Heterogeneity of intrahepatic fat distribution determined by <Superscript>18</Superscript>F-FDG PET and CT

Objectives

Hepatic steatosis is common but less is known of the heterogeneity of hepatic fat distribution and its clinical significance. Our objective was to measure the regional variabilities within the liver of standardised uptake values (SUV) as potential markers of hepatic fat distribution heterogeneity.

Methods

Twenty-four patients having routine, clinically indicated PET/CT with ¹⁸F-FDG and a wide range of fatty liver severity were selected. Maximum SUV (SUV_max), average SUV (SUV_ave), both calculated using lean body mass, and CT density were measured in 12 × 2-cm diameter ROIs in each patient. SUV_ave was also measured over the left ventricular cavity (SUV_LV). Mean values of SUV indices, their ratios with SUV_LV, and CT density in the 12 ROIs were calculated. Regional variabilities of SUV indices were expressed as coefficients of variation (CV; standard deviation/mean). Body mass index (BMI) was estimated from height and body weight, and %body fat and lean body mass from height, weight and gender.

Results

Mean SUV_max/SUV_ave correlated significantly with mean CT density (r = ?0.51; p < 0.02). In contrast, mean SUV_max, mean SUV_ave and their ratios with SUV_LV showed no correlation with CT density. Mean CT density correlated with weight (r = ?0.59; p < 0.005), BMI (r = ?0.57; p < 0.01) and %body fat (r = ?0.49; p < 0.02). Corresponding correlation coefficients for mean SUV_max/SUV_ave were 0.74 (p < 0.001), 0.65 (p < 0.001) and 0.46 (p < 0.03). In contrast, mean SUV_max, mean SUV_ave and their ratios with SUV_LV showed no correlation with BMI, weight and %body fat. The CV of SUV_max/SUV_ave (r = ?0.67; p < 0.001), but not the CVs of SUV_max or SUV_ave, correlated with mean CT density.

Conclusions

SUV_max/SUV_ave and CT density are markers of hepatic steatosis. The regional variability of SUV_max/SUV_ave may be a marker of hepatic fat distribution heterogeneity. The novel concept is introduced that hepatic fat distribution heterogeneity may be a marker of hepatic pathology and of clinical value, and deserves further exploration with texture analysis.

     

Repeatability of FDG quantification in tumor imaging: averaged SUVs are superior to SUVmax

PurposeReliable ¹⁸F-fluorodeoxyglucose (FDG) uptake quantification is crucial for cancer treatment monitoring. While interobserver variability has been found to be lower for a maximum standard uptake value (SUV)_max than for an averaged SUV (SUV_mean), the repeatability has not been investigated yet. In this study, we determined the repeatability of SUV values in two sequential measurements 5 min apart.MethodsPositron emission tomography data of malignant chest tumors were acquired dynamically during 45 min in 20 patients. SUV values were derived from the hottest (SUV_max), the mean of the 5 (SUV₅) and 10 (SUV₁₀) hottest voxels and the mean of a volume of interest (SUV_mean). The repeatability of the SUV measurements was determined as the standard deviation of the difference between the values at 40 and 45 min and represented as Bland–Altman graphs.ResultsThe standard deviation of the difference between the two sequential scans for SUV_max, SUV₅, SUV₁₀ and SUV_mean was 1.01, 0.53, 0.37 and 0.28.ConclusionThe repeatability of SUV is markedly increased by deriving the value from multiple voxels. Compared to SUV_max, the variability in SUV measurements is reduced by a factor of 2.7 (2.7=1.01/0.37) if 10 voxels are pooled.     

Lesion-based detection of early chemosensitivity using serial static FDG PET/CT in metastatic colorectal cancer

Purpose

Medical oncology needs early identification of patients that are not responding to systemic therapy. ¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) performed before and early during treatment has been proposed for this purpose. However, the best way to assess the change in FDG uptake between two scans has not been identified. We studied cutoff thresholds to identify responding tumours as a function of the method used to measure tumour uptake.

Methods

The study included 28 metastatic colorectal cancer (mCRC) patients who underwent 2 FDG PET/CT scans (baseline and at day 14 of the first course of polychemotherapy). For 78 tumour lesions, 4 standardized uptake value (SUV) indices were measured: maximum SUV (SUV_max) and mean SUV in a region obtained using an isocontour (SUV_40?%), with each of these SUV normalized either by the patient body weight (BW) or body surface area (BSA). The per cent change and absolute change in tumour uptake between the baseline and the early PET scans were measured based on these four indices. These changes were correlated to the RECIST 1.0-based response using contrast-enhanced CT at baseline and at 6–8?weeks on treatment.

