Impact of 18F-fluoride PET in patients with known prostate cancer: initial results from the National Oncologic PET Registry

Application of next-generation imaging in biochemically recurrent prostate cancer

BACKGROUND

Biochemical recurrence (BCR) following primary interventional treatment occurs in approximately one-third of patients with prostate cancer (PCa). Next-generation imaging (NGI) can identify local and metastatic recurrence with greater sensitivity than conventional imaging, potentially allowing for more effective interventions. This narrative review examines the current clinical evidence on the utility of NGI for patients with BCR.

METHODS

A search of PubMed was conducted to identify relevant publications on NGI applied to BCR. Given other relevant recent reviews on the topic, this review focused on papers published between January 2018 to May 2023.

RESULTS

NGI technologies, including positron emission tomography (PET) radiotracers and multiparametric magnetic resonance imaging, have demonstrated increased sensitivity and selectivity for diagnosing BCR at prostate-specific antigen (PSA) concentrations <2.0 ng/ml. Detection rates range between 46% and 50%, with decreasing PSA levels for choline (1-3 ng/ml), fluciclovine (0.5-1 ng/ml), and prostate-specific membrane antigen (0.2-0.49 ng/ml) PET radiotracers. Expert working groups and European and US medical societies recommend NGI for patients with BCR.

CONCLUSIONS

Available data support the improved detection performance and selectivity of NGI modalities versus conventional imaging techniques; however, limited clinical evidence exists demonstrating the application of NGI to treatment decision-making and its impact on patient outcomes. The emergence of NGI and displacement of conventional imaging may require a reexamination of the current definitions of BCR, altering our understanding of early recurrence. Redefining the BCR disease state by formalizing the role of NGI in patient management decisions will facilitate greater alignment across research efforts and better reflect the published literature.

Bone Metastases

ABSTRACT

Bone metastases occur frequently in common malignancies such as breast and prostate cancer. They are responsible for considerable morbidity and skeletal-related events. Fortunately, there are now several systemic, focal, and targeted therapies that can improve quality and length of life, including radionuclide therapies. It is therefore important that bone metastases can be detected as early as possible and that treatment can be accurately and sensitively monitored. Several bone-specific and tumor-specific single-photon emission computed tomography and positron emission tomography molecular imaging agents are available, for detection and monitoring response to systemic therapeutics, as well as theranostic agents to confirm target expression and predict response to radionuclide therapies.

Nuclear medicine imaging for bone metastases assessment: what else besides bone scintigraphy in the era of personalized medicine?

Accurate detection and reliable assessment of therapeutic responses in bone metastases are imperative for guiding treatment decisions, preserving quality of life, and ultimately enhancing overall survival. Nuclear imaging has historically played a pivotal role in this realm, offering a diverse range of radiotracers and imaging modalities. While the conventional bone scan using 99mTc marked bisphosphonates has remained widely utilized, its diagnostic performance is hindered by certain limitations. Positron emission tomography, particularly when coupled with computed tomography, provides improved spatial resolution and diagnostic performance with various pathology-specific radiotracers. This review aims to evaluate the performance of different nuclear imaging modalities in clinical practice for detecting and monitoring the therapeutic responses in bone metastases of diverse origins, addressing their limitations and implications for image interpretation.

Hybrid Ga-68 prostate-specific membrane antigen PET/MRI in the detection of skeletal metastasis in patients with newly diagnosed prostate cancer: Contribution of each part to the diagnostic performance

PURPOSE

Bone metastasis is essential in patients with prostate cancer (PCa) as it determines prognosis and survival. Hybrid PET/MRI allows simultaneous acquisition of PET and MRI data, thus combining the strength of both technologies allows the detection of bone marrow metastases that are missed by PET/CT. In this retrospective study, we aimed to evaluate the diagnostic efficiency of hybrid PET/MRI with Ga-68 prostate-specific membrane antigen (PSMA) in detecting skeletal metastases in newly diagnosed PCa patients and compared the effectiveness of stand-alone PSMA PET reviewing versus stand-alone whole-body (WB) MRI evaluation. We also investigated the effect of the interpretation of all PET/MR data together on clinical management.

METHODS

We studied 74 newly diagnosed PCa patients who underwent PSMA PET/MRI for staging purposes. At first, PET and MRI were evaluated separately for bone lesions on a patient-and-lesion basis and then a further joint PSMA PET/MRI interpretation was made.

RESULTS

Patient-based sensitivity, specificity, positive predictive value, negative predictive value and accuracy analysis for bone metastasis was, respectively, 1.0, 0.83, 0.54, 1.0, 0.86 for PET; 0.75, 0.96, 0.81, 0.95, 0.93 for WB MRI and 0.91, 0.95, 0.78, 0,98, 0.94 for PET/MRI. The combined PET/MRI evaluation changed the clinical impact in 13.5% of patients (eight correct and two wrong decisions) compared to PET stand-alone interpretation.

CONCLUSION

PSMA PET imaging showed superior sensitivity to WB MRI in detecting bone metastases in newly diagnosed PCa patients, whereas WB MRI has superior specificity and PPV. Furthermore, the specificity and PPV of joint PET/MRI evaluation are better than PSMA PET alone. Despite the longer acquisition period, adding WB MRI sequences to PSMA PET imaging appears beneficial for PCa patient management.

Prospective study of Na[18F]F PET/CT for cancer staging in morbidly obese patients compared with [99mTc]Tc-MDP whole-body planar, SPECT and SPECT/CT

PURPOSE

This prospective study aims to assess the diagnostic test characteristics of Na[¹⁸F]F PET/CT for the skeletal staging of cancer in morbidly obese patients compared with ^99mTc-methylene diphosphonate (MDP), whole-body planar (WBS), SPECT, and SPECT/CT acquisitions.

MATERIAL AND METHODS

One hundred seventeen obese patients (BMI 46.5 ± 6.1 kg/m² and mean age, 59.0 years; range 32-89 years) with BMI > 40 kg/m² were prospectively enrolled and underwent [^99mTc]Tc-MDP WBS, SPECT, SPECT/CT, and Na[¹⁸F]F PET/CT within two weeks for the osseous staging of a malignancy. Images were assessed qualitatively using a 3-point scale. Patient and lesion-based diagnostic test characteristics were estimated using an optimistic and pessimistic dichotomization method.

