Appropriateness criteria of FDG PET/CT in oncology

An evaluation of the physiological uptake range of 18F-fluoro-2-deoxy-D-glucose in normal ovaries of seven dogs using positron emission tomography/computed tomography

Introduction

This study evaluated the physiological uptake range of 18F-fluoro-2-deoxy-D-glucose (18F-FDG) in the normal ovaries of seven dogs using positron emission tomography/computed tomography (PET/CT).

Materials and methods

The dogs were subjected to general anesthesia and were positioned in ventral recumbency for PET/CT scans. The dosage of 18F-FDG ranged from 0.14 to 0.17 mCi/kg and was administered intravenously followed by 0.9% NaCl flushing; PET/CT images of each dog were obtained precisely 60 min after the injection of 18F-FDG. The regions of interest were drawn manually, and standardized uptake values (SUV) were calculated to evaluate the 18F-FDG uptake in each ovary. The maximum and mean SUVs (SUV max and SUV mean) for all the ovaries of the dogs were then computed.

Results

The range of SUV max and SUV mean of the normal ovaries of the dogs were 1.28-1.62 and 1.07-1.31 (mean ± standard deviation), respectively.

Conclusion

This is the first study to investigate the normal 18F-FDG uptake baseline data of normal canine ovaries using PET/CT scans. These data will help clinicians in identifying malignant tumors before anatomical changes in the ovary through PET/CT scans.

CANCER RISK ESTIMATION FOR PATIENTS UNDERGOING WHOLE-BODY PET/CT SCANS

The objective of this paper was to compute the effective dose, as well as the lifetime attributable risk (LAR) of cancer related to whole-body positron emission tomography (PET)/computed tomography (CT) scan for 193 adult patients. The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. Since PET/CT scans are associated with a high dose and a risk of developing cancer, it was important to balance the advantages and risks before conducting any scans. This is especially important for younger patients and those who are overweight.

Modern Imaging Techniques in the Study and Disease Diagnosis of the Mammary Glands of Animals

The study of the structure and function of the animals' mammary glands is of key importance, as it reveals pathological processes at their onset, thus contributing to their immediate treatment. The most frequently studied mammary diseases are mastitis in cows and ewes and mammary tumours in dogs and cats. Various imaging techniques such as computed tomography, positron emission tomography, magnetic resonance imaging, and ultrasonographic techniques (Doppler, contrast-enchanced, three-dimensional and elastography) are available and can be applied in research or clinical practice in order to evaluate possible abnormalities in mammary glands, as well as to assist in the differential diagnosis. In this review, the above imaging technologies are described, and the perspectives of each method are highlighted. It is inferred that ultrasonographic modalities are the most frequently used imaging techniques for the diagnosis of clinical or subclinical mastitis and treatment guidance on a farm. In companion animals, a combination of imaging techniques should be applied for a more accurate diagnosis of mammary tumours. In any case, the confirmation of the diagnosis is provided by laboratory techniques.

Imaging in translational cancer research

This review is aimed at presenting some of the recent developments in translational cancer imaging research, with a focus on novel, recently established, or soon to be established cross-sectional imaging techniques for computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET) imaging, including computational investigations based on machine-learning techniques.

Role of 18F-FDG PET/CT in evaluation of recently diagnosed breast cancer patients

Background

Breast cancer is the most frequent malignant disease in women and usually affects people of all ages, races, socioeconomic classes, and geographic locations. Once breast cancer is diagnosed, tumor staging should be assessed precisely before treatment and prognosis could be determined. The purpose of this study was to determine the diagnostic usefulness of PET/CT in the initial assessment of patients with newly diagnosed breast cancer who were referred for tumor staging, pre-therapeutic or preoperative evaluation.

Results

In the examined 50 patients, PET/CT has higher sensitivity and accuracy compared to CT alone (reaching 100% for PET/CT and 96% for CT) in detecting malignant breast lesions, regional and distant nodal deposits as well as distant deposits, with subsequent upstaging in two patients.

Conclusions

18F-FDG PET/CT is a single valuable technique that detects metastatic illness in newly diagnosed breast cancer patients in an efficient, accurate, and noninvasive manner, resulting in modification of the initial staging, which in turn reflected on the patients' therapeutic plans.