Results

The 78 tumours were classified as non-responding (NRL, n?=?58) and responding lesions (RL, n?=?20). Receiver-operating characteristic (ROC) curves characterizing the performance in NRL/RL classification using early FDG PET uptake had areas under the curve between 0.75 and 0.84, without significant difference between the indices. The cutoff threshold in FDG uptake per cent change to get a 95?% sensitivity of RL detection depended on the way uptake was measured: ?14?% (specificity of 53?%) and ?22?% (specificity of 64?%) for SUV_max and SUV_40?%, respectively. Thresholds expressed as absolute SUV decrease instead of per cent change were less sensitive to the SUV definition: an SUV decline by 1.2 yielded a sensitivity of RL detection of 95?% for SUV_max and SUV_40?%. For a given cutoff threshold, the sensitivity was the same whatever the normalization (by BSA or BW).

Conclusion

A 14?% drop of tumour FDG SUV_max, 22?% drop of SUV_40?% or 1.2 drop of SUV_max or SUV_mean after one single course of polychemotherapy predicts objective response in mCRC lesions with a high sensitivity, potentially allowing the early identification of non-responding patients.     

Value of <Emphasis Type="Italic">O</Emphasis>-(2-[<Superscript>18</Superscript>F]fluoroethyl)-<Emphasis Type="SmallCaps">l</Emphasis>-tyrosine PET for the diagnosis of recurrent glioma

Purpose The prognosis of patients with recurrent gliomas depends on reliable and early diagnosis of tumour recurrence after initial therapy. In this context, magnetic resonance imaging (MRI) and computed tomography (CT) often fail to differentiate between radiation- and tumour-induced contrast enhancement. Furthermore, absence of contrast enhancement, or even of ¹⁸F-fluorodeoxyglucose uptake in PET, does not exclude recurrence. The aim of this study was to establish the diagnostic value of O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (FET) PET in recurrent gliomas.Methods Fifty-three patients with glioma (primary grading: 27=WHO grade IV, 16=grade III, 9=grade II, 1=grade I) and clinically suspected recurrence underwent FET PET scans 4–180 months after different treatment modalities. For semiquantitative evaluation, maximal SUV (SUV_max) and mean SUV within 80% and 70% isocontour thresholds (SUV₈₀/SUV₇₀) were evaluated and the respective ratios to the background (BG) were calculated. PET results were correlated with MRI/CT, clinical follow-up or biopsy findings.Results All patients presented with FET uptake, of varying intensity, in the area of the primary tumour after initial therapy. In the 42 patients with confirmed recurrence, there was additional distinct focal FET uptake with significantly higher values compared with those in the 11 patients without clinical signs of recurrence and showing only low and homogeneous FET uptake at the margins of the resection cavity. With respect to tumour grading, there was a slight but non-significant increase from WHO II (SUV_max/BG: 2.53±0.28) to WHO III (SUV_max/BG: 2.84±0.49) and WHO IV (SUV_max/BG: 3.55±1.07) recurrence.Conclusion FET PET reliably distinguishes between post-therapeutic benign lesions and tumour recurrence after initial treatment of low- and high-grade gliomas.     

Correlation of apparent diffusion coefficients measured by 3T diffusion-weighted MRI and SUV from FDG PET/CT in primary cervical cancer

Purpose  Diffusion-weighted magnetic resonance imaging (DWI) and fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) are oncological feasible techniques. Currently, apparent diffusion coefficient (ADC) measured by DWI and standard uptake value (SUV) from FDG PET/CT have similar applications in clinical oncology. The aim of this study was to assess the correlation between ADC and SUV in primary cervical cancer. Materials and methods  Patients with documented primary cervical cancer were recruited. All participants underwent abdominopelvic DWI at 3T and FDG PET/CT within 2 weeks. For the primary tumor, ADC was measured as minimum ADC (ADC_min) and mean ADC (ADC_mean) within the whole tumor by DWI. Maximum SUV (SUV_max) and mean SUV (SUV_mean) were measured by FDG PET/CT. Results  A total of 33 patients were included. There was no significant correlation either between ADC_min and SUV_max or between ADC_mean and SUV_mean. The relative ADC_min (rADC_min) defined as ADC_min/ADC_mean ratio was significantly inversely correlated with the relative SUV_max (rSUV_max) defined as SUV_max/SUV_mean ratio (r = –0.526, P = 0.0017) in all study patients. A significantly inverse correlation between rADC_min and rSUV_max was observed in patients with adenocarcinoma/adenosquamous carcinoma (r = –0.685, P = 0.0012) and those with well-to-moderate differentiated tumor (r = –0.631, P = 0.0050). No significant correlation was demonstrated in patients with squamous cell carcinoma or poorly differentiated tumor. Conclusions  The significantly inverse correlation between rADC_min and rSUV_max in primary cervical tumor suggests that DWI and FDG PET/CT might play a complementary role for the clinical assessment of this cancer type.     