RESULTS

Bone metastases were confirmed in 44 patients. Patient-based optimistic diagnostic test characteristics were (sensitivity, specificity, overall accuracy): Na[¹⁸F]F PET/CT (95.5%, 95.9%, 95.7%), [^99mTc]Tc-MDP WBS (52.3%, 71.2%, 64.1%), SPECT (61.4%, 80.8%, 73.5%) and SPECT/CT (65.9%, 91.8%, 82.1%). Lesion-based optimistic diagnostic test characteristics were: Na[¹⁸F]F PET/CT (97.7%, 97.9%, 97.7%), [^99mTc]Tc-MDP WBS (39%, 67%, 48.9%), SPECT (52.9%, 93.6%, 67.3%) and SPECT/CT (65.9%, 91.8%, 82.1%). There was no significant difference in the specificity of Na[¹⁸F]F and SPECT/CT. All other pairwise comparisons were significant (p<.001). ROC curve analysis showed a high overall accuracy of Na[¹⁸F]F with significantly higher AUCs for Na[¹⁸F]F PET/CT compared to [^99mTc]Tc-MDP WBS, SPECT, and SPECT/CT on both patient and lesion-based analysis (p<.001). Moreover, Na[¹⁸F]F PET/CT changed patient management in 38% of patients.

CONCLUSIONS

Na[¹⁸F]F PET/CT may be the preferred imaging modality for skeletal staging in morbidly obese patients. The technique provides excellent diagnostic test characteristics superior to [^99mTc]Tc-MDP bone scan (including SPECT/CT), impacts patient management, has an acceptable radiation exposure profile, and is well-tolerated. Further cost-effectiveness evaluations are warranted.

Observer experience and accuracy of 18F-sodium-fluoride PET/CT for the diagnosis of bone metastases in prostate cancer

OBJECTIVE

To evaluate the diagnostic accuracy of observers with different levels of experience in reading 18F-sodium fluoride (NaF) PET/CT images for the diagnosis of bone metastases in prostate cancer (PCa) patients.

METHODS

Nine observers with varying NaF PET/CT experience, ranging from no experience to 2000+ examinations, evaluated 211 NaF PET/CT scans from PCa patients participating in one of four prospective trials. Each observer evaluated each NaF PET/CT on a patient level using a trichotomous scale: M0 (no bone metastases), Me (equivocal for bone metastases) and M1 (bone metastases). Subsequently, a dichotomous evaluation was conducted (M0/M1). The final diagnosis was retrieved from the original study. For each observer, ROC curves and the diagnostic accuracy were calculated based on dichotomous and trichotomous scales; in the latter case, Me was first regarded as M1 and then M0.

RESULTS

Across all experience levels, the sensitivity, specificity and accuracy using the dichotomous scale ranged from 0.81 to 0.89, 0.93 to 1.00 and 0.91 to 0.94, respectively. Employing the trichotomous scale, novice and experienced observers chose Me in up to 20 vs. 10% of cases, respectively. Considering Me as M0, the sensitivity, specificity and accuracy ranged from 0.78 to 0.89, 0.95 to 1.00 and 0.91 to 0.95, respectively. Considering Me as M1, the sensitivity, specificity and accuracy ranged from 0.86 to 0.92, 0.71 to 0.96 and 0.77 to 0.94, respectively.

CONCLUSION

Novice observers used the equivocal option more frequently than observers with NaF PET/CT experience. However, on the dichotomous scale, all observers exhibited high and satisfactory accuracy for the detection of bone metastases, making NaF PET/CT an effective imaging modality even in unexperienced hands.

Therapy-induced bone changes in oncology imaging with 18F-sodium fluoride (NaF) PET-CT

¹⁸F-Sodium fluoride (¹⁸F-NaF) is a PET tracer that is mostly used in the evaluation of bone metastasis in oncology cases. Recently, ¹⁸F-NaF PET/CT is gaining wide popularity owing to its higher sensitivity over the other conventional bone tracer with higher and rapid single-pass extraction, negligible plasma protein binding, rapid blood, and renal clearance. In the era of constant evolution of cancer therapy regimens, considerable bone health impact is seen in the form of avascular necrosis, insufficiency fractures, among others. A significant number of these therapy-induced changes show high bone turnover and thereby ¹⁸F-NaF accumulation, mimicking metastatic lesions. This article summarizes and illustrates the pattern and morphological features of ¹⁸F-NaF PET/CT findings in these changes in the context of clinical and therapeutic history.

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.

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.

Computerized Tomography (CT) Updates and Challenges in Diagnosis of Bone Metastases During Prostate Cancer

Prostate cancer is one of the most common cancers in men. This cancer is often associated with indolent tumors with little or no lethal potential. Some of the patients with aggressive prostate cancer have increased morbidity and early deaths. A major complication in advanced prostate cancer is bone metastasis that mainly results in pain, pathological fractures, and compression of spinal nerves. These complications in turn cause severe pain radiating to the extremities and possibly sensory as well as motor disturbances. Further, in patients with a high risk of metastases, treatment is limited to palliative therapies. Therefore, accurate methods for the detection of bone metastases are essential. Technical advances such as single-photon emission computed tomography/ computed tomography (SPECT/CT) have emerged after the introduction of bone scans. These advanced methods allow tomographic image acquisition and help in attenuation correction with anatomical co-localization. The use of positron emission tomography/CT (PET/CT) scanners is also on the rise. These PET scanners are mainly utilized with 18F-sodium-fluoride (NaF), in order to visualize the skeleton and possible changes. Moreover, NaF PET/CT is associated with higher tracer uptake, increased target-to-background ratio and has a higher spatial resolution. However, these newer technologies have not been adopted in clinical guidelines due to lack of definite evidence in support of their use in bone metastases cases. The present review article is focused on current perspectives and challenges of computerized tomography (CT) applications in cases of bone metastases during prostate cancer.

18F-Sodium Fluoride PET/CT Findings in Osteitis Condensans Ilii

ABSTRACT

Osteitis condensans ilii (OCI) is a benign cause of low back pain for which no clear etiology has been identified. We report cases of 2 women with breast cancer referred for 18F-NaF PET/CT for skeletal staging. Both cases show characteristic findings of OCI on CT images, with 18F-NaF PET uptake in symptomatic patient and no uptake in asymptomatic. 18F-NaF PET CT can be useful in evaluating back pain and may be used as an adjunctive biological maker for assessing OCI as a potential cause of pain.

