[18F]FDG PET/CT for the assessment of the volume of the spleen.

BACKGROUND: The aim of this study was to report on the feasibility and accuracy of spleen volume determination on FDG PET/CT imaging using region growing and the CT part of the PET/CT examination as anatomical landmark (PET-CT based spleen volume method PBM) and volume summation of axial CT sections of the spleen as gold standard (true spleen volume (TSV). We also aimed to compare results obtained to the estimative methods (ESV). METHODS: Thirty-nine FDG PET/CT images taken from 32 patients (15 women, age range: 16-83 years) suffering from lymphoma, covering a wide range of spleen volumes based on visual CT assessment, in whom CT as well as FDG PET images revealed no focal spleen abnormalities were included for analysis. ESV1, ESV2 and PBM were determined on all examinations and compared to TSV. RESULTS: ESV1 volumes were significantly larger (median 668 cm3 [range: 121-4303 cm3] [P=0.0001]) and ESV2 volumes significantly smaller (median 424 cm3 [range: 84-2679 cm3] [P=0.0001]) when compared to TSV volumes (median 582 cm3 [range: 105-4847 cm3] which was not so for PBS volumes (median 540cm3 [range: 120-4560 cm3]). Time needed for TSV assessment (median: 17 min. [range: 6-65 min.]) was related to spleen volume (r=0.691 [P=0.0001]). The mean and standard deviation of the percentage spread (ESV1, ESV2, PBM-TSV/100%) around the mean (ESV1, ESV2, PBM+TSV/2) were respectively 18%±15.6% (ESV1 vs. TSV), -25%±15.6% (ESV2 vs. TSV) and -2.8%±12.3% (PBM vs. TSV). Mean SUVmax of the spleen was 4.8 SUV (SD: 2.6 SUV), mean percentage cut-off for region growing was 7.3% (sd: 5.8%). Spleen volumes defined by PBM correlated with their corresponding SUVmax value (r=0.469 [P=0.03]). Time needed for PBM measurements was between 2-3 min in all patients. CONCLUSION: Spleen volumes may be rapidly and accurately derived from the FDG PET part of the PET/CT examination through region growing and by using the CT part of the PET/CT examination as anatomical landmark for contour delineation. As opposed to ESV1 and ESV2, the PBM method does not suffer from a systematic bias and shows a smaller variation against the mean percentage difference. Combining functional and morphological data for spleen volume assessment is time-saving.

Radiolabelled probes targeting tumor hypoxia for personalized medicine.

Hypoxia is a characteristic feature of many solid tumors which has been described in a wide range of tumor types. Its presence impairs the effectiveness of common anti-cancer therapies and accordingly, tumor hypoxia has been associated with an aggressive tumor phenotype, poor response to radio- and chemotherapy, and worse prognosis. In order to predict outcome and identify patients with a worse prognosis and/or patients that would benefit from appropriate treatments, in vivo measurement of tumor hypoxia is required. Given the difficulties associated with invasive methods, a non-invasive method is of major clinical interest. Although several candidate molecules have been labeled with PET and SPECT labels, none of them is used in daily clinical routine due to a number of difficulties that complicate their use. This review aims to give an overview of the most important hypoxia tracers, their prognostic significance and how these tracers can play a role in tomorrows personalized medicine.

Pharmacologic activation of tumor hypoxia: a means to increase tumor 2-deoxy-2-[18F]fluoro-D-glucose uptake?

