Prospective comparison of whole-body bone SPECT and sodium 18F-fluoride PET in the detection of bone metastases from breast cancer

Radiation Dose Savings Associated with Personalized CT Scan Range in 18F-NaF Bone PET/CT

A disadvantage of 18F-NaF PET/CT compared with other types of bone scintigraphy is the additional radiation dose from the standard whole-body CT scan for lesion localization and characterization (L/C). This study investigated whether the L/C CT region can be personalized to reduce CT radiation dose, according to uptake in the PET images. Methods: Attenuation-corrected 18F-NaF PET images were reviewed for the clinically required L/C CT range by 1 medical observer and 1 technologist observer in 25 patients with breast cancer scanned before neoadjuvant chemotherapy. For each patient, effective doses were estimated for whole-body L/C CT, personalized L/C CT, and whole-body CT for attenuation correction only. Dose savings for the personalized method incorporating both whole-body CT for attenuation correction and personalized L/C CT were expressed relative to standard whole-body L/C CT. The clinical impact of the personalized method was determined by evaluating whether lesions clinically requiring coverage had been missed from the L/C CT region. Results: Potential dose savings of 43%-54% were estimated for the personalized CT method, according to the observers. From the 25 patients reviewed, the medical observer did not miss any clinically significant lesions from the L/C CT region, whereas the technologist observer missed 2 clinically significant lesions of 61 suggestive lesions identified by medical observer follow-up. Conclusion: Mean CT dose could be reduced by around half in this patient group with personalized CT. Future work should further evaluate whether this method can be implemented in clinical practice without compromising clinical image evaluation.

Diagnosing Bone Metastases in Breast Cancer: A Systematic Review and Network Meta-Analysis on Diagnostic Test Accuracy Studies of 2-[18F]FDG-PET/CT, 18F-NaF-PET/CT, MRI, Contrast-Enhanced CT, and Bone Scintigraphy

This systematic review and network meta-analysis aimed to compare the diagnostic accuracy of 2-[18F]FDG-PET/CT, 18F-NaF-PET/CT, MRI, contrast-enhanced CT, and bone scintigraphy for diagnosing bone metastases in patients with breast cancer. Following PRISMA-DTA guidelines, we reviewed studies assessing 2-[18F]FDG-PET/CT, 18F-NaF-PET/CT, MRI, contrast-enhanced CT, and bone scintigraphy for diagnosing bone metastases in high-stage primary breast cancer (stage III or IV) or known primary breast cancer with suspicion of recurrence (staging or re-staging). A comprehensive search of MEDLINE/PubMed, Scopus, and Embase was conducted until February 2024. Inclusion criteria were original studies using these imaging methods, excluding those focused on AI/machine learning, primary breast cancer without metastases, mixed cancer types, preclinical studies, and lesion-based accuracy. Preference was given to studies using biopsy or follow-up as the reference standard. Risk of bias was assessed using QUADAS-2. Screening, bias assessment, and data extraction were independently performed by two researchers, with discrepancies resolved by a third. We applied bivariate random-effects models in meta-analysis and network meta-analyzed differences in sensitivity and specificity between the modalities. Forty studies were included, with 29 contributing to the meta-analyses. Of these, 13 studies investigated one single modality only. Both 2-[18F]FDG-PET/CT (sensitivity: 0.94, 95% CI: 0.89-0.97; specificity: 0.98, 95% CI: 0.96-0.99), MRI (0.94, 0.82-0.98; 0.93, 0.87-0.96), and 18F-NaF-PET/CT (0.95, 0.85-0.98; 1, 0.93-1) outperformed the less sensitive modalities CE-CT (0.70, 0.62-0.77; 0.98, 0.97-0.99) and bone scintigraphy (0.83, 0.75-0.88; 0.96, 0.87-0.99). The network meta-analysis of multi-modality studies supports the comparable performance of 2-[18F]FDG-PET/CT and MRI in diagnosing bone metastases (estimated differences in sensitivity and specificity, respectively: 0.01, -0.16 - 0.18; -0.02, -0.15 - 0.12). The results from bivariate random effects modelling and network meta-analysis were consistent for all modalities apart from 18F-NaF-PET/CT. We concluded that 2-[18F]FDG-PET/CT and MRI have high and comparable accuracy for diagnosing bone metastases in breast cancer patients. Both outperformed CE-CT and bone scintigraphy regarding sensitivity. Future multimodality studies based on consented thresholds are warranted for further exploration, especially in terms of the potential role of 18F-NaF-PET/CT in bone metastasis diagnosis in breast cancer.

