Antigen-Drug Conjugates as a Novel Therapeutic Class for the Treatment of Antigen-Specific Autoimmune Disorders.

Multiple sclerosis represents the world's most common cause of neurological disability in young people and is attributed to a loss of immune tolerance toward proteins of the myelin sheath. Typical treatment options for MS patients involve immunomodulatory drugs, which act nonspecifically, resulting in global immunosuppression. The study discussed herein aims to demonstrate the efficacy of antigen-specific immunotherapies involving the conjugation of disease causing autoantigen, PLP139-151, and a potent immunosuppressant, dexamethasone. Antigen-drug conjugates (AgDCs) were formed using copper-catalyzed azide-alkyne cycloaddition chemistry with the inclusion of a hydrolyzable linker to maintain the activity of released dexamethasone. Subcutaneous administration of this antigen-drug conjugates to SJL mice induced with experimental autoimmune encephalomyelitis, protected the mice from a symptom onset throughout the 25 day study, demonstrating enhanced efficacy in comparison to dexamethasone treatment. These results highlight the benefits of co-delivery of autoantigens with immunosuppressant drugs as AgDCs for the treatment of autoimmune diseases.

Soluble Antigen Arrays for Selective Desensitization of Insulin-Reactive B Cells.

Autoimmune diseases are believed to be highly dependent on loss of immune tolerance to self-antigens. Currently, no treatments have been successful clinically in inducing autoantigen-specific tolerance, including efforts to utilize antigen-specific immunotherapy (ASIT) to selectively correct the aberrant autoimmunity. Soluble antigen arrays (SAgAs) represent a novel autoantigen delivery system composed of a linear polymer, hyaluronic acid (HA), displaying multiple copies of conjugated autoantigen. We have previously reported that soluble antigen arrays displaying proteolipid peptide (SAgAPLP) induced tolerance to this specific multiple sclerosis (MS) autoantigen. Utilizing SAgA technology, we have developed a new ASIT as a possible type 1 diabetes (T1D) therapeutic by conjugating human insulin to HA, known as soluble antigen array insulin (SAgAIns). Three types were synthesized, low valency lvSAgAIns (2 insulins per HA), medium valency mvSAgAIns (4 insulins per HA), and, high valency hvSAgAIns (9 insulins per HA), to determine if valency differentially modulates the ex vivo activity of insulin-binding B cells (IBCs). Extensive biophysical characterization was performed for the SAgA molecules. SAgAIns molecules were successfully used to affect the biologic activity of IBCs by inducing desensitization of the B cell antigen receptors (BCR). SAgAIns bound specifically to insulin-reactive B cells without blocking epitopes recognized by antibodies against the Fc regions of membrane immunoglobulin or CD79 transducer components of the BCR. Preincubation of IBCs (125Tg) with SAgAIns, but not HA alone, rendered the IBCs refractory to restimulation. SAgAIns induced a decrease in BCR expression and IP3R-mediated intracellular calcium release. Surprisingly, SAgAIns binding to BCR on the surface of IBCs induced the observed effects at both high and low SAgAIns valency. Future studies aim to test the effects of SAgAIns on disease progression in the VH125.NOD mouse model of T1D.

Acute B-Cell Inhibition by Soluble Antigen Arrays Is Valency-Dependent and Predicts Immunomodulation in Splenocytes.

Antigen valency plays a fundamental role in directing the nature of an immune response to be stimulatory or tolerogenic. Soluble antigen arrays (SAgAs) are an antigen-specific immunotherapy that combats autoimmunity through the multivalent display of autoantigen. Although mechanistic studies have shown SAgAs to induce T- and B-cell anergy, the effect of SAgA valency has never been experimentally tested. Here, SAgAs of discrete antigen valencies were synthesized by click chemistry and evaluated for acute B-cell signaling inhibition as well as downstream immunomodulatory effects in splenocytes. Initial studies using the Raji B-cell line demonstrated SAgA valency dictated the extent of calcium flux. Lower valency constructs elicited the largest reductions in B-cell activation. In splenocytes from mice with experimental autoimmune encephalomyelitis, the same valency-dependent effects were evident in the downregulation of the costimulatory marker CD86. The reduction of calcium flux observed in Raji B-cells correlated strongly with downregulation in splenocyte CD86 expression after 72 h. Here, a thorough analysis of SAgA antigenic valency illustrates that low, but not monovalent, presentation of autoantigen was ideal for eliciting the most potent immunomodulatory effects.

