The incremental value of <Superscript>18</Superscript>F-FDG PET/CT in paediatric malignancies

PURPOSE: (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) imaging has been used in the assessment of paediatric malignancies. PET/CT increases the diagnostic accuracy in adult cancer patients. The present study assesses the incremental value of FDG PET/CT in paediatric malignancies. METHODS: A total of 118 (18)FDG PET/CT studies of 46 paediatric patients were reviewed retrospectively. PET and PET/CT results were classified as malignant, equivocal or benign, compared on a site- and study-based analysis, and also compared with the clinical outcome. RESULTS: Three hundred and twenty-four sites of increased FDG uptake were detected. Discordant PET and PET/CT interpretations were found in 97 sites (30%) in 27 studies (22%). PET yielded a statistically significant higher proportion of equivocal and a lower proportion of benign lesion and study results (p<0.001) than PET/CT. With PET there were 153 benign (47%), 84 (26%) equivocal and 87 (27%) malignant sites, while PET/CT detected 226 benign (70%), 10 (3%) equivocal and 88 (27%) malignant lesions. PET/CT mainly improved the characterisation of uptake in brown fat (39%), bowel (17%), muscle (8%) and thymus (7%). The study-based analysis showed that 17 equivocal and seven positive PET studies (20%) were interpreted as benign on PET/CT, while three equivocal studies were interpreted as malignant. The study-based sensitivity and specificity of PET/CT were 92% and 78% respectively. CONCLUSION: PET/CT significantly improved the characterisation of abnormal (18)FDG foci in children with cancer, mainly by excluding the presence of active malignancy in sites of increased tracer activity.     

Diagnostic value of <Superscript>18</Superscript>F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis

Purpose To retrospectively evaluate the diagnostic value of ¹⁸F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis. Methods Thirty-three partial body ¹⁸F-FDG PET/CT scans were performed in 33 patients with trauma suspected of having chronic osteomyelitis. In 10 and 23 patients, infection was suspected in the axial and appendicular skeleton, respectively. In 18 patients, PET/CT was performed in the presence of metallic implants. Histopathology or bacteriological culture was used as the standard of reference. For statistical analysis, sensitivity, specificity and accuracy were calculated in relation to findings of the reference standard. Results Of 33 PET/CT scans, 17 were true positive, 13 true negative, two false positive and one false negative. Eighteen patients had chronic osteomyelitis and 15 had no osseous infection according to the reference standard. Sensitivity, specificity and accuracy for ¹⁸F-FDG PET/CT was 94%, 87% and 91% for the whole group, 88%, 100% and 90% for the axial skeleton and 100%, 85% and 91% for the appendicular skeleton, respectively. Conclusion ¹⁸F-FDG PET/CT is a highly sensitive and specific method for the evaluation of chronic infection in the axial and appendicular skeleton in patients with trauma. PET/CT allows precise anatomical localisation and characterisation of the infectious focus and demonstrates the extent of chronic osteomyelitis with a high degree of accuracy.     

The impact of <Superscript>18</Superscript>F-FDG PET/CT in patients with liver metastases

Purpose The aim of this study was to assess the performance of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) versus dedicated contrast-enhanced CT (CECT) in the detection of metastatic liver disease. Methods All patients that presented to our Institution with suspected metastatic liver disease who underwent ¹⁸F-FDG PET/CT and CECT within 6 weeks of each other, were retrospectively analyzed, covering a 5-year period. One hundred and thirty-one patients (67 men, 64 women; mean age 62) were identified. Seventy-five had colorectal carcinoma and 56 had other malignancies. The performance of CECT and that of ¹⁸F-FDG-PET/CT in detecting liver metastases were compared. The ability of each to detect local recurrence, extrahepatic metastases and to alter patient management was recorded. The final diagnosis was based on histology, clinical and radiological follow-up (mean 23 months). Results In detecting hepatic metastases, ¹⁸F-FDG-PET/CT yielded 96% sensitivity and 75% specificity, whilst CECT showed 88% sensitivity and 25% specificity. ¹⁸F-FDG-PET/CT and CECT were concordant in 102 out of 131 patients (78%). In the colorectal group ¹⁸F-FDG-PET/CT showed 94% sensitivity and 75% specificity, whilst CECT had 91% sensitivity and 25% specificity. In the noncolorectal group ¹⁸F-FDG-PET/CT showed 98% sensitivity and 75% specificity whilst CECT had 85% sensitivity and 25% specificity. Overall, ¹⁸F-FDG-PET/CT altered patient management over CECT in 25% of patients. CECT did not alter patient management over ¹⁸F-FDG-PET/CT alone in any patients. Conclusion ¹⁸F-FDG-PET/CT performed better in detecting metastatic liver disease than CECT in both colorectal and noncolorectal malignancies, and frequently altered patient management. The future role of CECT in these patients may need to be re-evaluated to avoid potentially unnecessary duplication of investigation where ¹⁸F-PET/CT is readily available. Authors stated no financial relationship to disclose     

