[Intravesical radioimmunotherapy of carcinoma in situ of the urinary bladder after BCG failure]. / Intravesikale Radioimmuntherapie des Carcinoma in situ der Harnblase nach BCG-Versagen.

BACKGROUND: In failure to respond to bacillus Calmette-Guérin (BCG) in patients with carcinoma in situ (CIS) of the urinary bladder, radical cystectomy remains the mainstay after BCG failure. OBJECTIVES: The aim of this pilot study was to evaluate tolerability and safety of the α­emitter radioimmunoconjugate instillation in patients after BCG failure. MATERIALS AND METHODS: Nine patients were included. After emptying the bladder via a transurethral catheter, Bi-213-anti-EGFR-mAb was instilled. Treatment was terminated by emptying of the radioimmunoconjugate from the bladder 120 min after instillation. Efficacy was evaluated via endoscopy and histology 6 weeks after instillation. RESULTS: All patients showed excellent toleration of the treatment without any side effects. Treatment resulted in complete eradication of tumor cells in 3 patients and persistent tumor detection in the other 6 patients. CONCLUSIONS: Intravesical instillation of Bi-213-anti-EGFR-mAb is a promising therapeutic option for treatment of in situ bladder cancer after BCG failure for patients who wish to preserve the bladder.

Non-invasive imaging of implanted peritoneal carcinomatosis in mice using PET and bioluminescence imaging.

BACKGROUND: Non-invasive imaging of peritoneal carcinomatosis remains challenging. The aim of this study was to compare positron emission tomography (PET) and bioluminescence imaging (BLI) for the early detection of peritoneal carcinomatosis in a mouse model. METHODS: Female nude mice were inoculated intraperitoneally with 1×10(7) HSC45-M2-luc gastric cancer cells. The cells were stably transfected with the gene coding for firefly luciferase. Tumour development was monitored using PET and BLI and in two subgroups, on days 3 and 4 or on days 6 and 7 after tumour cell inoculation. Tumour nodules found on post mortem examination served as the reference standard for evaluating the images. RESULTS: PET detected 58/82 lesions (sensitivity 71 %). This method detected all (100 %) nodules larger than 6 mm, 88 % of nodules in the range of >2-4 mm, and even 58 % of small nodules measuring only 1-2 mm. BLI identified a total of 40/82 lesions (sensitivity 49 %). The difference between PET and BLI was statistically significant at p < 0.05 (PET/BLI chi-square 8.2). CONCLUSIONS: PET was more sensitive than BLI for the detection of early peritoneal carcinomatosis in our mouse model. The sensitivity of BLI largely depended on the site of the lesions in relation to the imaging device.

[[¹¹C]choline as a pharmacodynamic marker for docetaxel therapy. Response assessment in a LNCaP prostate cancer xenograft mouse model]. / Ansprechen auf eine Docetaxeltherapie im LNCaP-Prostatakarzinom-Xenograft-Mausmodell. Untersuchung mit der [¹¹C]Cholin-Kleintier-PET/CT.

UNLABELLED: The AIM of this study was to determine whether [¹¹C]choline can be used for docetaxel therapy response assessment in a LNCaP-prostate cancer xenograft mouse model using [¹¹C]choline small-animal PET/CT. ANIMALS, METHODS: The androgen-dependent human prostate cancer cell line LNCaP was implanted subcutaneously into the left flanks of 17 SCID-mice, 12.5 mg testosterone platelets were implanted in the neck wrinkle. All mice were injected 4-6 weeks after xenograft implantation with 37 MBq [¹¹C]choline via the tail vein. Dynamic imaging was performed for 60 minutes with a small-animal PET/CT scanner. After the first [¹¹C]choline PET/CT imaging 8 mice were subsequently injected intravenously with docetaxel twice (days 1 and 5) at a dose of 3 mg/kg body weight. 8 mice were treated with PBS as a control. [¹¹C]choline PET/CT imaging was performed on day 7, 14 and 21 after treatment. Image analysis was performed using tumor/muscle (T/M) ratios (ROI(T)/ROI(M) = T/M ratio). RESULTS: All LNCaP tumours could be visualized by [¹¹C]choline PET/CT. Before treatment the mean T/M ratio was 2.0 ± 0.2 in the docetaxel-treated group and 1.9 ± 0.2 in the control group (p = 0.837). There was a reduction in the mean [¹¹C]choline uptake after docetaxel treatment of the tumours of the LNCaP cell line as early as 1 week after initiation of therapy (T/M(mean) ratio 1.5 ± 0.2 after one week, 1.3 ± 0.2 after 2 weeks and 1.4 ± 0.2 after 3 weeks). There was no decrease in [¹¹C]choline uptake in the control group. CONCLUSION: Our results show that [¹¹C]choline has the potential for use in the early monitoring of the therapeutic effect of docetaxel in a LNCaP prostate cancer xenograft animal model.