Diagnostic performance of 18F‑FDG PET/CT vs. 18F‑NaF PET/CT in breast cancer with bone metastases: An indirect comparative meta‑analysis

Breast cancer remains the leading cause of cancer-related death in women, with 5-year survival rates of as high as 90% for patients with early-stage breast cancer without metastasis, falling to 10% once bone metastases (BM) occur. Currently, there is no cure for breast cancer with BM. However, appropriate treatment can extend survival and improve patients' quality of life. Therefore, it is important to accurately evaluate the presence of BM in patients with breast cancer. The present meta-analysis evaluated the diagnostic performance of 18F-FDG and 18F-NaF as PET/CT tracers for breast cancer-associated BM. The present study aimed to compare the diagnostic performance of fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomographs (PET/CT) and 18F-sodium fluoride (18F-NaF) PET/CT in patients with breast cancer and BM. The PubMed and Embase databases were searched for English literature on the diagnostic performance of 18F-FDG PET/CT and 18F-NaF PET/CT for breast cancer BM, and two authors independently extracted data. All included studies presented data that could be used to construct a 2×2 contingency table. The methodological quality of the selected studies was assessed using QUADAS-2, and forest plots were generated based on the sensitivity and specificity of 18F-FDG PET/CT and 18F-NaF PET/CT in the diagnosis of BM associated with breast cancer. A total of 14 articles were identified, including eight on the analysis of 18F-FDG PET/CT, five on 18F-NaF PET/CT and one on both. The studies on 18F-FDG PET/CT and 18F-NaF PET/CT included 530 and 270 patients, respectively. The pooled sensitivities were 0.88 [95% confidence interval (95% CI), 0.76-0.94] for 18F-FDG PET/CT and 0.98 (95% CI, 0.92-1.00) for 18F-NaF PET/CT, and the pooled specificities were 0.99 (95% CI, 0.97-1.00) and 0.91 (95% CI: 0.76-0.97), respectively. The area under the summary receiver operating characteristic curve for both 18F-FDG PET/CT and 18F-NaF PET/CT was 0.99 (95% CI, 0.98-1.00). Lesion-based analysis using 18F-FDG PET/CT was performed for 909 lesions, with a sensitivity of 0.84 (95% CI, 0.67-1.00) and specificity of 1.00 (95% CI, 0.98-1.00). Compared with 18F-FDG PET/CT, 18F-NaF PET/CT showed higher sensitivity (98 vs. 88%) but lower specificity (91 vs. 99%), although the difference between methods was not statistically significant. In conclusion, the results of the present study indicated that 18F-NaF PET/CT and 18F-FDG PET/CT are both accurate methods for the detection of BM in patients with breast cancer, and have comparable diagnostic accuracy.

Whole-Body SPECT/CT: Protocol Variation and Technical Consideration-A Narrative Review

Introducing a hybrid imaging approach, such as single-photon emission computerized tomography with X-ray computed tomography (SPECT)/CT, improves diagnostic accuracy and patient management. The ongoing advancement of SPECT hardware and software has resulted in the clinical application of novel approaches. For example, whole-body SPECT/CT (WB-SPECT/CT) studies cover multiple consecutive bed positions, similar to positron emission tomography-computed tomography (PET/CT). WB-SPECT/CT proves to be a helpful tool for evaluating bone metastases (BM), reducing equivocal findings, and enhancing user confidence, displaying effective performance in contrast to planar bone scintigraphy (PBS). Consequently, it is increasingly utilized and might substitute PBS, which leads to new questions and issues concerning the acquisition protocol, patient imaging time, and workflow process. Therefore, this review highlights various aspects of WB-SPECT/CT acquisition protocols that need to be considered to help understand WB-SPECT/CT workflow processes and optimize imaging protocols.