Head-to-head intra-individual comparison of biodistribution and tumor uptake of 68Ga-FAPI and 18F-FDG PET/CT in cancer patients

PURPOSE

FAPI ligands (fibroblast activation protein inhibitor), a novel class of radiotracers for PET/CT imaging, demonstrated in previous studies rapid and high tumor uptake. The purpose of this study is the head-to-head intra-individual comparison of ⁶⁸Ga-FAPI versus standard-of-care ¹⁸F-FDG in PET/CT in organ biodistribution and tumor uptake in patients with various cancers.

MATERIAL AND METHODS

This international retrospective multicenter analysis included PET/CT data from 71 patients from 6 centers who underwent both ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT within a median time interval of 10 days (range 1-89 days). Volumes of interest (VOIs) were manually drawn in normal organs and tumor lesions to quantify tracer uptake by SUVmax and SUVmean. Furthermore, tumor-to-background ratios (TBR) were generated (SUVmax tumor/ SUVmax organ).

RESULTS

A total of 71 patients were studied of, which 28 were female and 43 male (median age 60). In 41 of 71 patients, the primary tumor was present. Forty-three of 71 patients exhibited 162 metastatic lesions. ⁶⁸Ga-FAPI uptake in primary tumors and metastases was comparable to ¹⁸F-FDG in most cases. The SUVmax was significantly lower for ⁶⁸Ga-FAPI than ¹⁸F-FDG in background tissues such as the brain, oral mucosa, myocardium, blood pool, liver, pancreas, and colon. Thus, ⁶⁸Ga-FAPI TBRs were significantly higher than ¹⁸F-FDG TBRs in some sites, including liver and bone metastases.

CONCLUSION

Quantitative tumor uptake is comparable between ⁶⁸Ga-FAPI and ¹⁸F-FDG, but lower background uptake in most normal organs results in equal or higher TBRs for ⁶⁸Ga-FAPI. Thus, ⁶⁸Ga-FAPI PET/CT may yield improved diagnostic information in various cancers and especially in tumor locations with high physiological ¹⁸F-FDG uptake.

Head-to-head intra-individual comparison of biodistribution and tumor uptake of 68Ga-FAPI and 18F-FDG PET/CT in cancer patients

Purpose

FAPI ligands (fibroblast activation protein inhibitor), a novel class of radiotracers for PET/CT imaging, demonstrated in previous studies rapid and high tumor uptake. The purpose of this study is the head-to-head intra-individual comparison of ⁶⁸Ga-FAPI versus standard-of-care ¹⁸F-FDG in PET/CT in organ biodistribution and tumor uptake in patients with various cancers.

Material and Methods

This international retrospective multicenter analysis included PET/CT data from 71 patients from 6 centers who underwent both ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT within a median time interval of 10 days (range 1–89 days). Volumes of interest (VOIs) were manually drawn in normal organs and tumor lesions to quantify tracer uptake by SUVmax and SUVmean. Furthermore, tumor-to-background ratios (TBR) were generated (SUVmax tumor/ SUVmax organ).

Results

A total of 71 patients were studied of, which 28 were female and 43 male (median age 60). In 41 of 71 patients, the primary tumor was present. Forty-three of 71 patients exhibited 162 metastatic lesions. ⁶⁸Ga-FAPI uptake in primary tumors and metastases was comparable to ¹⁸F-FDG in most cases. The SUVmax was significantly lower for ⁶⁸Ga-FAPI than ¹⁸F-FDG in background tissues such as the brain, oral mucosa, myocardium, blood pool, liver, pancreas, and colon. Thus, ⁶⁸Ga-FAPI TBRs were significantly higher than ¹⁸F-FDG TBRs in some sites, including liver and bone metastases.

Conclusion

Quantitative tumor uptake is comparable between ⁶⁸Ga-FAPI and ¹⁸F-FDG, but lower background uptake in most normal organs results in equal or higher TBRs for ⁶⁸Ga-FAPI. Thus, ⁶⁸Ga-FAPI PET/CT may yield improved diagnostic information in various cancers and especially in tumor locations with high physiological ¹⁸F-FDG uptake.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05307-1.