Sodium iodide symporter (NIS)-mediated radiovirotherapy of hepatocellular cancer using a conditionally replicating adenovirus.

In this study, we determined the in vitro and in vivo efficacy of sodium iodide symporter (NIS) gene transfer and the therapeutic potential of oncolytic virotherapy combined with radioiodine therapy using a conditionally replicating oncolytic adenovirus. For this purpose, we used a replication-selective adenovirus in which the E1a gene is driven by the mouse alpha-fetoprotein (AFP) promoter and the human NIS gene is inserted in the E3 region (Ad5-E1/AFP-E3/NIS). Human hepatocellular carcinoma cells (HuH7) infected with Ad5-E1/AFP-E3/NIS concentrated radioiodine at a level that was sufficiently high for a therapeutic effect in vitro. In vivo experiments demonstrated that 3 days after intratumoral (i.t.) injection of Ad5-E1/AFP-E3/NIS HuH7 xenograft tumors accumulated approximately 25% ID g(-1) (percentage of the injected dose per gram tumor tissue) (123)I as shown by (123)I gamma camera imaging. A single i.t. injection of Ad5-E1/AFP-E3/NIS (virotherapy) resulted in a significant reduction of tumor growth and prolonged survival, as compared with injection of saline. Combination of oncolytic virotherapy with radioiodine treatment (radiovirotherapy) led to an additional reduction of tumor growth that resulted in markedly improved survival as compared with virotherapy alone. In conclusion, local in vivo NIS gene transfer using a replication-selective oncolytic adenovirus is able to induce a significant therapeutic effect, which can be enhanced by additional (131)I application.

[Demonstration of angiogenesis and the effect on an antiangiogenetic therapy with 99mTc labeled erythrocytes]. / Darstellung der Angiogenese und der Effekte einer antiangiogenetischen Therapie mit 99mTc-markierten Erythrozyten.

AIM: To evaluate, whether scintigraphic studies with radiolabeled erythrocytes may be used to demonstrate the formation of new vessels during angiogenesis and if an effect on antiangiogenetic therapy could be detected. METHODS: As an angiogenesis model we used the ingrowth of blood vessels in matrigel, subcutaneously injected into mice. In order to measure the relative blood volume in the matrigel non-invasively, mouse erythrocytes were labeled with Technetium-99m DTPA. The amount of activity in the matrigel was measured 30 minutes after injection of the radiolabeled erythrocytes with a gammacamera (in-vivo) and a gammacounter (ex-vivo). These results were correlated with the concentration of hemoglobin in the matrigel and the immunhistochemically evaluated density of blood vessels. The influence of the angiogenesis stimulating growth factor (bFGF) and the antiangiogenetic effect of the cyclooxigenase type 2 inhibitor (COX-2) NS398 were tested. RESULTS: There was a close correlation between the activity concentration in the matrigel and the hemoglobin content. Treatment with bFGF significantly increased the activity concentration from 1.74% +/- ID/g to 4.06% +/- 0.36 (p < 0.01), whereas treatment with NS398 significantly inhibited tracer uptake from 2.83% ID/g +/- 0.33 to 0.87% ID/g +/- 0.12 (p < 0.01). CONCLUSION: These results demonstrate the feasibility of using (99m)Tc labelled erythrocytes for scintigraphic imaging to assess the effects of angiogenesis stimulating and inhibiting interventions non-invasively.

Alpha-fetoprotein promoter-targeted sodium iodide symporter gene therapy of hepatocellular carcinoma.

