Spine metastases in prostate cancer: comparison of technetium-99m-MDP whole-body bone scintigraphy, [(18) F]choline positron emission tomography(PET)/computed tomography (CT) and [(18) F]NaF PET/CT

Stereotactic body radiation therapy for bone oligometastases

Stereotactic body radiation therapy is effective for the local management of oligometastases (at most five metastases) with a benefit in survival and local control. Most studies on the management of oligometastases focus on all oligometastatic sites in primary cancer and very few focus on a single oligometastatic site. In particular, there are few data on bone oligometastases, which represent one of the preferred sites for secondary cancer locations. This article focuses on the benefit of stereotactic radiotherapy for bone oligometastases of all cancers by histological types, and reviews the results of major studies in this field.

Tumor Burden of Iodine-Avid Bone Metastatic Thyroid Cancer Identified via 18F-Sodium Fluoride PET/CT Imaging

BACKGROUND

Patients with differentiated thyroid cancer (DTC) are referred to radioactive 131I (RAI) therapy and post-therapy 131I whole-body scintigraphy (WBS) to identify local and/or remote metastases. Positron emission tomography (PET)/computed tomography (CT) imaging with 18F-fluoro-D-glucose (FDG) or 18F-sodium fluoride (NaF) may also be used with these patients for the evaluation of bone metastases. We compared the role of 18F-NaF PET/CT and 18F-FDG-PET/CT in patients with DTC and documented bone metastases at post-therapy WBS.

METHODS

Ten consecutive DTC patients with iodine avid bone metastasis at post-therapy WBS referred to 18F-NaF PET/CT and 18F-FDG PET/CT were studied. The findings of the three imaging procedures were compared for abnormal detection rates and concordance.

RESULTS

At post-therapy 131I WBS, all patients had skeletal involvement with a total of 21 bone iodine avid lesions. At 18F-FDG PET/TC, 19 bone lesions demonstrated increased tracer uptake and CT pathological alterations, while 2 lesions did not show any pathological finding. At 18F-NaF PET/CT, the 19 bone lesions detected at 18F-FDG PET/TC also demonstrated abnormal tracer uptake, and the other 2 bone iodine avid foci did not show any pathological finding.

CONCLUSIONS

In patients with DTC, 18F-NaF PET/CT did not obtain more information on the metastatic skeletal involvement than post-therapy 131I WBS and 18F-FDG PET/CT.

Bone Metastasis in Prostate Cancer: Bone Scan Versus PET Imaging

Prostate cancer is the second most common cause of malignancy among men, with bone metastasis being a significant source of morbidity and mortality in advanced cases. Detecting and treating bone metastasis at an early stage is crucial to improve the quality of life and survival of prostate cancer patients. This objective strongly relies on imaging studies. While CT and MRI have their specific utilities, they also possess certain drawbacks. Bone scintigraphy, although cost-effective and widely available, presents high false-positive rates. The emergence of PET/CT and PET/MRI, with their ability to overcome the limitations of standard imaging methods, offers promising alternatives for the detection of bone metastasis. Various radiotracers targeting cell division activity or cancer-specific membrane proteins, as well as bone seeking agents, have been developed and tested. The use of positron-emitting isotopes such as fluorine-18 and gallium-68 for labeling allows for a reduced radiation dose and unaffected biological properties. Furthermore, the integration of artificial intelligence (AI) and radiomics techniques in medical imaging has shown significant advancements in reducing interobserver variability, improving accuracy, and saving time. This article provides an overview of the advantages and limitations of bone scan using SPECT and SPECT/CT and PET imaging methods with different radiopharmaceuticals and highlights recent developments in hybrid scanners, AI, and radiomics for the identification of prostate cancer bone metastasis using molecular imaging.

Role of 18F-NaF PET/CT in bone metastases

The use of 18F sodium fluoride (18F-NaF) in positron emission tomography (PET/CT) is increasing. This resurgence of an old tracer has been driven by several factors, including its superior diagnostic performance over standard 99mTc-based bone scintigraphy (BS), availability of PET/CT imaging systems, a shortened examination time and an increase in the number of regional commercial PET radiotracer distribution. In this special article, we aimed to highlight the current place of the 18F-NaF PET/CT in the imaging of bone metastases (BM) in a variety of malignancies. A special focus is given to the following ones: breast cancer (BC), prostate cancer (PCa). Also, other malignancies such as bladder cancer, lung cancer, thyroid cancer, multiple myeloma, head and neck cancer, hepatocellular carcinoma have been addressed. At last, we summarize the advantages and limits of the 18F-NaF PET/CT compared to other imaging modalities in these settings.

Diagnostic and therapeutic impact of PET/CT with 18F-DCFPyL versus 18F-Fluorocholine in initial staging of intermediate-/high-risk prostate cancer: a pilot study

AIM

To assess the diagnostic and therapeutic impact of PET/CT with 18F-DCFPyL with respect to 18F-Fluorocholine in initial staging of intermediate-/high-risk prostate cancer (PCa).

MATERIAL AND METHODS

Patients with recent diagnosis of intermediate-/high-risk PCa without androgen deprivation therapy and previous 18F-Fluorocholine-PET/CT (negative for extraprostatic disease or with oligometastatic disease) were referred to 18F-DCFPyL-PET/CT. Patients' disease characteristic as grade group, D'Amico risk category (intermediate/high), prostate-specific antigen (PSA) closest to PET/CTs and its kinetics were obtained. The overall detection rate (DR) and molecular imaging TNM (miTNM) stage according to the prostate cancer molecular imaging standardized evaluation (PROMISE) criteria were assessed for both radiotracers, and their concordance (Kappa coefficient) was analyzed. The diagnostic and therapeutic impact of 18F-DCFPyL with respect to 18F-Fluorocholine was evaluated.

RESULTS

Fifty-eight patients were analyzed (84.5% high-risk). 18F-Fluorocholine showed a higher DR than 18F-DCFPyL of prostate gland involvement (100% versus 93.1%) and pelvic node disease (37.9% versus 31%; k = 0.436, p = 0.001). On the other hand, 18F-DCFPyL-PET/CT showed a higher DR of metastatic disease than 18F-Fluorocholine-PET/CT, 9/58 patients (15.5%): 3 M1a, 5 M1b and 1 M1c) versus 5/58 (8.6%) patients: 1 M1a and 4 M1b), k = 0.426; p = 0.001. No significant association was found between clinical characteristics (grade group, risk category, PSA level and kinetic) and 18F-Fluorocholine or 18F-DCFPyL results. The results of 18F-DCFPyL-PET/CT modified the previously planned treatment compared to 18F-Fluorocholine-PET/CT in 13 patients (22.4%).

CONCLUSIONS

18F-Fluorocholine and 18F-DCFPyL PET/CT showed a similar DR of prostate gland and lymph node involvement, although with moderate concordance for the latter. 18F-DCFPyL was superior to 18F-Fluorocholine in detecting regional and distant metastasis with a therapeutic impact in one of every five patients.

