent respiratory tract infections, and pain in the genital area. His karyotype was normal and cystic fibrosis and coeliac disease were excluded prior to further investigation. An abdominopelvic computed tomography scan revealed a prostatic mass. Transrectal ultrasound-guided prostate biopsy was therefore performed and pathological examination revealed a carcinoid tumor. A robotic radical prostatectomy was performed. As this is an innovative surgical approach, we describe the surgical technique used.

Liquid Biopsy in Oligometastatic Prostate Cancer-A Biologist's Point of View

Prostate cancer (PCa) is the main cause of cancer-related mortality in males and the diagnosis, treatment, and care of these patients places a great burden on healthcare systems globally. Clinically, PCa is highly heterogeneous, ranging from indolent tumors to highly aggressive disease. In many cases treatment-generally either radiotherapy (RT) or surgery-can be curative. Several key genetic and demographic factors such as age, family history, genetic susceptibility, and race are associated with a high incidence of PCa. While our understanding of PCa, which is mainly based on the tools of molecular biology-has improved dramatically in recent years, efforts to better understand this complex disease have led to the identification of a new type of PCa-oligometastatic PCa. Oligometastatic disease should be considered an individual, heterogeneous entity with distinct metastatic phenotypes and, consequently, wide prognostic variability. In general, patients with oligometastatic disease typically present less biologically aggressive tumors whose metastatic potential is more limited and which are slow-growing. These patients are good candidates for more aggressive treatment approaches. The main aim of the presented review was to evaluate the utility of liquid biopsy for diagnostic purposes in PCa and for use in monitoring disease progression and treatment response, particularly in patients with oligometastatic PCa. Liquid biopsies offer a rapid, non-invasive approach whose use t is expected to play an important role in routine clinical practice to benefit patients. However, more research is needed to resolve the many existing discrepancies with regard to the definition and isolation method for specific biomarkers, as well as the need to determine the most appropriate markers. Consequently, the current priority in this field is to standardize liquid biopsy-based techniques. This review will help to improve understanding of the biology of PCa, particularly the recently defined condition known as "oligometastatic PCa". The presented review of the body of evidence suggests that additional research in molecular biology may help to establish novel treatments for oligometastatic PCa. In the near future, the treatment of PCa will require an interdisciplinary approach involving active cooperation among clinicians, physicians, and biologists.

Nuclear medicine: workplace monitoring and internal occupational exposure during a ventilation/perfusion single-photon emission tomography

The administration of ^99mTc-HDP to diagnose pulmonary thromboembolisms leads to the presence of ^99mTc in the environment of a nuclear medicine department, which could pose a potential risk of internal contamination to medical staff. Therefore, air samples from the administration room, gamma camera room and corridor of such a department were taken for the purpose of performing a workplace monitoring program of the medical centre under study, with maximum activity values of 640 ± 30 kBq/m³, 1.5 ± 0.1 kBq/m³ and 54 ± 3 kBq/m³, respectively, being obtained. These results correspond to committed effective doses received by exposed employees, via inhalation, when one ventilation/perfusion single-photon emission tomography study was performed, of 0.7 μSv, 0.004 μSv and 0.2 μSv, respectively. As inhalation is the employees' main exposure pathway to radio-aerosols, the internal dose of the nuclear medicine department's medical staff was also evaluated via urine bioassay measurements. Nuclear medicine nurses showed the highest ^99mTc activity in 24-h urine samples (2100 ± 130 Bq/day), resulting in a committed effective dose of 21 μSv for each diagnostic study performed. Even so, the performance of ventilation/perfusion diagnostic studies did not constitute a substantial radiological risk since the annual dose limit for exposed employees was not exceeded.

18F-NaF-PET/CT for the detection of bone metastasis in prostate cancer: a meta-analysis of diagnostic accuracy studies

PURPOSE

This meta-analysis aims to establish the diagnostic performance of ¹⁸F-NaF-PET/CT for the detection of bone metastases in prostate cancer patients. The performance of ¹⁸F-NaF-PET/CT was compared with other imaging techniques in the same cohort of patients.

METHODS

A systematic search was performed in PubMed/Medline and EMBASE (last Updated, September 28, 2018). Studies with histopathology confirmation and/or clinical/imaging follow-up as reference standard were eligible for inclusion.

RESULTS

A total of 14 studies were included. Twelve studies including 507 patients provided per-patient basis information. The pooled sensitivity, specificity, diagnostic odds ratio (DOR) and the area under the summary receiver operating characteristics curve (AUC) of ¹⁸F-NaF-PET/CT for the detection of bone metastases were 0.98 (95% CI 0.95-0.99), 0.90 (95% CI 0.86-0.93), 123.2 and 0.97, respectively. Seven studies provided the lesion-based accuracy information of 1812 lesions identified on ¹⁸F-NaF-PET/CT with the pooled sensitivity, specificity, DOR and AUC of 0.97 (95% CI 0.95-0.98), 0.84 (95% CI 0.81-0.87), 206.8 and 0.97, respectively. The overall diagnostic performance of ¹⁸F-NaF-PET/CT is superior to ^99mTc-bone scintigraphy (AUC 0.842; P < 0.001; four studies) and ^99mTc-SPECT (AUC 0.896; P < 0.001, four studies). Compared to ¹⁸F NaF-PET/CT, whole-body MRI with diffusion-weighted imaging (DWI) was shown to have lower sensitivity (0.83, 95% CI 0.68-0.93), with no significant difference in the overall performance (AUC 0.947; P = 0.18, four studies).

CONCLUSION

¹⁸F-NaF-PET/CT has excellent diagnostic performance in the detection of bone metastases in staging and restaging of high-risk prostate cancer patients. The performance of ¹⁸F-NaF-PET/CT is superior to ^99mTc bone scintigraphy and SPECT, and comparable to DWI-MRI.

Imaging modalities in synchronous oligometastatic prostate cancer

Purpose

Along with a number of other malignancies, the term “oligometastatic” prostate cancer has recently emerged. It represents an attempt to define a subtype of cancer with a limited metastatic load that might perform more favorably than a distinctly disseminated disease, or even one that may be managed in a potentially curative way. Since there is currently a knowledge gap of what imaging modalities should be utilized to classify patients as having this type of tumor, we aimed to shed light on the role of conventional and marker-based imaging in the setting of synchronous oligometastatic prostate cancer as well as summarize the available evidence for its clinical application.

Methods

A literature search on December 15th 2017 was conducted using the Pubmed database.

Results

Functional imaging techniques like ⁶⁸Ga PSMA. ⁶⁸Ga PSMA PET-CT has currently been shown the best detection rates for the assessment of nodal, bone and visceral metastases, especially for smaller lesions at low PSA levels.

Conclusions

Functional imaging helps detect low-burden disease metastatic patients. However, these imaging modalities are not available in every center and thus clinicians may be prone to prescribe systemic treatment rather than referring patients for cytoreductive treatments. We hope that the ongoing prospective trials will help guide clinicians in making a more personalized management of synchronous metastatic patients.