Due to limited treatment options the prognosis of patients with advanced hepatocellular cancer (HCC) has remained poor. To investigate an alternative therapeutic approach, we examined the feasibility of radioiodine therapy of HCC following human sodium iodide symporter (NIS) gene transfer using a mouse alpha-fetoprotein (AFP) promoter construct to target NIS expression to HCC cells. For this purpose, the murine Hepa 1-6 and the human HepG2 hepatoma cell lines were stably transfected with NIS cDNA under the control of the tumor-specific AFP promoter. The stably transfected Hepa 1-6 cell line showed a 10-fold increase in iodide accumulation, while HepG2 cells accumulated (125)I approximately 60-fold. Tumor-specific NIS expression was confirmed on mRNA level by northern blot analysis, and on protein level by immunostaining, that revealed primarily membrane-associated NIS-specific immunoreactivity. In an in vitro clonogenic assay up to 78% of NIS-transfected Hepa 1-6 and 93% of HepG2 cells were killed by (131)I exposure, while up to 96% of control cells survived. In vivo NIS-transfected HepG2 xenografts accumulated 15% of the total (123)I administered per gram tumor with a biological half-life of 8.38 h, resulting in a tumor absorbed dose of 171 mGy MBq(-1) (131)I. After administration of a therapeutic (131)I dose (55.5 MBq) tumor growth of NIS expressing HepG2 xenografts was significantly inhibited. In conclusion, tumor-specific iodide accumulation was induced in HCC cells by AFP promoter-directed NIS expression in vitro and in vivo, which was sufficiently high to allow a therapeutic effect of (131)I. This study demonstrates the potential of tumor-specific NIS gene therapy as an innovative treatment strategy for HCC.

The sensitivity of the alkaline comet assay in detecting DNA lesions induced by X rays, gamma rays and alpha particles.

Experiments were designed and performed in order to investigate whether or not the different cellular energy deposition patterns of photon radiation with different energies (29 kV, 220 kV X rays; Co-60, Cs-137-gamma-rays) and alpha-radiation from an Am-241 source differ in DNA damage induction capacity in human cells. For this purpose, the alkaline comet assay (single cell gel electrophoresis) was applied to measure the amount of DNA damage in relation to the dose received. The comet assay data for the parameters '% DNA in the tail' and 'tail moment' for human peripheral lymphocytes did not indicate any difference in the initial radiation damage produced by 29 kV X rays relative to the reference radiations, 220 kV X rays and the gamma rays, whether for the total mean dose range of 0-3 Gy nor in the low-dose range. In contrast, when the 'tail length' data were analysed saturation of the fitted dose response curve appeared for X rays at about 1.5 Gy but was not apparent for gamma rays up to 3 Gy. Preliminary data for alpha exposures of HSC45-M2 cells showed a significant increase in DNA damage only at high doses (>2 Gy Am-241), but the damage at 2 Gy exceeded the damage induced at 2 Gy by Cs-137-gamma-rays by a factor of 2.5. In contrast, other experiments involving different cell systems and DNA damage indicators such as chromosomal aberrations have detected a significant increase in DNA damage at much lower doses, that is at 0.02 Gy for Am-241 and depicte a higher biological effectiveness. These results indicate that differences in biological effects arise through downstream processing of complex DNA damage.

Targeting of gelatinase activity with a radiolabeled cyclic HWGF peptide.

Matrix metalloproteinases (MMPs) are a family of proteinases that play an important role in cancer as well as in numerous diseases. In this article, we describe the labeling of a phage display selected cyclic decapeptide containing the HWGF (histidine-tryptophane-glycine-phenylalanine) sequence to target MMP-2 and MMP-9. To evaluate the ability of this labeled peptide to monitor non invasively MMP-2 and MMP-9 activity, in vitro studies, biodistribution, competition studies and plasma metabolites analyses in Lewis Lung cancer tumor bearing mice were performed.

Targeted alpha therapy in vivo: direct evidence for single cancer cell kill using 149Tb-rituximab.

This study demonstrates high-efficiency sterilisation of single cancer cells in a SCID mouse model of leukaemia using rituximab, a monoclonal antibody that targets CD20, labelled with terbium-149, an alpha-emitting radionuclide. Radio-immunotherapy with 5.5 MBq labelled antibody conjugate (1.11 GBq/mg) 2 days after an intravenous graft of 5.10(6) Daudi cells resulted in tumour-free survival for >120 days in 89% of treated animals. In contrast, all control mice (no treatment or treated with 5 or 300 micro g unlabelled rituximab) developed lymphoma disease. At the end of the study period, 28.4%+/-4% of the long-lived daughter activity remained in the body, of which 91.1% was located in bone tissue and 6.3% in the liver. A relatively high daughter radioactivity concentration was found in the spleen (12%+/-2%/g), suggesting that the killed cancer cells are mainly eliminated through the spleen. This promising preliminary in vivo study suggests that targeted alpha therapy with (149)Tb is worthy of consideration as a new-generation radio-immunotherapeutic approach.