Tumor hypoxia and tumor metabolism are linked through the activation of metabolic genes following hypoxia-inducible factor 1 (HIF-1) activation. This raises the question of whether this relationship can be exploited to improve 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography ([(18)F]FDG-PET). To do this, [(18)F]FDG uptake was investigated after chemical induction of hypoxia and chemical activation of HIF-1 in an in vitro and an in vivo model of a human colorectal carcinoma. [(18)F]FDG uptake, HIF-1α protein levels, and messenger ribonucleic acid expression of glucose transporter 1 (GLUT1), hexokinase 2, HIF-1α, and carbonic anhydrase IX (CA IX) were determined in HT29 cells after treatment with 200 µM CoCl(2) and 500 µM dimethyloxalylglycine (DMOG). In an HT29 xenograft, the distribution of endogenous and exogenous markers of hypoxia was investigated using immunohistochemistry, and tumor [(18)F]FDG uptake was determined after treatment with a single dose of 5 mg/kg hydralazine and 8 mg DMOG. Treatment of HT29 cells with CoCl(2) and DMOG induced functional HIF-1 and resulted in increased [(18)F]FDG uptake. In an HT29 xenograft, a similar spatial distribution of pimonidazole, CA IX, and GLUT1 was found, and treatment with DMOG resulted in significant increases in maximum and mean standardized uptake values using [(18)F]FDG-PET. Chemical activation of HIF-1 can increase in vitro and in vivo [(18)F]FDG uptake. Imaging after pharmacologic HIF-1 activation might increase tumor [(18)F]FDG uptake when using [(18)F]FDG-PET.

SIRT of liver metastases: physiological and pathophysiological considerations.

Available literature on the differences in circulation and microcirculation of normal liver and liver metastases as well as in rheology of the different radiolabelled microspheres [(99m)Tc-labelled macroaggregates of albumin (MAA), (90)Y-TheraSpheres and (90)Y-SIR-spheres] used in selective internal radiation therapy (SIRT) are reviewed and implications thereof on the practice of SIRT discussed. As a result of axial accumulation and skimming, large microspheres are preferentially deposited in regions of high flow, whereas smaller microspheres are preferentially diverted to regions of low flow. As flow to normal liver tissue is considerably variable between segments and also within one segment, microspheres will be delivered heterogeneously within the microvasculature of normal liver tissue. This non-uniformity in microsphere distribution in normal liver tissue has a significant "liver-sparing" effect on the dose distribution of (90)Y-labelled microspheres. Arterial flow to liver metastases is most pronounced in the hypervascular rim of metastases, followed by the smaller metastases and finally by the central hypoperfused region of the larger metastases. Because of the wide variability in size of labelled MAAs and because of the skimming effect, existing differences in flow between metastatic lesions of variable size are likely exaggerated on (99m)Tc-MAA scintigraphy when compared to (90)Y-TheraSpheres and (90)Y-SIR-spheres (smaller variability in size and probably also in specific activity). Ideally, labelled MAAs would contain a size range similar to that of (90)Y-SIR-spheres or (90)Y-TheraSpheres. Furthermore, the optimal number of MAA particles to inject for the pretreatment planning scintigraphy warrants further exploration as it was shown that concentrated suspensions of microspheres produce more optimal tumour to normal liver distribution ratios. Finally, available data suggest that the flow-based heterogeneous distribution of microspheres to metastatic lesions of variable size might be optimized, that is rendered more homogeneous, through the combined use of angiotensin II and degradable starch microspheres.

Single-photon emission computed tomographic imaging of the early time course of therapy-induced cell death using technetium 99m tricarbonyl His-annexin A5 in a colorectal cancer xenograft model.

As apoptosis occurs over an interval of time after administration of apoptosis-inducing therapy in tumors, the changes in technetium 99m ((99m)Tc)-tricarbonyl (CO)3 His-annexin A5 (His-ann A5) accumulation over time were examined. Colo205-bearing mice were divided into six treatment groups: (1) control, (2) 5-fluorouracil (5-FU; 250 mg/kg), (3) irinotecan (100 mg/kg), (4) oxaliplatin (30 mg/kg), (5) bevacizumab (5 mg/kg), and (6) panitumumab (6 mg/kg). (99m)Tc-(CO)3 His-ann A5 was injected 4, 8, 12, 24, and 48 hours posttreatment, and micro-single-photon emission computed tomography was performed. Immunostaining of caspase-3 (apoptosis), survivin (antiapoptosis), and LC3-II (autophagy marker) was also performed. Different dynamics of (99m)Tc-(CO)3 His-ann A5 uptake were observed in this colorectal cancer xenograft model, in response to a single dose of three different chemotherapeutics (5-FU, irinotecan, and oxaliplatin). Bevacizumab-treated mice showed no increased uptake of the radiotracer, and a peak of (99m)Tc-(CO)3 His-ann A5 uptake in panitumumab-treated mice was observed 24 hours posttreatment, as confirmed by caspase-3 immunostaining. For irinotecan-, oxaliplatin-, and bevacizumab-treated tumors, a significant correlation was established between the radiotracer uptake and caspase-3 immunostaining (r  =  .8, p < .05; r  =  .9, p < .001; r  =  .9, p < .001, respectively). For 5-FU- and panitumumab-treated mice, the correlation coefficients were r  =  .7 (p  =  .18) and r  =  .7 (p  =  .19), respectively. Optimal timing of annexin A5 imaging after the start of different treatments in the Colo205 model was determined.

