Tumour thrombosis and patterns of fluorine-18 fluorodeoxyglucose uptake: a pictorial review

Utility of metabolic ratios in the diagnosis of tumor Thrombus on F-18 FDG PET/CT

BACKGROUND

This study aims to predict quantitative parameter in form of metabolic ratios to diagnose tumor thrombus on F-18 FDG PET/CT.

METHODS

This is a retrospective study from Nuclear Medicine department at All India Institute of Medical Sciences, Jodhpur, India. Patients with malignancies who underwent F-18 FDG PET/CT in our department or images sent for review from February 2020 till September 2022 were screened for tumor thrombus that comprised study group. Control group had patients with malignancy and no imaging evidence of tumor thrombus. Metabolic activities (SUVmax) of tumor thrombus, liver and descending aorta in study group, and that of IVC, liver and descending aorta in control group were recorded. Metabolic ratios of tumor thrombus to liver (SUR L) and to aorta (SUR A) in study group, and IVC to liver (SUR* L) and to aorta (SUR*A) in control group were compared using receiver operator curves.

RESULTS

Of 2277 studies screened, 12 had tumor thrombus. The most common primary malignant site and vessel involved were lung and IVC respectively. The median (IQR) SUR L, SUR A, SUR* L and SUR* A were 2.5 (3.25), 2.6  (6), 0.67 (0.18) and 1 (0.17) respectively. Area under ROC for SUR L and SUR A were 0.983 [95% CI: 0.955-1.0] and 0.958 [95% CI: 0.90-1.0] respectively. The ideal cut-off for SUR L was 0.953 (sensitivity 92.3%, specificity 98.0%) and for SUR A was 1.42 (sensitivity 84.6%, specificity 98.0%).

CONCLUSION

Metabolic ratios of tumor thrombus to liver (SUR L) and aorta (SUR A) have good diagnostic performance and can be useful in studies with non-iodinated contrast CT.

The role of 18F-FDG PET/CT in distinguishing benign from malignant portal vein thrombosis

Background

Diagnosis of tumour thrombosis and differentiating it from benign thrombosis are essential for managing patients, planning treatments, and minimising unneeded anticoagulation therapy. Bland thrombi occur in both cancer and non-cancer patients; tumour thrombi and bland can coexist. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is useful in detecting and diagnosing tumour thrombosis and distinguishing it from benign thrombosis.

Objective

This study’s aim was to assess the value of 18F-FDG PET/CT in distinguishing benign from malignant portal vein thrombosis (PVT) in liver cirrhosis patients.

Methods

A retrospective study was conducted on 38 patients who had PVT that was histopathologically confirmed and performed 18F-FDG PET/CT scans at our institute between January 2021 and April 2022. For all patients, sociodemographic data, visual analysis, semiqualitative analysis (SUVmax value), and associated hepatic pathology were collected.

Results

The SUVmax values were significantly higher in the tumour thrombosis group (6.26 ± 1.94), compared to the bland thrombosis group (1.79 ± 0.69), (P < 0.001). The ROC curve of semiqualitative analysis (SUVmax) revealed a sensitivity of 96.3% and a specificity of 36.4%, at area under curve of 0.827 with SUVmax > 3.5 as the pathological cut-off value to distinguish tumour from bland thrombi.

Conclusions

By using semiqualitative analysis, 18F-FDG PET/CT is a valuable new technique in differentiating between neoplastic and bland PV thrombi, with optimal cut-off SUVmax value > 3.5 as a criterion.

Uncommon Testicular Germ Cell Tumor Thrombus in Azygos Vein Detected by FDG PET/CT

ABSTRACT

A 40-year old man admitted to the nuclear medicine department to undergo PET/CT for restaging of known testicular germ cell tumor. The patient had a history of orchiectomy for left testis and left nephrectomy with retroperitoneal lymph node dissection. Histopathology revealed testicular germ cell tumor. During the follow-up period, there is a rapidly expanding mass in posterior mediastinum. PET reveals increased FDG activity in the azygos vein. Contrast-enhanced CT of the thorax showed distended azygos vein with heterogeneously enhancing thrombus and peripheral fat stranding. Findings are consistent with azygos vein tumor thrombosis related to testicular germ cell tumor.

Tumor thrombus: ancillary findings on FDG PET/CT in an oncologic population

PURPOSE

Thrombosis in cancer may manifest itself as venous thromboembolic disease or tumor thrombosis (TT). We present our experience with incidentally detected TT on FDG PET/CT in 21 oncologic patients.

PATIENTS AND METHODS

We retrospectively reviewed all FDG PET/CT examinations during a 5-year period at the Army Hospital Research and Referral in New Delhi, India, and included all oncology cases with FDG-avid thrombosis in the report. The diagnosis of TT was based on FDG-avid solid masses inside the vessels in patients with known malignancy. The SUVmax was calculated.

