Assessment of atherosclerosis in oncologic patients using ¹⁸F-fluoride PET/CT

Sodium fluoride in cardiovascular disorders: A systematic review

BACKGROUND

18-Fluorine sodium fluoride is a well-known radiotracer used for bone metastasis diagnosis. Its uptake correlation with cardiovascular (CV) risk was primarily suggested in oncological patients. Moreover, as a specific marker of microcalcification, it seems to correlate with CV disease progression and plaque instability.

METHODS AND RESULTS

Our purpose was to systematically review clinical studies that characterized the use of this marker in CV conditions. In atherosclerosis, most studies report a positive correlation with the burden of CV risk factors and vascular calcification. A higher uptake was found in culprit plaques/rupture sites in coronary and carotid arteries and it was also linked to high-risk features in histology and intravascular imaging analysis of the plaques. In aortic stenosis, this tracer displayed an increasing uptake with disease severity.

CONCLUSIONS

Sodium fluoride positron emission tomography is a promising non-invasive technique to identify high-risk plaques, which sets ground to a potential use of this tracer in evaluating atherosclerotic disease progression and degenerative changes in aortic valve stenosis. Nevertheless, there is a need for further prospective evidence that demonstrates this technique's value in predicting clinical events, adjusting treatment strategies, and improving patient outcomes.

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.

18FDG PET/CT & arterial inflammation: predicting cardiovascular events in lung cancer

BACKGROUND

18F-FDG PET/CT predicts cardiovascular disease. To analyze the predictive value of cardiovascular events from inflammation and arterial calcification in patients who underwent an 18F-FDG PET/CT for lung cancer.

METHODS

A retrospective study of 274 patients with primary lung neoplasia. We determined: (i) TBR (target-to-background ratio), and (ii) the calcium score, at eight common arterial segments. We took as arteriosclerosis, a TBR ≥1.6 and ≥15 Calcium Score sum. We registered cardiovascular risk factors, comorbidities, histology, stage, treatment, status at the last clinical review, cause of death and cardiovascular event during the follow-up.

RESULTS

The territory presenting the greatest uptake of 18F-FDG, was the thoracic aorta with an average of 1.77 (± 0.27 TBR) in the aortic arch, while the greatest degree of calcification was obtained in the abdominal aorta (52% with a Calcium Score ≥ 3). 24% of the patients presented a sum Calcium Score ≥15, and 17% a TBR ≥1.6. Patients with high TBR, (17%), had not a higher frequency of cardiovascular comorbidities beforehand, nor did they in the follow-up. However, those with a sum Calcium Score ≥15 (24%), were older, had more cardiovascular risk factors and ischemic events during follow-up. The calcium score, but not the TBR, predicted the emergence of a cardiovascular event (HR 4.9 IC95% 2.1-9.1, P < 0.05).

CONCLUSION

In our cohort, a high Calcium Score was an independent predictor for developing cardiovascular events.

Metabolic Alterations, Aggressive Hormone-Naïve Prostate Cancer and Cardiovascular Disease: A Complex Relationship

Background: Epidemiological studies suggest a possible relationship between metabolic alterations, cardiovascular disease and aggressive prostate cancer, however, no clear consensus has been reached. Objective: The aim of the study was to analyze the recent literature and summarize our experience on the association between metabolic disorders, aggressive hormone-naïve prostate cancer and cardiovascular disease. Method: We identified relevant papers by searching in electronic databases such as Scopus, Life Science Journals, and Index Medicus/Medline. Moreover, we showed our experience on the reciprocal relationship between metabolic alterations and aggressive prostate cancer, without the influence of hormone therapy, as well the role of coronary and carotid vasculopathy in advanced prostate carcinoma. Results: Prostate cancer cells have an altered metabolic homeostatic control linked to an increased aggressivity and cancer mortality. The absence of discrimination of risk factors as obesity, systemic arterial hypertension, diabetes mellitus, dyslipidemia and inaccurate selection of vascular diseases as coronary and carotid damage at initial diagnosis of prostate cancer could explain the opposite results in the literature. Systemic inflammation and oxidative stress associated with metabolic alterations and cardiovascular disease can also contribute to prostate cancer progression and increased tumor aggressivity. Conclusions: Metabolic alterations and cardiovascular disease influence aggressive and metastatic prostate cancer. Therefore, a careful evaluation of obesity, diabetes mellitus, dyslipidemia, systemic arterial hypertension, together with a careful evaluation of cardiovascular status, in particular coronary and carotid vascular disease, should be carried out after an initial diagnosis of prostatic carcinoma.