Diagnostic Accuracy of PET with Different Radiotracers versus Bone Scintigraphy for Detecting Bone Metastases of Breast Cancer: A Systematic Review and a Meta-Analysis

Due to the importance of correct and timely diagnosis of bone metastases in advanced breast cancer (BrC), we performed a meta-analysis evaluating the diagnostic accuracy of [18F]FDG, or Na[18F]F PET, PET(/CT), and (/MRI) versus [99mTc]Tc-diphosphonates bone scintigraphy (BS). The PubMed, Embase, Scopus, and Scholar electronic databases were searched. The results of the selected studies were analyzed using pooled sensitivity and specificity, diagnostic odds ratio (DOR), positive-negative likelihood ratio (LR+-LR-), and summary receiver-operating characteristic (SROC) curves. Eleven studies including 753 BrC patients were included in the meta-analysis. The patient-based pooled values of sensitivity, specificity, and area under the SROC curve (AUC) for BS (with 95% confidence interval values) were 90% (86-93), 91% (87-94), and 0.93, respectively. These indices for [18F]FDG PET(/CT) were 92% (88-95), 99% (96-100), and 0.99, respectively, and for Na[18F]F PET(/CT) were 96% (90-99), 81% (72-88), and 0.99, respectively. BS has good diagnostic performance in detecting BrC bone metastases. However, due to the higher and balanced sensitivity and specificity of [18F]FDG PET(/CT) compared to BS and Na[18F]F PET(/CT), and its advantage in evaluating extra-skeletal lesions, [18F]FDG PET(/CT) should be the preferred multimodal imaging method for evaluating bone metastases of BrC, if available.

Intra-individual comparison of 18F-sodium fluoride PET-CT and 99mTc bone scintigraphy with SPECT in patients with prostate cancer or breast cancer at high risk for skeletal metastases (MITNEC-A1): a multicentre, phase 3 trial

BACKGROUND

Detection of skeletal metastases in patients with prostate cancer or breast cancer remains a major clinical challenge. We aimed to compare the diagnostic performance of ^99mTc-methylene diphosphonate (^99mTc-MDP) single-photon emission CT (SPECT) and ¹⁸F-sodium fluoride (¹⁸F-NaF) PET-CT for the detection of osseous metastases in patients with high-risk prostate or breast cancer.

METHODS

MITNEC-A1 was a prospective, multicentre, single-cohort, phase 3 trial conducted in ten hospitals across Canada. Patients aged 18 years or older with breast or prostate cancer with a WHO performance status of 0-2 and with high risk or clinical suspicion for bone metastasis, but without previously documented bone involvement, were eligible. ¹⁸F-NaF PET-CT and ^99mTc-MDP SPECT were done within 14 days of each other for each participant. Two independent reviewers interpreted each modality without knowledge of other imaging findings. The primary endpoint was the overall accuracy of ^99mTc-MDP SPECT and ¹⁸F-NaF PET-CT scans for the detection of bone metastases in the per-protocol population. A combination of histopathological, clinical, and imaging follow-up for up to 24 months was used as the reference standard to assess the imaging results. Safety was assessed in all enrolled participants. This study is registered with ClinicalTrials.gov, NCT01930812, and is complete.

FINDINGS

Between July 11, 2014, and March 3, 2017, 290 patients were screened, 288 of whom were enrolled (64 participants with breast cancer and 224 with prostate cancer). 261 participants underwent both ¹⁸F-NaF PET-CT and ^99mTc-MDP SPECT and completed the required follow-up for statistical analysis. Median follow-up was 735 days (IQR 727-750). Based on the reference methods used, 109 (42%) of 261 patients had bone metastases. In the patient-based analysis, ¹⁸F-NaF PET-CT was more accurate than ^99mTc-MDP SPECT (84·3% [95% CI 79·9-88·7] vs 77·4% [72·3-82·5], difference 6·9% [95% CI 1·3-12·5]; p=0·016). No adverse events were reported for the 288 patients recruited.