Practical Considerations, Challenges, and Limitations of Bioconjugation via Azide-Alkyne Cycloaddition.

Interrogating biological systems is often limited by access to biological probes. The emergence of "click chemistry" has revolutionized bioconjugate chemistry by providing facile reaction conditions amenable to both biologic molecules and small molecule probes such as fluorophores, toxins, or therapeutics. One particularly popular version is the copper-catalyzed azide-alkyne cycloaddition (AAC) reaction, which has spawned new alternatives such as the strain-promoted azide-alkyne cycloaddition reaction, among others. This focused review highlights practical approaches to AAC reactions for the synthesis of peptide or protein bioconjugates and contrasts current challenges and limitations in light of recent advances in the field. The conical success of antibody drug conjugates has expanded the toolbox of linkers and payloads to facilitate practical applications of bioconjugation to create novel therapeutics and biologic probes. The AAC reaction in particular is poised to enable a large set of functionalized molecules as a combinatorial approach to high-throughput bioconjugate generation, screening, and honing of lead compounds.

Soluble antigen arrays provide increased efficacy and safety over free peptides for tolerogenic immunotherapy.

Autoantigen-specific immunotherapy using peptides offers a more targeted approach to treat autoimmune diseases, but clinical implementation has been challenging. We previously showed that multivalent delivery of peptides as soluble antigen arrays (SAgAs) efficiently protects against spontaneous autoimmune diabetes in the non-obese diabetic (NOD) mouse model. Here, we compared the efficacy, safety, and mechanisms of action of SAgAs versus free peptides. SAgAs, but not their corresponding free peptides at equivalent doses, efficiently prevented the development of diabetes. SAgAs increased the frequency of regulatory T cells among peptide-specific T cells or induce their anergy/exhaustion or deletion, depending on the type of SAgA used (hydrolysable (hSAgA) and non-hydrolysable 'click' SAgA (cSAgA)) and duration of treatment, whereas their corresponding free peptides induced a more effector phenotype following delayed clonal expansion. Over time, the peptides induced an IgE-independent anaphylactic reaction, the incidence of which was significantly delayed when peptides were in SAgA form rather than in free form. Moreover, the N-terminal modification of peptides with aminooxy or alkyne linkers, which was needed for grafting onto hyaluronic acid to make hSAgA or cSAgA variants, respectively, influenced their stimulatory potency and safety, with alkyne-functionalized peptides being more potent and less anaphylactogenic than aminooxy-functionalized peptides. Immunologic anaphylaxis occurred in NOD mice in a dose-dependent manner but not in C57BL/6 or BALB/c mice; however, its incidence did not correlate with the level of anti-peptide antibodies. We provide evidence that SAgAs significantly improve the efficacy of peptides to induce tolerance and prevent autoimmune diabetes while at the same time reducing their anaphylactogenic potential.

Soluble antigen arrays improve the efficacy and safety of peptide-based tolerogenic immunotherapy.

Autoantigen-specific immunotherapy using peptides offers a more targeted approach to treat autoimmune diseases, but the limited in vivo stability and uptake of peptides impedes clinical implementation. We previously showed that multivalent delivery of peptides as soluble antigen arrays (SAgAs) efficiently protects against spontaneous autoimmune diabetes in the non-obese diabetic (NOD) mouse model. Here, we compared the efficacy, safety, and mechanisms of action of SAgAs versus free peptides. SAgAs, but not their corresponding free peptides at equivalent doses, efficiently prevented the development of diabetes. SAgAs increased the frequency of regulatory T cells among peptide-specific T cells or induce their anergy/exhaustion or deletion, depending on the type of SAgA (hydrolysable (hSAgA) and non-hydrolysable 'click' SAgA (cSAgA)) and duration of treatment, whereas their corresponding free peptides induced a more effector phenotype following delayed clonal expansion. Moreover, the N-terminal modification of peptides with aminooxy or alkyne linkers, which was needed for grafting onto hyaluronic acid to make hSAgA or cSAgA variants, respectively, influenced their stimulatory potency and safety, with alkyne-functionalized peptides being more potent and less anaphylactogenic than aminooxy-functionalized peptides. Both SAgA variants significantly delayed anaphylaxis compared to their respective free peptides. The anaphylaxis, which occurred in NOD mice but not in C57BL/6 mice, was dose-dependent but did not correlate with the production of IgG1 or IgE against the peptides. We provide evidence that SAgAs significantly improve the efficacy and safety of peptide-based immunotherapy.

