(211)At-antiCD33 in NMRI nu/nu mice. Biodistribution, in vivo stability and radiotoxicity.

UNLABELLED: The aim of this study is to verify the in vivo stability, to determine the biodistribution and to estimate the unspecific radiotoxicity of an (211)At-labelled CD33-antibody ((211)At-antiCD33) in mice with a view to therapeutic application in treating leukaemia. ANIMALS, METHODS: (211)At was produced via the (209)Bi(a,2n)(211)At reaction and was linked via 3-(211)At-succinimidyl-benzoate to the antiCD33-antibody. The biodistribution and the in vivo stability in serum were determined after i.v.-injection in NMRI nu/nu-mice. For toxicity experiments, mice received either three times 315-650 kBq (211)At-antiCD33 or unlabelled antibody and NaCl-solution respectively. RESULTS: (211)At-antiCD33 showed a characteristic biodistribution complying with the unspecific antibody retention in the reticular endothelial system. The largest proportion of radioactivity remained in blood and blood-rich tissues with a minor accumulation in the thyroid and stomach. After 21 h, >85% of activity in serum still represented intact antibody. Mice showed no difference in unspecific toxicity of (211)At-labelled antibodies over six months compared to those treated with unlabelled antibody and NaCl-solution respectively, with regard to histopathologic lesions, survival time, behaviour and haemograms. CONCLUSION: The radiolabelling method yielded adequate in vivo stability of (211)At-antiCD33. Biodistribution with rapid elimination of free (211)At via kidneys and urine complies with requirements for targeted therapy. Activity doses potentially required for treatment do not elicit radiotoxicity to normal organs in mice. Further development is required to enhance the apparent specific activity and to verify the efficacy in an adequate animal model before phase I clinical studies in leukaemia can be envisaged.

124I-PET dosimetry in advanced differentiated thyroid cancer: therapeutic impact.

PURPOSE: This study evaluated the impact of (124)I-positron emission tomography (PET) dosimetry on post-primary surgery therapy in radioiodine-naïve patients with advanced differentiated thyroid cancer (DTC). PATIENTS, MATERIAL, METHODS: In each of 28 thyroidectomized patients with high-risk DTC (one or more of pT4, pN1 or pM1), we gave 23-50 MBq of (124)I as an oral capsule and performed PET dosimetry to calculate the individualized therapeutic (131)I activity that would, insofar as possible, achieve a radioiodine dose >or=100 Gy to all metastases without exceeding 2 Gy to the blood (a surrogate for bone marrow toxicity). We thus determined the absorbed lesion dose per GBq of administered 131I activity (LDpA) based on serial PET (4, 24, 48, 72 and 96 h after oral 124I intake) and PET/computed tomography (25 h after (124)I intake) and the critical blood activity (CBA) based on blood and whole-body radiation counting (2, 4, 24, 48, 72, 96 h after 124I intake). We compared the dosimetry-based interventions with our standard empirical protocol. RESULTS: 25 patients had a total of 126 iodine-positive metastases. 18 (72%) of the 25 had solely iodine-avid metastases, while seven (28%) had both iodine-avid and -non-avid metastases. In two patients (8%), none of the iodine-avid metastases could have been practically treated with a sufficient radiation dose. Relative to the empirical protocol, (124)I-PET dosimetry findings changed management in 7 (25%) patients, e.g. allowing application of activities >11 GBq (131)I. Further changes included implementation of hematological back-up in a patient found to be at risk of life-threatening marrow toxicity, and early multimodal therapy in 9 (32%) patients. CONCLUSION: 124I-PET dosimetry is a useful routine procedure in advanced DTC and may allow safer or more effective radioiodine activities and earlier multimodal interventions than do standard empirical protocols.

Functional activity of human sodium/iodide symporter in tumor cell lines.

AIM: The sodium/iodide symporter (NIS) actively transports iodide into thyrocytes. Thus, NIS represents a key protein for diagnosis and radioiodine therapy of differentiated thyroid cancer. Additionally, in the future the NIS gene may be used for cancer gene therapy of non-thyroid-derived malignancies. In this study we evaluated the functionality of NIS with respect to iodide uptake in a panel of tumor cell lines and compared this to gene transfer efficiency. METHODS: A human NIS-containing expression vector and reporter-gene vectors encoding beta-Galactosidase- or EGFP were used for transient transfection of 13 tumor cell lines. Following transfection measurements of NIS-mediated radioiodide uptake using Na(125)I and of transfection efficiency were performed. The latter included beta-Galactosidase activity measurements using a commercial kit and observation by fluorescence microscopy for EGFP expression. RESULTS: In contrast to respective parental cells, most NIS-transfected cell lines displayed high, perchlorate-sensitive radioiodide uptake. Differences in radioiodide uptake between cell lines apparently corresponded to transfection efficiencies, as judged from reporter-gene assays. CONCLUSION: With respect to iodide uptake we provide evidence that NIS is functional in different cellular context. As iodide uptake capacity appears to be well correlated to gene transfer efficiency, cell type-specific actions on NIS (e. g. post-translational modification such as glycosylation) are not inhibitory to NIS function. Our data support the promising role of NIS in cancer gene therapy strategies.

