Israel Medical Association Journal

Fever of unknown origin (FUO) is defined as the repeated occurrence of elevated body temperature above 38.3°C (101°F) lasting for at least 3 weeks with no clear diagnosis despite a thorough investigation of more than one-week duration. FUO cases could be categorized into three major etiologies: infectious, neoplastic, and systemic inflammatory. Despite novel diagnostic modalities, clinicians still encounter a significant number of unresolved FUO cases, accounting for as many as 50% of cases [1]. Prolonged futile FUO investigations may be a source of frustration for many clinicians [2]. We described a unique cause for FUO that shares the complexity of the diagnostic workup and emphasizes the importance of ¹⁸F-fluorodeoxyglucose positron-emission tomography/computed tomography (PET/CT) modality in the process of investigating FUO.

Background: Multiple myeloma (MM) affects the long bones in 25% of patients. The advent of positron-emission tomography/computed tomography (PET/CT) scanners offers the possibility of both metabolic and radiographic information and may help determine fracture risk. To the best of our knowledge, no published study correlates these two factors with long bone fractures.

Objective: To evaluate the impact of PET/CT on fracture risk assessment in multiple myeloma patients.

Methods: We identified all bone marrow biopsy proven multiple myeloma patients from 1 January 2010 to 31 January 2015 at a single institution. We prospectively followed patients with long bone lesions using PET/CT scan images.

Results: We identified 119 patients (59 males/60 females) with 256 long bone lesions. Mean age at diagnosis was 58 years. The majority of lesions were in the femur (n=150, 59%) and humerus (n=84, 33%); 13 lesions in 10 patients (8%) required surgery for impending (n=4) or actual fracture (n=9). Higher median SUVmax was measured for those with cortical involvement (8.05, range 0–50.8) vs. no involvement (5.0, range 2.1–18.1). SUVmax was found to be a predictor of cortical involvement (odds ratio = 1.17, P = 0.026). No significant correlation was found between SUVmax and pain or fracture (P = 0.43).

Conclusions: Improved medical treatment resulted improvement in 8% of patients with an actual or impending fracture. The orthopedic surgeons commonly use the Mirels classification for long bone fracture prediction. Adding PET/CT imaging to study in myeloma long bone lesions did not predict fracture risk directly but suggested it indirectly by cortical erosion.

Background: Implant-related spinal infections are a surgical complication associated with high morbidity. Due to infection, hardware removal may be necessary, which could lead to pseudarthrosis and the loss of stability and alignment.

Objectives: To evaluate the accuracy and diagnostic value of ¹⁸F-fluorodeoxyglucose positron-emission tomography/computed tomography (¹⁸F-FDG PET/CT) in the workup of patients with suspected implant-related infections of the spine and to assess the clinical impact of PET/CT results on the management of these infections.

Methods: The study included nine consecutive patients with a history of spinal surgery who underwent PET/CT for evaluation of suspected spinal implant related infection. All imaging studies were performed between January 2011 and December 2013. All ¹⁸F-FDG PET/CT scans were performed on an 8 slice PET/CT following an ¹⁸F-FDG injection. Images were scored both visually and semi-quantitatively by a radiology expert. Results were compared to additional imaging studies when available, which were correlated to clinical and bacteriological findings allowing calculation of sensitivity, specificity and accuracy.

Results: Among the patients, five experienced hardware-related spinal infection. ¹⁸F-FDG PET/CT sensitivity was 80%, specificity 100%, and accuracy 88.9%. One scan produced a false negative; however, a second PET/CT scan revealed an infection.

Conclusions: PET/CT was found to be valuable for the diagnosis of postoperative hardware-related spinal infection, especially when other imaging modalities were uninformative or inconclusive. As such, PET/CT could be useful for management of infection treatment.

Background: Ga-prostate-specific membrane antigen positron emission tomography/computerized tomography (Ga-PSMA PET/CT) is part of the initial workup of patients with intermediate and high-risk prostate cancer provided by the Israeli national health services.

Objectives: To assess the incidence of metastatic spread in consecutive patients with newly diagnosed cancer, and the potential added value of Ga-PSMA PET/CT to the staging imaging algorithm.

Methods: Patients with newly diagnosed intermediate- and high-risk prostate cancer were referred for initial staging by Ga-PSMA PET/CT between May 2016 and April 2017. Blood prostate-specific antigen (PSA) levels, clinical history, imaging reports and histopathological reports (including Gleason scores) were obtained. Maximal standardized uptake values (SUVmax) were determined for the primary lesions detected within the prostate.

Results: The study included 137 consecutive patients with intermediate- and high-risk disease who underwent Ga-PSMA PET/CT staging. Of these, 75 had Ga-PSMA uptake in both prostate lobes, 57 had unilateral uptake, and 5 patients had no uptake. SUVmax in the primary tumor correlated significantly with PSA levels. Thirty-five patients had increased uptake compatible with metastatic disease involving lymph nodes, bone, and viscera. Twenty-seven patients had available bone scintigraphy results: 18 (69%) of their 26 bone metastases detected by Ga-PSMA PET/CT were missed on bone scintigraphy.

Conclusions: Ga-PSMA PET/CT shows promise as a sole whole-body imaging modality for assessing the presence of soft tissue and bone metastases in the setting of prostate cancer.

Background: Evidence has been emerging that Helicobacter pylori may also impact colorectal cancer (CRC). Positron emission tomography/computed tomography (PET/CT) imaging can predict overall survival in CRC patients.

Objectives: To determine a possible association between H. pylori seropositivity and all-cause mortality among CRC patients evaluated by PET/CT scans.