Radiation-Induced Metabolic Shifts in the Hepatic Parenchyma: Findings from 18F-FDG PET Imaging and Tissue NMR Metabolomics in a Mouse Model for Hepatocellular Carcinoma

Purpose: By taking advantage of 18F-FDG PET imaging and tissue nuclear magnetic resonance (NMR) metabolomics, we examined the dynamic metabolic alterations induced by liver irradiation in a mouse model for hepatocellular carcinoma (HCC). Methods: After orthotopic implantation with the mouse liver cancer BNL cells in the right hepatic lobe, animals were divided into two experimental groups. The first received irradiation (RT) at 15 Gy, while the second (no-RT) did not. Intergroup comparisons over time were performed, in terms of 18F-FDG PET findings, NMR metabolomics results, and the expression of genes involved in inflammation and glucose metabolism. Results: As of day one post-irradiation, mice in the RT group showed an increased 18F-FDG uptake in the right liver parenchyma compared with the no-RT group. However, the difference reached statistical significance only on the third post-irradiation day. NMR metabolomics revealed that glucose concentrations peaked on day one post-irradiation both, in the right and left lobes—the latter reflecting a bystander effect. Increased pyruvate and glutamate levels were also evident in the right liver on the third post-irradiation day. The expression levels of the glucose-6-phosphatase (G6PC) and fructose-1, 6-bisphosphatase 1 (FBP1) genes were down-regulated on the first and third post-irradiation days, respectively. Therefore, liver irradiation was associated with a metabolic shift from an impaired gluconeogenesis to an enhanced glycolysis from the first to the third post-irradiation day. Conclusion: Radiation-induced metabolic alterations in the liver parenchyma occur as early as the first post-irradiation day and show dynamic changes over time.

[Diagnostic and therapeutic management of operable bronchopulmonary carcinoid tumours]

INTRODUCTION

Bronchial carcinoid tumours (CT), divided into typical carcinoid (TC) or atypical carcinoid (AC), are rare tumours whose therapeutic management remains unspecified.

METHODS

Retrospective study collecting cases of bronchial CT operated at the thoracic surgery department of Abderrahmane-Mami hospital of Ariana and recruited from the pneumology departments of Northern Tunisia, during a 12-year period.

RESULTS

Ninety patients were collected (74 cases of TC and 16 cases of AC). The mean age was 45 years and the sex ratio H/F=0.5. The chest X-ray was normal in 11 cases, as well as flexible bronchoscopy in seven cases. The tumour was classified: stage IA (10 cases), IIA (28 cases), IIB (31 cases), IIIA (15 cases) and IIIB (six cases). Surgery resulted in a complete resection in 78 patients, an extensive resection in six patients, and a conservative resection in six patients. Adjuvant chemotherapy was given in 10 patients. The survival was 84% at five years and 42% at 10 years.

CONCLUSION

The prognosis of CT depends directly on the histological subtype. It is excellent for TC after complete resection, unlike ACs that are similar to well-differentiated bronchial carcinomas.

Role of PET/CT in patients with unexplained rising alpha fetoprotein post HCC interventional management

Background

Positron emission tomography–computed tomography (PET/CT) is considered a powerful modality in the follow-up of hepatocellular carcinoma (HCC) patients. In this study, PET/CT was done in an evaluation of patients with unexplained rising alpha fetoprotein (AFP) post hepatocellular carcinoma (HCC) interventional management in 40 patients (16 females and 24 males); their age ranged from 25 to 82 years, had undergone interventional management for HCC and underwent PET/CT follow-up within an 8-month duration from their intervention. Whole-body PET/CT was performed after injection of (18)-FDG, and the results were read in a masked manner by two specialists, and diagnostic performance was assessed from the results of consensus masked reading. All the results were evaluated with the Barcelona criteria and biopsy correlation.

Results

During the follow-up PET/CT, 24 patients had complete response and 8 patients showed focal residual while the rest 8 patients showed newly developed lesions.

Conclusion

PET/CT is an excellent method for the evaluation of HCC patients with equivocal results after interventional management.