Design, synthesis and identification of a new class of triarylmethyl amine compounds as inhibitors of apolipoprotein E production.

We have identified a new class of triarylmethyl amine compounds that can inhibit apolipoprotein E (apoE) production. ApoE is a cholesterol- and lipid-carrier protein implicated in aging, atherosclerosis, Alzheimer's Disease (AD), and other neurological and lipid-related disorders. Attenuation of apoE production is generally considered to be of therapeutic value. A majority of the apoE in the brain is produced by astrocytes. Here, we describe the design, synthesis, and biological screening of a small library of compounds that led to the identification of four triarylmethyl amines as potent inhibitors of apoE production in CCF-STTG1 astrocytoma cells.

Soluble Antigen Arrays Efficiently Deliver Peptides and Arrest Spontaneous Autoimmune Diabetes.

Antigen-specific immunotherapy (ASIT) offers a targeted treatment of autoimmune diseases that selectively inhibits autoreactive lymphocytes, but there remains an unmet need for approaches that address the limited clinical efficacy of ASIT. Soluble antigen arrays (SAgAs) deliver antigenic peptides or proteins in multivalent form, attached to a hyaluronic acid backbone using either hydrolysable linkers (hSAgAs) or stable click chemistry linkers (cSAgAs). They were evaluated for the ability to block spontaneous development of disease in a nonobese diabetic mouse model of type 1 diabetes (T1D). Two peptides, a hybrid insulin peptide and a mimotope, efficiently prevented the onset of T1D when delivered in combination as SAgAs, but not individually. Relative to free peptides administered at equimolar dose, SAgAs (particularly cSAgAs) enabled a more effective engagement of antigen-specific T cells with greater persistence and induction of tolerance markers, such as CD73, interleukin-10, programmed death-1, and KLRG-1. Anaphylaxis caused by free peptides was attenuated using hSAgA and obviated using cSAgA platforms. Despite similarities, the two peptides elicited largely nonoverlapping and possibly complementary responses among endogenous T cells in treated mice. Thus, SAgAs offer a novel and promising ASIT platform superior to free peptides in inducing tolerance while mitigating risks of anaphylaxis for the treatment of T1D.

[Diagnostic and therapeutic impact of 18F-FDG-PET/CT in patients with suspected breast cancer recurrence]. / Impacto diagnóstico y terapéutico de la (18)F-FDG-PET/TAC en pacientes con sospecha de recidiva de cáncer de mama.

Breast cancer is a tumor with high prevalence in our environment. Thus, it is essential to make an early diagnosis in both the primary disease and its recurrence, given the high mortality of the cases with the advanced disease. Our study has aimed to evaluate the impact of (18)F-FDG-PET/CT in patients with suspected breast cancer recurrence and their therapeutic management. This study analyzed the PET/CT of 70 patients with a background of breast cancer and suspicion of recurrence, either because of elevation of tumor markers (n=28), doubtful findings on other imaging techniques (n=56) and/or suspicious symptoms (n=1). All the patients underwent a standard FDG-PET study acquired in combination with low-dose CT. The studies were considered pathological in 34 of the 70 patients, with 29 true positive, 32 true negative, 5 false positive and 4 false negative results. The final diagnosis was established either by histopathologic confirmation (n=17), other imaging techniques (n=26) and/or clinical radiological follow-up (n=27, mean 12.7 months). The sensitivity, specificity, positive predictive value and negative predictive values obtained were 87.8%, 86.4%, 85.2% and 88.8%, respectively. Therapeutic management was modified in 41% of the patients. In conclusion, PET/CT is a technique with high diagnostic yield in patients with suspected breast cancer recurrence.