Predictive value of early and late residual 18F-fluorodeoxyglucose and 18F-fluorothymidine uptake using different SUV measurements in patients with non-small-cell lung cancer treated with erlotinib

Purpose

To evaluate the predictive value of early and late residual ¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-fluorothymidine (FLT) uptake using different SUV measurements in PET in patients with advanced non-small-cell lung cancer (NSCLC) treated with erlotinib.

Methods

We retrospectively reviewed data from 30 patients with untreated stage IV NSCLC who had undergone a combined FDG PET and FLT PET scan at 1?week (early) and 6?weeks (late) after the start of erlotinib treatment. Early and late residual FDG and FLT uptake were measured in up to five lesions per scan with different quantitative standardized uptake values (SUV_max, SUV_2Dpeak, SUV_3Dpeak, SUV₅₀, SUV_A50, SUV_A41) and compared with short-term outcome (progression vs. nonprogression after 6?weeks of erlotinib treatment). Receiver-operating characteristics (ROC) curve analysis was used to determine the optimal cut-off value for detecting nonprogression after 6?weeks. Kaplan-Meier analysis and the log-rank test were used to evaluate the association between residual uptake and progression-free survival (PFS).

Results

Nonprogression after 6?weeks was associated with a significantly lower early and late residual FDG uptake, measured with different quantitative parameters. In contrast, nonprogression after 6?weeks was not associated with early and late residual FLT uptake. Furthermore, patients with a lower early residual FDG uptake measured in terms of SUV_max and SUV_2Dpeak had a significantly prolonged PFS (282?days vs. 118?days; p?=?0.022) than patients with higher values. Similarly, lower late residual FDG uptake and early residual FLT uptake measured in terms of SUV_3Dpeak, SUV_A50 and SUV_A41, and late FLT uptake measured in terms of SUV_3Dpeak and SUV_A50 was associated with an improved PFS.

Conclusion

Early and late residual FDG uptake, measured using different quantitative SUV parameters, are predictive factors for short-term outcome in patients with advanced NSCLC treated with erlotinib. Additionally, low residual FDG and FLT uptake early and late in the course of erlotinib treatment is associated with improved PFS.     

Dual-time-point [18F]-FDG PET/CT in the diagnostic evaluation of suspicious breast lesions

Purpose

The authors sought to evaluate whether the reacquisition of images 3 h after administration of radiotracer improves the sensitivity of fluorine-18 fluorodeoxyglucose positron emission tomography computed tomography ([¹⁸F]-FDG PET/CT) in patients with suspicious breast lesions.

Materials and methods

Forty-eight patients with 59 breast lesions underwent an [¹⁸F]-FDG PET/CT study in the prone position with a dual-time-point acquisition performed in the early phase 1 h after FDG administration (PET-1) and in the delayed phase 3 h after FDG administration (PET-2). Both examinations were evaluated qualitatively and semiquantitatively with calculation of the mean percentage variation of the standard uptake values (Δ% SUV_max) between PET-1 and PET-2. All lesions with an SUV_max ≥2.5 at PET-1 or a reduction in SUV between PET-1 and PET-2 were considered benign. The definitive histopathological diagnosis was available for all patients included in the study.

Results

The dual-time-point acquisition of [¹⁸F]-FDG PET/CT displayed an accuracy of 85% for lesions with an SUV_max ≥2.5 and/or positive Δ% SUV_max, with sensitivity and specificity values of 81% and 100% compared with 69%, 63% (both p<0.001) and 100% (p=n.s.), respectively, for the single-time-point acquisition. Malignant lesions showed an increase in FDG uptake between PET-1 and PET-2, with a Δ% SUV_max of 10±7 (p<0.04). In contrast, benign lesions showed a decrease in SUV between PET-1 and PET-2, with aΔ% SUV_max of ?21±7 (p<0.001).

Conclusions

The delayed repeat acquisition of PET images improves the accuracy of [¹⁸F]-FDG PET/CT in patients with suspicious breast lesions with respect to the single-time-point acquisition. In addition, malignant breast lesions displayed an increase in FDG uptake over time, whereas benign lesions showed a reduction. These variations in FDG uptake between PET-1 and PET-2 are a reliable parameter that can be used for differentiating between benign and malignant breast lesions.     

FDG uptake heterogeneity evaluated by fractal analysis improves the differential diagnosis of pulmonary nodules

Purpose

The present study aimed to determine whether fractal analysis of morphological complexity and intratumoral heterogeneity of FDG uptake can help to differentiate malignant from benign pulmonary nodules.