The metabolic clinical risk score as a new prognostic model for surgical decision-making in patients with colorectal liver metastases

BACKGROUND AND OBJECTIVES

Selection for surgery in patients with colorectal liver metastases (CRLM) remains inaccurate. We evaluated if CRLM baseline metabolic characteristics, assessed by [18]F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸ FDG-PET/CT), could predict postoperative outcomes.

METHODS

In a retrospective series of patients undergoing surgery for CRLM, we defined two groups: the long-term survival (LTS) and early relapse (ER) groups, where the postoperative recurrence-free survivals were ≥5 years or <1 year, respectively. We analyzed the patients in whom baseline ¹⁸ FDG-PET/CT was available. Clinicopathologic parameters, clinical risk score (CRS), and baseline ¹⁸ FDG-PET/CT characteristics were compared between LTS and ER groups. A metabolic CRS (mCRS) was implemented, adding one point to the standard five-point CRS when the highest tumor standardized uptake values (SUV_max )/normal liver mean SUV (SUV_mean(liver) ) ratios were >4.3, defining low- and high-risk mCRS by scores of 0 to 2 and 3 to 6, respectively.

RESULTS

From a series of 450 patients operated for CRLM (mean follow-up of 58 months), we included for analysis 23 and 30 patients in the LTS and ER groups, respectively. Clinicopathologic parameters and CRS were similar in the LTS and ER groups. Median SUV_max /SUV_mean(liver) ratios were higher in ER vs LTS patients (4.2 and 2.8, P = .008, respectively). mCRS was increased in ER patients (P = .024); 61% of LTS patients had low-risk mCRS and 73% of the ER patients had high-risk mCRS (P = .023).

CONCLUSIONS

¹⁸ FDG-PET/CT characteristics combined with traditional CRS may represent a new tool to improve selection for surgery in patients with CRLM.

Targeting uptake transporters for cancer imaging and treatment

Cancer cells reprogram their gene expression to promote growth, survival, proliferation, and invasiveness. The unique expression of certain uptake transporters in cancers and their innate function to concentrate small molecular substrates in cells make them ideal targets for selective delivering imaging and therapeutic agents into cancer cells. In this review, we focus on several solute carrier (SLC) transporters known to be involved in transporting clinically used radiopharmaceutical agents into cancer cells, including the sodium/iodine symporter (NIS), norepinephrine transporter (NET), glucose transporter 1 (GLUT1), and monocarboxylate transporters (MCTs). The molecular and functional characteristics of these transporters are reviewed with special emphasis on their specific expressions in cancers and interaction with imaging or theranostic agents [e.g., I-123, I-131, ¹²³I-iobenguane (mIBG), ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ¹³C pyruvate]. Current clinical applications and research areas of these transporters in cancer diagnosis and treatment are discussed. Finally, we offer our views on emerging opportunities and challenges in targeting transporters for cancer imaging and treatment. By analyzing the few clinically successful examples, we hope much interest can be garnered in cancer research towards uptake transporters and their potential applications in cancer diagnosis and treatment.

18F-FDG-PET/CT in Canine Mammary Gland Tumors

Medical imaging techniques play a central role in clinical oncology, helping to obtain important information about the extent of disease, and plan treatment. Advanced imaging modalities such as Positron Emission Tomography-Computed Tomography (PET/CT), may help in the whole-body staging in a single procedure, although the lesions should be carefully interpreted. PET/CT is becoming commonly used in canine cancer patients, but there is still limited information available on specific tumors such as mammary cancer. We evaluated the utility of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG)-PET/CT to detect malignant lesions in eight female dogs with naturally occurring mammary tumors. A whole-body scan was performed prior to surgery, and mammary and non-mammary lesions detected either on PET/CT or during pre-surgical physical exam were resected when possible and submitted for histopathological examination. Multiple mammary lesions involving different mammary glands were detected in 5/8 dogs, for a total of 23 lesions; there were 11 non-mammary-located lesions in 6/8 dogs, three of these were lung or lymph node metastasis. A total of 34 lesions were analyzed: 22 malignant (19 mammary tumors and three metastatic lesions), and 12 benign (four mammary lesions and eight of non-mammary tissues). Glucose uptake by maximum standardized uptake value (SUVmax) was analyzed and correlated with tumor size, and benign vs. malignant pathology. We found that the minimum tumor size needed to distinguish malignant lesions according to the SUVmax was 1.5 cm; benign and malignant lesions <1.5 cm did not differ in glucose uptake (mean SUVmax = 1.1). In addition, a SUVmax value >2 was 100% sensitive for malignancy. Combining these data, lesions >1.5 cm with a SUVmax >2 had a positive predictive value of 100%. Finally, we did not find an association between SUVmax and histologic subtype or grade, which may be present in a larger sample. Thus, ¹⁸F-FDG PET/CT is useful for distinguishing malignant from benign lesion but further imaging of dogs with diverse tumors, should establish characteristic SUV value cutoffs for detecting primary and metastatic disease, and distinguishing them from benign lesions.