Differences in sodium fluoride-18 uptake in the normal skeleton depending on the location and characteristics of the bone

AIM

The aim of this study was to evaluate the normal distribution of sodium fluoride-18 (NaF-18) and to clarify the differences in uptake according to location and the type of the bone using positron emission tomography (PET) / computed tomography (CT).

METHODS

We retrospectively reviewed NaF-18 PET/CT images from 30 patients with hip joint disorders. PET/CT scans were performed 40 min after injection of approximately 185 MBq of NaF-18. To evaluate the relationship between the distribution of NaF-18 uptake and bone density, we compared the maximum standardised uptake values (SUV_max) on PET and the Hounsfield Units (HUs) on CT of the lumbar vertebra, ilium, and proximal and distal femurs. Regions of interests were defined both outside and inside the cortical bone to measure whole bone and cancellous bone only, respectively.

RESULTS

The distribution of NaF-18 differed according to the skeletal site. The lumbar vertebra showed the highest SUV_max for both whole bone and cancellous bone, followed by the ilium, proximal femur, and distal femur. The bones differed significantly in SUV_max. The distal femur showed the highest HU, followed by the proximal femur, ilium, and vertebra. Profile curve analyses demonstrated that the cancellous bones showed higher SUV_max and lower HU than the cortical bones.

CONCLUSIONS

Our results demonstrate the difference in NaF-18 uptake between cancellous and cortical bones, which may explain differences in uptake by location. NaF-18 uptake does not appear to be strongly correlated with bone density, but rather with bone turnover and blood flow.

Future imaging of atherosclerosis: molecular imaging of coronary atherosclerosis with (18)F positron emission tomography

Atherosclerosis is characterized by the formation of complex atheroma lesions (plaques) in arteries that pose risk by their flow-limiting nature and propensity for rupture and thrombotic occlusion. It develops in the context of disturbances to lipid metabolism and immune response, with inflammation underpinning all stages of plaque formation, progression and rupture. As the primary disease process responsible for myocardial infarction, stroke and peripheral vascular disease, atherosclerosis is a leading cause of morbidity and mortality on a global scale. A precise understanding of its pathogenic mechanisms is therefore critically important. Integral to this is the role of vascular wall imaging. Over recent years, the rapidly evolving field of molecular imaging has begun to revolutionize our ability to image beyond just the anatomical substrate of vascular disease, and more dynamically assess its pathobiology. Nuclear imaging by positron emission tomography (PET) can target specific molecular and biological pathways involved in atherosclerosis, with the application of (18)Fluoride PET imaging being widely studied for its potential to identify plaques that are vulnerable or high risk. In this review, we discuss the emergence of (18)Fluoride PET as a promising modality for the assessment of coronary atherosclerosis, focusing on the strengths and limitations of the two main radionuclide tracers that have been investigated to date: 2-deoxy-2-((18)F)fluoro-D-glucose ((18)F-FDG) and sodium (18)F-fluoride ((18)F-NaF).

Sodium 18F-fluoride PET/CT of bone, joint, and other disorders

The use of (18)F-sodium fluoride ((18)F-NaF) with PET/CT is increasing. This resurgence of an old tracer has been fueled by several factors including superior diagnostic performance over standard (99m)Tc-based bone scintigraphy, growth in the availability of PET/CT imaging systems, increase in the number of regional commercial distribution centers for PET radiotracers, the recent concerns about potential recurring shortages with (99m)Tc-based radiotracers, and the recent decision by the Centers for Medicare and Medicaid Services to reimburse for (18)F-NaF PET/CT for evaluation of patients with known or suspected bone metastases through the National Oncologic PET Registry. The major goal of this article is to review the current evidence on the diagnostic utility of (18)F-NaF in the imaging assessment of the bone and joint in a variety of clinical conditions.