Prospective comparison of combined <Superscript>18</Superscript>F-FDG and <Superscript>18</Superscript>F-NaF PET/CT vs. <Superscript>18</Superscript>F-FDG PET/CT imaging for detection of malignancy

Purpose  

Typically, ¹⁸F-FDG PET/CT and ¹⁸F-NaF PET/CT scans are done as two separate studies on different days to allow sufficient time for the radiopharmaceutical from the first study to decay. This is inconvenient for the patients and exposes them to two doses of radiation from the CT component of the examinations. In the current study, we compared the clinical usefulness of a combined ¹⁸F-FDG/¹⁸F-NaF PET/CT scan with that of a separate ¹⁸F-FDG-only PET/CT scan.     

The management of pyothorax-associated lymphoma using <Superscript>18</Superscript>F-FDG PET/CT

Objective  

Pyothorax-associated lymphoma (PAL) is a rare form of lymphoma and its management on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) combined computed tomography (CT) has not been well reported. The purpose of this study was to evaluate the usefulness of FDG PET/CT in patients with PAL.     

Diagnostic value of combining <Superscript>11</Superscript>C-choline and <Superscript>18</Superscript>F-FDG PET/CT in hepatocellular carcinoma

Purpose

In this prospective study, our goal was to emphasize the diagnostic value of combining ¹¹C-choline and ¹⁸F-FDG PET/CT for hepatocellular carcinoma (HCC) in patients with chronic liver disease.

Methods

Thirty-three consecutive patients were enrolled. All patients were suspected to have HCC based on CT and/or MRI imaging. A final diagnosis was obtained by histopathological examination or by imaging alone according to American Association for the Study of Liver Disease criteria. All patients underwent PET/CT with both tracers within a median of 5 days. All lesions showing higher tracer uptake than normal liver were considered positive for HCC. We examined how tracer uptake was related to biological (serum α-fetoprotein levels) and pathological (differentiation status, peritumoral capsule and vascular invasion) prognostic markers of HCC, as well as clinical observations at 6 months (recurrence and death).

Results

Twenty-eight HCC, four cholangiocarcinomas and one adenoma were diagnosed. In the HCC patients, the sensitivity of ¹¹C-choline, ¹⁸F-FDG and combined ¹¹C-choline and ¹⁸F-FDG PET/CT for the detection of HCC was 75 %, 36 % and 93 %, respectively. Serum α-fetoprotein levels >200 ng/ml were more frequent among patients with ¹⁸F-FDG-positive lesions than those with ¹⁸F-FDG-negative lesions (p?<?0.05). Early recurrence (n=2) or early death (n=5) occurred more frequently in patients with ¹⁸F-FDG-positive lesions than in those with ¹⁸F-FDG-negative lesions (p?<?0.05).

Conclusion

The combined use of ¹¹C-choline and ¹⁸F-FDG PET/CT detected HCC with high sensitivity. This approach appears to be of potential prognostic value and may facilitate the selection of patients for surgical resection or liver transplantation.

     

Influence of <Superscript>18</Superscript>F-FDG PET/CT on therapy management in patients with stage III/IV malignant melanoma

Purpose

To evaluate the influence of ¹⁸F-FDG PET/CT in comparison to CT alone on treatment decisions in patients with advanced melanoma and to analyse the 5-year survival data in comparison to literature data.

Methods

Therapy management in 64 consecutive patients (primary staging n?=?52; surveillance n?=?12) with stage III/IV melanoma who underwent ¹⁸F-FDG PET/CT between 2004 and 2005 in our department was retrospectively analysed. Treatment decisions were made by two dermatooncologists for each patient twice, first based on the CT results and then based on the PET/CT results. Therapy changes based on the PET/CT results were classified as “major” (e.g. change from metastasectomy to systemic therapy) or “minor” (e.g. change from first to second line chemotherapy). The 5-year survival data of different patient cohorts were calculated.