Automated quantification of PET/CT skeletal tumor burden in prostate cancer using artificial intelligence: The PET index

PURPOSE

Consistent assessment of bone metastases is crucial for patient management and clinical trials in prostate cancer (PCa). We aimed to develop a fully automated convolutional neural network (CNN)-based model for calculating PET/CT skeletal tumor burden in patients with PCa.

METHODS

A total of 168 patients from three centers were divided into training, validation, and test groups. Manual annotations of skeletal lesions in [¹⁸F]fluoride PET/CT scans were used to train a CNN. The AI model was evaluated in 26 patients and compared to segmentations by physicians and to a SUV 15 threshold. PET index representing the percentage of skeletal volume taken up by lesions was estimated.

RESULTS

There was no case in which all readers agreed on prevalence of lesions that the AI model failed to detect. PET index by the AI model correlated moderately strong to physician PET index (mean r = 0.69). Threshold PET index correlated fairly with physician PET index (mean r = 0.49). The sensitivity for lesion detection was 65-76% for AI, 68-91% for physicians, and 44-51% for threshold depending on which physician was considered reference.

CONCLUSION

It was possible to develop an AI-based model for automated assessment of PET/CT skeletal tumor burden. The model's performance was superior to using a threshold and provides fully automated calculation of whole-body skeletal tumor burden. It could be further developed to apply to different radiotracers. Objective scan evaluation is a first step toward developing a PET/CT imaging biomarker for PCa skeletal metastases.

Comparison of 68Ga-PSMA PET/CT with fluoride PET/CT for detection of bone metastatic disease in prostate cancer

Background

¹⁸F-NaF positron emission tomography/computed tomography (fluoride PET/CT) is considered the most sensitive technique to detect bone metastasis in prostate cancer (PCa). ⁶⁸Ga-PSMA-11 (PSMA) PET/CT is increasingly used for staging of PCa. This study primarily aimed to compare the diagnostic performance of fluoride PET/CT and gallium-based PSMA PET/CT in identifying bone metastasis followed by a comparison of PSMA PET/CT with contrast-enhanced CT (CE-CT) in identifying soft tissue lesions as a secondary objective.

Methods

Twenty-eight PCa patients with high suspicion of disseminated disease following curative treatment were prospectively evaluated. PET/CT examinations using fluoride and PSMA were performed. All suspicious bone lesions were counted, and the tracer uptake was measured as standardized uptake values (SUV) for both tracers. In patients with multiple findings, ten bone lesions with highest SUV_max were selected from which identical lesions from both scans were considered for direct comparison of SUV_max. Soft tissue findings of local and lymph node lesions from CE-CT were compared with PSMA PET/CT.

Results

Both scans were negative for bone lesions in 7 patients (25%). Of 699 lesions consistent with skeletal metastasis in 21 patients on fluoride PET/CT, PSMA PET/CT identified 579 lesions (83%). In 69 identical bone lesions fluoride PET/CT showed significantly higher uptake (mean SUV_max: 73.1 ± 36.8) compared to PSMA PET/CT (34.5 ± 31.4; p < 0.001). Compared to CE-CT, PSMA PET/CT showed better diagnostic performance in locating local (96% vs 61%, p = 0.004) and lymph node (94% vs 46%, p < 0.001) metastasis.

Conclusion

In this prospective comparative study, PSMA PET/CT detected the majority of bone lesions that were positive on fluoride PET/CT. Further, this study indicates better diagnostic performance of PSMA PET/CT to locate soft tissue lesions compared to CE-CT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41824-022-00127-4.

Artificial intelligence-based measurements of PET/CT imaging biomarkers are associated with disease-specific survival of high-risk prostate cancer patients

OBJECTIVE

Artificial intelligence (AI) offers new opportunities for objective quantitative measurements of imaging biomarkers from positron-emission tomography/computed tomography (PET/CT). Clinical image reporting relies predominantly on observer-dependent visual assessment and easily accessible measures like SUV_max, representing lesion uptake in a relatively small amount of tissue. Our hypothesis is that measurements of total volume and lesion uptake of the entire tumour would better reflect the disease`s activity with prognostic significance, compared with conventional measurements.

METHODS

An AI-based algorithm was trained to automatically measure the prostate and its tumour content in PET/CT of 145 patients. The algorithm was then tested retrospectively on 285 high-risk patients, who were examined using ¹⁸F-choline PET/CT for primary staging between April 2008 and July 2015. Prostate tumour volume, tumour fraction of the prostate gland, lesion uptake of the entire tumour, and SUV_max were obtained automatically. Associations between these measurements, age, PSA, Gleason score and prostate cancer-specific survival were studied, using a Cox proportional-hazards regression model.

RESULTS

Twenty-three patients died of prostate cancer during follow-up (median survival 3.8 years). Total tumour volume of the prostate (p = 0.008), tumour fraction of the gland (p = 0.005), total lesion uptake of the prostate (p = 0.02), and age (p = 0.01) were significantly associated with disease-specific survival, whereas SUV_max (p = 0.2), PSA (p = 0.2), and Gleason score (p = 0.8) were not.

CONCLUSION

AI-based assessments of total tumour volume and lesion uptake were significantly associated with disease-specific survival in this patient cohort, whereas SUV_max and Gleason scores were not. The AI-based approach appears well-suited for clinically relevant patient stratification and monitoring of individual therapy.

Magnetic resonance imaging for assessing treatment response in bone marrow metastases

Cancer metastasis to bone is a frequent observation in malignancy that may result in complications such as pathological fractures and spinal cord compression. Monitoring treatment effects is the main concern in oncology; however, the evaluation of treatment response in bone is particularly challenging as it lacks well-established criteria. In addition, bone metastases have traditionally been considered non-measurable manifestations of cancer. Magnetic resonance imaging (MRI) is one of the most specific and sensitive methods for imaging skeletal metastases. The aim of this article is to highlight the diagnostic performance of MRI in the treatment monitoring of bone metastases, to review the current literature, and to provide an overview of recommendations for the evaluation of treatment response in bone.

Prostate-specific membrane antigen targeted PET/CT for recurrent prostate cancer: a clinician's guide

INTRODUCTION

PSMA-targeted PET/CT is a 'Next Generation Imaging' technique with superior sensitivity and specificity for detecting recurrent prostate cancer compared with conventional imaging, allowing more accurate staging and re-staging.

AREAS COVERED

This article reviews the role of PSMA-targeted PET/CT in clinical management of men with recurrent prostate cancer.