Soluble Antigen Arrays Displaying Mimotopes Direct the Response of Diabetogenic T Cells.

Type 1 diabetes (T1D) is an autoimmune disorder which develops when insulin-producing, pancreatic beta cells are destroyed by an aberrant immune response. Current therapies for T1D either treat symptoms or cause global immunosuppression, which leave patients at risk of developing long-term complications or vulnerable to foreign pathogens. Antigen-specific immunotherapies have emerged as a selective approach for autoimmune diseases by inducing tolerance while mitigating global immunosuppression. We previously reported SAgAs with multiple copies of a multiple sclerosis (MS) autoantigen grafted onto hyaluronic acid (HA) as an efficacious therapy in experimental autoimmune encephalomyelitis. While the immune response of MS is distinct from that of T1D, the mechanism of SAgAs was hypothesized to be similar and via induction of immune tolerance to diabetes antigens. We synthesized SAgAs composed of HA polymer backbone conjugated with multiple copies of the T1D autoantigen mimotope p79 using aminooxy chemistry (SAgAp79) or using copper-catalyzed alkyne-azide cycloaddition (cSAgAp79) chemistry. SAgAs constructed using the hydrolyzable aminooxy linkage, thus capable of releasing p79, exhibited physicochemical properties similar to the triazole linkage. Both SAgAp79 versions showed high specificity and efficacy in stimulating epitope-specific T cells. SAgAs can be taken up by most immune cell populations but do not induce their maturation, and conventional dendritic cells are responsible for the brunt of antigen presentation within splenocytes. cSAgAp79 was more stimulatory than SAgAp79 both in vitro and in vivo, an effect that was ascribed to the peptide modification rather than the type of linkage. In summary, we provide here the first proof-of-principle that SAgA therapy could also be applicable to T1D.

Glatiramer acetate persists at the injection site and draining lymph nodes via electrostatically-induced aggregation.

Glatiramer acetate (GA) is widely prescribed for the treatment of relapsing-remitting multiple sclerosis, however, the mechanism of action is still not fully understood. We investigated the structural properties of GA and examined alterations to the drug upon injection into the subcutaneous space. First, a variety of biophysical characterization techniques were employed to characterize GA in solution. GA was found to exist as alpha helices in solution with a hydrodynamic radius of ~3 nm in size. To simulate GA behavior at the site of injection, GA was injected into a solution of 1.5 MDa hyaluronic acid (HA). Visible aggregates were observed immediately upon injection and subsequent testing indicated aggregation was driven by electrostatic interactions between the positively-charged GA and negatively-charged HA. In vivo testing confirmed GA formed spherical particles in the nano- to micrometer size range, suggesting this mechanism contributes to persistence at the injection site and in draining lymph nodes. The aggregates were found to associate with glycosaminoglycans, suggesting an electrostatic mechanism of induced aggregation like the simulated injection. These novel observations may help explain the complex immunomodulatory mechanisms of GA and adverse injection site reactions seen in patients.

[Transcultural validation in Spanish of the Actionable Bladder Symptoms Screening Tool]. / Validacion transcultural al castellano del Actionable Bladder Symptoms Screening Tool.

INTRODUCTION: Disorders of the lower urinary tract are frequent in patients with multiple sclerosis throughout the course of the disease and reach variable prevalences close to 75%. It is essential to obtain an early diagnosis in the initial phases and to implement an optimal therapeutic management. Burks et al developed the Actionable Bladder Symptoms Screening Tool (ABSST) as a useful screening test in such disorders. Later, Bates et al developed a short version of the ABSST with the objective of minimising the time required to complete it and making it easier to use. AIMS: To carry out the transcultural validation into Spanish of the short version of the ABSST. PATIENTS AND METHODS: The ABSST was translated into Spanish and then back-translated into English, which confirmed the semantic equivalence. A field test was conducted on 40 patients with multiple sclerosis, with two extra questions being included at the end in order to check the comprehension and acceptability of the tool, together with a final item that asked for the time spent on completing it. RESULTS: Forty patients were selected In accordance with the eligibility and exclusion criteria; 67.5% of them were females and the overall mean age was 46.2 years. The rate of comprehension of the test was 100%, and that of acceptability was 97.5%. Results showed that 57.5% obtained scores >= 3, and an average of 5.33 minutes were spent on completing it. CONCLUSIONS: As a brief screening questionnaire for urinary disorders in multiple sclerosis, the ABSST is a useful tool for detecting them at an early stage and has now been validated for use in Spanish.