Potential Therapies for Infectious Diseases Based on Targeting Immune Evasion Mechanisms That Pathogens Have in Common With Cancer Cells

Many global infectious diseases are not well-controlled, underlining a critical need for new, more effective therapies. Pathogens and pathogen-infected host cells, like cancer cells, evade immune surveillance via immune evasion mechanisms. The present study indicates that pathogenic bacteria, endoparasites, and virus-infected host cells can have immune evasion mechanisms in common with cancers. These include entry into dormancy and metabolic reprogramming to aerobic glycolysis leading to excessive secretion of lactic acid and immobilization of local host immunity. The latter evasion tactic provides a therapeutic target for cancer, as shown by our recent finding that patient-derived cancer xenografts can be growth-arrested, without major host toxicity, by inhibiting their lactic acid secretion (as mediated by the MCT4 transporter)-with evidence of host immunity restoration. Accordingly, the multiplication of bacteria, endoparasites, and viruses that primarily depend on metabolic reprogramming to aerobic glycolysis for survival may be arrested using cancer treatment strategies that inhibit their lactic acid secretion. Immune evasion mechanisms shared by pathogens and cancer cells likely represent fundamental, evolutionarily-conserved mechanisms that may be particularly critical to their welfare. As such, their targeting may lead to novel therapies for infectious diseases.

FDG PET/CT and Conventional Imaging Methods in Cancer of Unknown Primary: an Approach to Overscanning

Purpose

To compare the performance of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) with conventional imaging methods (CIM), including computed tomography (CT), magnetic resonance imaging (MRI), and mammography (MMG) in cancer of unknown primary (CUP).

Methods

A total of 36 patients with CUP, who referred to our clinic for a FDG PET/CT scan, were enrolled in this study. Thirty of the patients were also examined through either diagnostic CT/MRI and/or MMG. The diagnostic performance of both methods for the primary cancer location was analyzed. The results of FDG PET/CT and CIM were compared based on the standard reference of the histopathology and/or clinical and laboratory follow-up.

Results

The primary cancer locations were detected in 24 patients (66.6%, 24/36) by FDG PET/CT, whereas CIM identified the locations in 16 patients (53.3%, 16/30). Sensitivity, specificity, PPV, NPV, and accuracy rates of the detection of the primary tumor localizations were as follows: 83, 70, 89, 58, and 79% for FDG PET/CT; 70, 62, 84, 42, and 68% for CIM, respectively. There was no statistical significance between modalities regarding any of the categories in 30 patients.

Conclusion

FDG PET/CT detected the primary tumors of the patients with CUP more than CIM did. However, the difference between them was not found to be statistically significant. It may be considered that FDG PET/CT scan can be performed as a first-line tool in the initial diagnosis of the patients with CUP and to add radiodiagnostic imaging in selective cases. We conclude that if the first-line examination of a CUP patient has been already performed by a CIM and the result was negative or inconclusive, FDG PET/CT can be considered to avoid unnecessary imaging procedures.

Increased Utilization of Positron Emission Tomography/Computed Tomography (PET/CT) Imaging and Its Economic Impact for Patients Diagnosed With Bladder Cancer

BACKGROUND

The purpose of this study was to examine temporal nationwide utilization patterns and predictors for use of positron emission tomography/computed tomography (PET/CT) in comparison with magnetic resonance imaging (MRI) and computed tomography (CT) among patients diagnosed with bladder cancer.