A new class of drugs for BNCT? Borylated derivatives of ferrocenium compounds in animal experiments.

A new class of drugs, borylated derivatives of ferrocenium compounds, which show a comparatively facile synthesis is investigated on their boron neutron capture accumulation. Investigations focused on the fast and effective testing of 12 ferrocene derivatives with tetracoordinated boron atoms, which should accumulate in rodent tumors. The macroscopic studies on time-dependent boron distributions and boron concentrations in mice were carried out by inductively coupled plasma-atomic emission spectrometry, inductively coupled plasma-mass spectrometry, and quantitative neutron capture radiography. The determination of boron concentrations after injection of 2b showed high boron contents in spleen, liver, kidneys, less in lung and muscle, and poor in integral blood, blood plasma, tumor, and brain. It is interesting to note that 2b penetrates the blood-brain barrier which may be advantageous in the treatment of astrocytomas and glioblastomas.

Comparison of sestamibi, tetrofosmin, and Q12 retention in porcine myocardium.

UNLABELLED: Although there are several 99mTc perfusion tracers introduced for clinical use, there are no data available directly comparing these tracers with microsphere-determined flow. The aim of this study was to compare the myocardial retention of sestamibi, tetrofosmin, and Q12 in a porcine model. METHODS: We used a pig model with (n = 6) or without (n = 3) coronary occlusion. Each pig received a simultaneous injection of sestamibi and either tetrofosmin (group 1, n = 5) or Q12 (group 2, n = 4) labeled with either 99mTc or 95mTc (physical half-life, 61 d; photon energy, 204 keV) during pharmacologic vasodilation. Absolute myocardial retention of each tracer was calculated from the myocardial tracer activity and arterial input function. RESULTS: The plot of all three tracers versus flow achieved a plateau at a higher flow range. However, sestamibi showed a higher mean retention than either tetrofosmin (group 1, 0.27 +/- 0.11 vs. 0.16 +/- 0.06 mL/g/min, respectively; P < 0.01) or Q12 (group 2, 0.32 +/- 0.13 vs. 0.09 +/- 0.03 mL/g/min, respectively; P < 0.01). Furthermore, when a linear regression analysis was performed to assess the relationship between retention and microsphere-determined flow, sestamibi showed a greater increment in retention than did tetrofosmin or Q12. CONCLUSION: Although all of the tracers showed a nonlinear increase in retention as flow increased, sestamibi may display more favorable characteristics as a flow tracer in the porcine heart.

Highly specific tumor binding of a 213Bi-labeled monoclonal antibody against mutant E-cadherin suggests its usefulness for locoregional alpha-radioimmunotherapy of diffuse-type gastric cancer.

A monoclonal antibody (E-cadherin delta 9-1) directed against a characteristic E-cadherin mutation (in-frame deletion of exon 9), found in diffuse-type gastric cancer but not in any normal tissue, was conjugated with the high linear energy transfer alpha-emitter 213Bi and tested for its binding specificity in s.c. and i.p. nude mice tumor models. After intratumoral application in s.c. tumors expressing mutant E-cadherin, the 213Bi-labeled antibody was specifically retained at the injection site as shown by autoradiography. After injection into the peritoneal cavity, uptake in small i.p. tumor nodules expressing mutant E-cadherin was 17-fold higher than in tumor nodules expressing wild-type E-cadherin (62% injected dose/g versus 3.7% injected dose/g). 78% of the total activity in the ascites fluid was bound to free tumor cells expressing mutant E-cadherin, whereas in control cells, binding was only 18%. The selective binding of the 213Bi-labeled, mutation-specific monoclonal antibody E-cadherin delta 9-1 suggests that it will be successful for alpha-radioimmunotherapy of disseminated tumors after locoregional application.

Noninvasive imaging of alpha(v)beta3 integrin expression using 18F-labeled RGD-containing glycopeptide and positron emission tomography.