[Follow-up of differentiated thyroid cancer patients using rhTSH--preliminary results]. / Nachsorge des differenzierten Schilddrüsenkarzinoms unter Verwendung von rhTSH--vorläufige Ergebnisse.

AIM: In the follow-up of patients with advanced stage thyroid cancer radioiodine scintigraphy, F-18-FDG PET and tumormarker hTg using stimulation with recombinant human TSH (rhTSH) were compared to the results of same diagnostic procedures during TSH-suppression or endogenous TSH-stimulation. METHODS: 30 patients were investigated in hypothyroidism and after application of rhTSH regarding the serum hormone concentrations, hTg, radioiodine scans and FGD-PET scans. RESULTS: Radioiodine avidity and FDG uptake were significantly higher in 7/30 and 3/5 patients, respectively, compared to endogenous stimulation or TSH-suppression. In about one third of patients hTg increased more than 30%. CONCLUSION: Our preliminary results indicate a sufficient feasibility and sensitivity of rhTSH not only in the follow-up by hTg and radioiodine scan but also in FDG-PET.

Thyroid remnant dose: 124I-PET/CT dosimetric comparison of rhTSH versus thyroid hormone withholding before radioiodine remnant ablation in differentiated thyroid cancer.

AIM: Recombinant human thyroid-stimulating hormone (rhTSH) recently was approved as an alternative to thyroid hormone withholding (THW) to elevate TSH for thyroid remnant ablation in differentiated thyroid carcinoma patients. High ablation success rates are reported with diverse rhTSH-aided (131)I activities. Improved renal function causes approximately 50% faster radioiodine clearance under euthyroidism versus hypothyroidism. Knowledge of comparative remnant radioiodine kinetics, particularly the remnant radiation dose in Gy/GBq of administered (131)I activity (RDpA), could assist in choosing rhTSH-aided ablative activities. MATERIAL AND METHODS: To compare the RDpA, determined through (124)I-positron emission tomography/computed tomography (PET/CT), under the two stimulation methods, we retrospectively divided into two groups 55 consecutive totally-thyroidectomized, radioiodine-naïve patients. The rhTSH group (n=16) received (124)I on thyroid hormone, 24 h after two consecutive daily intramuscular injections of rhTSH, 0.9 mg. The THW group (n=39) received (124)I after weeks-long THW, when serum TSH first measured > or = 25 mIU/L. We performed PET investigations 4 h, 24 h, 48 h, 72 h and 96 h and PET/CT 25 h after (124)I administration. RESULTS: Median stimulated serum thyroglobulin was 15 times higher (p=0.023) and M1 disease almost twice as prevalent (p=0.05) in rhTSH versus THW patients. Mean+/-standard deviation RDpA was statistically equivalent between the groups: rhTSH, 461+/-600 Gy/GBq, THW, 302+/-329 Gy/GBq, two-sided p=0.258. CONCLUSIONS: rhTSH or THW deliver statistically equivalent radiation doses to thyroid remnant and may be chosen based on safety, quality-of-life, convenience and pharmacoeconomic factors. Institutional fixed radioiodine activities formulated for use with THW need not be adjusted for rhTSH-aided ablation.

Oncofoetal fibronectin--a tumour-specific marker in detecting minimal residual disease in differentiated thyroid carcinoma.