MATERIALS AND METHODS

A total of 36,855 patients aged 66 years or older diagnosed with clinical stage TI-IV, N0M0 bladder cancer from 2004 to 2011 were analyzed. We used multivariable logistic regression analyses to discern factors associated with receipt of imaging within 12 months from diagnosis. The Cochran-Armitage test for trend was used to determine changes in the proportion of patients receiving imaging after cancer diagnosis.

RESULTS

Independent of clinical stage, there was marked increase in use of PET/CT throughout the study period (2011 vs. 2004: odds ratio, 17.55; 95% confidence interval, 10.14-30.38; P < .001). Although use of CT imaging remained stable during the study period, there was significantly decreased utilization of MRI (odds ratio, 0.60; 95% confidence interval, 0.49-0.75; P < .001) in 2011 versus 2004. The mean incremental cost of PET/CT versus CT and MRI was $1040 and $612 (in 2016 dollars), respectively. Extrapolating these findings to the patients with bladder cancer in the United States results in excess spending of $11.6 million for PET/CT imaging.

CONCLUSION

We identified rapid adoption of PET/CT imaging independent of clinical stage, resulting in excess national spending of $11.6 million for this imaging modality alone. Further value-based research discerning the clinical versus economic benefits of advanced imaging among patients with bladder cancer are needed.

Reliability of 18F-FDG PET Metabolic Parameters Derived Using Simultaneous PET/MRI and Correlation With Prognostic Factors of Invasive Ductal Carcinoma: A Feasibility Study

OBJECTIVE

The objective of our study was to correlate semiquantitative PET parameters-standardized uptake value (SUV) and total lesion glycolysis (TLG)-derived in simultaneous PET/MRI using MRI-based attenuation correction with clinical and histopathologic prognostic factors in patients with breast cancer.

MATERIALS AND METHODS

Eighty-two invasive ductal carcinomas in 69 women were included in the study. All the subjects underwent whole-body (WB) PET/MRI (supine WB mode) and dedicated PET/MRI of the breast (prone breast imaging mode) for staging on a simultaneous PET/MRI system. The SUV and TLG values were calculated from ¹⁸F-FDG PET data using MRI-based attenuation correction (2-point Dixon sequence for tissue segmentation). Relationships between SUV and TLG values and clinical and histopathologic parameters (i.e., tumor size, tumor grade, Ki-67 status, and hormonal receptor expression status) were evaluated using Spearman correlation coefficient analysis.

RESULTS

A significant correlation was observed between mean SUV (SUV_mean) and maximum SUV (SUV_max) values derived with WB PET and regional PET of the breasts performed simultaneously with MRI (r = 0.88 and 0.89, respectively). A significant difference (p < 0.05) was observed in SUV_mean, SUV_max, and TLG values between the grades and molecular subtypes of breast cancer. High SUV_mean, SUV_max, and TLG values were found to correlate with larger tumor size (p < 0.01), higher proliferation index (p < 0.05), higher grade (p < 0.01), and triple-negative hormonal receptor status (p < 0.01, p < 0.05).

CONCLUSION

Semiquantitative FDG parameters derived with MRI-based attenuation correction in simultaneous PET/MRI are reliable and correlate with clinicopathologic features such as grade as well as subtype and thus could be used in the prognostication of breast cancer.

Association of pharmacokinetic and metabolic parameters derived using simultaneous PET/MRI: Initial findings and impact on response evaluation in breast cancer

PURPOSE

To study relationships among pharmacokinetic and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET parameters obtained through simultaneous PET/MRI in breast cancer patients and evaluate their combined potential for response evaluation.

METHODS

The study included 41 breast cancer patients for correlation study and 9 patients (pre and post therapy) for response evaluation. All patients underwent simultaneous PET/MRI with dedicated breast imaging. Pharmacokinetic parameters and PET parameters for tumor were derived using an in- house developed and vendor provided softwares respectively. Relationships between SUV and pharmacokinetic parameters and clinical as well as histopathologic parameters were evaluated using Spearman correlation analysis. Response to chemotherapy was derived as percentage reduction in size and in parameters post therapy.