TITLE: Validacion transcultural al castellano del Actionable Bladder Symptoms Screening Tool.Introduccion. Los trastornos del tracto urinario inferior son frecuentes en pacientes con esclerosis multiple a lo largo del transcurso de la enfermedad y alcanzan prevalencias variables cercanas al 75%. Es primordial realizar un diagnostico precoz en fases tempranas y un abordaje terapeutico optimo. Burks et al elaboraron el Actionable Bladder Symptoms Screening Tool (ABSST) como herramienta de cribado util de dichos trastornos. Posteriormente, Bates et al desarrollaron una version corta del ABSST con el objetivo de minimizar el tiempo de realizacion y facilitar su manejo. Objetivo. Realizar la validacion transcultural al castellano de la version breve del ABSST. Pacientes y metodos. Se realizo la traduccion al castellano del ABSST y una posterior retrotraduccion al ingles que confirmaba su equivalencia semantica. Se llevo a cabo una prueba de campo en 40 pacientes con esclerosis multiple, incluyendo dos preguntas finales para comprobar la comprension y aceptabilidad de la herramienta y un ultimo item que recogia el tiempo empleado para su realizacion. Resultados. Se seleccionaron 40 pacientes conforme a los criterios de inclusion y exclusion; el 67,5% eran mujeres y la media global de edad era de 46,2 años. La comprension del test fue del 100%, y la aceptabilidad, del 97,5%. El 57,5% obtuvo puntuaciones >= 3, y se emplearon 5,33 minutos de media. Conclusiones. El ABSST como cuestionario de cribado breve de trastornos urinarios en la esclerosis multiple es una herramienta util para su deteccion temprana y queda validado para su uso en castellano.

[(18)F-FDG PET/CT in the evaluation of patients suspected of paraneoplastic neurological syndrome]. / PET/TC con (18)F-FDG en la valoración de pacientes con sospecha de síndrome paraneoplásico neurológico.

OBJECTIVE: This study aimed to determine the diagnostic impact of (18)F-FDG PET/CT based on the clinical features of paraneoplastic neurological syndrome (PNS). MATERIAL AND METHODS: Multicenter retrospective and longitudinal study of patients with suspicion of PNS. The clinical picture was classified into classic (CS) and non-classic syndrome (NCS). After the follow-up, the definitive or possible diagnosis of PNS was established. The pictures that did not match any of the previous criteria were categorized as non-classifiable. The state of the onco-neural antibodies was studied. The PET/CT was classified as positive or negative for the detection of malignancy. The relationship between PET/CT findings and the final diagnosis was determined. The differences between variables (Pearson test X(2)) and the relationship between the results of the PET/CT and the final diagnosis were analyzed. RESULTS: A total of 64 patients were analyzed, classifying 30% as CS and 42% as NCS. After the follow-up, 20% and 16% of subjects were diagnosed as possible and definitive PNS, respectively. Positive onco-neural antibodies were found in 13% of the patients. A definitive diagnosis of PNS was associated with a positive PET/CT (P=.08). A significant relation between antibodies expression and final diagnosis of neoplasia (P=.04) was demonstrated. The PET/CT correctly localized malignancy in 5/7 cases of invasive cancer. CONCLUSIONS: The PET/CT showed a higher percentage of positive results in patients with definitive diagnosis of PNS. Despite the low prevalence of malignancy in our series, the PET/CT detected malignancy in a significant proportion of patients with invasive cancer.

Dual time point 2-deoxy-2-[18F]fluoro-D-glucose PET/CT: nodal staging in locally advanced breast cancer.