Results

In the 52 patients in the primary staging group, the results of ¹⁸F-FDG PET/CT led to therapy change in 59 % and a major therapy change in 52 %. ¹⁸F-FDG PET/CT led to the avoidance of futile operations in 13 patients with suspicious lesions on CT that were deemed nontumorous on PET/CT. In the 12 patients in the surveillance group, the results of ¹⁸F-FDG PET/CT led to therapy change in 33 % and a major change in 17 %. The 5-year survival rates were 30 % in the entire cohort, 34 % in the primary staging group, and 17 % in the surveillance group. A significant overall survival benefit was observed in patients in whom ¹⁸F-FDG PET/CT excluded metastases or in whom metastases could be completely removed compared with patients who were not eligible for surgery (41 % vs. 10 %).

Conclusion

Primary staging of patients with stage III/IV melanoma should be performed with ¹⁸F-FDG PET/CT, leading to higher diagnostic accuracy and enabling individualized therapeutic management, especially optimal patient selection for metastasectomy. This strategy may extend long-term survival even in patients with advanced disease.

     

Clinical correlation of metabolic parameters on <Superscript>18</Superscript>F-FDG PET/CT in idiopathic frozen shoulder

Objective

Because positron emission tomography/computed tomography (PET/CT) using fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) can be used to visualize inflammation of the musculoskeletal system, it may help elucidate the pathophysiology of frozen shoulder (FS). The purpose of this study was to characterize the uptake pattern on ¹⁸F-FDG PET/CT in patients with idiopathic FS and to determine if there is a correlation between its metabolic parameters and clinical findings.

Methods

¹⁸F-FDG PET/CT was conducted to 35 patients with unilateral idiopathic FS. Clinical data including pain, functional scores, and passive range of motion (ROM) were collected. Maximum standardized uptake values (SUVmax) were measured at the four regions of interest (ROIs): rotator interval (RI), anterior joint capsule (AJC), axillary recess (AR), and posterior joint capsule (PJC) from the attenuation-corrected axial images.

Results

Mean SUVmax values for four ROIs of the affected shoulder were significantly higher than those of the unaffected shoulder. Mean SUVmax values of RI and AR were significantly higher than those of AJC and PJC and mean SUVmax of AJC was significantly higher than that of PJC in the affected side. Three recognizable patterns of increased uptake were noted: (1) AR dominant type (15 patients); (2) RI dominant type (9 patients); (3) both RI and AR dominant type (11 patients). The SUVmax of AR showed negative correlation with abduction and forward flexion. The SUVmax of RI showed negative correlation with external rotation and internal rotation. The SUVmax of AJC showed negative correlation with all ROMs. However, there was no significant correlation between the SUVmax of PJC and any ROM.

Conclusion

Our study demonstrates that the anterior–inferior capsular portion, including RI and AR, is the main pathologic site of idiopathic FS and reveals significant correlations between ROM and metabolic parameters on ¹⁸F-FDG PET/CT. These results imply that AR and RI lesions are related to elevational limitations and rotational limitations, respectively.

     

Role of <Superscript>18</Superscript>F-FDG PET/CT in patients affected by Langerhans cell histiocytosis

Purpose

Langerhans cell histiocytosis (LCH) is a rare hematological disorder for which the utility of¹⁸F-FDG PET/CT is unclear. Our aim was to explore the metabolic features of LCH and the possible role of¹⁸F-FDG PET/CT in LCH evaluation.

Materials and methods

We found 17 patients with histologically proven LCH who underwent 17¹⁸F-FDG PET/CT scans for staging and 42 scans for restaging/follow-up purposes. PET/CT results were compared with those obtained from other conventional imaging modalities (bone scintigraphy, plain radiogram, computed tomography, magnetic resonance).

Results

¹⁸F-FDG PET/CT was positive in 15/17 patients, and it detected 36/37 lesions; all bone and extraskeletal lesions, except for a cecal lesion, were¹⁸F-FDG-avid. Only 1/4 of the patients with lung LCH had hypermetabolic lesions. The average SUV_max of the FDG-avid lesions was 7.3 ± 6.7, the average lesion-to-liver SUV_max ratio was 3.4 ± 2.5, and the average lesion-to-blood pool SUV_max ratio was 4 ± 3.2. In comparison to other imaging methods,¹⁸F-FDG PET/CT detected additional lesions or was able to evaluate treatment response earlier in 33/74 cases; it was confirmatory in 38/74 and detected fewer lesions in 3/74 (all three with lung LCH).

