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Contains fulltext : 57827.pdf (Publisher’s version ) (Closed access) A single, low dose of recombinant human thyroid-stimulating hormone (rhTSH) doubles 24-h RAIU and causes a more homogeneous distribution of radioiodine on thyroid scintigrams of patients with nodular goiter. Pretreatment with rhTSH allows the therapeutic dose of (131)I to be reduced by 50%-60% without compromising the result of thyroid volume reduction. The present study focused on the dosimetric aspects of therapy with a reduced dose of (131)I after pretreatment with rhTSH in patients with nodular goiter. METHODS: Thirty-six patients were treated with (131)I to reduce thyroid volume. Nine patients were pretreated with a single dose of 0.01 mg of rhTSH, and 9 patients, with 0.03 mg of rhTSH. Two control groups of 9 patients, matched for thyroid weight and 24-h radioactive iodide uptake, were not pretreated with rhTSH. The therapeutic dose of (131)I was aimed at being sufficient to result in retention of 3.7 MBq of (131)I per gram of thyroid tissue at 24 h. Thyroid radioactivity after (131)I administration was measured every 24 h for 3 d and on days 7, 10, 14, 21, and 28. A model of iodine biokinetics was used to estimate absorbed doses in organs. Protein-bound (131)I activity was measured at 1, 2, 3, 7, and 10 d and at 2, 3, and 4 wk after (131)I therapy. RESULTS: The administered activities were 1.5 times lower in the 0.01-mg rhTSH group and 1.9 times lower in the 0.03-mg rhTSH group than in the control groups. The absorbed dose in the thyroid was similar in the rhTSH-pretreated groups and in the control groups. In the organs of excretion (bladder) and uptake (stomach) of inorganic iodide, the absorbed doses were 2- to 3-fold lower in the pretreated groups than in the control groups. The effective dose equivalent outside the thyroid was considerably lower in the rhTSH-pretreated groups than in their respective control groups (1.6-fold in the 0.01-mg rhTSH group and 2.3-fold in the 0.03-mg rhTSH group). The time course of protein-bound (131)I activity in serum and the cumulated protein-bound (131)I activity in serum did not differ significantly between rhTSH-pretreated and control groups. CONCLUSION: (131)I therapy after pretreatment with a single, low dose of rhTSH, with the dose reduced according to the rhTSH-induced increase in 24-h radioactive iodide uptake, caused lower radiation-absorbed doses in extrathyroidal organs and tissues, especially bladder and stomach, and no significant increase in the release of (131)I-labeled thyroid hormones into the circulation of patients with nodular goiter. Thus, this mode of therapy can be recommended, especially when the dose of radioiodine to be administered without rhTSH pretreatment is high.

Item does not contain fulltext PURPOSE: There is increasing evidence that the chimeric monoclonal antibody G250 (cG250) can be internalized by G250 antigen-expressing renal cell carcinoma (RCC) cells. Thus, accumulation in tumors of cG250 labeled with residualizing radionuclides might be higher than that of nonresidualizing (131)I-cG250. Here, we present a study comparing intrapatiently the accumulation of (131)I-cG250 and (111)In-cG250 in RCC metastases. EXPERIMENTAL DESIGN: Five patients were i.v. injected with 222 MBq (111)In-ITC-DTPA-cG250 and 222 MBq (131)I-cG250 on days 0 and 4, respectively. Directly and 4 days after the injection of both antibody preparations, whole body gamma camera images were acquired. The scintigraphic images were analyzed visually and quantitatively. The radioactivity in tissues was calculated and expressed as percentage injected dose in organs or percentage injected dose/g in metastases. For the latter, tumor:blood ratios were also calculated. Twenty-five metastases were analyzed completely. RESULTS: At 4 days postinjection, the (111)In-ITC-DTPA-cG250 images revealed more metastatic lesions (n = 47) than (131)I-cG250 (n = 30). Quantitative analysis of the images showed higher activities of (111)In-ITC-DTPA-cG250 than (131)I-cG250 in 20 of 25 lesions. The mean overall half-life of both antibody preparations in plasma was similar. CONCLUSIONS: (111)In-ITC-DTPA-cG250 outperformed (131)I-cG250 for visualization of metastatic RCC lesions, not just because of the superior gamma camera characteristics of (111)In, but more importantly, also because higher tumor:blood ratios were obtained. The higher activities of (111)In-ITC-DTPA-cG250 in metastatic lesions might be caused by internalization and subsequent intracellular retention of the radiolabel, implying that in future radioimmunotherapy trials with cG250 in RCC patients, the use of a residualizing radionuclide should be considered.