AIM: To assess dual time point 2-deoxy-2-[(18)F]fluoro-D-glucose (18)(F)FDG PET-CT accuracy in nodal staging and in detection of extra-axillary involvement. MATERIAL AND METHODS: Dual time point [(18)F] FDG PET/CT scan was performed in 75 patients. Visual and semiquantitative assessment of lymph nodes was performed. Semiquantitative measurement of SUV and ROC-analysis were carried out to calculate SUV(max) cut-off value with the best diagnostic performance. Axillary and extra-axillary lymph node chains were evaluated. RESULTS: Sensitivity and specificity of visual assessment was 87.3% and 75%, respectively. SUV(max) values with the best sensitivity were 0.90 and 0.95 for early and delayed PET, respectively. SUV(max) values with the best specificity were 1.95 and 2.75, respectively. Extra-axillary lymph node involvement was detected in 26.7%. CONCLUSION: FDG PET/CT detected extra-axillary lymph node involvement in one-fourth of the patients. Semiquantitative lymph node analysis did not show any advantage over the visual evaluation.

[Prevalence of obesity and cardiovascular risk factors in a group of paediatric patients with type 1 diabetes]. / Prevalencia de obesidad y de factores de riesgo cardiovascular en una población de pacientes pediátricos con diabetes tipo 1.

OBJECTIVE: To establish the prevalence of overweight-obesity and metabolic syndrome in a group of paediatric patients with type 1 diabetes (DM1), and to determine the effects on the lipoprotein profile and metabolic control. METHODS: A group of 115 patients (5-16 years) with DM1, and on intensive insulin therapy was studied. Weight, height, body mass index (BMI), waist circumference (WC), blood pressure (BP), glycosylated haemoglobin (HbA1c), total cholesterol (TC), HDL-cholesterol (HDL-c), LDL-cholesterol (LDL-c) and triglycerides (TG) were measured. The results were stratified by sex and age (< 11 years and ≥ 11 years). RESULTS: The prevalence of overweight and obesity (according to Hernández's reference values) was 28.69% and 18.26%, respectively, with female predominance in both cases. The prevalence of metabolic syndrome (according to the International Diabetes Federation criteria) was 3.22%. 3.47% The WC adjusted for age and sex was > 90th percentile in 3.47% of cases, and 2.6% had a systolic BP ≥ 130 mmHg and/or a diastolic BP ≥ 85 mmHg. An HDL-c < 40 mg/dl was seen in 4.34%, and 2.6% had TG ≥ 150 mg/dl. Obese patients had lower HDL-c levels and higher LDL-c levels than non-obese subjects. There were no significant differences in HbA1c between patients with overweight-obesity and the rest. CONCLUSIONS: Overweight and obesity are common in paediatric patients with DM1. Nevertheless, the prevalence of metabolic syndrome and cardiovascular risk factors is lower than in adult patients. The group of diabetic children with obesity had a lipoprotein profile of cardiovascular risk.

[Quantitative and qualitative evaluation of the interim PET/CT in lymphoma treatment in the prediction of complete metabolic response]. / Evaluación cuantitativa y cualitativa de la PET/TC a mitad del tratamiento en linfomas en la predicción de respuesta metabólica completa.

OBJECTIVE: To compare two different methods for the interpretation of interim PET/CT (PET/CT-i) in lymphomas, and to establish which one best predicts a complete metabolic response (CMR) in the PET/CT study at the end of treatment (PET/CT-et). MATERIAL AND METHODS: Retrospective longitudinal analysis of the PET/CT studies for staging (PET/CT-s), PET/CT-i and PET/CT-et of 65 patients, 35 Hodgkin's lymphoma (HL) and 30 Non-HL. The PET/CT-i was performed between the second and fourth chemotherapy cycle. It was interpreted using two different criteria: qualitative criteria (5 point visual scale), semiquantitative criteria (percentage difference between the lesion with more SUVmax in the PET/CT-s and PET/CT-i). We analyzed the likelihood of obtaining a CMR in the PET/CT-et according to the results obtained on the PET/CT-i with these two criteria. RESULTS: We obtained sensitivity (S), specificity (Sp), positive predictive values (PPV), negative predictive values (NPV) and likelihood ratio (LR) for the qualitative/semiquantitative method of 91%/80%, 76.2%/67%, 88.9%/83.3%, 80%/60.9% and 32%/7.8%, respectively, to predict a CMR in the PET/CT-et. There were no statistically significant differences between the LR of both methods (p=0.1942). CONCLUSION: We found clear differences in S, Sp, PPV and NPV between both interpretation criteria for the PET/CT-i to predict a CMR in the PET/CT-et. Nevertheless, we cannot confirm the superiority of the qualitative method over the semiqualitative method for this purpose as no statistically significance differences were found in their LR in our study.