EXPERT OPINION

Through enhanced spatial characterization of recurrent prostate cancer, PSMA-targeted PET/CT has shown significant impact on management decisions. In particular, by identifying men with recurrence confined to the prostate or pelvic nodes, PSMA-targeted PET/CT enables selective deployment of localized salvage therapies for management of biochemical failure after primary treatment with prostatectomy or radiotherapy. In oligometastatic disease, PSMA-targeted PET/CT may improve patient selection and treatment accuracy for metastasis-directed therapy and early phase II studies show encouraging results in delaying the need for systemic therapy. Further, quantitative PSMA-targeted PET/CT for monitoring response and therapeutic PSMA-targeted radiopharmaceuticals are emerging as encouraging treatment options in the setting of castrate-resistant disease.

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.

Clinical value of dual-phase F-18 sodium fluoride PET/CT for diagnosing bone metastasis in cancer patients with solitary bone lesion

Background

The present study aimed to investigate whether dual-phase F-18 sodium-fluoride (NaF) positron emission tomography/computed tomography (PET/CT) could improve the diagnostic accuracy of detecting bone metastasis in cancer patients with a solitary bone lesion compared to conventional F-18 NaF PET/CT.

Methods

We retrospectively enrolled 113 cancer patients who underwent dual-phase F-18 NaF PET/CT for the differential diagnosis of a solitary bone lesion seen on bone scintigraphy. According to the dual-phase PET/CT protocol, an early-phase scan was acquired immediately after radiotracer injection and a conventional F-18 NaF PET/CT scan was performed. The diagnostic abilities of the visual analysis of conventional and dual-phase PET/CT scans and two quantitative parameters (lesion-to-blood pool uptake ratio on early-phase scan and lesion-to-bone uptake ratio on conventional scan) for detecting bone metastasis were compared. The final diagnosis of bone metastasis was made by histopathological confirmation or follow-up imaging studies.

Results

A metastatic bone lesion was diagnosed in 28 patients (24.8%). The sensitivity, specificity, and accuracy were 100.0%, 70.6%, and 77.9%, respectively, for visual analysis of conventional F-18 NaF PET/CT, 92.9%, 42.4%, 54.9%, respectively, for lesion-to-bone uptake ratio, 96.4%, 88.2%, and 90.3%, respectively, for visual analysis of dual-phase PET/CT, and 92.9%, 81.2%, and 83.2%, respectively, for lesion-to-blood pool uptake ratio. Visual analysis of dual-phase PET/CT was shown to have the highest area under the receiver operating characteristic curve value (0.923; 95% CI, 0.858-0.965) among all parameters.

Conclusions

Dual-phase F-18 NaF PET/CT showed a high diagnostic ability for detecting bone metastasis with improved specificity and accuracy compared to conventional F-18 NaF PET/CT in cancer patients. Dual-phase F-18 NaF PET/CT might help diagnose bone metastasis in patients with malignancies who were shown to have a solitary bone lesion on bone scintigraphy.

Artificial intelligence-based detection of lymph node metastases by PET/CT predicts prostate cancer-specific survival

INTRODUCTION

Lymph node metastases are a key prognostic factor in prostate cancer (PCa), but detecting lymph node lesions from PET/CT images is a subjective process resulting in inter-reader variability. Artificial intelligence (AI)-based methods can provide an objective image analysis. We aimed at developing and validating an AI-based tool for detection of lymph node lesions.

METHODS

A group of 399 patients with biopsy-proven PCa who had undergone ¹⁸ F-choline PET/CT for staging prior to treatment were used to train (n = 319) and test (n = 80) the AI-based tool. The tool consisted of convolutional neural networks using complete PET/CT scans as inputs. In the test set, the AI-based lymph node detections were compared to those of two independent readers. The association with PCa-specific survival was investigated.

RESULTS

The AI-based tool detected more lymph node lesions than Reader B (98 vs. 87/117; p = .045) using Reader A as reference. AI-based tool and Reader A showed similar performance (90 vs. 87/111; p = .63) using Reader B as reference. The number of lymph node lesions detected by the AI-based tool, PSA, and curative treatment was significantly associated with PCa-specific survival.

CONCLUSION

This study shows the feasibility of using an AI-based tool for automated and objective interpretation of PET/CT images that can provide assessments of lymph node lesions comparable with that of experienced readers and prognostic information in PCa patients.

Treatment of spine metastases in cancer: a review

As a consequence of the improvements in diagnostic technology along with gains in life expectancy of cancer patients, the incidence of spine metastases has increased. Spine metastases can affect the patient's quality of life and negatively impact on their prognosis. Multidisciplinary treatments involve surgery, chemotherapy, radiosurgery and radiotherapy. Spine metastases should be treated using a multidisciplinary and integrated approach that involves spinal surgeons, medical oncologists and radiologists. More research is required to elucidate the pathological mechanisms involved in the aetiology of spine metastasis. This review describes the current situation regarding the diagnosis of spine metastasis, what is understood about the pathological development of spine metastasis and the evolution of the multidisciplinary treatments that are available for patients with spine metastases.

Deep learning-based quantification of PET/CT prostate gland uptake: association with overall survival

Aim

To validate a deep‐learning (DL) algorithm for automated quantification of prostate cancer on positron emission tomography/computed tomography (PET/CT) and explore the potential of PET/CT measurements as prognostic biomarkers.

Material and methods

Training of the DL‐algorithm regarding prostate volume was performed on manually segmented CT images in 100 patients. Validation of the DL‐algorithm was carried out in 45 patients with biopsy‐proven hormone‐naïve prostate cancer. The automated measurements of prostate volume were compared with manual measurements made independently by two observers. PET/CT measurements of tumour burden based on volume and SUV of abnormal voxels were calculated automatically. Voxels in the co‐registered ¹⁸F‐choline PET images above a standardized uptake value (SUV) of 2·65, and corresponding to the prostate as defined by the automated segmentation in the CT images, were defined as abnormal. Validation of abnormal voxels was performed by manual segmentation of radiotracer uptake. Agreement between algorithm and observers regarding prostate volume was analysed by Sørensen‐Dice index (SDI). Associations between automatically based PET/CT biomarkers and age, prostate‐specific antigen (PSA), Gleason score as well as overall survival were evaluated by a univariate Cox regression model.

Results

The SDI between the automated and the manual volume segmentations was 0·78 and 0·79, respectively. Automated PET/CT measures reflecting total lesion uptake and the relation between volume of abnormal voxels and total prostate volume were significantly associated with overall survival (P = 0·02), whereas age, PSA, and Gleason score were not.

Conclusion

Automated PET/CT biomarkers showed good agreement to manual measurements and were significantly associated with overall survival.