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Contains fulltext : 59348.pdf (Publisher’s version ) (Open Access) INTRODUCTION: Clinical and animal studies of chimeric monoclonal antibody G250 (moAb cG250) for the targeting of clear-cell renal cell carcinoma (RCC), to date, have been with the intact IgG form. To determine whether F(ab')2 fragments are more suited for radioimmunotherapy (RIT) than intact IgG, biodistribution experiments in nude mice were performed, and a pilot study in RCC patients was carried out. In these studies, the biodistribution, pharmacokinetics, and tumor-targeting characteristics of 131I-cG250-F(ab')2 fragments were determined. METHODS: The biodistribution of intact IgG and F(ab')2 fragments (moAb cG250) was directly compared in mice with subcutaneous (s.c.) RCC xenografts that were coinjected with 125I-cG250-IgG and 131I-cG250-F(ab')2 fragments. Groups of 5 mice were dissected at 1, 2, 3, 5, and 7 days postinjection (p.i.). The activity in tumor and normal tissues was expressed as the percentage of the injected dose per gram (%ID/g). Five (5) patients with evidence of primary RCC on computed tomography (CT) and scheduled for nephrectomy received a diagnostic infusion of 150 MBq 131I-cG250-F(ab')2. At various time points after injection of the antibody preparation (5 minutes, 3 hours, and 1, 2, 3, and 4 days), whole-body gamma camera images were acquired. After surgery, histology was determined and immunohistochemistry was performed. The scintigraphic images were analyzed visually and quantitatively. Radioactivity in whole-body, normal tissues and primary RCC was calculated and expressed as %ID. RESULTS: In mice, 131I-cG250-F(ab')2 fragments cleared faster from the blood and other tissues, and absolute uptake in tumor (3.4 +/- 0.9 %ID/g at 24 hours p.i.) and normal tissues was considerably lower compared to intact 125I-cG250. However, the tissue-to-blood ratios for both antibody preparations were similar for most tissues and at most time points. The results in patients corresponded with the results of the studies in mice. The 131I-cG250-F(ab')2 fragments cleared rapidly from the blood and body. The half-life of the distribution and elimination phase (t(1/2)alpha and t(1/2)beta) in blood of RCC patients were 4.8 +/- 0.9 hours and 29.0 +/- 3.3 hours, respectively. At 4 days p.i., whole-body activity was 20%ID. Faint visualization of tumor was observed in only 2 of 5 patients. CONCLUSIONS: In mice, the tissue-to-blood ratios were similar for intact IgG and the 131I-cG250-F(ab')2 fragments for most tissues and at most time points, although absolute uptake in all tissues was considerably lower for the F(ab')2 fragments. In patients with primary RCC, tumorous kidney tissue was faintly visualized with 131I-cG250-F(ab')2 fragments. The intact IgG form of cG250 appears to be more suitable than cG250-F(ab')2 fragments for targeting clear-cell RCC.

Item does not contain fulltext From December 1999 until July 2001, a phase I dose escalation study was performed with (186)Re-labeled bivatuzumab, a humanized monoclonal antibody against CD44v6, on patients with inoperable recurrent or metastatic head and neck cancer. The aim of the trial was to assess the safety and tolerability of intravenously administered (186)Re-bivatuzumab and to determine the maximum tolerated dose (MTD) of (186)Re-bivatuzumab. The data were also used for dosimetric analysis of the treated patients. Dosimetry is used to estimate the absorbed doses by nontarget organs, as well as by tumors. It can also help to explain toxicity that is observed and to predict organs at risk because of the therapy given. METHODS: Whole-body scintigraphy was used to draw regions around sites or organs of interest. Residence times in these organs and sites were calculated and entered into the MIRDOSE3 program, to obtain absorbed doses in all target organs except for red marrow. The red marrow dose was calculated using a blood-derived method. Twenty-one studies on 18 patients, 5 female and 16 male, were used for dosimetry. RESULTS: The mean red marrow doses were 0.49 +/- 0.03 mGy/MBq for men and 0.64 +/- 0.03 mGy/MBq for women. The normal organ with the highest absorbed dose appeared to be the kidney (mean dose, 1.61 +/- 0.75 mGy/MBq in men and 2.15 +/- 0.95 mGy/MBq in women; maximum kidney dose in all patients, 11 Gy), but the doses absorbed are not expected to lead to renal toxicity. Other organs with doses exceeding 0.5 mGy/MBq were the lungs, the spleen, the heart, the liver, the bones, and the testes. The doses delivered to the tumor, recalculated to the MTD level of 1.85 GBq/m(2), ranged from 3.8 to 76.4 Gy, with a median of 12.4 Gy. A good correlation was found between platelet and white blood cell counts and the administered amount of activity per kilogram of body weight (r = -0.79). CONCLUSION: Dosimetric analysis of the data revealed that the range of doses to normal organs seems to be well within acceptable and safe limits. Tumor doses ranged from 4 to 76 Gy. Given the acceptable tumor doses, (186)Re-labeled bivatuzumab could be a good candidate for future adjuvant radioimmunotherapy in patients with minimal residual disease.

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Contains fulltext : 19827.pdf (Publisher’s version ) (Closed access)

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Contains fulltext : 146672.pdf (Publisher’s version ) (Open Access) 163 p.

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Contains fulltext : 24743___.PDF (Publisher’s version ) (Open Access)

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Contains fulltext : 23737___.PDF (Publisher’s version ) (Open Access)