18F-NaF PET/CT of Obese Patients on a Lutetium-Yttrium Oxyorthosilicate PET/CT System: Patient Dosimetry, Optimization of Injected Activity, and Acquisition Time

¹⁸F-NaF PET/CT has a rapid single-pass extraction and fast clearance from soft tissues, resulting in a good target-to-background ratio. This study aimed to establish the optimum acquisition time and dosimetry for ¹⁸F-NaF PET/CT to evaluate bone metastases in obese patients. A secondary objective was to evaluate the impact of acquisition time on image quality, lesion detection rate, noise level, and radiation burden in this patient group. Methods: In total, 60 patients were included in the study (20 patients with a body mass index (BMI) of 30.0-34.9 kg/m², 20 with a BMI of 35-39.9 kg/m², and 20 with a BMI of >40 kg/m²). Images were acquired after intravenous injection of a 2.2 MBq/kg (0.06 mCi/kg) dose of ¹⁸F-NaF. Data were acquired in list mode using ordered-subset expectation maximization reconstruction. The raw data were rebinned to simulate scans with acquisition times of 2, 2.5, and 3 min per bed position. The scans were visually analyzed by 2 observers and scored by rank against a panel of parameters (overall image quality, noise level, background soft tissue, and lesion detectability), and the contrast-to-noise ratio (CNR) was calculated. Results: The mean CNR was 20.19 ± 8.39 for a 2-min acquisition, 21.03 ± 8.35 for 2.5 min, and 22.16 ± 8.37 for 3 min. There were no statistically significant differences in CNR among the 3 different acquisition durations (P > 0.05). Lesion delineation was excellent and independent of the acquisition time. All relevant lesions could be identified with all 3 acquisition times. A mean activity of 215.4 ± 31.3 MBq was injected, with estimated mean effective absorbed doses of 4.09 ± 0.59 mSv for ¹⁸F-NaF PET and 7.88 ± 1.66 mSv for CT alone. Conclusion: ¹⁸F-NaF PET/CT can be beneficial in obese patients because of its good pharmacokinetics. Optimal osseous staging can be achieved with relatively low doses and radiation burden. Lesion delineation was excellent regardless of acquisition time. However, it is recommended that an acquisition of 3 min per bed position be used in patients with a BMI of more than 40.

Rare Thyroid Cartilage Metastasis From Breast Cancer Visualized on 18F-NaF PET/CT

Metastatic involvement of the thyroid cartilage is rare due to the absence of vessels within the cartilaginous tissue. We present the case of a 65-year-old woman recently diagnosed with breast cancer referred for skeletal staging with F-NaF PET/CT. She was found to have multiple osteoblastic metastases along with thyroid cartilage metastasis. Rare thyroid cartilage metastasis on F-NaF PET/CT may have prognostic significance in cancer patients.

18F-sodium fluoride bone deposition quantitation with PET in Mice: Variation with age, sex, and circadian rhythm

Aim The aim of this study was to establish a data base for normal 18F-sodium fluoride (18F-NaF) bone uptake as a function of age, sex and circadian rhythm in mice.

Methods In 12 female (F) and 12 male (M) C57BL/6N mice PET images were acquired 90 min after intravenous injection of 20 MBq 18F-NaF for 30 minutes. Each mouse was imaged in follow-up studies at 1, 3, 6, 13 and 21 months of age. In order to assess for physiologic changes related to circadian rhythm, animals were imaged during light (sleep phase) as well as during night conditions (awake phase). Bone uptake is described as the median percentage of the injected activity (%IA) and in relation to bone volume (%IA/ml).

Results A significant smaller bone volume was found in F (1.79 ml) compared to M (1.99 ml; p < 0.001). In sex-pooled data, highest bone uptake occurred at an age of 1 month (61.1 %IA, 44.5 %IA/ml) with a significant reduction (p < 0.001) at age 3 months (43.6 %IA, 23.6 %IA/ml), followed by an increase between 13 (47.3 %IA, 24.5 %IA/ml) and 21 months (52.2 %IA, 28.1 %IA/ml). F had a significantly higher total uptake (F 48.2 %IA, M 43.8 %IA; p = 0.026) as well as a higher uptake per ml bone tissue (F 27.0 %IA/ml; M 22.4 %IA/ml; p < 0.001). A significant impact of circadian rhythm was only found for F at ages of 3 and 6 months with a higher uptake during the sleep phase.

Conclusion Circadian rhythm had a significant impact on uptake only in F of 3 and 6 months. Regarding sex, F showed generally higher uptake rates than M. The highest uptake values were observed during bone growth at age 1 month in both sexes, a second uptake peak occurred in elderly F. Designing future bone uptake studies with M, attention must be paid to age only, while in F circadian rhythm and age must be taken into account.

Meeting report from the Prostate Cancer Foundation PSMA theranostics state of the science meeting

INTRODUCTION

The Prostate Cancer Foundation (PCF) convened a PCF prostate-specific membrane antigen (PSMA) Theranostics State of the Science Meeting on 18 November 2019, at Weill Cornell Medicine, New York, NY.

METHODS

The meeting was attended by 22 basic, translational, and clinical researchers from around the globe, with expertise in PSMA biology, development and use of PSMA theranostics agents, and clinical trials. The goal of this meeting was to discuss the current state of knowledge, the most important biological and clinical questions, and critical next steps for the clinical development of PSMA positron emission tomography (PET) imaging agents and PSMA-targeted radionuclide agents for patients with prostate cancer.

RESULTS

Several major topic areas were discussed including the biology of PSMA, the role of PSMA-targeted PET imaging in prostate cancer, the physics and performance of different PSMA-targeted PET imaging agents, the current state of clinical development of PSMA-targeted radionuclide therapy (RNT) agents, the role of dosimetry in PSMA RNT treatment planning, barriers and challenges in PSMA RNT clinical development, optimization of patient selection for PSMA RNT trials, and promising combination treatment approaches with PSMA RNT.

DISCUSSION

This article summarizes the presentations from the meeting for the purpose of globally disseminating this knowledge to advance the use of PSMA-targeted theranostic agents for imaging and treatment of patients with prostate cancer.