18F-Sodium Fluoride PET: History, Technical Feasibility, Mechanism of Action, Normal Biodistribution, and Diagnostic Performance in Bone Metastasis Detection Compared with Other Imaging Modalities

The skeleton is the third most common site for metastasis overall, after the lungs and liver. Accurate diagnosis of osseous metastasis is critical for initial staging, treatment planning, restaging, treatment monitoring, and survival prediction. Currently, ^99mTc-methylene diphosphonate whole-body scanning is the cornerstone of imaging to detect osseous metastasis. Although ¹⁸F-sodium fluoride (¹⁸F-NaF) was one of the oldest medical tracers for this purpose, it was replaced by other tracers because of their better physical properties, until recently. Continued development of PET scanners has opened a new era for ¹⁸F-NaF, and given its higher sensitivity, there have been increasing applications in imaging. In this review, we will discuss the history, technical aspects, radiobiology, and biodistribution of this tracer. Finally, we compare the accuracy of ¹⁸F-NaF PET with other conventional imaging methods for detection of osseous metastasis.

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.

Relationship between lower lumbar spine shape and patient bone metabolic activity as characterised by 18F NaF bio-markers

Chronic lower lumbar pain has been associated with elevated bone metabolic activity in the spine. Diagnosis of bone metabolic activity is currently through integrating Positron Emission Tomography (PET) with Sodium Fluoride (¹⁸F-NaF) biomarkers. It has been reported that numerous observable pathologies including lumbar fusion, disc abnormalities and scoliosis have often been associated with increased ¹⁸F-NaF uptake. The aim of this study was to identify what features of lower lumbar shape most strongly correlate with ¹⁸F-NaF uptake. Following a principal component analysis of 23 patients who presented with lumbar pain and underwent ¹⁸F-NaF PET-CT, it was revealed that three modes interpreted as (i) sacral tilt, (ii) vertebral disc spacing and (iii) spine size were the three characteristics that described 88.7% of spine shape in our study population. ¹⁸F-NaF was described by two modes including ¹⁸F-NaF intensity and spatial variation (anterior-inferior to posterior-superior). ¹⁸F-NaF was most sensitive to sacral tilt followed by vertebral disc spacing. A predictive model derived from that spine population was able to predict ¹⁸F-NaF 'hot-spot' locations with 85 ± 5% accuracy and with 71 ± 3% accuracy for the ¹⁸F-NaF magnitude. These results suggest that patients reporting with lower lumbar pain and who present with increased sacral tilt profiles and/or reduced disc spacing are good candidates for further ¹⁸F-NaF PET-CT imaging, evidenced by the high association between those shape profiles and ¹⁸F-NaF uptake.

The Established Nuclear Medicine Modalities for Imaging of Bone Metastases

Background:

The skeleton is one of the frequent site of metastases in advanced cancer. Prostate, breast and renal cancers mostly metastasize to bone.

Discussion:

Malignant tumors lead to significant morbidity and mortality. Identification of bone lesions is a crucial step in diagnosis of disease at early stage, monitoring of disease progression and evaluation of therapy. Diagnosis of cancer metastases is based on uptake of bone-targeted radioactive tracer at different bone remodeling sites.

Conclusion:

This manuscript summarizes already established and evolving nuclear medicine modalities (e.g. bone scan, SPECT, SPECT/CT, PET, PET/CT) for imaging of bone metastases.

18F-Fluoromethylcholine-positron emission tomography/computed tomography for diagnosing bone and lymph node metastases in patients with intermediate- or high-risk prostate cancer

Background

The use of molecular imaging in staging of prostate cancer (PC) is debated. In patients with newly diagnosed PC we investigated the diagnostic value of ¹⁸F-flouromethylcholine positron emission tomography/computed tomography (¹⁸F-FCH-PET/CT) for the detection of bone and lymph node metastases compared to whole-body bone scintigraphy (WBS) with technetium-99-methylene diphosphonate (^99mTc-MDP) and results of extended pelvic lymph node dissection, respectively.

Materials and methods

Between January 2013 and April 2016, 143 patients, aged 49-83, mean 69, years with newly diagnosed PC and disease characteristics necessitating WBS underwent both WBS and ¹⁸F-FCH-PET/CT using magnetic resonance imaging as standard. Eighty of these patients underwent pelvic lymph node dissection as part of radical prostatectomy or prior to external beam radiation and in these results of ¹⁸F-FCH-PET/CT were compared to histologic findings.

Results

Bone metastases were detected in 8/143 patients and sensitivity and specificity of WBS were 37.5% and 85.2% versus 100.0% and 96.3% with ¹⁸F-FCH-PET/CT, P=0.63 and 0.002, respectively. Histologically confirmed metastases to regional lymph nodes were found in 25/80 patients. Suspicious choline uptake on PET/CT in pelvic lymph nodes was found in 35 patients. Sensitivity, specificity, PPV, NPV and accuracy of ¹⁸F-FCH-PET/CT in detection of lymph node metastases were 62.5%, 69.6%, 46.9%, 81.3% and 67.5%, respectively.

Conclusions

Findings in this study suggested that ¹⁸F-FCH-PET/CT is a more sensitive and specific method for detection of bone metastases from PC than WBS and could potentially reduce the need for confirmatory imaging if used instead of WBS. However, ¹⁸F-FCH-PET/CT performs sub-optimally in pre-operative staging of lymph node metastases in patients undergoing extended pelvic lymph node dissection.

Does therapy of the primary tumor matter in oligometastatic prostate cancer? A prospective 10-year follow-up study

Objective: The effect of curative treatment for oligometastatic prostate cancer patients is unsolved, both with regard to morbidity and mortality. With this study, we provide some of the first long-term follow-up data on progression and mortality in oligometastatic prostate cancer patients after curative treatment of their primary tumor.

Methods: A cohort of 210 patients with diagnosed prostate cancer was established between 2008 and 2010. All patients were scheduled for intended curative treatment, and all underwent blinded ¹⁸F-choline positron-emission tomography/computed tomography at inclusion prior to curative treatment. Upon unblinding, 12 patients (6%) were recategorized as being oligometastatic. They had a mean age of 64 years, median prostate-specific antigen of 18 ng/mL, and median Gleason score of 7. Six patients were staged as T3, one T2, and five T1. The patients had a median of one bone metastasis (range 1–2). All underwent intended curative radiotherapy or prostatectomy. Mean follow-up was 10.1 (8.9–11.0) years.

Results: During follow-up of the 12 patients, three (25%) had biochemical recurrence, two developed castration-resistant disease, and one died due to prostate cancer.

Conclusion: Our results suggest that intended curative treatment of the primary tumor in oligometastatic prostate cancer may have a role in highly selected patients.