INTERPRETATION

¹⁸F-NaF has the potential to displace ^99mTc-MDP as the bone imaging radiopharmaceutical of choice in patients with high-risk prostate or breast cancer.

FUNDING

Canadian Institutes of Health Research.

Imaging of Bone Metastases in Breast Cancer

Bone metastases are a common site of spread in advanced breast cancer and responsible for morbidity and high health care costs. Imaging contributes to staging and response assessment of the skeleton and has been instrumental in guiding patient management for several decades. Historically this has been with radiographs, computed tomography and bone scans. More recently, molecular and hybrid imaging methods have undergone significant development, including the addition of single photon emission computed tomography/computed tomography to the bone scan, positron emission tomography, with bone-specific and tumor-specific tracers, and magnetic resonance imaging with complementary functional diffusion-weighted imaging. These have allowed different aspects of the abnormal biology associated with bone metastases to be explored. There is ability to interrogate the bone microenvironment with bone-specific tracers and cancer cell characteristics with tumor-specific methods that complement morphological appearances on computed tomography or magnetic resonance imaging. Alongside the advent of novel, more effective and nuanced therapies for bone metastases in breast cancer, there is accumulating evidence that the developments in imaging allow more sensitive and specific detection of bone metastases as well as more accurate and earlier assessment of treatment response leading to improvements in patient management.

Clinical Significance of Radiologically Detected Small Indeterminate Extra-Mammary Lesions in Breast Cancer Patients

Objective

Patients with breast cancer who have indeterminate extra-mammary lesions, for example in lung, liver or bone, without other metastatic lesions pose a clinical dilemma regarding subsequent management. This study aimed to investigate the prevalence, characteristics and outcomes of such lesions detected on initial staging imaging, and address the clinical significance of these incidental findings.

Materials and Methods

Medical records of patients with newly diagnosed breast cancer who underwent computed tomography scans and bone scintigraphy between January 1, 2015 and June 30, 2021 were reviewed. Patients with indeterminate extra-mammary lesions on imaging were included. Patients with obvious metastatic disease were excluded. Lesion characteristics, breast cancer staging, duration of follow-up and natural history of disease progression were analysed.

Results

The study included 52 patients with indeterminate lesions on pre-operative imaging. The median follow-up duration was 14 (range: 6-41) months. The most common site of occurrence of indeterminate lesions was the lung (60.9%) followed by the liver (26.1%). Forty-six had lesions that remained stable (88.5%), while six (11.5%) had progression to metastatic disease. Out of these six, only two (3.8%) developed metastasis in the same site as the original indeterminate lesion, whereas the remaining four developed metastases in other sites.

Conclusion

Patients with breast malignancy found to have indeterminate extra-mammary lesions without obvious distant metastasis on initial staging scans are associated with a small risk of subsequently developing metastatic disease. Although most of these lesions remain quiescent, surveillance imaging is recommended because a small but significant proportion of patients with such lesions eventually harbour actual metastatic disease.

Lesion detection in 18F-sodium fluoride bone imaging: a comparison of attenuation-corrected versus nonattenuation-corrected PET reconstructions from modern PET-CT systems

OBJECTIVES

An earlier study demonstrated comparable lesion detection between attenuation-corrected (AC) and nonattenuation-corrected (NAC) 18F-sodium fluoride (NaF) PET images, which is relevant for computed tomography (CT) radiation dose-saving. However, this finding may not be applicable to newer systems. The aim was to compare lesion detection between AC and NAC NaF PET images on modern PET-CT systems.

METHODS

One expert and one nonexpert observer retrospectively surveyed NaF PET data in 25 breast cancer patients. At both lesion and patient level, each observer classified bone abnormalities as malignant, equivocal or benign, from NAC and AC PET images in the absence of CT. Expert interpretation of NaF PET-CT with the review of all diagnostic imaging/pathology reports for at least the subsequent 12 months provided reference standard metastases status at the patient level. Two-tailed Wilcoxon signed-rank tests measured statistically significant differences in total lesion detection between AC and NAC PET. Quadratic-weighted kappa score measured agreement in patient metastases status between observers.