Materials and methods

We retrospectively analyzed data from 54 patients with suspected non-small cell lung cancer (NSCLC) who were examined by FDG PET/CT. Pathological assessments of biopsy specimens confirmed 35 and 19 nodules as NSCLC and inflammatory lesions, respectively. The morphological fractal dimension (m-FD), maximum standardized uptake value (SUV_max) and density fractal dimension (d-FD) of target nodules were calculated from CT and PET images. Fractal dimension is a quantitative index of morphological complexity and tracer uptake heterogeneity; higher values indicate increased complexity and heterogeneity.

Results

The m-FD, SUV_max and d-FD significantly differed between malignant and benign pulmonary nodules (p < 0.05). Although the diagnostic ability was better for d-FD than m-FD and SUV_max, the difference did not reach statistical significance. Tumor size correlated significantly with SUV_max (r = 0.51, p < 0.05), but not with either m-FD or d-FD. Furthermore, m-FD combined with either SUV_max or d-FD improved diagnostic accuracy to 92.6% and 94.4%, respectively.

Conclusion

The d-FD of intratumoral heterogeneity of FDG uptake can help to differentially diagnose malignant and benign pulmonary nodules. The SUV_max and d-FD obtained from FDG-PET images provide different types of information that are equally useful for differential diagnoses. Furthermore, the morphological complexity determined by CT combined with heterogeneous FDG uptake determined by PET improved diagnostic accuracy.     

Prognostic Value of 18F-Fluorodeoxyglucose Positron Emission Tomography–Computed Tomography in Predicting Survival in Patients with Unresectable Metastatic Melanoma to the Liver Undergoing Yttrium-90 Radioembolization

PurposeTo investigate the prognostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) in predicting survival in patients with unresectable metastatic melanoma to the liver undergoing yttrium-90 (⁹⁰Y) radioembolization.Materials and MethodsA retrospective review of 12 patients with unresectable hepatic melanoma metastases (5 patients with cutaneous metastases, 7 patients with ocular metastases) who underwent ¹⁸F-FDG PET-CT before ⁹⁰Y was performed. Metabolically significant tumors, defined as having a long-axis diameter ≥ 1 cm and maximum standardized uptake value (SUV_max) ≥ 2.5, were identified on ¹⁸F-FDG PET-CT. SUV_max, glycolytic activity, and volume were determined for each tumor. Overall SUV_max, total tumor glycolytic activity (TGA), total metabolic tumor volume (MTV), and metabolic tumor burden (MTB) based on percentage of liver involvement (MTV/total liver volume) were calculated. Kaplan-Meier method, life-table analysis, and Cox proportional hazards model were used for statistical analysis.ResultsMedian SUV_max was 10.9 (range, 4.6–15.3), median TGA was 377.0 SUV/cm³ (range, 53.6–20,393.4 SUV/cm³), median MTV was 85.4 cm³ (range, 11.5–2,504.1 cm³), and median MTB was 5.5% (range, 0.1%–54.0%). MTB was found to be a significant negative prognostic marker of survival on univariate (P = .020) and multivariate (P = .018) analyses accounting for age and duration from metastatic diagnosis to first ⁹⁰Y treatment. A 60th percentile MTB of 7.0% (hazard ratio, 5.704; P = .040) was a statistically significant cutoff. Median survivals from first ⁹⁰Y treatment in patients with MTB < 7.0% and ≥ 7.0% were 10.8 months (95% confidence interval [CI], 6.8–14.8) and 4.7 months (95% CI, 1.6–7.8), respectively. SUV_max (P = .422), TGA (P = .064), and MTV (P = .065) were not found to be statistically significant.ConclusionsMTB based on ¹⁸F-FDG PET-CT performed before treatment was found to be a negative prognostic factor for patient survival after ⁹⁰Y radioembolization for unresectable metastatic melanoma to liver.     

Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Purpose

Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods

This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results

Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADC_mean, ADC_min, SUV_max and SUV_mean values for intra-observer and inter-observer agreement. Mean ADC_mean and ADC_min in HNSCC were 1.05?±?0.34 × 10^?3?mm²/s and 0.65?±?0.29 × 10^?3?mm²/s, respectively. Mean SUV_mean and mean SUV_max were 7.61?±?3.87 and 12.8?±?5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson’s correlation analysis showed no significant correlation between ADC and SUV measurements (r ?0.103, ?0.051; p 0.552, 0.777).

Conclusion

Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.     