18F-FDG semi-quantitative parameters and biological prognostic factors in locally advanced breast cancer.

AIM: To analyse the correlation between (18)F-FDG uptake assessed by PET/CT in locally advanced breast tumours and histopathological and immunohistochemical prognostic factors. MATERIAL AND METHODS: Thirty-six women with breast cancer were prospectively evaluated. PET/CT was requested in the initial staging previous to adjuvant chemotherapy (multicentric study). All the patients underwent an (18)F-FDG PET/CT with a dual-time-point acquisition. Both examinations were evaluated qualitatively and semiquantitatively with calculation of SUVmax values in PET-1 (SUV-1) and in PET-2 (SUV-2) and the percentage variation of the standard uptake values (retention index) between PET-1 and PET-2. Clinical and metabolic stages were assessed according to TNM classification. The biological prognostic parameters, such as the steroid receptor status, p53 and c-erbB-2 expression, proliferation rate (Ki-67), and grading were determined from tissue of the primary tumour. Metabolic and biological parameters were correlated. RESULTS: A positive relationship was found between semiquantitative metabolic parameters and biological parameters. SUV-1 and SUV-2 values did not show significant statistical correlation (p<.05) except for the clinical tumour size. About the biological parameters, retention index showed the best results with positive and significant relation (p<.05) with estrogen and progesterone receptor status and Ki-67. Isolated SUV values did not show significant relation to these parameters. CONCLUSION: Retention index showed the best relation with biological parameters compared to isolated SUVmax values. These data suggest that SUV change over time is a prognostic marker.

(18)F-FDG PET-CT respiratory gating in characterization of pulmonary lesions: approximation towards clinical indications.

AIM: To evaluate the effect of the 18F-FDG PET-CT respiratory gating (4D) study in the correct documentation of pulmonary lesions with faint uptake in standard PET-CT. METHODS: Forty-two pulmonary lesions with a low or no detectable uptake of FDG (SUV(max) < 2.5) in 3D PET-CT were prospectively evaluated in 28 patients (19 males and 9 females), mean age 66.5 years (41-81). 22 patients had neoplastic background. A conventional PET-CT (3D) total body scan was performed approximately 60 min after iv injection of a mean dose of 370 MBq. Furthermore, a 4D PET-CT (synchronized with respiratory movement) thorax study was acquired. SUV(max) was determined for each lesion in both studies. For the 4D studies, we selected the SUV(max) in respiratory period with the highest uptake ("best bin"). We calculated the SUV(max) percentage difference between 3D and 4D PET-CT (% difference = SUV(max) 4D - SUV(max) 3D/SUV(max) 3D x 100) and the relation of this value with the size and locations of the lesions. In 4D study, any lesion with SUV(max) > or = 2.5 was classified as malignant. We assessed the changes of lesion classification (from benign to malignant) applying the 4D technique. The final diagnosis was obtained by histological assessment or clinical and radiological follow-up longer than 12 months. RESULTS: Forty out of 42 lesions showed an increase of SUV(max) in the 4D study with respect to 3D. The mean SUV(max) in the 3D and 4D PET-CT studies were 1.33 (+/-0.59) and 2.26 (+/-0.87), respectively. The SUV(max) percentage difference mean between both techniques was 83.3% (+/-80.81).The smaller the lesion the greater was the SUV(max) percentage difference (P < 0.05). No differences were observed depending on the location of the lesion. In 40% of cases, there was a change in the final classification of lesions from benign to malignant. In the final diagnosis, 24 lesions were malignant. 4D PET-CT diagnosed correctly the 52% of them. CONCLUSIONS: The 4D PET-CT study permitted a better characterization of malignant lung lesions compared with the standard PET-CT, because of its higher sensitivity. 4D PET-CT is a recommendable technique in the early diagnosis of malignant lesions.