Imaging with radiolabelled bisphosphonates

Radiolabeled bisphosphonates were developed in the 1970s for scintigraphic functional imaging of the skeleton in benign and malignant disease. Tracers such as 99mTc-methylene diphosphonate, that map focal or global changes in mineralization in the skeleton qualitatively and quantitatively, have been the backbone of nuclear medicine imaging for decades. While competing technologies are evolving, new indications and improvements in scanner hardware, in particular hybrid imaging (e.g. single photon emission computed tomography combined with computed tomography), have allowed improved diagnostic accuracy and a continued role for radiolabeled bisphosphonate imaging in current practice.

Molecular Imaging of Bone Metastases and Their Response to Therapy

Bone metastases are common, especially in more prevalent malignancies such as breast and prostate cancer. They cause significant morbidity and draw on health-care resources. Molecular and hybrid imaging techniques, including SPECT/CT, PET/CT, and whole-body MRI with diffusion-weighted imaging, have improved diagnostic accuracy in staging the skeleton compared with previous standard imaging methods, allowing earlier tailored treatment. With the introduction of several effective treatment options, it is now even more important to detect and monitor response in bone metastases accurately. Conventional imaging, including radiographs, CT, MRI, and bone scintigraphy, are recognized as being insensitive and nonspecific for response monitoring in a clinically relevant time frame. Early reports of molecular and hybrid imaging techniques, as well as whole-body MRI, promise an earlier and more accurate prediction of response versus nonresponse but have yet to be adopted routinely in clinical practice. We summarize the role of new molecular and hybrid imaging methods, including SPECT/CT, PET/CT, and whole-body MRI. These modalities are associated with improvements in diagnostic accuracy for the staging and response assessment of skeletal metastases over standard imaging methods, being able to quantify biologic processes related to the bone microenvironment as well as tumor cells. The described improvements in the imaging of bone metastases and their response to therapy have led to adoption of some of these methods into routine clinical practice in some centers. These methods also provide a better way to assess the treatment response of bone metastases in clinical trials.

Imaging and Management of Prostate Cancer

Prostate cancer (PCa) is the most common noncutaneous malignancy in men and the second leading cause of cancer related death in the United States. Men with clinical suspicion of PCa undergo tissue sampling and based on features including the Gleason score, Prostate Specific antigen (PSA) levels and clinical tumor (T) stage, patients are risk stratified into 6 major groups based on National Comprehensive Cancer Network (NCCN) guidelines. This forms the basis for deciding imaging and management. Active surveillance is the preferred approach for less aggressive tumors. Surgery or radiation +/- androgen deprivation therapy continue to be the primary treatment options for localized disease. Imaging plays a critical role in the diagnosis, staging and management of PCa. Multiparametric magnetic resonance imaging (mpMRI) is currently the imaging modality of choice for locoregional staging. MRI, computed tomography and bone scan remain the preferred modalities for evaluation of nodal, soft tissue, and bone metastases, respectively. Advanced positron emission tomography imaging using novel radiotracers are being developed but are not yet integrated in the diagnostic guidelines for initial staging. In this review, we will discuss the imaging and treatment algorithms based on the NCCN risk groups, describe the utility of individual modalities, review Prosate Imaging and Reporting and Data System (PIRADS) version 2.1 for the reporting of mpMRI of the prostate.

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.

Observer Agreement and Accuracy of 18F-Sodium Fluoride PET/CT in the Diagnosis of Bone Metastases in Prostate Cancer

Our aim was to evaluate the interobserver agreement in ¹⁸F-sodium fluoride (NaF) PET/CT for the detection of bone metastases in patients with prostate cancer (PCa). Methods: ¹⁸F-NaF PET/CT scans were retrieved from all patients who participated in 4 recent prospective trials. Two experienced observers independently evaluated the ¹⁸F-NaF PET/CT scans on a patient level using a 3-category scale (no bone metastases [M0], equivocal for bone metastases, and bone metastases present [M1]) and on a dichotomous scale (M0/M1). In patients with no more than 10 lesions, the location and number of lesions were recorded. On a patient level, the diagnostic performance was calculated using a sensitivity analysis, in which equivocal lesions were handled as M0 as well as M1. Results: ¹⁸F-NaF PET/CT scans from 219 patients with PCa were included, of whom 129 patients were scanned for primary staging, 67 for biochemical recurrence, and 23 for metastatic castration-resistant PCa. Agreement between the observers was almost perfect on a patient level (3-category unweighted κ = 0.83 ± 0.05, linear weighted κ = 0.90 ± 0.06, and dichotomous κ = 0.91 ± 0.07). On a lesion level (dichotomous scale), the observers agreed on the number and location of bone metastases in 205 (93.6%) patients. In the remaining 14 patients, the readers disagreed on the number of lesions in 13 patients and the location of bone metastases in 1 patient. A final diagnosis of bone metastases was made for 211 of 219 patients. The sensitivity ranged from 0.86 to 0.92, specificity from 0.83 to 0.97, positive predictive value from 0.70 to 0.93, and negative predictive value from 0.94 to 0.96. Conclusion: The interobserver agreement on ¹⁸F-NaF PET/CT for the detection of bone metastases in patients with PCa was very high among trained observers, both on a patient level and on a lesion level. Moreover, the diagnostic performance of ¹⁸F-NaF PET/CT was satisfactory, rendering ¹⁸F-NaF PET/CT a robust tool in the diagnostic armamentarium.

Molecular imaging of bone metastases using bone targeted tracers

Molecular imaging using bone targeted tracers has been used in clinical practice for almost fifty years and still plays an essential role in the diagnosis and follow-up of bone metastases. It includes both [99mTc]bisphosphonates for bone scan and [18F]NaF for positron emission tomography/computed tomography (PET/CT) which are very sensitive to detect osteoblastic activity, but it is important to consider several aspects to increase the specificity of reported findings (such as specific tracer characteristics and mechanism of action, patient's clinical history, common metastatic patterns, changes after treatment, limitations of the technique, variations and pitfalls). This will enable useful information for clinical management being provided in the report. Furthermore, iatrogenic skeletal adverse events are common and they should also be identified, as they have impact on patient's quality of life. This review makes a brief summary of the mechanism of action of bone targeted tracers, followed by a discussion of classic patterns of bone metastasis, treatment response assessment and iatrogenic skeletal complications. The value of hybrid imaging techniques with bone targeted tracers, including single photon emission computed tomography and PET/CT is also explored. The final part summarizes new bone targeted tracers with superior imaging characteristics that are being developed, and which may further enhance the applications of radionuclide bone imaging.