Correlation of high 18F-FDG uptake to clinical, pathological and biological prognostic factors in breast cancer

Purpose

The aim of this study was to determine the impact of the main clinicopathological and biological prognostic factors of breast cancer on ¹⁸F-fluorodeoxyglucose (FDG) uptake. Only women with tumours larger than 20?mm (T2?CT4) were included in order to minimize bias of partial volume effect.

Methods

In this prospective study, 132 consecutive women received FDG PET/CT imaging before starting neoadjuvant chemotherapy. Maximum standardized uptake values (SUV_max) were compared to tumour characteristics as assessed on core biopsy.

Results

There was no influence of T and N stage on SUV. Invasive ductal carcinoma showed higher SUV than lobular carcinoma. However, the highest uptake was found for metaplastic tumours, representing 5% of patients in this series. Several biological features usually considered as bad prognostic factors were associated with an increase in FDG uptake: the median of SUV_max was 9.7 for grade 3 tumours vs 4.8 for the lower grades (p?p?=?0.003); triple-negative tumours (oestrogen and progesterone receptor negative, no overexpression of c-erbB-2) had an SUV of 9.2 vs 5.8 for all others (p = 0005); p53 mutated tumours also had significantly higher SUV (7.8 vs 5.0; p?Conclusion Knowledge of the factors influencing uptake is important when interpreting FDG PET/CT scans. Also, findings that FDG uptake is highest in those patients with poor prognostic features (high grade, hormone receptor negativity, triple negativity, metaplastic tumours) is helpful to determine who are the best candidates for baseline staging.     

Glucose corrected standardized uptake value (SUVgluc) in the evaluation of brain lesions with 18F-FDG PET

Purpose

To retrospectively assess the utility of ¹⁸F fluorodeoxyglucose (FDG) positron emission tomography (PET) images of standardized uptake values corrected for blood glucose (SUV_gluc), and to compare this to various quantitative methods to identify the presence or absence of high grade malignancy.

Methods

A retrospective review in 42 patients, found 81 central nervous system (CNS) lesions. Fifty one were malignant and 30 were benign or post treatment changes based on pathology (n?=?32) and on clinical outcome (n?=?49). Dynamic FDG PET scans were processed to generate parametric images of SUV_gluc, SUV, glucose metabolic rate (GMR), and lesion to cerebellum ratios (SUV_Rc), and contralateral white matter ratios (SUV_Rw). The SUV_gluc was calculated from $ {{{\mathrm{SU}{{\mathrm{V}}_{\max }}*\mathrm{BG}}} \left/ {{\left[ {100\,\mathrm{mg}/\mathrm{dl}} \right]}} \right.} $ , where SUV_max is the maximum SUV and BG is the blood glucose level (mg/dL).

Results

Using a malignant threshold for SUV_gluc of 4.5 and GMR of 13.0 μmole/min/100 g, the accuracies were similar for the SUV_gluc (80 %) and GMR (81 %) and were higher than the conventional SUV_max (73 %). The area under the receiver operating characteristic (ROC) curve for the SUV_gluc (0.8661) was better than that for the SUV_max (0.7955) (p?<?0.02) and was similar to those of the GMR (0.8694), SUV_Rc (0.8278), and SUV_Rw (0.8559).

Conclusion

These results suggest that the SUV_gluc may assist in the interpretation of FDG PET brain images in patients with CNS lesions. The SUV_gluc method avoids the complexity of kinetic modeling and the definition of a reference region.     

The impact of systemic chemotherapy on testicular FDG activity in young men with Hodgkin’s lymphoma

Purpose

Based on prior reports suggesting a positive correlation between fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET)/CT and total sperm count and concentration, we sought to identify changes in testicular FDG uptake over the course of chemotherapy in young men with Hodgkin’s lymphoma.

Methods

Fifty-two patients with a mean age of 24.2 years (range 15.5–44.4) at diagnosis monitored with FDG PET/CT to assess treatment response for Hodgkin’s lymphoma were selected for this retrospective analysis under an Institutional Review Board waiver. Of the patients, 26 were treated with a chemotherapy regimen known to cause prolonged and sometimes permanent azoospermia (BEACOPP—bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisolone) and 26 with a regimen known to have a much milder effect on gonadal function (ABVD—doxorubicin, bleomycin, vincristine, and dacarbazine). Each patient underwent one FDG PET/CT before treatment and at least one FDG PET/CT after start of chemotherapy. In all examinations, FDG activity was measured in the testes with different quantification metrics: maximum standardized uptake value (SUV_max), SUV_mean, functional volume (FV) and total testicular glycolysis (TTG), and blood pool activity determined (SUV_mean).