Supposedly, thyrocyte-specific transcripts such as thyroglobulin (Tg) and thyroid-stimulating hormone receptor (TSH-R) were proposed to be useful for the diagnosis of circulating tumour cells in patients suffering from differentiated thyroid carcinoma (DTC). However, several research groups reported blood-borne Tg transcripts in healthy individuals. This study determines in particular the origin of Tg mRNA in nucleated blood cells and analyses whether other tumour-associated sequences are absent in leukocytes, but widely expressed in DTC. Therefore, expression analyses for Tg, TSH-R, cytokeratin 19 (CK 19), human telomerase reverse transcriptase (hTERT) and oncofoetal fibronectin (onfFN) were carried out using cDNAs derived from (1) leukocyte fractions, (2) 18 follicular thyroid carcinomas (FTCs) and 48 papillary thyroid carcinomas (PTCs), and (3) leukocytes of two thyrocyte-depleted individuals treated for C-cell carcinoma of the thyroid. Expression of onfFN was additionally analysed by semiquantitative RT-PCR and by quantitative fluorescence-based real-time PCR. Tg and TSH-R expression was demonstrated not only in both athyroid individuals, but in all leukocyte subgroups tested, while hTERT was absent in resting CD4+ cells and only weakly expressed in the CD8+ group. CK 19 was notable in each leukocyte population except for resting CD14(+), as well as for activated and resting CD19+ cells. All blood cell fractions proved negative for onfFN mRNA, whereas its presence in thyroid carcinoma was 78/98% (FTC/PTC). Threshold cycle values were calculated at: porphobilinogen deaminase (PBGD) = 25.95+/-0.73 (FTC)/24.55+/-5.43 (PTC) (P = 0.2878); onfFN = 25.48+/-3.15 (FTC)/21.44+/-3.44 (PTC) (*P = 0.0001). Finally, onfFN transcripts were detected in blood samples of six out of nine patients with known DTC metastases, demonstrating a reliable assay functionality. We propose that real-time RT-PCR of onfFN mRNA is superior to other markers in monitoring minimal residual disease in DTC with regard to both assay sensitivity and specificity.

Influence of rhTSH on [(18)F]fluorodeoxyglucose uptake by differentiated thyroid carcinoma.

The influence of serum TSH levels on fluorine-18 fluorodeoxyglucose (FDG) uptake by recurrences or metastases of differentiated thyroid carcinomas has not yet been clarified. The aim of this study was to ascertain whether the administration of recombinant human thyrotropin (rhTSH) stimulates FDG uptake by such lesions. In this prospective study, 30 patients with positive or equivocal thyroglobulin (Tg) levels and negative or equivocal iodine-131 and/or morphological imaging results (ultrasound, MRI, CT) underwent FDG positron emission tomography (PET) under exogenous TSH suppression and under exogenous TSH stimulation of serum levels by injection of rhTSH. The mean interval between the FDG-PET studies under these two conditions was 9.3+/-8.8 weeks. Serum TSH levels and free thyroid hormones were determined on each occasion. FDG uptake was quantitated using tumour to background ratios (TBRs) and standardised uptake values (SUVs). Under TSH suppression there was focal FDG accumulation in nine subjects (22 tumour-like lesions). The total number of foci was 45. After exogenous TSH stimulation, the number of patients in whom FDG foci were detected was 19, and the number of foci identified was 82 (78 tumour-like lesions). TBR of regions showing positive FDG contrast with either of the modalities averaged 2.54+/-1.89, and under stimulated TSH levels, 5.51+/-2.99 ( P<0.0001). Corresponding SUVs were 2.05+/-1.45 versus 2.77+/-1.58 ( P<0.001). In a small number ( n=4) of foci related to inflammatory lymph nodes, TBR and SUV were only marginally increased under TSH stimulation (2.01+/-0.38 and 1.07+/-0.38, respectively), and the values did not differ significantly from those obtained under suppression. These results provide the first direct evidence that TSH stimulates FDG uptake by differentiated thyroid carcinoma and that, therefore, FDG-PET is more accurate under rhTSH than under suppression.

Establishment of radioactive astatine and iodine uptake in cancer cell lines expressing the human sodium/iodide symporter.