The alpha(v)beta3 integrin is an important cell adhesion receptor involved in tumor-induced angiogenesis and tumor metastasis. Here we describe the 18F-labeling of the RGD-containing glycopeptide cyclo(-Arg-Gly-Asp-D-Phe-Lys(sugar amino acid)-) with 4-nitrophenyl 2-[18F]fluoropropionate and the evaluation of this compound in vitro and in tumor mouse models. Binding assays with isolated immobilized alpha(v)beta3, alpha(v)beta5, and alpha(IIb)beta3 as well as in vivo studies using alpha(v)beta3-positive and -negative murine and xenotransplanted human tumors demonstrated receptor-specific binding of the radiolabeled glycopeptide yielding high tumor:background ratios (e.g., 120 min postinjection: tumor:blood, 27.5; tumor:muscle, 10.2). First imaging results using a small animal positron emission tomograph suggest that this compound is suitable for noninvasive determination of the alpha(v)beta3 integrin status and therapy monitoring.

Glycosylated RGD-containing peptides: tracer for tumor targeting and angiogenesis imaging with improved biokinetics.

UNLABELLED: The alpha(v)beta3 integrin plays an important role in metastasis and tumor-induced angiogenesis. Targeting with radiolabeled ligands of the alpha(v)beta3 integrin may provide information about the receptor status and enable specific therapeutic planning. Previous studies from our group resulted in tracers that showed alpha(v)beta3-selective tumor uptake. However, these first-generation compounds predominantly revealed hepatobiliary excretion with high radioactivity found in the liver. In this report, the synthesis and biological evaluation of the first glycosylated RGD-containing peptide (RGD-peptide) for the noninvasive imaging of alpha(v)beta3 expression are described. METHODS: Peptides were assembled on a solid support using fluorenylmethoxycarbonyl-coupling protocols. The precursor cyclo(-Arg-Gly-Asp-D-Tyr-Lys(SAA)-) GP1 was synthesized by coupling 3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-beta-D-glycero-D-gulo-heptonic acid (SAA(Bn3)) with cyclo(-Arg(Mtr)-Gly-Asp(OtBu)-D-Tyr(tBu)-Lys-) and subsequent removal of the protection groups. Iodine labeling was performed by the Iodo-Gen method (radiochemical yield > 50%). The in vitro binding assays were performed using purified immobilized alpha(IIb)beta3, alpha(v)beta5, and alpha(v)beta3 integrins. For in vivo experiments, nude mice bearing xenotransplanted melanomas and mice with osteosarcomas were used. RESULTS: The glycosylated peptide 3-iodo-Tyr4-cyclo(-Arg-Gly-Asp-D-Tyr-Lys(SAA)-) GP2 showed high affinity and selectivity for alpha(v)beta3 in vitro (50% inhibitory concentration = 40 nmol/L). Pretreatment studies indicate specific binding of [125I]GP2 on alpha(v)beta3-expressing tumors in vivo. Comparison of the pharmacokinetics of [125I]GP2 and [125I]-3-iodo-Tyr4-cyclo(-Arg-Gly-Asp-D-Tyr-Val-) [125I]P2 revealed for [125I]GP2 an increased activity concentration in the blood (e.g., 3.59 +/- 0.35 percentage injected dose [%ID]/g vs. 1.72 +/- 0.44 %ID/g at 10 min postinjection) and a significantly reduced uptake in the liver (e.g., 2.59 +/- 0.24 %ID/g vs. 21.96 +/- 2.78 %ID/g at 10 min postinjection). Furthermore, a clearly increased activity accumulation in the tumor was found (e.g., 3.05 +/- 0.31 %ID/g vs. 0.92 +/- 0.16 %ID/g at 240 min postinjection), which remained almost constant between 60 and 240 min postinjection. This resulted in good tumor-to-organ ratios for the glycosylated tracer (e.g., 240-min postinjection osteosarcoma model: tumor-to-blood = 16; tumor-to-muscle = 7; tumor-to-liver = 2.5), which were confirmed by the first gamma-camera images of osteosarcoma-bearing mice at 240 min postinjection. CONCLUSION: This study demonstrates that the introduction of a sugar moiety improves the pharmakokinetic behavior of a hydrophobic peptide-based tracer. Additionally, this alpha(v)beta3-selective glycosylated radioiodinated second-generation tracer GP2 shows high tumor uptake and good tumor-to-organ ratios that allow noninvasive visualization of alpha(v)beta3-expressing tumors and monitoring therapy with alpha(v)beta3 antagonists. Finally, the favorable biokinetics make the glycosylated RGD-peptide a promising lead structure for tracers to quantify the alpha(v)beta3 expression using PET.