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.

Impact of sodium 18F-fluoride PET/CT, 18F-fluorocholine PET/CT and whole-body diffusion-weighted MRI on the management of patients with prostate cancer suspicious for metastasis: a prospective multicentre study

PURPOSE

To compare the impact of 18F-sodium-fluoride (NaF) PET/CT, 18F-fluorocholine (FCH) PET/CT and diffusion-weighted whole-body MRI (DW-MRI) on the management of patients with prostate cancer (PCa) suspicious for distant metastasis.

METHODS

Prostate cancer patients were prospectively included between December 2011 and August 2014 and benefited from these three whole-body imaging (WBI) modalities within 1 month in addition to the standard PCa workup. Management was prospectively decided by clinicians during two multidisciplinary meetings, before and after the whole-body imaging workup. Rates of induced changes of whole-body imaging modalities were compared by Cochran's Q test.

RESULTS

One-hundred-one patients (27 at staging, 59 at first biochemical recurrence (BCR) and 15 at first episode of rising serum level of prostate-specific antigen during androgen-deprivation therapy) were included. The overall rate of management changes was 52%: 29% as a consequence of WBI, higher for FCH-PET/CT than for NaF-PET/CT or DW-MRI (p < 0.0001) and highest (41%) for FCH-PET/CT at BCR. Actual management was adequate in all patients but two.

CONCLUSIONS

Whole-body imaging induced a change in management in approximately a third of PCa patients suspicious for metastasis. The impact rate was determined to be greatest at first BCR using FCH-PET/CT. NaF-PET/CT and DW-MRI seemed less useful in this context.

Role of PET imaging for biochemical recurrence following primary treatment for prostate cancer

Prostate cancer is one of the most common cancers in men worldwide, and primary prostate cancer is typically treated with surgery, radiation, androgen deprivation, or a combination of these therapeutic modalities. Despite technical advances, approximately 30% of men will experience biochemical recurrent within 10 years of definitive treatment. Upon detection of a rise in serum prostate specific antigen (PSA), there is great need to accurately stage these patients to help guide further therapy. As a result, there are considerable efforts underway to establish the role of positron emission tomography (PET) in the diagnostic algorithm of biochemically recurrent prostate cancer. This manuscript provides an overview of PET tracers used for the detection and localization of prostate cancer in the setting of biochemical recurrence with a focus on PET tracers that are currently being used in clinical practice in the United States.

Prospective comparative study of 18F-sodium fluoride PET/CT and planar bone scintigraphy for treatment response assessment of bone metastases in patients with prostate cancer

AIM

To compare ¹⁸F-sodium fluoride positron emission tomography/computed tomography (NaF PET/CT) and ^99mTc-labelled diphosphonate bone scan (BS) for the monitoring of bone metastases in patients with prostate cancer undergoing anti-cancer treatment.

MATERIAL AND METHODS

Data from 64 patients with prostate cancer were included. The patients received androgen-deprivation therapy (ADT), next-generation hormonal therapy (NGH) or chemotherapy. The patients had a baseline scan and 1-3 subsequent scans during six months of treatment. Images were evaluated by experienced nuclear medicine physicians and classified for progressive disease (PD) or non-PD according to the Prostate Cancer Working Group 2 (PCWG-2) criteria. The patients were also classified as having PD/non-PD according to the clinical and prostate-specific antigen (PSA) responses.

RESULTS

There was no difference between NaF PET/CT and BS in the detection of PD and non-PD during treatment (McNemar's test, p = .18). The agreement between BS and NaF PET/CT for PD/non-PD was moderate (Cohen's kappa 0.53, 95% confidence interval 0.26-0.79). Crude agreement between BS and NaF PET/CT for the assessment of PD/non-PD was 86% (89% for ADT, n = 28; 88% for NGH, n = 16, and 80% for chemotherapy, n = 20). In most discordant cases, BS found PD when NaF PET/CT did not, or BS detected PD on an earlier scan than NaF PET/CT. Biochemical progression (27%) occurred more frequently than progression on functional imaging (BS, 22% and NaF PET/CT, 14%). Clinical progression was rare (11%), and almost exclusively seen in patients receiving chemotherapy.

CONCLUSION

There was no difference between NaF PET/CT and BS in the detection of PD and non-PD; however, BS seemingly detects PD by the PCWG-2 criteria earlier than NaF-PET, which might be explained by the fact that NaF-PET is more sensitive at the baseline scan.

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.

Anatomic and Molecular Imaging in Prostate Cancer

Prostate cancer is characterized by a complex set of heterogeneous disease states. This review aims to describe how imaging has been studied within each specific state. As physicians transition into an era of precision medicine, multiparametric magnetic resonance imaging (mpMRI) is proving to be a powerful tool leading the way for a paradigm shift in the diagnosis and management of localized prostate cancer. With further research and development, molecular imaging modalities will likely change the way we approach recurrent and metastatic disease. Given the range of possible oncological progression patterns, a thorough understanding of the underlying carcinogenesis, as it relates to imaging, is a requisite if we are to appropriately manage prostate cancer in future decades.

Site specific measurements of bone formation using [18F] sodium fluoride PET/CT

Dynamic positron emission tomography (PET) imaging with fluorine-18 labelled sodium fluoride ([¹⁸F]NaF) allows the quantitative assessment of regional bone formation by measuring the plasma clearance of fluoride to bone at any site in the skeleton. Today, hybrid PET and computed tomography (CT) dual-modality systems (PET/CT) are widely available, and [¹⁸F]NaF PET/CT offers a convenient non-invasive method of studying bone formation at the important osteoporotic fracture sites at the hip and spine, as well as sites of pure cortical or trabecular bone. The technique complements conventional measurements of bone turnover using biochemical markers or bone biopsy as a tool to investigate new therapies for osteoporosis, and has a potential role as an early biomarker of treatment efficacy in clinical trials. This article reviews methods of acquiring and analyzing dynamic [¹⁸F]NaF PET/CT scan data, and outlines a simplified approach combining venous blood sampling with a series of short (3- to 5-minute) static PET/CT scans acquired at different bed positions to estimate [¹⁸F]NaF plasma clearance at multiple sites in the skeleton with just a single injection of tracer.

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.