In vitro 2-deoxy-2-[18F]fluoro-D-glucose uptake: practical considerations.

In oncology 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]-FDG), a glucose analogue, is the most used positron emission tomography (PET) tracer. There are however some limitations due to low metabolic activity or high surrounding physiological uptake in several tumors or regions. Investigating new tracers or methods is expensive and elaborative when animal experiments or phase I clinical trials are used. In vitro experiments can overcome these limitations. We analyzed the influence of incubation time, cell medium conditions, administered activity, and cell density on [(18)F]-FDG uptake in six different cell cultures. Glucose transporter 1 (GLUT1)- and hexokinase 2 (HK2)-expression at high and low cell density was analyzed using immunocytochemistry. FDG-uptake increases over time and absence of glucose in the incubation medium increases uptake. By increasing the administered activity, uptake per protein also increases and tracer uptake per protein is lower at higher cell densities. Immunocytochemical analysis reveals a lower expression of both GLUT1 and HK2 at higher cell concentrations. All investigated parameters influenced FDG uptake and therefore we can conclude it is of utmost importance to keep administered activity, incubation medium, and time constant and to correct uptake when cell density changes due to environmental conditions, such as therapy.

99mTc-labeled tricarbonyl his-CNA35 as an imaging agent for the detection of tumor vasculature.

UNLABELLED: Given the importance of angiogenesis for a tumor's survival and growth, several therapeutic strategies rely on the selective inhibition of angiogenesis and the destruction of existing tumor vasculature. These strategies raise the need for a noninvasive tool to evaluate tumor vasculature. We describe the radiosynthesis and evaluation of an imaging tracer that specifically binds tumor subendothelial collagen and thereby images tumor vasculature. METHODS: (99m)Tc-tricarbonyl was prepared and labeled with His-collagen-binding adhesion protein 35 (CNA35). After in vitro specificity testing, in vivo biodistribution and dosimetric studies were performed in healthy nude mice via planar imaging. (99m)Tc-(CO)(3) His-CNA35 was evaluated for in vivo imaging of tumor vasculature in a HT29 colorectal carcinoma xenograft. RESULTS: The labeling procedure yielded a compound with 95%-99% radiochemical purity and good in vitro stability. An in vitro binding test confirmed specificity and functionality. (99m)Tc-(CO)(3) His-CNA35 rapidly cleared from the blood and predominantly accumulated in the kidneys and liver. The effective dose for a proposed single injection of 500 MBq of (99m)Tc-(CO)(3) His-CNA35 is 3.70 mSv per organ or 2.01 mSv/g of tissue. Tumors were successfully visualized, and uptake correlated with ex vivo immunohistochemical staining of tumor vasculature. CONCLUSION: (99m)Tc-(CO)(3) His-CNA35 may be a useful radioligand for the in vivo detection of tumor vasculature through subendothelial collagen binding. A noninvasive method of imaging tumor vasculature that could provide a reliable assessment of tumor vasculature would allow evaluation of the effectiveness of commonly used antiangiogenic therapies and determination of their optimal dosing and scheduling.

Expression and prognostic value of glucose transporters and hexokinases in tonsil and mobile tongue squamous cell carcinoma.