Conclusions

¹⁸F-FDG PET/CT seems to be useful for evaluating LCH when compared to conventional imaging, except in pulmonary cases. It can be used both for staging and restaging purposes.

     

<Superscript>18</Superscript>F-FDG PET/CT imaging factors that predict ischaemic stroke in cancer patients

Purpose

¹⁸F-FDG PET/CT can acquire both anatomical and functional images in a single session. We investigated which factors of ¹⁸F-FDG PET/CT imaging have potential as biomarkers for an increased risk of ischaemic stroke in cancer patients.

Methods

From among cancer patients presenting with various neurological symptoms and hemiparesis, 134 were selected as eligible for this retrospective analysis. A new infarct lesion on brain MRI within 1 year of FDG PET/CT defined future ischaemic stroke. The target-to-background ratio (TBR) of each arterial segment was used to define arterial inflammation on PET imaging. Abdominal obesity was defined in terms of the area and proportion of visceral adipose tissue (VAT), subcutaneous adipose tissue and total adipose tissue (TAT) on a single CT slice at the umbilical level.

Results

Ischaemic stroke confirmed by MRI occurred in 30 patients. Patients with stroke had higher TBRs in the carotid arteries and abdominal aorta (P?<?0.001) and a higher VAT proportion (P?=?0.021) and TAT proportion (P?=?0.041) than patients without stroke. Multiple logistic regression analysis showed that TBRs of the carotid arteries and abdominal aorta, VAT and TAT proportions, and the presence of a metabolically active tumour were significantly associated with future ischaemic stroke. Combining PET and CT variables improved the power for predicting future ischaemic stroke.

Conclusion

Our findings suggest that arterial FDG uptake and hypermetabolic malignancy on PET and the VAT proportion on CT could be independent predictors of future ischaemic stroke in patients with cancer and could identify those patients who would benefit from medical treatment.

     

Pictorial review of <Superscript>18</Superscript>F-FDG PET/CT findings in musculoskeletal lesions

We herein reviewed ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) findings in a number of musculoskeletal lesions including malignant tumors, benign tumors, and tumor-like lesions with correlations to other radiographic imaging modalities, and described the diversity of the ¹⁸F-FDG PET/CT findings of this entity. Malignant primary musculoskeletal tumors are typically ¹⁸F-FDG avid, whereas low-grade malignant tumors show mild uptake. Benign musculoskeletal tumors generally show a faint uptake of ¹⁸F-FDG, and tumor-like conditions also display various uptake patterns of ¹⁸F-FDG. Although musculoskeletal tumors show various uptakes of ¹⁸F-FDG on PET/CT, its addition to morphological imaging modalities such as CT and MRI is useful for the characterization and differentiation of musculoskeletal lesions.     

The role of <Superscript>18</Superscript>F-FDG PET/CT in the detection of osteosarcoma recurrence

Aim

The aim of this study was to investigate the diagnostic accuracy of ¹⁸F-FDG-PET/CT in osteosarcoma patients suspicious for disease recurrence after adequate surgical therapy.

Methods

Inclusion criteria were: a) adequate surgical treatment for proven osteosarcoma and documented complete remission after therapy; b) ¹⁸F-FDG-PET/CT performed during follow-up for clinical/diagnostic suspicion of relapse; c) new surgical treatment with excision of the suspected lesions; d) histological validation of ¹⁸F-FDG-PET/CT findings. Thirty-seven patients matching all inclusion criteria were retrospectively enrolled (20 men and 17 female). Primary surgical treatment consists of resection (31 cases) or amputation (six cases). ¹⁸F-FDG-PET/CT performance was assessed with a per-patient and per-site evaluation of sensitivity, specificity, accuracy, positive predicting value (PPV), and negative predicting value (NPV). The sites of relapse were classified as local, lung, lymphnodes (LNs), and distant (other skeletal segments and/or distant soft tissue). The disease-free survival (DFS) and the overall survival (OS) after 18F-FDG PET/CT were evaluated.