Biodistribution of 99mTc-glutathione in mice with osteosarcoma: effect of gamma irradiation on tumour uptake.

The aim of this study was to determine the efficacy of 99mTc-glutathione (GSH) in scintigraphic demonstration of osteosarcoma tumour in mice and the effect of gamma irradiation of tumour on tumour uptake of 99mTc-GSH. The biodistribution of 99mTc-GSH was studied in 30 Balb C mice 3 weeks after isotransplanting osteosarcoma OTS-64 in their thighs. The mice were injected with 400 microCi of 99mTc-GSH in 0.1 ml through the tail vein. They were equally divided into two groups. In the second group the tumours were subjected to gamma irradiation for 10 min (20 Gy). The mice in both groups were killed at 1, 3 and 6 h. Scintigrams were obtained at each time point. The organs, tumours, some muscle and some blood were removed, weighed and assayed for radioactivity. Tumour, liver and muscle sections were also obtained for gross autoradiographic studies. The tumours were well visualized on scintigrams. The tumour uptake values as a function of time after injection were 3.27+/-0.80, 1.53+/-0.69, and 1.51+/-0.55 for the control and 5.18+/-1.28, 0.399+/-0.120, and 1.67+/-1.05%/g for the irradiated groups at 1, 3 and 6 h, respectively. The tumor-to-muscle concentration ratios were 34.03+/-12.2, 21.4+/-11.3 and 18.7+/-11.4 for the control and 18.8+/-7.2, 3.63+/-1.9, and 24.1+/-9.0 for the irradiated groups, respectively. The gross autoradiographic images of tumour sections indicated focal sites of increased uptake within tumour tissue, indicating the presence of necrotic areas. In conclusion, 99mTc-GSH accumulated in osteosarcoma and resulted in high tumour-to-other tissue concentration ratios in mice. The increase in uptake values after tumour irradiation might be a result of increased demand of tumour cells for GSH attributable to its well-known biological function as a reducing agent in addition to increased blood flow and capillary permeability in malignant tissues.

Radiolabeled thymidine: a sensitive tracer for early tumor response and recurrence after irradiation.

UNLABELLED: This study evaluated the sensitivity of a radiolabeled thymidine tracer for assessment of early tumor response and recurrence after irradiation. METHODS: SW707 human colon carcinoma implanted into nude mice was irradiated with 6 or 20 Gy. Tumor volume was determined for an interval of 14 d. At 4, 8 and 24 h and at 2, 3, 7, 10 and 14 d after irradiation, [14C]thymidine uptake into the tumor was determined with a liquid scintillation counter and the intratumoral distribution of [14C]thymidine was visualized and evaluated semiquantitatively by autoradiography using a phosphor imager. RESULTS: In both groups, tumor volume decreased until day 7 after irradiation; afterward, regrowth occurred in only the group that had received 6 Gy. A decrease in thymidine uptake was found as early as 8 h after irradiation. On day 3 after irradiation, thymidine uptake increased again in the 6-Gy group, before the increase in tumor volume, but remained unchanged in the 20-Gy group. Also on day 3, multiple foci of thymidine uptake suggesting proliferation preceding tumor recurrence were seen on autoradiographs from the 6-Gy group but not from the 20-Gy group. Histological findings correlated with the results of autoradiography. CONCLUSION: The results show that radiolabeled thymidine is a sensitive tracer for assessment of early tumor response and recurrence after irradiation. The rapid decrease in uptake, however, does not allow any prediction about tumor recurrence.

[Radioiodine therapy of functional autonomy of the thyroid gland. Treatment results in view of pretreatment scintigraphic diagnosis and early response of triiodothyronine levels to treatment]. / Die Radiojodtherapie der funktionellen Schilddrüsenautonomie. Behandlungsergebnisse unter Berücksichtigung der Autonomieform und des frühen posttherapeutischen Trijodthyroninspiegels.