RESULTS

Significant correlations were observed between SUVmean, max, peak, TLG with K^trans (ρ=0.446, 0.417, 0.491, 0.430; p≤0.01); with Kep(ρ=0.303, ρ=0.315, ρ=0.319; p≤0.05); and with iAUC(ρ=0.401, ρ=0.410, ρ=0.379; p≤0.05, p≤0.01). The ratio of ve/iAUC showed significant negative correlation to SUVmean, max, peak and TLG (ρ=0.420, 0.446, 0.443, 0.426; p≤0.01). Ability of SUV as well as pharmacokinetic parameters to predict response to therapy matched the RECIST criteria in 9 out of 11 lesions in 9 patients. Maximum post therapy quantitative reduction was observed in SUVpeak, TLG and K^trans.

CONCLUSION

Simultaneous PET/MRI enables illustration of close interactions between glucose metabolism and pharmacokinetic parameters in breast cancer patients and potential of their simultaneity in response assessment to therapy.

How far to investigate presumed psychosomatic symptoms: Lessons from a particular case…

We describe a 43-year-old patient with subacute appearance of neurological and atypical complaints of anergia, anorexia and weight loss six months earlier. In spite of several admissions in different hospitals, no underlying somatic cause could be found and he was admitted to a psychiatric hospital with a tentative diagnosis of major depressive disorder. Subsequently, he was referred to the unit of medically unexplained physical symptoms within the department of general internal medicine for assessment by the psychiatrist, involved in this programme. Based on clinical suspicion and red flag symptoms such as involuntary weight loss, a broader internal medicine reassessment, including FDG whole-body PET-CT was requested. Neurological clinical exam showed minor deviations, but neither brain imaging nor a lumbar puncture were contributory. However, FDG PET-CT revealed abnormal moderately to intensely FDG positive lymph nodes in the retroperitoneum. Laparoscopic lymph node biopsy indicated germ cell tumour metastasis. Anti-NMDA antibody positivity allowed a diagnosis of paraneoplastic anti-NMDA encephalitis. Treatment of the underlying disease, a pure seminoma stadium II, consisting of orchidectomy and chemotherapy, resulted in a spectacular regression of 'psychosomatic' symptoms with long-term ability to return to work, and documented disappearance of the anti-NMDA antibody response.

The prognostic value of tumor shadow disappearance rate on integrated PET/CT evaluation of solitary pulmonary nodules with low glucose metabolism

OBJECTIVE

This study aimed to determine the prognostic value of the tumor shadow disappearance rate (TDR) on integrated PET/computed tomography (PET/CT) evaluation of solitary pulmonary nodules (SPNs) with low glucose uptake.

MATERIALS AND METHODS

From January 2008 to September 2010, 99 patients who underwent fluorine-18 fluorodeoxyglucose PET (F-FDG-PET)/CT scanning for the evaluation of SPNs with a maximum standardized uptake value (SUVmax) below 2.75 (2.5+10%) were retrospectively reviewed. Among the 99 SPNs from these patients, 67 were malignant and 32 were benign, based on surgical pathology. Differences in baseline characteristics between the two groups were examined by means of the independent t-test, the Mann-Whitney U-test, and the χ-test. To test the efficacy of TDR for determining malignancy, the sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and positive and negative likelihood ratios (LR+ and LR-, respectively) with 95% confidence intervals were calculated using the pathological test as the gold standard.

RESULTS

Patients with malignant nodules were older than those with benign nodules (64.5 vs. 55.1 years, respectively, P<0.001) and had higher TDRs (0.8 vs. 0.3, respectively, P<0.001). The optimal cutoff point for the TDR was 0.4886 where the sensitivity, specificity, positive predictive value, and negative predictive value were 0.851, 0.844, 0.919, and 0.730, respectively, and the LR+ and LR- were 5.443 and 0177, respectively. A significant negative correlation between TDR and SUVmax was found only in the malignant group.

CONCLUSION

The diagnostic value of TDR complements the PET/CT evaluation of SPNs with a low F-FDG uptake.