Results

¹⁸F-FDG-PET/CT was positive in 89.2% (33/37) of patients. Local uptake only was observed in 35.1% patients (13/37); lung uptake only in 18.9% (7/37); distant uptake only in 2.7% (1/37) case; multiple sites of uptake in 32.4% (12/37). Histology resulted positive in 92% (34/37) of patients. A total of 51 pathologic lesions were evaluated (22 local relapse, 11 lung metastasis, 10 metastatic LNs, eight distant metastatic lesions). On a per-patient analysis ¹⁸F-FDG-PET/CT showed a sensitivity, specificity, accuracy, PPV, and NPV of 91%, 75%, 89%, 97%, 50%. On a per-site analysis the performance for local relapse was 96%, 100%, 97%, 100%, 93%, while for lung relapse detection was 80%, 100%, 92%, 100%, 88%. The mean follow-up after ¹⁸F-FDG-PET/CT was 21.5 months. At the last follow-up, 19% (7/37) of patients were death with disease, 38% (14/37) were alive with disease, and 43% (16/37) had no evidence of disease. Overall survival was 90% and 75% at 24 and 60 months, respectively.

Conclusion

¹⁸F-FDG-PET/CT showed valuable results for detecting recurrence(s) in osteosarcoma patients with suspicious of relapse after treatment, particularly in the detection of local relapse and lung metastasis.

     

Treatment response evaluation with <Superscript>18</Superscript>F-FDG PET/CT and <Superscript>18</Superscript>F-NaF PET/CT in multiple myeloma patients undergoing high-dose chemotherapy and autologous stem cell transplantation

Aim

The aim of this study was to assess the combined use of the radiotracers ¹⁸F-FDG and ¹⁸F-NaF in treatment response evaluation of a group of multiple myeloma (MM) patients undergoing high-dose chemotherapy (HDT) followed by autologous stem cell transplantation (ASCT) by means of static (whole-body) and dynamic PET/CT (dPET/CT).

Patients and methods

Thirty-four patients with primary, previously untreated MM scheduled for treatment with HDT followed by ASCT were enrolled in the study. All patients underwent PET/CT scanning with ¹⁸F-FDG and ¹⁸F-NaF before and after therapy. Treatment response by means of PET/CT was assessed according to the European Organization for Research and Treatment of Cancer (EORTC) 1999 criteria. The evaluation of dPET/CT studies was based on qualitative evaluation, semi-quantitative (SUV) calculation, and quantitative analysis based on two-tissue compartment modelling and a non-compartmental approach leading to the extraction of fractal dimension (FD).

Results

An analysis was possible in 29 patients: three with clinical complete response (CR) and 26 with non-CR (13 patients near complete response-nCR, four patients very good partial response-VGPR, nine patients partial response-PR). After treatment, ¹⁸F-FDG PET/CT was negative in 14/29 patients and positive in 15/29 patients, showing a sensitivity of 57.5 % and a specificity of 100 %. According to the EORTC 1999 criteria, ¹⁸F-FDG PET/CT-based treatment response revealed CR in 14 patients (¹⁸F-FDG PET/CT CR), PR in 11 patients (¹⁸F-FDG PET/CT PR) and progressive disease in four patients (¹⁸F-FDG PET/CT PD). In terms of ¹⁸F-NaF PET/CT, 4/29 patients (13.8 %) had a negative baseline scan, thus failed to depict MM. Regarding the patients for which a direct lesion-to-lesion comparison was feasible, ¹⁸F-NaF PET/CT depicted 56 of the 129 ¹⁸F-FDG positive lesions (43 %). Follow-up ¹⁸F-NaF PET/CT showed persistence of 81.5 % of the baseline ¹⁸F-NaF positive MM lesions after treatment, despite the fact that 64.7 % of them had turned to ¹⁸F-FDG negative. Treatment response according to ¹⁸F-NaF PET/CT revealed CR in one patient (¹⁸F-NaF PET/CT CR), PR in five patients (¹⁸F-NaF PET/CT PR), SD in 12 patients (¹⁸F-NaF PET/CT SD), and PD in seven patients (¹⁸F-NaF PET/CT PD). Dynamic ¹⁸F-FDG and ¹⁸F-NaF PET/CT studies showed that SUV_average, SUV_max, as well as the kinetic parameters K₁, influx and FD from reference bone marrow and skeleton responded to therapy with a significant decrease (p?<?0.001).

Conclusion

F-FDG PET/CT demonstrated a sensitivity of 57.7 % and a specificity of 100 % in treatment response evaluation of MM. Despite its limited sensitivity, the performance of ¹⁸F-FDG PET/CT was satisfactory, given that 6/9 false negative patients in follow-up scans (66.7 %) were clinically characterized as nCR, a disease stage with very low tumor mass. On the other hand, ¹⁸F-NaF PET/CT does not seem to add significantly to ¹⁸F-FDG PET/CT in treatment response evaluation of MM patients undergoing HDT and ASCT, at least shortly after therapy.