Biological principles and clinical application of positron emission tomography-tracers in prostate cancer: a review

Prostate carcinoma is the most common malignancy in men and the second cause of death by cancer in the western world. Currently, prostate carcinoma's diagnosis is achieved by transrectal ultrasound-guided biopsy (gold-standard), usually requested after an elevation of prostate specific antigen (PSA) levels or an abnormal digital rectal exam or transrectal ultrasound. Nevertheless, this diagnosis sequence sometimes presents with significant limitations. Therefore, there is a need of a diagnosis modality that improves the tumor detection rates and that offers information for its accurate staging, allowing the treatment's planning and administration. Molecular imaging by the means of positron emission tomography uses radiopharmaceuticals labeled with positron-emitting radioisotopes to detect metabolic changes that might be suggestive of cancer tissue. Recently, this technique has suffered a huge dynamic development, and researchers have been working on novel radiotracers agents to improve accuracy in targeting and detecting prostate tumors. On this review, it is highlighted that the most promising positron emission tomography-tracers that will, in a near future, not only improve diagnostic abilities for prostate carcinoma but also open new possibilities for theranostic approaches to treat this malignancy at a world level.

Comparing the Staging/Restaging Performance of 68Ga-Labeled Prostate-Specific Membrane Antigen and 18F-Choline PET/CT in Prostate Cancer: A Systematic Review and Meta-analysis

PURPOSE

PET/CT using prostate-specific membrane antigen (PSMA) and choline radiotracers is widely used for diagnosis of prostate cancer. However, the roles of and differences in diagnostic performance between these 2 radiotracers for prostate cancer are unclear. The aim of this study was to compare the staging and restaging performance of Ga-labeled PSMA and F-choline PET/CT imaging in prostate cancer.

METHODS

A comprehensive search was performed in PubMed for studies reporting the staging performance of Ga-PSMA and F-choline PET/CT in prostate cancer from the inception of the database to October 1, 2018, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Thirty-five studies were included in this systematic review and meta-analysis. Pooled estimates of patient- and lesion-based sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) for Ga-PSMA and F-choline PET/CT were calculated alongside 95% confidence intervals. Summary receiver operating characteristic curves were plotted, and the area under the summary receiver operating characteristic curve (AUC) was determined alongside the Q* index.

RESULTS

The patient-based overall pooled sensitivity, specificity, PLR, NLR, DOR, and AUC of Ga-PSMA PET/CT for staging in prostate cancer (13 studies) were 0.92, 0.94, 7.91, 0.14, 79.04, and 0.96, respectively, whereas those of F-choline PET/CT (16 studies) were 0.93, 0.83, 4.98, 0.10, 68.27, and 0.95. The lesion-based overall pooled sensitivity, specificity, PLR, NLR, DOR, and AUC of Ga-PSMA PET/CT for staging in prostate cancer (9 studies) were 0.83, 0.95, 23.30, 0.17, 153.58, and 0.94, respectively, and those of F-choline PET/CT (4 studies) were 0.81, 0.92, 8.59, 0.20, 44.82, and 0.98. In both patient- and lesion-based imaging, there was no statistically significant difference in the abilities of detecting or excluding prostate cancer between Ga-PSMA PET/CT and F-choline PET/CT.

CONCLUSIONS

For staging and restaging performance in patients with prostate cancer, there was no significant difference between Ga-PSMA PET/CT and F-choline PET/CT. Ga-PSMA PET/CT and F-choline PET/CT have demonstrated high diagnostic performance for accurate staging and restaging in patients with prostate cancer, and thus both should be considered for staging in this disease.

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.

Deep learning for segmentation of 49 selected bones in CT scans: First step in automated PET/CT-based 3D quantification of skeletal metastases

PURPOSE

The aim of this study was to develop a deep learning-based method for segmentation of bones in CT scans and test its accuracy compared to manual delineation, as a first step in the creation of an automated PET/CT-based method for quantifying skeletal tumour burden.

METHODS

Convolutional neural networks (CNNs) were trained to segment 49 bones using manual segmentations from 100 CT scans. After training, the CNN-based segmentation method was tested on 46 patients with prostate cancer, who had undergone ¹⁸F-choline-PET/CT and ¹⁸F-NaF PET/CT less than three weeks apart. Bone volumes were calculated from the segmentations. The network's performance was compared with manual segmentations of five bones made by an experienced physician. Accuracy of the spatial overlap between automated CNN-based and manual segmentations of these five bones was assessed using the Sørensen-Dice index (SDI). Reproducibility was evaluated applying the Bland-Altman method.

RESULTS

The median (SD) volumes of the five selected bones were by CNN and manual segmentation: Th7 41 (3.8) and 36 (5.1), L3 76 (13) and 75 (9.2), sacrum 284 (40) and 283 (26), 7th rib 33 (3.9) and 31 (4.8), sternum 80 (11) and 72 (9.2), respectively. Median SDIs were 0.86 (Th7), 0.85 (L3), 0.88 (sacrum), 0.84 (7th rib) and 0.83 (sternum). The intraobserver volume difference was less with CNN-based than manual approach: Th7 2% and 14%, L3 7% and 8%, sacrum 1% and 3%, 7th rib 1% and 6%, sternum 3% and 5%, respectively. The average volume difference measured as ratio volume difference/mean volume between the two CNN-based segmentations was 5-6% for the vertebral column and ribs and ≤3% for other bones.

CONCLUSION

The new deep learning-based method for automated segmentation of bones in CT scans provided highly accurate bone volumes in a fast and automated way and, thus, appears to be a valuable first step in the development of a clinical useful processing procedure providing reliable skeletal segmentation as a key part of quantification of skeletal metastases.

Quantifying downstream impact of inappropriate staging imaging in a cohort of veterans with low- and intermediate-risk incident prostate cancer

INTRODUCTION

According to current National Comprehensive Cancer Network guidelines, routine imagining for staging low-risk prostate cancer is not recommended. However, extensive overuse of guideline-discordant imaging continues to persist. Incidental findings are common on imaging and little is known about the optimal management. Rates of incidental findings vs. false positive diagnosis from inappropriate imaging are poorly understood and have yet to be quantified for low- and intermediate-risk prostate cancer patients.

OBJECTIVE

To determine the frequency of positive radiologic findings in patients with low- and intermediate-risk prostate cancer during initial staging at VA New York Harbor Healthcare System.

METHODS

We retrospectively reviewed all low- and intermediate-risk prostate cancer patients' medical records from the VA New York Harbor Healthcare System for diagnosis from 2005 to 2015. We reviewed each individual's prebiopsy prostate specific antigen (PSA), Gleason score, and clinical stage. We also determined if imaging obtained yielded a false positive, incidental finding, or if metastatic disease occurred within the 6 months following initial diagnosis.

RESULTS

There were 414 men, who were classified as low- to intermediate-risk prostate cancer and underwent inappropriate staging imaging of 4,306 men diagnosed with prostate cancer. Of these 414 men, 178 (43%) had additional follow-up imaging for positive findings. We calculated an incidental finding rate of 10% and a false positive rate of 38% for patients. Five (1%) patients had metastatic disease.

CONCLUSION

Despite guideline recommendations, imaging overuse remains an issue for low-intermediate-risk prostate cancer patients. The false positive rate found in this analysis is alarmingly high at 38%. This use of scans is burdensome to the healthcare system and patient. This study highlights the frequency of inappropriate imaging and its negative consequences.