Results

Testicular FDG uptake (SUV_max) was significantly associated with blood pool activity (p?<?0.001). Furthermore, testicular FDG uptake metrics incorporating volume (e.g., FV and TTG) were associated with age. There was no significant change in SUV_max, SUV_mean, FV, and TTG from the PET/CT at baseline to the PET/CTs over the course of chemotherapy either for patients treated with BEACOPP or for patients treated with ABVD.

Conclusion

For patients undergoing chemotherapy for Hodgkin’s lymphoma, there is a significant association between testicular FDG uptake and blood pool activity, but no significant changes in FDG uptake over the course of chemotherapy. Therefore, FDG uptake may not be a feasible surrogate marker for fertility monitoring in patients with Hodgkin’s lymphoma undergoing chemotherapy.     

[<Superscript>18</Superscript>F]FDG-PET predicts complete pathological response of breast cancer to neoadjuvant chemotherapy

Purpose To evaluate, in breast cancer patients treated by neoadjuvant chemotherapy, the predictive value of reduction in FDG uptake with regard to complete pathological response (pCR). Methods Forty-seven women with non-metastatic, non-inflammatory, large or locally advanced breast cancer were included. Tumour uptake of FDG was evaluated before and after the first course of neoadjuvant chemotherapy. Four indices were used: maximal and average SUV without or with correction by body surface area and glycaemia (SUV_max, SUV_avg, SUV_max-BSA-G and SUV_avg-BSA-G, respectively). The predictive value of reduction in FDG uptake with respect to pCR was studied by logistic regression analysis. Relationships between baseline [¹⁸F]FDG uptake and prognostic parameters were assessed. Results The relative decrease in FDG uptake (ΔSUV) after the first course of neoadjuvant chemotherapy was significantly greater in the pCR group than in the non-pCR group (p < 0.000066). The four FDG uptake indices were all strongly correlated with each other. A decrease in SUV_max-BSA-G of 85.4% ± 21.9% was found in pCR patients, versus 22.6% ± 36.6% in non-pCR patients. ΔSUV_max-BSA-G <−60% predicted the pCR with an accuracy of 87% and ΔSUVs were found to be only factors predictive of the pCR at multivariate analysis. An elevated baseline SUV was associated with high mitotic activity (p < 0.0016), tumour grading (p < 0.004), high nuclear pleomorphism score (p < 0.03) and negative hormonal receptor status (p < 0.005). Conclusion In breast cancer patients, after only one course of neoadjuvant chemotherapy the reduction in FDG uptake is an early and powerful predictor of pCR.     

Intra-patient Variability of FDG Standardized Uptake Values in Mediastinal Blood Pool,Liver, and Myocardium during R-CHOP Chemotherapy in Patients with Diffuse Large B-cell Lymphoma

Purpose

¹⁸F-fluorodeoxyglucose (FDG) PET/CT is useful for staging and evaluating treatment response in patients with diffuse large B-cell lymphoma (DLBCL). A five-point scale model using the mediastinal blood pool (MBP) and liver as references is a recommended method for interpreting treatment response. We evaluated the variability in standardized uptake values (SUVs) of the MBP, liver, and myocardium during chemotherapy in patients with DLBCL.

Methods

We analyzed 60 patients with DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) treatment and underwent baseline, interim, and final FDG PET/CT scans. The FDG uptakes of lymphoma lesions, MBP, liver, and myocardium were assessed, and changes in the MBP and liver SUV and possible associated factors were evaluated.

Results

The SUV of the liver did not change significantly during the chemotherapy. However, the SUV_mean of MBP showed a significant change though the difference was small (p?=?0.019). SUV_mean of MBP and liver at baseline and interim scans was significantly lower in patients with advanced Ann Arbor stage on diagnosis. The SUV_mean of the MBP and liver was negatively correlated with the volumetric index of lymphoma lesions in baseline scans (r?=?-0.547, p?<?0.001; r?=?-0.502, p?<?0.001). Positive myocardial FDG uptake was more frequently observed in interim and final scans than in the baseline scan, but there was no significant association between the MBP and liver uptake and myocardial uptake.

Conclusions

The SUV of the liver was not significantly changed during R-CHOP chemotherapy in patients with DLBCL, whereas the MBP SUV of the interim scan decreased slightly. However, the SUV of the reference organs may be affected by tumor burden, and this should be considered when assessing follow-up scans. Although myocardial FDG uptake was more frequently observed after R-CHOP chemotherapy, it did not affect the SUV of the MBP and liver.

     

Hepatic FDG Uptake is not Associated with Hepatic Steatosis but with Visceral Fat Volume in Cancer Screening

Purpose

We aimed to evaluate the relation between visceral fat volume and fluorodeoxyglucose (FDG) uptake of the liver measured by maximum or mean standardized uptake value.