Methods: This prospective cohort study was comprised of 110 consecutive CRC patients who had undergone a PET/CT evaluation in a tertiary academic medical center. Data included demographics, body mass index (BMI), tumor node metastasis stage at diagnosis, treatment, time from diagnosis to PET/CT, and PET/CT findings. All patients were tested for anti-H. pylori immunoglobulin G (IgG) antibodies and followed for 36 months from the day of the PET/CT scan. Mortality was documented. Univariate and multivariate Cox regression was used to estimate the hazard ratio (HR) of H. pylori serological status.

Results: During the follow-up period, of the 110 CRC patients 41 (37.3%) died and 69 (62.7%) survived. Of the 41 patients, 26 (63.4%) were H. pylori seropositive and 15 (36.6%) were seronegative. Multivariate analysis showed that H. pylori seropositivity was associated with increased mortality (HR 3.46, 95% confidence interval 1.63–7.32), stage IV at diagnosis, metastatic disease found on PET/CT, longer time from diagnosis to PET/CT, lower BMI, and older age.

Conclusions: Our findings suggest that H. pylori infection may be a risk factor for all-cause mortality among CRC patients who are evaluated by PET/CT. Multicenter studies with larger patient groups are needed to confirm our findings.

Background: Pulmonary infiltrates (PIs) detected in patients with non-Hodgkin lymphoma (NHL) may present a diagnostic challenge due to their wide differential diagnosis, including infection, pulmonary lymphoma and immunochemotherapy-associated pulmonary toxicity.

Objectives: To characterize therapy-associated PIs by positron emission tomography/computed tomography (PET/CT) imaging.

Methods: We conducted a historical analysis of fluorodeoxyglucose-PET/CT (¹⁸F-FDG-PET/CT) PIs in NHL patients treated with combined immunochemotherapy including rituximab. Incidence of PIs, radiological features, patients’ characteristics, underlying NHL type, rituximab/chemotherapy dosing schedules, and symptoms were recorded. Therapy-associated PIs were defined as new or worsening PIs appearing after treatment onset, without evidence of active pulmonary lymphoma or infection.

Results: Among 80 patients who met the pre-specified criteria, therapy-associated PIs were identified in 17 (21%), 6 of whom had accompanying symptoms. Increased FDG uptake was observed in nine, and PI resolution in six. The incidence of PIs was higher in females and in patients with aggressive lymphoma, at advanced stages, and in those who had received treatment consisting of a combination of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone every 14 days (R-CHOP-14).

Conclusions: This characterization of therapy-associated PIs may support the clinician managing NHL patients. Further prospective studies are needed to establish the role of each therapeutic component and the natural history of this phenomenon.

Background: Despite the lack of clinical studies supporting the use of routine surveillance FDG-positron emission tomography (PET) in patients with diffuse large B cell lymphoma (DLBCL) who achieved remission, many centers still use this strategy, especially in high risk patients. Surveillance FDG-PET computed tomography (CT) is associated with a high false positive (FP) rate in DLBCL patients. 

Objectives: To investigate whether use of specific CT measurements could improve the positive predictive value (PPV) of surveillance FDG-PET/CT. 

Methods: This retrospective study included DLBCL patients treated with CHOP or R-CHOP who achieved complete remission and had at least one positive surveillance PET. CT-derived features of PET-positive sites, including long and short diameters and presence of calcification and fatty hilum within lymph nodes, were assessed. Relapse was confirmed by biopsy or consecutive imaging. The FP rate and PPV of surveillance PET evaluated with/without CT-derived measurements were compared. 

Results: Seventy surveillance FDG-PET/CT scans performed in 53 patients were interpreted as positive for relapse. Of these studies 25 (36%) were defined as true-positive (TP) and 45 (64%) as FP. Multivariate analysis found long or short axis measuring ≥ 1.5 and ≥ 1.0 cm, respectively, in PET-positive sites, International Prognostic Index (IPI) ≥ 2, lack of prior rituximab therapy and FDG uptake in a previously involved site, to be independent predictors of true positive surveillance PET (odds ratio 5.4, 6.89, 6.6, 4.9, P < 0.05 for all). 

Conclusion: PPV of surveillance PET/CT may be improved by its use in selected high risk DLBCL patients and combined assessment of PET and CT findings.

 

Background: Venous thromboembolism is a well-recognized and relatively frequent complication of malignancy, whereas tumor thrombosis is a rare complication of solid cancers. Correct diagnosis of tumor thrombosis and its differentiation from VTE[1] can alter patient management and prevent unnecessary long-term anticoagulation treatment.

Objectives: To evaluate the contribution of 18F-fluorodeoxyglucose positron emission tomography/computed tomography to the diagnosis of tumor thrombosis and its differentiation from VTE.

Methods: PET/CT[2] scans from 11 patients with suspected tumor thrombosis were retrospectively evaluated. Suspicion arose from positive PET/CT in eight cases, or from findings on contrast-enhanced CT in three patients. Criteria for positivity of PET/CT included increased focal or linear uptake of 18F-FDG[3] in the involved vessel. Findings were categorized as PET/CT positive, or PET/CT negative and compared to contrast-enhanced or ultrasound Doppler, pathology where available, and clinical follow-up.

Results: Eight occult tumor thromboses were identified by PET/CT-positive scans. Underlying pathologies included pancreatic, colorectal, renal cell, and head-neck squamous cell carcinoma, as well as lymphoma (4 patients). Three thrombotic lesions on contrast-enhanced CT were PET/CT negative, due to VTE (2 patients) and leiomyomatosis. Accuracy of PET/CT to differentiate between tumor thrombosis and benign VTE was 100% in this small study.

Conclusions: Contrast-enhanced CT defines the extent of thrombotic lesions, while the functional information from PET/CT characterizes the lesions. It appears that PET/CT may be helpful in the diagnosis of occult tumor thrombosis and its differentiation from VTE.