Diagnostic performance of 11C-choline PET/CT and bone scintigraphy in the detection of bone metastases in patients with prostate cancer

The aim of this study was to compare 11C-choline PET/CT and bone scintigraphy (BS) for detection of bone metastases in patients with prostate cancer. Twenty-one patients with histologically proven prostate cancer underwent 11C-choline PET/CT and BS before (n = 4) or after (n = 17) treatment. Patient-, region-, and lesion-based diagnostic performances of bone metastasis of both 11C-choline PET/CT and BS were evaluated using a five-point scale by two experienced readers. Bone metastases were present in 11 (52.4%) of 21 patients and 48 (32.7%) of 147 regions; 111 lesions were found to have bone metastases. Region-based analysis showed that the sensitivity, specificity, accuracy, and area under the receiver-operating-characteristic curves (AUC) of 11C-choline PET/CT were 97.9%, 99.0%, 98.6%, and 0.9989, respectively; those of BS were 72.9%, 99.0%, 90.5%, and 0.8386, respectively. Sensitivity, accuracy, and AUC significantly differed between the two methods (McNemar test, p = 0.0015, p = 0.0015, and p < 0.0001, respectively). 11C-choline PET/CT detected 110/111 metastatic lesions (99.1%); BS detected 85 (76.6%) (p < 0.0001). According to the CT morphological type, the visualization rates of 11C-choline-PET/BS were 100%/90.3% for the blastic type, 91.7%/8.3% for the lytic type, 100%/100% for the mixed type, and 100%/53.3% for the invisible type, respectively. Significant differences in blastic, lytic, and invisible types were observed between the two methods (p = 0.013, p = 0.0044, and p = 0.023, respectively). In conclusion, 11C-choline PET/CT had greater sensitivity and accuracy than BS for detection of bone involvement in patients with prostate cancer.

RETRACTED: Recommandations françaises du Comité de Cancérologie de l’AFU – Actualisation 2018–2020 : cancer de la prostate French ccAFU guidelines – Update 2018–2020: Prostate cancer

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). Cet article est retiré de la publication à la demande des auteurs car ils ont apporté des modifications significatives sur des points scientifiques après la publication de la première version des recommandations. Le nouvel article est disponible à cette adresse: DOI:10.1016/j.purol.2019.01.007. C’est cette nouvelle version qui doit être utilisée pour citer l’article. This article has been retracted at the request of the authors, as it is not based on the definitive version of the text because some scientific data has been corrected since the first issue was published. The replacement has been published at the DOI:10.1016/j.purol.2019.01.007. That newer version of the text should be used when citing the article.

18F-NaF/223RaCl2 theranostics in metastatic prostate cancer: treatment response assessment and prediction of outcome

Theranostics refers to companion agents with identical or similar structure targeted to a specific biological entity for imaging and treatment. Although the concept has a long history with radioiodine in thyroidology, but it has experienced remarkable recent renaissance in management of neuroendocrine tumors and prostate cancer. Bone scintigraphy based on osteoblastic reaction and targeted radionuclide therapy with the alpha-particle calcium-mimetic agent, 223RaCl2, also form a theranostic model for imaging and treatment of osseous metastatic disease. Since the regulatory approval of 223RaCl2 in 2013, there has been accumulating evidence on the potential use of 18F-NaF PET scintigraphy in the assessment of response and prediction of outcome in males with metastatic castrate-resistant prostate cancer who undergo 223RaCl2 therapy. We review the 18F-NaF/223RaCl2 as theranostic companion in the management of prostate cancer with emphasis on the utility of 18F-NaF and other relevant PET radiotracers in the therapy response and prognosis assessments.

Positron emission tomography in prostate cancer: An update on state of the art

Prostate cancer (PCa), one of the most common cancers in males, is a topic of active interest in imaging research. Positron emission tomography/computed tomography (PET/CT) and PET/magnetic resonance imaging (PET/MRI) have enabled the combination of morphologic and functional imaging with the promise of providing better information in guiding therapy. ¹⁸F-fluorodeoxyglucose, the workhorse radiopharmaceutical in PET imaging, has not found preference in PCa since these tumors show poor glucose uptake and can be obscured by the normal urinary excretion of the radiotracer. Hence, the last two decades have seen the development of multiple newer radiotracers and better optimization of the technical aspects of PET imaging. The combination of functional imaging and MRI holds great promise. We searched PubMed, Scopus, and Google Scholar for peer-reviewed literature concerning the advances and newer developments in the imaging of PCa between the years 2005 and 2017. This review aims at summarizing current evidence on the role of PET imaging in PCa and its impact on the diagnosis, staging, prognostication, response assessment, and restaging of this malignancy.

Prospective comparison of 68Ga-PSMA PET/CT, 18F-sodium fluoride PET/CT and diffusion weighted-MRI at for the detection of bone metastases in biochemically recurrent prostate cancer

PURPOSE

To prospectively compare diagnostic accuracies for detection of bone metastases by ⁶⁸Ga-PSMA PET/CT, ¹⁸F-NaF PET/CT and diffusion-weighted MRI (DW₆₀₀-MRI) in prostate cancer (PCa) patients with biochemical recurrence (BCR).

METHODS

Sixty-eight PCa patients with BCR participated in this prospective study. The patients underwent ⁶⁸Ga-PSMA PET/CT, a ¹⁸F-NaF PET/CT and a DW₆₀₀-MRI (performed in accordance with European Society of Urogenital Radiology guidelines, with b values of 0 and 600 s/mm²). Bone lesions were categorized using a three-point scale (benign, malignant or equivocal for metastases) and a dichotomous scale (benign or metastatic) for each imaging modality by at least two experienced observers. A best valuable comparator was defined for each patient based on study-specific imaging, at least 12 months of clinical follow-up and any imaging prior to the study and during follow-up. Diagnostic performance was assessed using a sensitivity analysis where equivocal lesions were handled as non-metastatic and then as metastatic.

RESULTS

Ten of the 68 patients were diagnosed with bone metastases. On a patient level, sensitivity, specificity and the area under the curve (AUC) by receiver operating characteristic analysis were, respectively, 0.80, 0.98-1.00 and 0.89-0.90 for ⁶⁸Ga-PSMA PET/CT (n = 68 patients); 0.90, 0.90-0.98 and 0.90-0.94 for ¹⁸NaF PET/CT (n = 67 patients); and 0.25-0.38, 0.87-0.92 and 0.59-0.62 for DW₆₀₀-MRI (n = 60 patients). The diagnostic performance of DW₆₀₀-MRI was significantly lower than that of ⁶⁸Ga-PSMA PET/CT and ¹⁸NaF PET/CT for diagnosing bone metastases (p < 0.01), and no significant difference in the AUC was seen between ⁶⁸Ga-PSMA PET/CT and ¹⁸NaF PET/CT (p = 0.65).