RESULTS

On a lesion-basis, AC PET images showed significantly more lesions than NAC for both the expert (122 versus 96; P = 0.002) and nonexpert (146 versus 132; P = 0.036) observers, with a large number of patients demonstrating disparity between AC and NAC images. For metastases status at the patient level without CT, NAC PET showed slightly better diagnostic accuracy than AC due to fewer false-positive results, as fewer lesions were identified.

CONCLUSION

AC PET data provided superior lesion detection to NAC in NaF bone examinations and are thus required for clinical interpretation.

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.

Imaging diagnosis of metastatic breast cancer

Numerous imaging modalities may be used for the staging of women with advanced breast cancer. Although bone scintigraphy and multiplanar-CT are the most frequently used tests, others including PET, MRI and hybrid scans are also utilised, with no specific recommendations of which test should be preferentially used. We review the evidence behind the imaging modalities that characterise metastases in breast cancer and to update the evidence on comparative imaging accuracy.

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.

Two decades of SPECT/CT - the coming of age of a technology: An updated review of literature evidence

PURPOSE

Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) was introduced as a hybrid SPECT/CT imaging modality two decades ago. The main advantage of SPECT/CT is the increased specificity achieved through a more precise localization and characterization of functional findings. The improved diagnostic accuracy is also associated with greater diagnostic confidence and better inter-specialty communication.

METHODS

This review presents a critical assessment of the relevant literature published so far on the role of SPECT/CT in a variety of clinical conditions. It also includes an update on the established evidence demonstrating both the advantages and limitations of this modality.

CONCLUSIONS

For the majority of applications, SPECT/CT should be a routine imaging technique, fully integrated into the clinical decision-making process, including oncology, endocrinology, orthopaedics, paediatrics, and cardiology. Large-scale prospective studies are lacking, however, on the use of SPECT/CT in certain clinical domains such as neurology and lung disorders. The review also presents data on the complementary role of SPECT/CT with other imaging modalities and a comparative analysis, where available.

Metastatic Seeding Attacks Bone Marrow, Not Bone: Rectifying Ongoing Misconceptions

Conventional modalities, such as bone scintigraphy, are commonly used to assess osseous abnormalities in skeletal metastasis. Fluorine-18 (¹⁸F)-sodium fluoride (NaF) PET similarly portrays osteoblastic activity but with improved spatial and contrast resolution and more accurate anatomic localization. However, these modalities rely on indirect evidence for tumor activity. PET imaging with ¹⁸F-fluorodeoxyglucose (FDG) and tumor-specific tracers may have an increased role by directly portraying the metabolic activity of cancer cells, which are often seeded in bone marrow and cause osseous disease after initial latency. This article describes the utility and limitations of these modalities in assessing skeletal metastases.

Prospective Study of Serial 18F-FDG PET and 18F-Fluoride PET to Predict Time to Skeletal-Related Events, Time to Progression, and Survival in Patients with Bone-Dominant Metastatic Breast Cancer