AIM: The goal of this retrospective study was to evaluate the results of radioiodine therapy of thyroid autonomy with respect to the underlying scintigraphic pattern, administered I-131 doses and pretherapeutic Tc-99m and I-131 uptake. Furthermore, early post-therapeutic free triiodothyronine (FT3) levels were measured during the first 6 weeks after radioiodine therapy with respect to a FT3-increase. PATIENTS AND METHODS: Thyroid autonomy in 632 patients was followed for at least 3 months (mean 10.9 months). The patients were divided into several groups based on scintigraphic pattern of unifocal (UA), a multifocal (MFA), a focal/disseminated (FDA) and a disseminated (DA) autonomy. The early effects of therapy on thyroid function were assessed by evaluation of FT3 values of 786 patients during the 1st, 2nd, 3rd, 4th and 6th week after therapy. RESULTS: Successful elimination of thyroid autonomy as defined by normalization of FT3 and TSH levels was observed in 92.1% (582/632) of the patients. In 2.2% (14/632) of the patients, immunogenic hyperthyroidism following I-131 therapy was observed. There was no significant difference in the success rates in patients with UA and MFA of 94.9% and 96.1%, respectively, using similar target doses based on the amount of autonomous tissue. The success rate in MFA (96.6%) was similar if target dose was calculated based on the volume of the whole thyroid gland. Compared to MFA (96.6%), however, FDA and DA were associated with significantly lower success rate with 82.7% and 75.5%, respectively, although the target doses were not significantly different. Considering the quantitative Tc-99m uptake prior to therapy, there was no significant difference in the success rate for Tc-99m uptake < or = 3% and > 3%, while the success rate in patients with I-131 uptake of < or = 50% was significantly higher (p = 0.032) than in those with an uptake of > 50%. The determination of FT3 levels during the first 6 weeks after radioiodine therapy revealed a dependence of the FT3 decrease and FT3 increase on the scintigraphic pattern and thyroid function. Patients with FDA and DA with hyperthyroidism showed an increase of FT3 (> 2 to 14.7 pmol/l) in 11 to 18% of the cases, during the first 2 weeks after therapy which occurred significantly more frequently in patients with FDA and DA than in UA and MFA. A similar increase in FT3 level in patients with FDA and DA compared to patients with UA and MFA was observed in 317 patients with euthyroid pretherapeutic hormone levels. A decrease in FT3 level following radioiodine therapy was observed significantly more often and earlier in patients with UA and MFA with hyperthyroid values than in patients with FDA and DA during the first 6 posttherapeutic weeks. Concerning patients with euthyroid FT3 levels, the decrease in FT3 level was observed significantly more frequently in patients with UA and MFA only after 6 weeks following radioiodine therapy. CONCLUSION: In contrast to the multifocal autonomy (MFA), the target dose of 150 to 200 Gy based on total thyroid volume did not result in a comparably high success rate of approximately 95% in disseminated and focal/disseminated types of thyroid autonomy. Therefore, an increase of target dose of 200 to 300 Gy is recommended. The transient FT3 increase particularly observed in FDA and DA in the first weeks following radioiodine therapy makes short-term controls of thyroid function necessary, especially in patients with cardiac risk, in order to initiate necessary therapy.

Investigation of transport mechanism and uptake kinetics of O-(2-[18F]fluoroethyl)-L-tyrosine in vitro and in vivo.

UNLABELLED: The aim of the study was to investigate the transport mechanism and uptake kinetics of the new 18F-labeled amino acid O-(2-[18F]fluoroethyl)-L-tyrosine (L-[18F]FET) and D-[18F]FET in human SW 707 colon carcinoma cells and the in vivo biodistribution of this tracer in SW 707 tumor-bearing mice. METHODS: SW 707 cells were incubated with L- and D-[18F]FET under physiologic amino acid concentrations with and without the competitive transport inhibitors 2-amino-2 norbornane-carboxylic acid and a-(methylamino)isobutyric acid plus serine. For the investigation of the transport capacity, unlabeled L-FET was added to the samples. In addition, xenotransplanted mice were injected intravenously with L-[18F]FET; killed 10, 30, 60 and 120 min after injection; and the radioactivity concentration in different organs was measured in a gamma counter. RESULTS: The in vitro kinetic experiments showed a fast initial uptake of L-[18F]FET into the cells up to 6 min, followed by a nearly constant tracer concentration. The accumulation factor, calculated as the ratio between intracellular and extracellular tracer concentration, ranged from 3.0 to 5.0. In comparison, D-[18F]FET did not accumulate in the cells. Washing the cells in medium at 37 degrees C, after a 30-min incubation with L-[F-18]FET, led to a rapid decrease of radioactivity, which demonstrates the bidirectional transport. In addition, experiments with increasing concentrations of unlabeled L-FET indicated a linear correlation between L-FET uptake rate and the extracellular concentration. Results of transport inhibition experiments with the specific competitive inhibitors demonstrated that the uptake of L-FET into SW 707 cells was caused mainly (>80%) by the transport system L. In the in vivo studies, the half-life (t1/2 beta) of L-[18F]FET in the plasma was determined to be 94 min and the uptake into the brain increased to 120 min with a brain-to-blood ratio of 0.86. The xenotransplanted tumor showed higher uptake of L-[18F]FET (>6 %ID/g) at 30 and 60 min than all other organs, except the pancreas. The tumor-to-blood ratio reached about 2 between 30 and 120 min. CONCLUSION: L-[18F]FET, which is transported by the specific amino acid transport system L, seems to be a potential amino acid tracer for tumor imaging and therapy monitoring with PET.