The aim of this study was to assess the expression pattern and prognostic value of the high affinity glucose transporters GLUT-1, 3, 4, 8 and 9, SGLT-1 and of hexokinases (HK) I, II and III in squamous cell carcinoma of the tonsil and mobile tongue (TTSCC) by means of immunohistochemistry. Seventy-one consecutive patients suffering from TTSCC were included. The intensity and amount of positive tumour cells in the immunoreaction (histology score (H-score)) for GLUT-1, 3, 4, 8 and 9 as well as for HK-I, II and III were assessed independently by two experienced observers, blinded to the clinical results. H-scores as well as clinical variables were related to patient outcome. Median follow-up time was 49 months (range 1-123 months). Mean H-scores for GLUT expression in decreasing order of magnitude were respectively 10.99 for GLUT-1 (sd 3.9), 5.7 for GLUT-8 (sd 4.0), 5.4 for GLUT-3 (sd 3.7), 1.0 for GLUT-4 (sd 2.0), 1.1 (sd 1.3) for SGLT-1, and 0.4 for GLUT-9 (sd 0.6); GLUT-1 > GLUT-8 = GLUT-3 > GLUT-4 = GLUT-9 = SGLT-1 (with > meaning significantly (p<0.05 on ANOVA + posthoc Bonferroni correction) higher than and =, meaning not significantly different from). Mean H-scores for hexokinase expression were respectively 5.8 for HK-I (sd 3.5), 4.6 for HK-II (sd 3.0) and 2.0 for HK-III (sd 2.0); HK-I > HK-II > HK-III. Finally high H-scores for GLUT-4 were favourably related to disease-free and overall survival on multivariate analysis. To conclude, TTSCC expresses a wide variety of glucose transporter systems and hexokinase enzymes with the "housekeeping" GLUT-1 and HK-I being the most intensely expressed. GLUT-4 over-expression appears to confer a favourable prognosis in squamous cell carcinoma of the tonsil and mobile tongue. Additional studies confirming this finding in larger cohorts of patients are mandatory.

In vivo imaging of apoptosis in oncology: an update.

In this review, data on noninvasive imaging of apoptosis in oncology are reviewed. Imaging data available are presented in order of occurrence in time of enzymatic and morphologic events occurring during apoptosis. Available studies suggest that various radiopharmaceutical probes bear great potential for apoptosis imaging by means of positron emission tomography and single-photon emission computed tomography (SPECT). However, for several of these probes, thorough toxicologic studies are required before they can be applied in clinical studies. Both preclinical and clinical studies support the notion that 99mTc-hydrazinonicotinamide-annexin A5 and SPECT allow for noninvasive, repetitive, quantitative apoptosis imaging and for assessing tumor response as early as 24 hours following treatment instigation. Bioluminescence imaging and near-infrared fluorescence imaging have shown great potential in small-animal imaging, but their usefulness for in vivo imaging in humans is limited to structures superficially located in the human body. Although preclinical tumor-based data using high-frequency-ultrasonography (US) are promising, whether or not US will become a routinely clinically useful tool in the assessment of therapy response in oncology remains to be proven. The potential of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) for imaging late apoptotic processes is currently unclear. Neither 31P MRS nor 1H MRS signals seems to be a unique identifier for apoptosis. Although MRI-measured apparent diffusion coefficients are altered in response to therapies that induce apoptosis, they are also altered by nonapoptotic cell death, including necrosis and mitotic catastrophe. In the future, rapid progress in the field of apoptosis imaging in oncology is expected.

Carbonic anhydrase IX expression correlates with FDG uptake by primary non-small cell lung cancer.