Methods

We retrospectively analyzed 96 consecutive records of positron emission tomography/computed tomography (PET/CT) performed for cancer screening between May 2011 and December 2011. Subjects were divided into 2 groups according to Hounsfield unit (HU) of the liver comparing with that of the spleen. The control group (20 women, 56 men) demonstrating HU of the liver equal or greater than that of the spleen included 76 patients, while the fatty liver group (2 women, 18 men) showing HU of the liver less than that of the spleen included 20 patients. We compared FDG uptake of the liver and visceral fat volume between two groups. We evaluated correlation of hepatic FDG uptake measured by maximum or mean standardized uptake value (SUV) with visceral fat volume and attenuation.

Results

The fatty liver disease group showed higher aspartate aminotransferase (AST)of (24.42 ± 7.22, p = 0.012), alanine aminotransferase (ALT) of (25.16 ± 11.68, p = 0.001), body mass index (BMI) of (24.58 ± 3.29, p = 0.021), and visceral fat volume (3063.53 ± 1561.43, p = 0.011) than the control group. There were no statistically significant differences of mean standardized uptake value of the liver (liver SUV_mean) (2.73 ± 0.19, p = 0.723), maximum standardized uptake value of the liver (liver SUV_max) (3.39 ± 0.53, p = 0.8248) and liver SUV_mean/spleen SUV_mean (1.13 ± 0.10, p = 0.081) between the two groups. Strong correlations were shown between liver SUV_mean and BMI (r = 0.609, p < 0.001) and between liver SUV_mean and visceral fat volume (r = 0.457, p < 0.001). Liver SUV_max was also strongly correlated with BMI (r = 0.622, p = 0.001) and visceral fat volume (r = 0.547, p < 0.001). There was no significant association of mean attenuation value of the liver (liver HU_mean) with liver SUV_mean (r = -0.003, p = 0.979) or liver SUV_max (r = -0.120, p = 0.244).

Conclusion

Hepatic FDG uptake quantified as SUV_mean or SUV_max is not correlated with hepatic steatosis but with visceral fat volume in cancer screening.     

Comparison of the effectiveness of MRI perfusion and fluorine-18 FDG PET-CT for differentiating radiation injury from viable brain tumor: a preliminary retrospective analysis with pathologic correlation in all patients

ObjectivesDifferentiating radiation injury from viable tumor is important for optimizing patient care. Our aim was to directly compare the effectiveness of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) and dynamic susceptibility-weighted contrast-enhanced (DSC) magnetic resonance (MR) perfusion in differentiating radiation effects from tumor growth in patients with increased enhancement following radiotherapy for primary or secondary brain tumors.Materials and methodsWe retrospectively identified 12 consecutive patients with primary and secondary brain tumors over a 1-year period that demonstrated indeterminate enhancing lesions after radiotherapy and that had undergone DSC MR perfusion, FDG PET-CT, and subsequent histopathologic diagnosis. The maximum standardized uptake value (SUV) of the lesion (SUV_{lesion max}), SUV_ratio (SUV_{lesion max}/SUV_{normal brain}), maximum relative cerebral blood volume, percentage of signal intensity recovery, and relative peak height were calculated from the positron emission tomography and MR perfusion studies. A prediction of tumor or radiation injury was made based on these variables while being blinded to the results of the surgical pathology.ResultsSUV_ratio had the highest predictive value (area under the curve=0.943) for tumor progression, although this was not statistically better than any MR perfusion metric (area under the curve=0.757–0.829).ConclusionsThis preliminary study suggests that FDG PET-CT and DSC MR perfusion may demonstrate similar effectiveness for distinguishing tumor growth from radiation injury. Assessment of the SUV_ratio may increase the sensitivity and specificity of FDG PET-CT for differentiating tumor and radiation injury. Further analysis is needed to help define which modality has greater predictive capabilities.     

The prognostic value of <Superscript>18</Superscript>F–FDG PET/CT prior to liver transplantation for nonresectable colorectal liver metastases

Purpose

The main objective of this study was to evaluate the prognostic value of volumetric and metabolic information derivied from F-18 fluorodeoxyglucose positron emission tomography (¹⁸F–FDG PET) in combination with computed tomography (CT) prior to liver transplantation (LT) in patients with nonresectable colorectal liver metastases (CLM). Due to scarcity of liver grafts, prognostic information enabling selection of candidates who will gain the highest survival after LT is of vital importance. ¹⁸F–FDG PET/CT was a part of the preoperative study protocol. Patients without evidence of extrahepatic malignant disease on ¹⁸F–FDG PET/CT who also fulfilled all the other inclusion criteria underwent LT.