The sodium/iodide symporter (NIS) has been recognized as an attractive target for radioiodine-mediated cancer gene therapy. In this study we investigated the role of human NIS for cellular uptake of the high LET alpha-emitter astatine-211 ((211)At) in comparison with radioiodine as a potential radionuclide for future applications. A mammalian NIS expression vector was constructed and used to generate six stable NIS-expressing cancer cell lines (three derived from thyroid carcinoma, two from colon carcinoma, one from glioblastoma). Compared with the respective control cell lines, steady state radionuclide uptake of NIS-expressing cell lines increased up to 350-fold for iodine-123 ((123)I), 340-fold for technetium-99m pertechnetate ((99m)TcO(4)(-)) and 60-fold for (211)At. Cellular (211)At accumulation was found to be dependent on extracellular Na(+) ions and displayed a similar sensitivity towards sodium perchlorate inhibition as radioiodide and (99m)TcO(4)(-) uptake. Heterologous competition with unlabelled NaI decreased NIS-mediated (211)At uptake to levels of NIS-negative control cells. Following uptake both radioiodide and (211)At were rapidly (apparent t(1/2) 3-15 min) released by the cells as determined by wash-out experiments. Data of scintigraphic tumour imaging in a xenograft nude mice model of transplanted NIS-modified thyroid cells indicated that radionuclide uptake in NIS-expressing tumours was up to 70 times ((123)I), 25 times ((99m)TcO(4)(-)) and 10 times ((211)At) higher than in control tumours or normal tissues except stomach (3-5 times) and thyroid gland (5-10 times). Thirty-four percent and 14% of the administered activity of (123)I and (211)At, respectively, was found in NIS tumours by region of interest analysis ( n=2). Compared with cell culture experiments, the effective half-life in vivo was greatly prolonged (6.5 h for (123)I, 5.2 h for (211)At) and preliminary dosimetric calculations indicate high tumour absorbed doses (3.5 Gy/MBq(tumour) for (131)I and 50.3 Gy/MBq(tumour) for (211)At). In conclusion, NIS-expressing tumour cell lines of different origin displayed specific radionuclide uptake in vitro and in vivo. We provide first direct evidence that the high-energy alpha-emitter (211)At is efficiently transported by NIS. Application of (211)At may direct higher radiation doses to experimental tumours than those calculated for (131)I. Thus, (211)At may represent a promising alternative radionuclide for future NIS-based tumour therapy.

Familial papillary thyroid carcinoma: genetics, criteria for diagnosis, clinical features, and surgical treatment.

Hereditable predisposition to papillary thyroid carcinoma (PTC) and multinodular goiter (MNG) without evidence of an association with other malignancies as a distinct entity was recognized only recently. A meta-review of the literature on familial PTC (FPTC) was undertaken, and characteristics of families with frequent occurrence of PTC or MNG (or both) were summarized. A database on thyroid cancer patients maintained in our institution was searched for potential FPTC families. Clinical examinations were performed in 6 of 12 Hannover kindreds identified, and blood samples of all family members were collected for genetic analyses. Clinical presentations and histopathologic features of the FPTC cases were compiled. Based on the FPTC meta-review and own experience, predictive criteria to identify families at risk were developed: Exclusion criteria were previous radiation exposure and coincidence with neoplasia syndromes. Primary criteria for susceptibility to FPTC are (1) PTC in two or more first-degree relatives and (2) MNG in at least three first- or second-degree relatives of a PTC patient. Secondary criteria are diagnosis in a patient younger than 33 years, multifocal or bilateral PTC, organ-exceeding tumor growth (T4), metastasis (N1, M1), and familial accumulation of adolescent-onset thyroid disease. A hereditary predisposition to PTC is considered if both primary criteria or one primary criterion plus three secondary criteria are present. Family history-taking is recommended for all PTC patients to identify FPTC kindreds at risk. Blood relatives of FPTC index patients who harbor MNG should undergo thorough and regular clinical screening. Suspicious lesions should prompt early surgical intervention.

Outcome after radioiodine therapy in 107 patients with differentiated thyroid carcinoma and initial bone metastases: side-effects and influence of age.

Initial bone metastases in patients with differentiated thyroid carcinoma are rare, especially in younger patients. Long duration of therapy and high activities of radioiodine are often necessary to induce remission of metastatic disease. The curative potential of radioiodine therapy, in particular in younger patients, has not yet been determined. In this retrospective study we evaluated the therapeutic outcome, total radioiodine activities and associated side-effects in 107 patients with initial bone metastases. Eight of the 107 patients were younger than 45 (37.5+/-7.3) years, and were classified as group 1 (stage II, "low risk", WHO classification). The remaining 99 patients were older than 45 (64.1+/-9.5) years, and formed group 2 (stage IV, "high risk", WHO classification). Total or partial remission was more frequently achieved in group 1 than in group 2 (62.5% vs 49.5%). Lower activities were needed in group 1 (18.89+/-15.08 GBq vs 41.97+/-31.25 GBq), and there were less marked alterations in the blood count in this group. In group 1, blood count alterations reached only grade I or II (WHO classification), whereas grade III and grade IV alterations as well as acute leukaemia were observed in group 2. In group 1, complete remission was achieved with radioiodine therapy (11.1 GBq) in three out of four patients with < or =3 bone metastases. Additional pulmonary metastases (present in 44 out of 107 patients) did not influence prognosis. We conclude that initial bone metastases in differentiated thyroid carcinoma can be treated with curative intent by means of radioiodine therapy, and that this approach has a particularly realistic chance of success in younger patients and those with a small number of metastases.

Pre-operative localisation of hyperfunctional parathyroid tissue with 11C-methionine PET.