Tumor cells are characterized by an increased rate of glucose consumption and glycolysis. This increased glucose consumption leads to tumor acidification, which represents a major obstacle for several therapeutic strategies. Tumor cells have adapted to this acidification by upregulation of several H(+)-extruding transporter systems and proteins to cope with this compromised situation. One of these proteins is carbonic anhydrase IX (CA IX), which catalyzes the reversible hydration of carbon dioxide to carbonic acid outside the cell, leading to an acidic extracellular pH and a physiological intracellular pH. The aim of this article was to study semiquantitatively the expression of CA IX in non-small cell lung cancer (NSCLC) and to assess the existence of a possible relationship between CA IX expression and tumor FDG uptake, reflecting glucose metabolism. The levels and the extent of CA IX expression were estimated in immunohistochemical stained, formalin-fixed, paraffin-embedded tissue samples from 18 patients with NSCLC and compared with FDG uptake in FDG-PET imaging. We found a statistically significant correlation between CA IX Hscores and SUVmax and SUVmean values of the primary tumor. This relationship provides indirect evidence for cotranscription of glucose transporters and hexokinases that drive tumor hyperglycolysis and for CA IX governed by hypoxia-inducible factor-1 and suggests that, in the future, it may be possible to identify NSCLC patients who are most likely to benefit from CA IX targeting therapy on the basis of FDG-PET imaging.

Combined effect of EPO and radiotherapy on the expression of endogenous molecular markers of tumor metabolism and metastasis.

Erythropoietin (EPO) has been used to correct cancer-related anemia and to improve tumor hypoxia, which both adversely affect the clinical condition of cancer patients and response to radiotherapy. Data available on the effects of EPO treatment in cancer are, however, conflicting. Several clinical studies investigating the influence of EPO treatment have given contradictory results as to whether or not this treatment positively influences survival. In light of these conflicting results, we studied the effects of EPO treatment either alone or in combination with radiotherapy on tumor oxygenation and on the expression pattern of several proteins related to tumor metabolism, survival, and spread in a rat colorectal cancer model. We found a statistically significant upregulation of hexokinase I, N-cadherin, and glucose transporter 3 when EPO treatment was combined with radiotherapy. Because these three proteins have distinct functions in protecting the cell in compromised conditions, these results indicate a detrimental role for the combination of EPO treatment and radiotherapy through the stimulation of tumor-cell metabolism, inhibition of apoptosis, and stimulation of tumor spread and seem to indicate that recombinant human EPO treatment negatively modulates radiotherapy efficacy.

Forcing cancer cells to commit suicide.

Apoptosis plays a crucial role in the normal development, homeostasis of multicellular organisms, carcinogenic process, and response of cancer cells to anticancer drugs. It is a genetically strictly regulated process, controlled by the balance between pro- and antiapoptotic proteins. Resistance to standard chemotherapeutics also seems to be an apoptosis-related process due to failure to activate the apoptotic machinery. Hence, the molecular pathways (extrinsic and intrinsic) regulating the apoptotic process are attractive targets for potential therapeutic intervention. The goal of proapoptotic drugs is to selectively induce apoptosis in the tumor cell while leaving healthy cells unharmed. Several proapoptotic receptor agonists have recently been developed, activating selectively the extrinsic pathway, and give promising results. Targets for the intrinsic pathway include the Bcl-2 family proteins, the inhibitor of apoptosis proteins, the p53 pathway, and many others. However, several studies have implicated that using monotherapy will probably not be sufficient to sensitize or induce apoptosis in all tumor cells. Most promising results, in terms of killing the tumor cell, will be achieved by the combination of various therapeutic strategies. In this review, promising apoptosis-inducing anticancer therapies are summarized.

Molecular imaging of hypoxia with radiolabelled agents.

Tissue hypoxia results from an inadequate supply of oxygen (O2) that compromises biological functions. Structural and functional abnormalities of the tumour vasculature together with altered diffusion conditions inside the tumour seem to be the main causes of tumour hypoxia. Evidence from experimental and clinical studies points to a role for tumour hypoxia in tumour propagation, resistance to therapy and malignant progression. This has led to the development of assays for the detection of hypoxia in patients in order to predict outcome and identify patients with a worse prognosis and/or patients that would benefit from appropriate treatments. A variety of invasive and non-invasive approaches have been developed to measure tumour oxygenation including oxygen-sensitive electrodes and hypoxia marker techniques using various labels that can be detected by different methods such as positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), autoradiography and immunohistochemistry. This review aims to give a detailed overview of non-invasive molecular imaging modalities with radiolabelled PET and SPECT tracers that are available to measure tumour hypoxia.