RESULTS

Twenty-one patients were included; the most common malignancies were renal cell carcinoma (n=6), hepatocellular carcinoma (n=3), and lung cancer (n=3). Indication for the scan was initial staging (n=15) and suspected recurrence (n=6). Several vessels were affected, the most common was the inferior vena cava (n=14), but most other major branches of the venous vasculature was represented, and some patients had thrombi in several vessels. FDG uptake was linear in 7 patients, linear with a dilated vessel in 6 patients, and focal in 7 patients. The mean SUVmax of the primary tumors was 10.3 (range, 2.6-31.2; median, 6.9), and the mean SUVmax of the thrombi was 7.85 (range, 1.7-23.2; median, 6.1). All but 2 patients had additional FDG-avid foci besides the thrombus.

CONCLUSIONS

This study supports results from other smaller studies regarding the usefulness of FDG PET/CT in TT and corroborates the hypothesis that the SUVmax and the patterns of FDG uptake can be helpful for differentiating BT from TT in oncological patients.

The role of 18F-FDG PET/CT in differentiating malignant from benign portal vein thrombosis

AIMS

In this retrospective study, we evaluated the role of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in differentiating malignant from benign portal vein thrombosis (PVT) in patients with known malignant tumors.

METHODS

Seventy-two patients with histologically or clinically confirmed PVT and who had undergone (18)F-FDG PET/CT were included. Visual and semiquantitative analyses of PET/CT scans were performed. Metabolic activity was measured using the maximum standardized uptake value (SUVmax) by drawing the region of interest at the site of thrombosis. Receiver operating characteristic analysis was conducted to identify the optimal cutoff of SUVmax for detecting neoplastic thrombosis. Malignancy was defined using the following criteria: (1) visual analysis and (2) SUVmax >3.35. PET/CT results were confirmed with histopathological results and clinical and imaging follow-up.

RESULTS

The SUVmax of tumor thrombus (6.37 ± 2.67) was significantly higher than that of bland thrombus (2.87 ± 1.47; P < 0.01). The sensitivities, specificities, and accuracies for the two criteria were 91.5 % and 93.6; 64.0 and 80.0 %; and 81.9 % and 88.9 %, respectively.

CONCLUSION

(18)F-FDG PET/CT is a promising new method for distinguishing between portal venous neoplastic thrombosis and bland thrombosis using semiquantitative analysis, with the optimal cutoff value of SUVmax >3.35 as a criterion.

Incidental diagnosis of tumor thrombosis on FDG PET/CT imaging

OBJECTIVE

Clinical data are presented on patients with tumor thrombosis (TT) incidentally detected on FDG PET/CT imaging, as well as determining its prevalence and metabolic characteristics.

MATERIALS AND METHODS

Out of 12,500 consecutive PET/CT examinations of patients with malignancy, the PET/CT images of 15 patients with TT as an incidental finding were retrospectively investigated. A visual and semiquantitative analyses was performed on the PET/CT scans. An evaluation was made of the pattern of FDG uptake in the involved vessel as linear or focal via visual analyses. For the semiquantitative analyses, the metabolic activity was measured using SUVmax by drawing the region of interest at the site of the thrombosis and tumor (if any).

RESULTS

The prevalence of occult TT was 0.12%. A total of 15 patients had various malignancies including renal (1 patient), liver (4), pancreas (2), stomach (1), colon (1), non-Hodgkin lymphoma (1), leiomyosarcoma (1), endometrial (1), ovarian (1), malign melanoma (1) and parotid (1). Nineteen vessels with TT were identified in 15 patients; three patients had more than one vessel. Various vessels were affected; the most common was the inferior vena cava (n=7) followed by the portal (n=5), renal (n=3), splenic (n=1), jugular (n=1), common iliac (n=1) and ovarian vein (n=1). The FDG uptake pattern was linear in 12 and focal in 3 patients. The mean SUVmax values in the TT and primary tumors were 8.40±4.56 and 13.77±6.80, respectively.

CONCLUSION

Occult TT from various malignancies and locations was found incidentally in 0.12% of patients. Interesting cases with malign melanoma and parotid carcinoma and with TT in ovarian vein were first described by FDG PET/CT. Based on the linear FDG uptake pattern and high SUVmax value, PET/CT may accurately detect occult TT, help with the assessment of treatment response, contribute to correct tumor staging, and provide additional information on the survival rates of oncology patients.

Migrating tumor thrombus trapped within the greenfield filter of the inferior vena cava and depicted by FDG PET/CT

A 72-year-old woman with leiomyosarcoma of the left thigh underwent a whole-body FDG PET/CT for staging, which demonstrated a large FDG-avid tumor in the left thigh and tumor thrombosis involving the profunda femoris artery/vein and superior femoral vein. A Greenfield filter was placed in the inferior vena cava before the radical resection of the tumor and thrombosis. Postoperative PET/CT showed an FDG-avid embolus trapped within the solid apical cap of the filter in the inferior vena cava. It was unknown if the tumor embolus migrated to the inferior vena cava before or during the surgical procedure of radical resection.