Assessing therapy response of breast cancer bone metastases is challenging. In retrospective studies, serial ¹⁸F-FDG PET was predictive of time to skeletal-related events (tSRE) and time to progression (TTP). ¹⁸F-NaF PET improves bone metastasis detection compared with bone scanning. We prospectively tested ¹⁸F-FDG PET and ¹⁸F-NaF PET to predict tSRE, TTP, and overall survival (OS) in patients with bone-dominant metastatic breast cancer (MBC). Methods: Patients with bone-dominant MBC were imaged with ¹⁸F-FDG PET and ¹⁸F-NaF PET before starting new therapy (scan1) and again at a range of times centered around approximately 4 mo later (scan2). Maximum standardized uptake value (SUV_max) and lean body mass adjusted standardized uptake (SUL_peak) were recorded for a single index lesion and up to 5 most dominant lesions for each scan. tSRE, TTP, and OS were assessed exclusive of the PET images. Univariate Cox regression was performed to test the association between clinical endpoints and ¹⁸F-FDG PET and ¹⁸F-NaF PET measures. mPERCIST (Modified PET Response Criteria in Solid Tumors) were also applied. Survival curves for mPERCIST compared response categories of complete response+partial response+stable disease versus progressive disease for tSRE, TTP, and OS. Results: Twenty-eight patients were evaluated. Higher ¹⁸F-FDG SUL_peak at scan2 predicted shorter time to tSRE (P = <0.001) and TTP (P = 0.044). Higher ¹⁸F-FDG SUV_max at scan2 predicted a shorter time to tSRE (P = <0.001). A multivariable model using ¹⁸F-FDG SUV_max of the index lesion at scan1 plus the difference in SUV_max of up to 5 lesions between scans was predictive for tSRE and TTP. Among 24 patients evaluable by ¹⁸F-FDG PET mPERCIST, tSRE and TTP were longer in responders (complete response, partial response, or stable disease) than in nonresponders (progressive disease) (P = 0.007, 0.028, respectively), with a trend toward improved survival (P = 0.1). An increase in the uptake between scans of up to 5 lesions by ¹⁸F-NaF PET was associated with longer OS (P = 0.027). Conclusion: Changes in ¹⁸F-FDG PET parameters during therapy are predictive of tSRE and TTP, but not OS. mPERCIST evaluation in bone lesions may be useful in assessing response to therapy and is worthy of evaluation in multicenter, prospective trials. Serial ¹⁸F-NaF PET was associated with OS but was not useful for predicting TTP or tSRE in bone-dominant MBC.

Intraindividual Comparison of 99mTc-Methylene Diphosphonate and Prostate-Specific Membrane Antigen Ligand 99mTc-MIP-1427 in Patients with Osseous Metastasized Prostate Cancer

The objective of this study was to evaluate the rate of detection of bone metastases obtained with the prostate-specific membrane antigen (PSMA)-targeting tracer ^99mTc-MIP-1427, as opposed to conventional bone scanning with ^99mTc-methylene diphosphonate (^99mTc-MDP), in a collective of patients with known advanced-stage osseous metastasized prostate cancer. Methods: Twenty-one patients with known metastatic disease were staged with both conventional bone scanning and PSMA ligand scintigraphy within a time frame of less than 10 d. Imaging included planar whole-body scanning and SPECT or SPECT/CT with 2 bed positions 3 h after injection of either 500-750 MBq of ^99mTc-MIP-1427 or 600-750 MBq of ^99mTc-MDP. Lesions were scored as typical tumor, equivocal (benign/malignant), or normal within a standard reporting schema divided into defined anatomic regions. Masked and consensus readings were performed with sequential unmasking: planar scans first, then SPECT/CT, the best evaluable comparator (including MRI), PET/CT, and follow-up examinations. Results: Eleven patients had PSMA-positive visceral metastases that were predictably not diagnosed with conventional bone scanning. However, SPECT/CT was required to distinguish between soft-tissue uptake and overlapping bone. Four patients had extensive ^99mTc-MDP-negative bone marrow lesions. Seven patients had superscan characteristics on bone scans; in contrast, the extent of red marrow involvement was more evident on PSMA scans. Only 3 patients had equivalent results on bone scans and PSMA scans. In 16 patients, more suspect lesions were detected with PSMA scanning than with bone scanning. In 2 patients (10%), a PSMA-negative tumor phenotype was present. Conclusion: PSMA scanning provided a clear advantage over bone scanning by reducing the number of equivocal findings in most patients. SPECT/CT was pivotal for differentiating bone metastases from extraosseous tumor lesions.

FDG avid breast cancer bone metastases silent on CT and scintigraphy: a case report with radiologic-pathologic correlation

Bone is the one of the most common distant metastatic sites in breast cancer. Routine initial breast cancer staging evaluation typically includes computed tomography (CT) and skeletal scintigraphy while 18F fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reserved for clinically high-risk cases. Since FDG PET-CT is not routinely performed during staging or surveillance evaluations, it is important for radiologists and clinicians to appreciate the limitations of bone metastasis detection on CT and scintigraphy. We present a case of bony metastases of invasive ductal carcinoma of the breast which were not detected on diagnostic CT or skeletal scintigraphy but were metabolically active on FDG PET-CT and evident on magnetic resonance. We provide a review of the literature and radiologic–pathologic correlation to explain the discordant imaging findings.