Radiolabeled alpha(v)beta3 integrin antagonists: a new class of tracers for tumor targeting.

UNLABELLED: The alpha(v)beta3 integrins play an important role during tumor metastasis and tumor-induced angiogenesis. Targeting of this receptor may provide information about the receptor status of the tumor and enable specific therapeutic planning. Cyclo(-Arg-Gly-Asp-D-Phe-Val-) has been shown to be a selective alpha(v)beta3 integrin antagonist with high affinity. In this study we describe the synthesis and biological evaluation of [125I]-3-iodo-D-Tyr4-cyclo(-Arg-Gly-Asp-D-Tyr-Val-) ([125I]P2), [125I]-3-iodo-Tyr5-cyclo(-Arg-Gly-Asp-D-Phe-Tyr-) ([125I]P4) and the negative control peptide [1251]-3-iodo-D-Tyr4-cyclo(-Arg-D-Ala-Asp-Tyr-Val-) ([125I]P6). METHODS: Peptides were assembled on a solid support using fluorenylmethoxycarbonyl amino acid coupling protocols. Radioiodination was performed using the iodogen method. The in vitro binding assays were performed using isolated, immobilized alphaIIbeta3 and alpha(v)beta3 integrins. Expression of the alphaVbeta3 receptor on the different tumors was validated by immunohistochemical methods using alpha(v) and alpha(v)beta3 specific antibodies. For biodistribution studies, nude mice with melanoma M21 or mammary carcinoma MaCaF and BALB/c mice with osteosarcoma were used. RESULTS: The in vitro binding assays demonstrate that the introduction of tyrosine and subsequent iodination have no influence on the high affinity and selectivity for alpha(v)beta3. Immunohistochemical staining clearly indicates the presence of the alpha(v)beta3 integrins on the tumor tissue of the melanoma and the osteosarcoma. Pretreatment and displacement studies show specific binding of [125I]P2 on melanoma M21-bearing nude mice and osteosarcoma-bearing BALB/c mice but less specific binding on mammary carcinomas. [125I]P2 exhibits fast elimination kinetics. The accumulation in the tumor 10 min postinjection is 2.07 +/- 0.32 %ID/g for the melanoma M21 and 3.50 +/- 0.49 %ID/g for the osteosarcoma and decreases to 1.30 +/- 0.13 %ID/g and 2.03 +/- 0.49 %ID/g 60 min postinjection, respectively. [125I]P4 shows even faster elimination kinetics, resulting in a tumor accumulation of 0.40 +/- 0.10 %ID/g 60 min postinjection for the osteosarcoma-bearing BALB/c mice. Both peptides reveal predominately hepatobiliary excretion. For [1251]P2, this also is confirmed by autoradiography. The negative control peptide [125I]P6 shows no specific activity accumulation. CONCLUSION: [125I]P2 exhibits high affinity and selectivity for the alpha(v)beta3 integrin in vitro and in vivo and, thus, represents the first radiolabeled alpha(v)beta3 antagonist for the investigation of angiogenesis and metastasis in vivo.

New drugs for BNCT: an experimental approach.

New kinds of boron-containing drugs were developed and tested in several murine tumor models. The boron-containing ether lipid B-Et-11-OMe was injected in mammary carcinoma (AT17) and osteosarcoma (OTS-64) bearing mice. Furthermore boron-substituted ferrocenium derivatives were tested. Two were excessively toxic; the third could be investigated. Boron accumulation and time-dependent biodistribution were determined using alpha-particle sensitive films and inductively coupled plasma-atomic emission pectrometry (ICP-AES) and -mass spectrometry (ICP-MS) of tumors, organs and tissues. Additionally, a new method of boron detection by NMR is in preparation.