Methods

The preoperative ¹⁸F–FDG PET/CT examinations of all patients included in the SECA (secondary cancer) study were retrospectively assessed. Maximum, mean and peak standardized uptake values (SUV_max, SUV_mean and SUV_peak), tumor to background (T/B) ratio, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were measured and calculated for all liver metastases. Total MTV and TLG were calculated for each patient. Cut-off values were determined for each of these parameters by using receiver operating characteristic (ROC) analysis dividing the patients into two groups. One, three and five-year overall survival (OS) and disease free survival (DFS) for patients over and under the cut-off value were compared by using the Kaplan–Meier method and log rank test.

Results

Twenty-three patients underwent LT in the SECA study. Total MTV and TLG under the cut-off values were significantly correlated to improved OS at three and five years (p = 0.027 and 0.026) and DFS (p = 0.01). One, three and five-year OS and DFS were not significantly related to SUV_max, SUV_mean, SUV_peak or T/B-ratio.

Conclusion

Total MTV and TLG from ¹⁸F FDG PET/CT prior to LT for nonresectable CLM were significantly correlated to improved three and five-year OS and DFS and can potentially improve the patient selection for LT.

     

The distribution of FDG at PET examinations constitutes a relative mechanism: significant effects at activity quantification in patients with a high muscular uptake

Purpose

At ¹⁸F-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) examinations a high tracer uptake of the skeletal muscles is sometimes encountered which can lead to reduced uptake in pathological lesions. This was evaluated in retrospect in patients being recalled for a repeat examination after reducing the muscular uptake.

Methods

Ten patients with increased muscular tracer uptake were examined with FDG PET/CT on two occasions with a mean of 6?days. All patients showed at least one pathological lesion with increased tracer uptake. The muscular uptake was reduced at the second examination by informing the patient to refrain from physical activity together with pretreatment with diazepam. The maximum standardized uptake value (SUV_max) of the pathological lesion and SUV_mean of certain skeletal muscles, liver, spleen, lungs, blood and certain bone marrow portions were calculated.

Results

In all patients, the muscular uptake was reduced to a normal level at visual evaluation as well as at comparison of SUVs with 25 consecutive clinical patients exhibiting a normal FDG distribution (p?<?0.001). The mean lesion SUV_max increased from 2.4 to 3.7 (54?%) between the examinations (p?<?0.05). All reference tissues/organs showed a significant increase of SUV at the second examination. Relating lesion SUV_max to the activity of any of the reference tissues/organs there was no significant difference between the studies.

Conclusion

The distribution of FDG constitutes a relative mechanism. This must be especially considered at longitudinal examinations in the same patient at therapy evaluations. In examinations with a somehow distorted general distribution of the activity, it may be more relevant to relate the lesion activity to a reference tissue/organ than relying on SUV assessments.     

Pretreatment quantitative 18F-FDG PET/CT parameters as a predictor of survival in adenoid cystic carcinoma of the salivary glands

PurposeThe aim of this study was to determine the unique prognostic value of quantitative ¹⁸F-FDG PET/CT parameters to assess progression-free survival (PFS), distant metastasis-free survival (DMFS), and overall survival (OS) in patients with salivary gland adenoid cystic carcinoma (ACC).MethodsWe performed a retrospective study including 23 patients (15 men, 8 women; median age, 58 years; range, 21–91 years) with salivary gland ACC between January 2009 and October 2017 who underwent ¹⁸F-FDG PET/CT scan prior to treatment. Maximum, mean, peak, tumor-to-mediastinal blood pool and tumor-to-liver standardized uptake values (SUV_max, SUV_mean, SUV_peak, SUV_ratio[med] and SUV_ratio[liver]), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were obtained from ¹⁸F-FDG PET/CT. The prognostic value of quantitative ¹⁸F-FDG PET/CT parameters and other clinicopathological variables were evaluated utilizing the Cox proportional regression analysis.ResultsThe 3-year and 5-year OS for all the patients were 90.9%, and 62.3%, respectively. Log rank test determined that the SUV_ratio[med], SUV_ratio[liver], MTV and TLG were predictive factors of DMFS, PFS, and OS (p < 0.05), furthermore, SUV_max, minor salivary gland tumors and DM at initial diagnosis (M1 stage) were predictor for PFS; M1 stage and overall stage 3–4 predicted DMFS (all p < 0.05). Cox regression analyses confirmed that the higher SUV_ratio[med], SUV_ratio[liver], MTV, and TLG values predicted DMFS, PFS and OS independently, whereas SUV_max was an independent predictor of only PFS (p < 0.05).ConclusionsThe pretreatment metabolic ¹⁸F-FDG PET/CT parameters may reflect tumor aggressiveness in patients with salivary gland ACC and may potentially be utilized as a prognostic biomarker.