CONCLUSION

⁶⁸Ga-PSMA PET/CT and ¹⁸F-NaF PET/CT showed comparable and high diagnostic accuracies for detecting bone metastases in PCa patients with BCR. Both methods performed significantly better than DW₆₀₀-MRI, which was inadequate for diagnosing bone metastases when conducted in accordance with European Society of Urogenital Radiology guidelines.

Functional and Hybrid Imaging of Bone Metastases

Bone metastases are common, cause significant morbidity, and impact on healthcare resources. Although radiography, computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy have frequently been used for staging the skeleton, these methods are insensitive and nonspecific for monitoring treatment response in a clinically relevant time frame. We summarize several recent reports on new functional and hybrid imaging methods including single photon emission CT/CT, positron emission tomography/CT, and whole-body MRI with diffusion-weighted imaging. These modalities generally show improvements in diagnostic accuracy for staging and response assessment over standard imaging methods, with the ability to quantify biological processes related to the bone microenvironment as well as tumor cells. As some of these methods are now being adopted into routine clinical practice and clinical trials, further evaluation with comparative studies is required to guide optimal and cost-effective clinical management of patients with skeletal metastases. © 2018 American Society for Bone and Mineral Research.

Circulating Tumor Cell Analysis in Preclinical Mouse Models of Metastasis

The majority of cancer deaths occur because of metastasis since current therapies are largely non-curative in the metastatic setting. The use of in vivo preclinical mouse models for assessing metastasis is, therefore, critical for developing effective new cancer biomarkers and therapies. Although a number of quantitative tools have been previously developed to study in vivo metastasis, the detection and quantification of rare metastatic events has remained challenging. This review will discuss the use of circulating tumor cell (CTC) analysis as an effective means of tracking and characterizing metastatic disease progression in preclinical mouse models of breast and prostate cancer and the resulting lessons learned about CTC and metastasis biology. We will also discuss how the use of clinically-relevant CTC technologies such as the CellSearch® and Parsortix™ platforms for preclinical CTC studies can serve to enhance the study of cancer biology, new biomarkers, and novel therapies from the bench to the bedside.

Molecular imaging of prostate cancer

Prostate cancer is a common malignancy with various treatments from surveillance, surgery, radiation and chemotherapy. The institution of appropriate, effective treatment relies in part on accurate imaging. Molecular imaging techniques offer an opportunity for increased timely detection of prostate cancer, its recurrence, as well as metastatic disease. Advancements within the field of molecular imaging have been complex with some agents targeting receptors and others acting as metabolic intermediaries. In this article, we provide an overview of the most clinically relevant radiotracers to date based on a combination of the five states model and the National Comprehensive Cancer Network Guidelines.

Innovations in imaging modalities for recurrent and metastatic prostate cancer: a systematic review

INTRODUCTION

The last decade has witnessed tremendous changes in the management of advanced and metastatic castration resistant prostate cancer. In the current systematic review, we analyze novel imaging techniques in the setting of recurrent and metastatic prostate cancer (PCa), exploring available data and highlighting future exams which could enter clinical practice in the upcoming years.

EVIDENCE ACQUISITION

The National Library of Medicine Database was searched for relevant articles published between January 2012 and August 2017. A wide search was performed including the combination of following words: "Prostate" AND "Cancer" AND ("Metastatic" OR "Recurrent") AND "imaging" AND ("MRI" OR "PET"). The selection procedure followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) principles and is presented using a PRISMA flow chart.

EVIDENCE SYNTHESIS

Novel imaging techniques, as multiparametric magnetic resonance imaging (MRI), whole-body MRI and Choline and prostate-specific membrane antigen (PSMA) PET imaging techniques are currently revolutioning the treatment planning in patients with advanced and metastatic PCa, allowing a better characterization of the disease. Multiparametric MRI performs well in the detection of local recurrences, with sensitivity rates of 67-98% and overall diagnostic accuracy of 83-93%, depending on the type of magnetic field strength (1.5 vs. 3T). Whole body MRI instead shows a high specificity (>95%) for bone metastases. PET imaging, and in particular PSMA PET/CT, showed promising results in the detection of both local and distant recurrences, even for low PSA values (<0.5 ng/mL). Sensitivity varies from 77-98% depending on PSA value and PSA velocity.

CONCLUSIONS

Whole body-MRI, NaF PET, Choline-PET/CT and PSMA PET/CT are flourishing techniques which find great application in the field of recurrent and metastatic PCa, in the effort to reduce treatment of "PSA only" and rather focus our therapies on clinical tumor entities. Standardization is urgently needed to allow adequate comparison of results and diffusion on a large scale.

18F-Fluorocholine PET Whole-Body MRI in the Staging of High-Risk Prostate Cancer

OBJECTIVE

The purpose of this study was to determine whether integrated ¹⁸F-fluorocholine (FCH) PET whole-body MRI (PET/WBMRI) depicts lymph node and distant metastases in patients with high-risk prostate cancer more frequently than does conventional staging.

SUBJECTS AND METHODS

A prospective study included 58 patients with untreated high-risk prostate cancer. After conventional staging (CT and bone scintigraphy), patients underwent FCH PET/WBMRI (n = 10) or FCH PET/CT and WBMRI (n = 48). Metastatic sites and disease stage were recorded for each modality (conventional imaging, PET, WBMRI, and PET/WBMRI) and compared with a standard of reference (histopathologic examination, imaging, and clinical follow-up) and early clinical outcomes.

RESULTS

In the detection of metastases, PET had significantly higher sensitivity (72/77 [93.5%]) than conventional imaging (49/77 [63.6%]; p < 0.001) and WBMRI (56/77 [72.7%]; p = 0.002). There was a trend toward improved detection with PET/WBMRI (77/77 [100%]) compared with PET alone (p = 0.059). For correct NM staging, PET and PET/WBMRI performed better than conventional imaging (p = 0.002) and WBMRI (p = 0.008). Twelve of 56 patients (21.4%) had early biochemical failure after radical treatment (median, 7 months; range, 1-20 months). This rate was higher for patients with M1a or M1b disease at PET/WBMRI than for others, but this finding did not reach statistical significance (4/8 [50%] vs 8/48 [16.7%]; p = 0.055).

CONCLUSION

In patients with high-risk prostate cancer, FCH PET and FCH PET/WBMRI depict significantly more metastatic lesions than do conventional imaging and WBMRI. Stage determined with PET/WBMRI may correlate with early outcomes.