PURPOSE: Previous studies have shown high sensitivity of positron emission tomography (PET) with 11C-methionine in the pre-operative localisation of parathyroid adenoma and hyperplasia. Nonetheless, in secondary and tertiary hyperparathyroidism (HPT) and in patients with recurrent disease, pre-operative localisation of adenomatous (PTA) or hyperplastic tissue is still a problem with all available methods. The aim of this study was to define the optimal imaging protocol and to compare the diagnostic value of 11C-methionine PET and 99mTc-methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT): in particular, we wished to define the benefit of 11C-methionine in those patients with inconclusive or negative conventional imaging. METHODS: Thirty highly pre-selected patients with HPT were enrolled. Sixteen patients had primary HPT, 12 patients had secondary HPT, and two patients had recurrences of parathyroid carcinomas. All patients had ultrasound of the neck, dual-phase scintigraphy with 99mTc-MIBI and PET with 11C-methionine. SUV(parathyroid)/SUV(cervical soft tissue) (target-to-background) and SUV(parathyroid tissue)/SUV(thyroid tissue) (target-to-non-target) ratios were calculated. After surgery, histology of specimens was obtained in all patients but one. RESULTS: In 12 patients with secondary or tertiary HPT, 36 hyperplastic parathyroid glands were histologically verified. Twenty-five of 36 lesions (69%) were detected with 11C-methionine PET and 17 (47%) with 99mTc-MIBI scintigraphy. PET studies were positive in 17/18 (94%) cases in which HPT was related to adenomas or carcinomas. 99mTc-MIBI scintigraphy/SPECT yielded pathological lesions in 9/18 cases (50%). All eight atypical localisations of parathyroid glands were detected with PET but only six of the eight were detected with 99mTc-MIBI scintigraphy/SPECT. In 10/11 patients with recurrent HPT and non-diagnostic scintigraphy/SPECT, hyperfunctional parathyroid tissue was identified with 11C-methionine PET. The highest SUV(parathyroid)/SUV(cervical soft tissue) ratio was found 10 min, and the highest SUV(parathyroid tissue)/SUV(thyroid tissue) ratio 40 min post injection. In three patients clear delineation of hyperfunctional tissue was only achieved after 40 min post injection. CONCLUSION: 11C-methionine PET is a clinically useful method in highly pre-selected patients with recurrent primary HPT as well as in secondary and tertiary HPT if ultrasound and 99mTc-MIBI SPECT are inconclusive or negative. PET imaging of atypical PTA localisations is more accurate than conventional scintigraphy. In order to achieve optimal contrast of parathyroid glands versus thyroid tissue and adjacent soft tissue, imaging at both 10 min and 40 min is recommended.

Positron emission tomography and cholangiocarcinoma in primary sclerosing cholangitis.

We present the case of a 44-year-old male patient with a history of primary sclerosing cholangitis who developed a cholangiocarcinoma with pulmonary metastasis. The cholangiocarcinoma was identified in the PET scan by its enhanced 18F-FDG-uptake. Prospective studies should be performed to demonstrate whether PET will be suited to detect small and early cholangiocarcinomas, particular in young patients, who could be treated immediately and curatively by liver transplantation.

Monitoring isotretinoin therapy in thyroid cancer using 18F-FDG PET.

Treatment with isotretinoin (13-cis-retinoic acid, 13-cis-RA) is a recent additional option in advanced, otherwise intractable differentiated thyroid cancers. The aim of this study was to evaluate fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the prediction and the monitoring of response to 13-cis-RA therapy. Twenty-one patients with advanced differentiated thyroid cancers were investigated using 18F-FDG PET and iodine-131 whole-body scans before and 3, 6 and 9 months after initiation of 13-cis-RA therapy. After 9 months, 13-cis-RA treatment was discontinued and imaging procedures repeated 3 months later. Average 18F-FDG uptake (SUV) decreased significantly during 13-cis-RA therapy but subsequently increased in five of eight patients after withdrawal of 13-cis-RA. 18F-FDG uptake (SUV) 3 months after onset of 13-cis-RA therapy was significantly lower in patients who developed increased 131I uptake in their tumour sites than in patients with no subsequent increase in 131I uptake. There was no relationship between serum thyroglobulin level on the one hand and simultaneously measured 131I or 18F-FDG uptake on the other hand. There was a tendency towards lower 18F-FDG uptake in tumour manifestations with a better outcome. Therefore, 18F-FDG PET at 3 months after the start of treatment promises to differentiate between those patients who will eventually benefit from 13-cis-RA and those who will not. In conclusion, these data indicate that 18F-FDG PET is a useful tool for the evaluation and monitoring of adjuvant therapy with 13-cis-RA in thyroid cancer.