Initial experience with 18F-sodium fluoride (NaF) PET-CT: a viable functional biomarker in symptomatic Os acromiale

OBJECTIVE

Os acromiale (OA) is a failure of complete fusion of the acromial process. It is usually asymptomatic and discovered incidentally. OA can contribute to shoulder impingement symptoms and rotator cuff tears. ¹⁸F Sodium Fluoride (NaF) Positron Emission Tomography -CT (PET-CT) is an emerging and highly sensitive modality for oncological skeletal staging, and can show a variety of non-malignant uptake. We have analysed the relationship between ¹⁸F-NaF uptake in OA and associated symptoms of shoulder pain.

METHODS

Study population included 21 patients (mean age 60.2 ± 12 years; 13 females and 8 males) with OA who underwent PET-CT scan by injecting 2.22 MBq kg^-1 of ¹⁸F-NaF. The relationship between ¹⁸F-NaF uptake and OA as a cause of pain was analysed. A 3-point grading system was used to evaluate uptake of ¹⁸F-NaF.

RESULTS

In total 27 OA (12 symptomatic and 15 asymptomatic) were enrolled. All symptomatic OA showed focal increase tracer uptake of Grade 2, while asymptomatic OA did not have significant activity Grade 0 (n = 11) and Grade 1 (n = 4).

CONCLUSION

¹⁸F-NaF PET-CT appears to be a useful adjunct in the assessment of symptomatic OA with its particular strength being its high negative predictive value. Advances in knowledge: ¹⁸F-NaF PET-CT may be used as an ancillary tool for identifying symptomatic OA  as a cause of shoulder pain in cases where other obvious causes of shoulder pain have been excluded.

Hospice Admission and Survival After 18F-Fluoride PET Performed for Evaluation of Osseous Metastatic Disease in the National Oncologic PET Registry

We have previously reported that PET using ¹⁸F-fluoride (NaF PET) for assessment of osseous metastatic disease was associated with substantial changes in intended management in Medicare beneficiaries participating in the National Oncologic PET Registry (NOPR). Here, we use Medicare administrative data to examine the association between NaF PET results and hospice claims within 180 d and 1-y survival. Methods: We classified NOPR NaF PET results linked to Medicare claims by imaging indication (initial staging [IS]; detection of suspected first osseous metastasis [FOM]; suspected progression of osseous metastasis [POM]; or treatment monitoring [TM]) and type of cancer (prostate, lung, breast, or other). Results were classified as definitely positive scan findings versus probably positive scan findings versus negative scan findings for osseous metastasis for IS and FOM; more extensive disease versus no change or less extensive disease for POM; and worse prognosis versus no change or better prognosis for TM, based on the postscan assessment. Our study included 21,167 scans obtained from 2011 to 2014 of consenting NOPR participants aged 65 y or older. Results: The relative risk of hospice claims within 180 d of a NaF PET scan was 2.0-7.5 times higher for patients with evidence of new or progressing osseous metastasis than for those without, depending on indication and cancer type (all P < 0.008). The percentage difference in hospice claims for those with a finding of new or more advanced osseous disease ranged from 3.9% for IS prostate patients to 28% for FOM lung patients. Six-month survival was also associated with evidence of new or increased osseous disease; risk of death was 1.8-5.1 times as likely (all P ≤ 0.0001), with percentage differences of approximately 30% comparing positive and negative scans in patients with lung cancer imaged for IS or FOM. Conclusion: Our analyses demonstrated that NaF PET scan results are highly associated with subsequent hospice claims and, ultimately, with patient survival. NaF PET provides important information on the presence of osseous metastasis and prognosis to assist patients and their physicians when making decisions on whether to select palliative care and transition to hospice or whether to continue treatment.

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.

Inguinal Herniation of Urinary Bladder on F-18 Sodium Fluoride (NaF) PET-CT

Inguinal herniation of urinary bladder is uncommon and usually an incidental finding in asymptomatic patients. In some of these patients, residual urine volume and consequently, urinary tracer activity can be higher in the herniated bladder than the native bladder, in which case interpretation can be challenging on conventional planar imaging. We describe an interesting case of physiological activity in a herniated bladder simulating a "tear-drop". This case serves an important reminder that whilst F-18 NaF PET-CT has a similar spectrum of urinary activity to conventional bone scintigraphy; morphological correlation on hybrid imaging is invaluable in ensuring the physiological nature of uptake.

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.

Intended Versus Inferred Treatment After 18F-Fluoride PET Performed for Evaluation of Osseous Metastatic Disease in the National Oncologic PET Registry

We have previously reported that PET with ¹⁸F-fluoride (NaF PET) for assessment of osseous metastatic disease led to changes in intended management in a substantial fraction of patients with prostate or other types of cancer participating in the National Oncologic PET Registry. This study was performed to assess the concordance of intended patient management after NaF PET and inferred management based on analysis of Medicare claims. Methods: We analyzed linked post-NaF PET data of consenting National Oncologic PET Registry participants age 65 y or older from 2011 to 2014 and their corresponding Medicare claims. Post-NaF PET treatment plans, including combinations of 2 modes of therapy, were assessed for their concordance with clinical actions inferred from Medicare claims. NaF PET studies were stratified by indication (initial staging [IS] or suspected first osseous metastasis [FOM]) and cancer type (prostate, lung, or other cancers). Agreement was assessed between post-NaF PET intended management plans for treatment (surgery, radiotherapy, or systemic therapy) within 90 d for lung and 180 d for prostate or other cancers, and for watching (the absence of treatment claims for ≥60 d) as compared with claims-inferred care. Results: Actions after 9,898 scans were assessed. After NaF PET for IS, there was claims agreement for planned surgery in 76.0% (19/25) lung, 75.4% (98/130) other cancers, and 58.9% (298/506) prostate cancer. Claims confirmed chemotherapy plans after NaF PET done for IS or FOM in 81.0% and 73.5% for lung cancer (n = 148 and 136) and 69.4% and 67.5% for other cancers (n = 111 and 228). For radiotherapy plans, agreement ranged from 80.0% to 84.4% after IS and 68.4% to 74.0% for suspected FOM. Concordance was greatest for androgen deprivation therapy (ADT) (86.0%, n = 308) alone or combined with radiotherapy in prostate cancer IS (80.8%, n = 517). In prostate FOM, the concordance across all treatment plans was lower if the patients had ADT claims within 180 d before NaF PET. Agreement with nontreatment plans was high for FOM (87.2% in other cancers and 78.6% if no prior ADT in prostate) and low after IS (40.7%-62.5%). Conclusion: Concordance of post-NaF PET plans and claims was substantial and higher overall for IS than for FOM.