     

Predictive value of <Superscript>18</Superscript>F-FDG PET/CT in restaging patients affected by ovarian carcinoma: a multicentre study

Purpose

Ovarian cancer is the eighth most common malignancy among women and has a high mortality rate. Prognostic factors able to drive an effective therapy are essential. ¹⁸F-Fluoro-2-deoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) has been investigated in patients with epithelial ovarian cancer and showed promise in diagnosing, staging, detecting recurrent lesions and monitoring treatment response. Conversely, its prognostic role remains unclear. We aimed at assessing the prognostic value of ¹⁸F-FDG PET/CT performed in the restaging process in a multicentre study.

Methods

We evaluated 168 patients affected by ovarian carcinoma, who underwent a restaging ¹⁸F-FDG PET/CT. The presence of local recurrences, lymph node involvement and distant metastasis was recorded as well as lesion dimensions, maximum and mean standardized uptake values (SUV_max and SUV_mean, respectively). Progression-free survival (PFS) and overall survival (OS) at 3 and 4 years were computed by using Kaplan-Meier curves. Increased odds ratio was assessed using Cox regression analysis testing all lesion parameters measured by PET/CT.

Results

PFS was significantly longer in patients with a negative than a positive restaging PET/CT study (3- and 4-year PFS 64 and 53 % vs 23 and 12 %, respectively; p?<?0.001). Similarly, a negative study was associated with a significantly higher OS rate after 4 years of follow-up (67 vs 25 % in negative and positive groups, respectively; p?<?0.001). Lymph node or distant involvement were also independently associated with an increased risk of disease progression [hazard ratio (HR) 1.6 and 2.2, respectively; p?=?0.003]. Moreover, PET/CT showed an incremental prognostic value compared to the International Federation of Gynecology and Obstetrics (FIGO) staging system. In the analysis of patient subsets, individuals with the same FIGO stage I–II but with negative PET had a significantly better 4-year OS than patients with low FIGO stage but positive PET. This implies that patients with the same FIGO stage can be further prognostically stratified using PET (p?=?0.01). At receiver-operating characteristic (ROC) analysis, no thresholds for semiquantitative parameters were predictive of a worse outcome.

Conclusion

¹⁸F-FDG PET/CT has an important prognostic value in assessing the risk of disease progression and mortality rate. An efficacious therapy planning might therefore effectively rely on ¹⁸F-FDG PET/CT findings. Semiquantitative data were not proven to be an effective tool to predict disease progression.

     

<Superscript>18</Superscript>F-FDG and <Superscript>18</Superscript>F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes

Purpose

There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently ¹⁸F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and ¹⁸F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant.

Materials and methods

A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT (within 1 week of each other). Lymph nodal tracer uptake was determined by calculation of standardized uptake value (SUV) with both the tracers. Results of PET/CT were compared with histopathology of the lymph nodes.

Results

Histopathology results showed thirty-seven patients with sarcoidosis, seven patients with tuberculosis, nine patients with non-small cell lung cancer, five patients with Hodgkin’s lymphoma and twelve patients with non-Hodgkin’s lymphoma. The mean FDG SUV_max of sarcoidosis, tuberculosis, Hodgkin’s and non-Hodgkin’s lymphoma was 12.7, 13.4, 8.2, and 8.8, respectively, and the mean FLT SUV_max was 6.0, 5.4, 4.4, and 3.8, respectively. It was not possible to characterize mediastinal lymphadenopathy as benign or malignant solely based on FDG SUV_max values (p > 0.05) or FLT SUV_max values (p > 0.05). There was no significant difference in FDG uptake (p > 0.9) or FLT uptake (p > 0.9) between sarcoidosis and tuberculosis. In lung cancer patients, the FDG SUV_max and FLT SUV_max of those lymph nodes with tumor infiltration on biopsy was 6.7 and 3.9, respectively, and those without nodal infiltration was 6.4 and 3.7, respectively, and both the tracers were not able to characterize the nodal status as malignant or benign (p > 0.05).

Conclusion

Though ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT reflect different aspects of biology, i.e., proliferation and metabolism, respectively, neither tracer could provide satisfactory categorization of benign and malignant lymph nodes. The results of this study clearly suggest that differentiation of mediastinal nodes into benign and malignant solely based on SUV_max values cannot be relied upon, especially in settings where tuberculosis and sarcoidosis are common.