Prostate-specific antigen cutoff value for ordering sodium fluoride positron emission tomography/computed tomography bone scan in patients with prostate cancer

The use of F-18 sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) bone scan is increasing because of its higher sensitivity and specificity over standard bone scintigraphy (BS). Studies previously reported a prostate-specific antigen (PSA) cutoff value for ordering standard BS. However, this has not been determined for NaF PET yet. In this study, our goal was to determine a PSA cutoff level for ordering NaF PET/CT bone scan. Newly diagnosed and previously treated prostate cancer patients who had NaF PET/CT scan and PSA measurements within 2 mos of PET study were selected for analysis. When available, other parameters, such as Gleason score (GS), clinical stage, alkaline phosphatase levels, skeletal symptoms, and correlative image findings, were recorded. Receiver operating characteristic (ROC) analysis was performed to determine PSA cutoff values. Sixty-two patients (32 newly diagnosed and 30 previously treated) met the inclusion criteria. Near half of previously treated patients were on hormone therapy. NaF PET/CT was positive in 9 newly diagnosed (PSA mean: 91.6 ng/ml, range: 6.2-226 ng/ml) and in 6 previously treated patients (PSA mean: 146.4 ng/ml, range: 6.6-675 ng/ml). ROC analysis indicated that PSA cutoff value for NaF PET/CT positivity was >20 ng/ml in newly diagnosed and >6 ng/ml in previously treated patients. PSA cutoff value for ordering NaF PET/CT in newly diagnosed patients does not seem significantly different than the previous results for BS (>20 ng/ml). However, we found a lower PSA cutoff value of >6 ng/ml in previously treated patients.

18-Fluoride labeled sodium fluoride positron emission tomography with computer tomography: the impact of pretreatment staging in intermediate- and high-risk prostate cancer

Background

18-Fluoride labeled sodium fluoride (Na-18-F) positron emission tomography with computer tomography (PET/CT) has a better sensitivity and specificity than whole body bone scan (WBBS) in detecting osseous metastatic prostate cancer. We performed a pilot study of 20 men to examine what level of impact Na-18-F PET/CT has on management plans when used for staging newly diagnosed prostate cancer.

Materials and methods

Twenty men were prospectively enrolled into the study in South Australia. Men were eligible if they had newly diagnosed, untreated, and biopsy-confirmed intermediate- or high-risk prostate cancer (D'Amico classification). WBBS and Na-18-F PET/CT scans were performed within 1 week of each other. Following review of the WBBS, treatment type and intent was documented by the treating urologist. The Na-18-F PET/CT scan was then reviewed. The impact of the Na-18-F PET/CT was measured on whether treatment modality or intent was subsequently altered: high impact = treatment intent or modality was changed; medium impact = treatment modality was modified; low impact = no change in treatment.

Results

In 18 men (90%), the WBBS and Na-18-F PET/CT were negative for osseous metastases. In one man (5%), the WBBS demonstrated widespread osseous metastases which were similarly demonstrated on the Na-18-F PET/CT. One man (5%) had a normal WBBS; however, the Na-18-F PET/CT demonstrated widespread osseous metastases. Subsequently, in 19 men (95%), the results of the two scans were congruent and the addition of the Na-18-F PET/CT scan demonstrated a low impact on management. In one man (5%), the addition of the Na-18-F PET/CT had a high impact as treatment type and intent was altered.

Conclusions

Our pilot study is the first of its kind in Australia, and our findings suggest that Na-18-F PET/CT is a safe and feasible modality for staging prostate cancer. However, its true impact on prostate cancer management warrants further investigation.

The use of PET/CT in prostate cancer

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) has recently emerged as a promising diagnostic imaging platform for prostate cancer. Several radiolabelled tracers have demonstrated efficacy for cancer detection in various clinical settings. In this review, we aim to illustrate the diverse use of PET/CT with different tracers for the detection of prostate cancer.

METHODS

We searched MEDLINE using the terms 'prostate cancer', 'PET', 'PET/CT' and 'PET/MR'). The current review was limited to ¹⁸F-NaF PET/CT, choline-based PET/CT, fluciclovine PET/CT and PSMA-targeted PET/CT, as these modalities have been the most widely adopted.

RESULTS

NaF PET/CT has shown efficacy in detecting bone metastases with high sensitivity, but relatively low specificity. Currently, choline PET/CT has been the most extensively studied modality. Although having superior specificity, choline PET/CT suffers from low sensitivity, especially at low PSA levels. Nevertheless, choline PET/CT was found to significantly improve upon conventional imaging modalities (CIM) in the detection of metastatic lesions at biochemical recurrence (BCR). Newer methods using fluciclovine and PSMA-targeted radiotracers have preliminarily demonstrated great promise in primary and recurrent staging of prostate cancer. However, their superior efficacy awaits confirmation in larger series.

CONCLUSIONS

PET/CT has emerged as a promising staging modality for both primary and recurrent prostate cancer. Newer tracers have increased detection accuracies for small, incipient metastatic foci. The clinical implications of these occult PET/CT detected disease foci require organized evaluation. Efforts should be aimed at defining their natural history as well as responsiveness and impact of metastasis-directed therapy.

3D skeletal uptake of 18F sodium fluoride in PET/CT images is associated with overall survival in patients with prostate cancer

BACKGROUND

Sodium fluoride (NaF) positron emission tomography combined with computer tomography (PET/CT) has shown to be more sensitive than the whole-body bone scan in the detection of skeletal uptake due to metastases in prostate cancer. We aimed to calculate a 3D index for NaF PET/CT and investigate its correlation to the bone scan index (BSI) and overall survival (OS) in a group of patients with prostate cancer.

METHODS

NaF PET/CT and bone scans were studied in 48 patients with prostate cancer. Automated segmentation of the thoracic and lumbar spines, sacrum, pelvis, ribs, scapulae, clavicles, and sternum were made in the CT images. Hotspots in the PET images were selected using both a manual and an automated method. The volume of each hotspot localized in the skeleton in the corresponding CT image was calculated. Two PET/CT indices, based on manual (manual PET index) and automatic segmenting using a threshold of SUV 15 (automated PET15 index), were calculated by dividing the sum of all hotspot volumes with the volume of all segmented bones. BSI values were obtained using a software for automated calculations.

RESULTS

BSI, manual PET index, and automated PET15 index were all significantly associated with OS and concordance indices were 0.68, 0.69, and 0.70, respectively. The median BSI was 0.39 and patients with a BSI >0.39 had a significantly shorter median survival time than patients with a BSI <0.39 (2.3 years vs not reached after 5 years of follow-up [p = 0.01]). The median manual PET index was 0.53 and patients with a manual PET index >0.53 had a significantly shorter median survival time than patients with a manual PET index <0.53 (2.5 years vs not reached after 5 years of follow-up [p < 0.001]). The median automated PET15 index was 0.11 and patients with an automated PET15 index >0.11 had a significantly shorter median survival time than patients with an automated PET15 index <0.11 (2.3 years vs not reached after 5 years of follow-up [p < 0.001]).

CONCLUSIONS

PET/CT indices based on NaF PET/CT are correlated to BSI and significantly associated with overall survival in patients with prostate cancer.