Diagnostic Challenge of Staging Metastatic Bone Disease in the Morbidly Obese Patients: A Primary Study Evaluating the Usefulness of 18F-Sodium Fluoride (NaF) PET-CT

PURPOSE

Optimizing diagnostic imaging may be challenging in obese patients. The quality of conventional bone scintigraphy can be poor in the morbidly obese due to a combination of factors including high background soft tissue activity. In comparison, sodium fluoride (F-NaF PET-CT) has a better target-to-background ratio attributed to rapid single-pass extraction and fast clearance from the soft tissues. The aim of the present study is to assess the diagnostic efficacy of F-NaF PET-CT in the evaluation of bone metastases in obese cancer patients.

PATIENTS AND METHODS

Two hundred twelve morbidly obese patients (body mass index, 45 ± 5.1 kg/m; mean age, 57 years; range, 32-81 years) with body mass index greater than 40 kg/m referred for NaF PET-CT for osseous staging of malignancy were retrospectively analyzed. All patients underwent PET-CT scan by injecting 2.2 MBq/kg (0.06 mCi/kg) of F-NaF.

RESULTS

F-NaF PET-CT was definitely benign in 145, possibly benign in 3, equivocal in 4, possibly malignant in 13, and definitely malignant in 47 patients. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of F-NaF PET-CT were 93.1%, 96.1%, 90%, 97.3%, and 95.2%, respectively (95% confidence interval).

CONCLUSIONS

The results of the present study indicate that F-NaF PET-CT retains its high diagnostic accuracy in morbidly obese patients and, by inference, can be a preferred functional modality in these patients.

Clinical PET Imaging in Prostate Cancer

Prostate cancer is the second most common cancer in men worldwide, with a wide spectrum of biologic behavior ranging from indolent low-risk disease to highly aggressive castration-resistant prostate cancer. Conventional imaging with computed tomography, magnetic resonance imaging, and bone scintigraphy is limited for the detection of nodal disease and distant bone metastases. In addition, advances in the available therapeutic options, both localized and systemic, drive the requirement for precise diagnostic and prognostic tools to refine the individual therapeutic approach at various times in the management of patients with prostate cancer. Positron emission tomography (PET) has a rapidly evolving role in the assessment of prostate cancer, particularly in the scenario of biochemical relapse. Fluorine 18 (¹⁸F) fluorodeoxyglucose, the most widely available PET tracer, has limitations, particularly in indolent prostate cancer. In the past decade, several PET tracers with specific molecular targets have reached the clinical domain. These tracers include ¹⁸F-sodium fluoride, which is a bone-specific biomarker of osteoblastic activity; ¹⁸F-choline and carbon 11-choline, which are directed at cell membrane metabolism; gallium 68-prostate-specific membrane antigen ligands; and, more recently, an amino acid analog, ¹⁸F-fluciclovine (anti-1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid; also known as FACBC), which is also directed at cell membrane turnover. The mechanisms of actions of the clinically available PET tracers are reviewed, as well as their role in the imaging of prostate cancer with reference to relevant guidelines and the technical and imaging pearls and pitfalls of these tracers. ^©RSNA, 2017.

Advances in medical imaging for the diagnosis and management of common genitourinary cancers

Medical imaging of the 3 most common genitourinary (GU) cancers-prostate adenocarcinoma, renal cell carcinoma, and urothelial carcinoma of the bladder-has evolved significantly during the last decades. The most commonly used imaging modalities for the diagnosis, staging, and follow-up of GU cancers are computed tomography, magnetic resonance imaging (MRI), and positron emission tomography (PET). Multiplanar multidetector computed tomography and multiparametric MRI with diffusion-weighted imaging are the main imaging modalities for renal cell carcinoma and urothelial carcinoma, and although multiparametric MRI is rapidly becoming the main imaging tool in the evaluation of prostate adenocarcinoma, biopsy is still required for diagnosis. Functional and molecular imaging using 18-fluorodeoxyglucose-PET and sodium fluoride-PET are essential for the diagnosis, and especially follow-up, of metastatic GU tumors. This review provides an overview of the latest advances in the imaging of these 3 major GU cancers.

Prostate cancer - major changes in the American Joint Committee on Cancer eighth edition cancer staging manual

Answer questions and earn CME/CNE The eighth edition of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) Staging Manual has been updated and improved to ensure the highest degree of clinical relevance and to improve its utility for patient evaluation and clinical research. Major changes include: 1) pathologically organ-confined disease is now considered pT2 and is no longer subclassified by extent of involvement or laterality, 2) tumor grading now includes both the Gleason score (as in the seventh edition criteria) and the grade group (introduced in the eighth edition criteria), 3) prognostic stage group III includes select, organ-confined disease based on prostate-specific antigen and Gleason/grade group status, and 4) 2 statistical prediction models are included in the staging manual. The AJCC will continue to critically analyze emerging prostate cancer biomarkers and tools for their ability to prognosticate and guide treatment decision making with the highest level of accuracy and confidence for patients and physicians. CA Cancer J Clin 2017;67:245-253. © 2017 American Cancer Society.

A Pilot Trial Evaluating Zoledronic Acid Induced Changes in [18F]FMAU-Positron Emission Tomography Imaging of Bone Metastases in Prostate Cancer

PURPOSE

We conducted a pilot trial utilizing [¹⁸F]FMAU [1-(2'-deoxy-2'-[¹⁸F]fluoro-β-D-arabinofuranosyl thymine] as a tumor tracer in positron emission tomography (PET) and evaluated its reproducibility, and changes in maximum and peak standardized uptake value (SUVmax and SUVpeak) with zoledronic acid treatment in castrate resistant prostate cancer (CRPC) patients with bone metastases (BM).

PROCEDURES

Eligible patients had CRPC with radiographic evidence of BM and creatinine clearance >30 ml/min. Two baseline [¹⁸F]FMAU-PET scans (about 1 week apart, range 2-12 days) were obtained for testing reproducibility. Zoledronic acid 4 mg was infused over 15 min within 1 week after second scan and a third PET scan was obtained 7 days later. The bony lesion with the highest uptake on the first scan was compared with later scans. Bone turnover markers and prostate-specific antigen (PSA) were obtained pre- and post-therapy. PET response was defined as decline in SUVmean of ≥15 % after zoledronic acid.

RESULTS

Eleven patients were evaluated, median age was 65 years, five were African-American and six were Caucasian, and median PSA level was 36.3 ng/ml (range 1.0-1209.3). Notably, the range of absolute percent SUVmax changes varied between 0.77 and 54.7, and only nine measurements were greater than one (1.09-2.19). Zoledronic acid did not appreciably change FMAU uptake. No clinical response was noted. Urine N-telopeptide (NTx) was markedly decreased in all patients after zoledronic acid and serum bone-specific alkaline phosphatase (BSAP) registered a modest change. Urine NTx correlated more closely with SUV max than serum BSAP.

CONCLUSIONS

FMAU tracer was able to detect bone metastases in CRPC patients but uptake was highly variable in bony lesions. Zoledronic acid did not produce an appreciable change in scans. Future investigations of FMAU tracer as a marker of early response in CRPC is recommended.

Role of radical prostatectomy in metastatic prostate cancer: A review

CONTEXT

Recent demonstration of efficacy with the use of chemohormonal therapy for men with metastatic prostate cancer (mPCa) has expanded the therapeutic options for these patients. Furthermore, multimodal therapy to treat systemic disease in the context of locoregional control has gained increasing interest. Concomitantly, the role of radical prostatectomy (RP) in multimodal treatment for locally advanced prostate cancer is expanding. As a result, there is interest in investigating the potential benefit of cytoreductive RP in mPCa.

OBJECTIVE

To review the literature regarding the role of cytoreductive prostatectomy in the setting of mPCa.

EVIDENCE ACQUISITION

MEDLINE and PubMed electronic databases were queried for English language articles related to patients with mPCa who underwent RP from January 1990 to June 2016. Key words used in our search included cytoreductive prostatectomy, radical prostatectomy, and metastatic prostate cancer. Preclinical, retrospective, and prospective studies were included.

EVIDENCE SYNTHESIS

There are no published randomized control trials examining the role of cytoreduction in mPCa. Local symptoms are high in mPCa and often provide a necessity for palliative procedures with the impact on oncologic outcomes being uncertain. Recently, preclinical and retrospective population-based data suggest a benefit from treatment of the primary tumor in metastatic disease. Potential mechanisms mediating this benefit include prevention of symptomatic local progression and modulation of disease biology, resulting in an improvement in progression-free and overall survival. Current literature supports the feasibility of cytoreductive prostatectomy as it is associated with acceptable side effects that are comparable to RP for high-risk localized disease. In aggregate, these data compel prospective evaluation of the hypothesis that cytoreductive prostatectomy improves the outcome of men with mPCa.

CONCLUSIONS

Cytoreductive prostatectomy in mPCa is a feasible procedure that may improve outcomes for men when combined with multimodal management. Preclinical, translational, and retrospective evidence supports local therapy for metastatic disease. However, currently, evidence is limited and is subject to bias. The results of ongoing prospective randomized trials are required before incorporating this therapeutic strategy into clinical practice.

18F-NaF PET-CT in Symptomatic Fabella Syndrome

Fabella is a sesamoid bone, located within the tendon of the lateral head of the gastrocnemius muscle. It may be associated with posterolateral knee pain because of repetitive friction over the posterolateral femoral condyle. We report a case of a 64-year-old woman presenting with right posterolateral knee pain. F-NaF PET-CT demonstrated increased uptake posterior to the right knee joint localizing to a fabella. Standard examination and radiographic imaging excluded other causes for posterolateral knee pain, and the increased activity was considered to be secondary to fabella syndrome. NaF PET-CT can provide useful information in the evaluation of posterolateral knee pain.

Prostate-Specific Antigen and Prostate-Specific Antigen Kinetics in Predicting 18F-Sodium Fluoride Positron Emission Tomography-Computed Tomography Positivity for First Bone Metastases in Patients with Biochemical Recurrence after Radical Prostatectomy

We evaluated the association between serum prostate specific antigen (PSA) level and kinetics to predict ¹⁸F-sodium fluoride positron emission tomography-computed tomography (¹⁸F-NaF PET-CT) positivity for first bone metastases in men with biochemical recurrence after radical prostatectomy. All ¹⁸F-NaF PET-CT scans that were performed at our institution during 2010–2014 were queried to find patients who demonstrated biochemical recurrence after radical prostatectomy. Records were reviewed to obtain data on PSA levels and kinetics at the time of ¹⁸F-NaF PET-CT and pathologic features of the prostatectomy specimen, which were then used for receiver operating characteristic (ROC) analysis to determine predictability for ¹⁸F-NaF PET positivity. Thirty-six patients met our inclusion criteria. Of these, 8 (22.2%) had positive ¹⁸F-NaF PET-CT scans. Mean values for PSA, PSA doubling time (PSADT), and PSA velocity (PSAV) were 2.02 ng/ml (range: 0.06–11.7 ng/ml), 13.2 months (range: 1.11–60.84), and 1.28 ng/ml/year (range: 0.1–5.28) for ¹⁸F-NaF PET-CT negative scans, and 4.11 ng/ml (range: 0.04–14.38 ng/ml), 8.9 months (range; 0.7–27.8), and 9.06 ng/ml/year (range: 0.04–50.2) for ¹⁸F-NaF PET-CT positive scans, respectively (P = 0.07, 0.47, and 0.02, respectively, for PSA, PSADT, and PSAV). ROC analysis for ¹⁸F-NaF PET-CT positivity resulted in area under the curve (AUC) values of 0.634 for PSA, 0.598 for PSADT, and 0.688 for PSAV. ROC analysis with combined models gave AUC values of 0.723 for a combination of PSA and PSADT, 0.689 for a combination of PSA and PSAV, and 0.718 for grouping of PSA, PSADT, and PSAV. There was no significant association between ¹⁸F-NaF PET-CT positivity and primary tumor Gleason score, TN staging, and status of surgical margins. ¹⁸F-NaF PET-CT detected first-time osseous metastases in 22.2% of our patients with biochemical recurrence after prostatectomy with the PSA level range ≤11.7 ng/ml. PSAV was statistically significant in predicting ¹⁸F-NaF PET-CT positivity. ROC analysis demonstrated higher AUCs when PSA was combined with PSA kinetics parameters.