Anti-proliferative effect of radiolabelled octreotide in a metastases model in rat liver

Most neuroendocrine tumours and several other tumours, such as breast carcinoma and malignant lymphoma, express somatostatin receptors (SS-Rs). Lesions expressing these receptors can be visualised by receptor scintigraphy using a low radioactive dose of the radiolabelled SS analogue [111In-DTPA0]octreotide. This radioligand is internalised and transported to the lysosomes with a long residence time of 111In. The aim of this experimental study in rats was to investigate whether the same agent, given in a high radioactive dose, can be used for therapy of hepatic metastases of different tumour cell lines. The development of hepatic metastases was determined 21 days after direct injection of SS-R-positive or -negative tumour cells into the vena porta in rats. On day 1 and/or 8, animals were treated with 370 MBq (0.5 microg) [111In-DTPA0]octreotide. In one experiment, using SS-R-positive tumour cells, animals were pre-treated with a high dose of cold octreotide to block the SS-R by saturation. The number of SS-R-positive liver metastases was significantly decreased after treatment with [111In-DTPA0]octreotide. Blocking the SS-R by octreotide substantially decreased the efficacy of treatment with [111In-DTPA0]octreotide, suggesting that the presence of SS-R is mandatory. This was confirmed by the finding that the number of SS-R-negative liver metastases was not affected by treatment with [111In-DTPA0]octreotide. Therefore, we conclude that (i) high radioactive doses of [111In-DTPA0]octreotide for PRRT (peptide receptor radionuclide therapy) can inhibit the growth of SS-R-positive liver metastases in an animal model, (ii) PRRT is effective only if SS-Rs are present on the tumours, (iii) the effect of PRRT with [111In-DTPA0]octreotide can be reduced by pre-treatment with cold octreotide, which indicates that receptor binding is essential for PRRT. Our data suggest that PRRT with radiolabelled octreotide might be a new promising treatment modality for SS-R-positive tumours.

Scintigraphic measurement of regional gastrointestinal transit in the dog

Scintigraphic techniques can measure sequentially gastric emptying, small bowel transit, and colonic transit in humans, and comparable methods for experimental studies in animals would be useful. We developed such a method in dogs and examined the effects of prokinetic drugs on regional transit. Two isotopes were given to fasting dogs. Polystyrene pellets labeled with 99mTc were mixed in a can of dog food and 111In- labeled pellets were given in a gelatin capsule coated with a pH-sensitive polymer, designed to dissolve in the distal bowel. Gamma camera images were obtained for up to 24 h. Prokinetic drugs were given by intravenous injection. Duplicate baseline studies showed good agreement in seven dogs. In a second group (n = 4), intra- and interanimal variabilities were established. Two novel prokinetic drugs (AU-116 and AU-130) accelerated small bowel and colonic transit. A simple noninvasive method for measuring whole gut transit in dogs was developed and validated. Two new prokinetics accelerated small bowel and colonic transit.

Dynamic distribution and dosimetric evaluation of human non-specific immunoglobulin G labelled with 111In or 99Tcm

This study presents data on the dynamic distribution and dosimetry of 111In- and 99Tcm-labelled human non-specific immunoglobulin G (IgG), two recently developed radiopharmaceuticals for the detection of infection and inflammation. Five healthy volunteers were injected with 20-75 MBq 111In-IgG and seven patients were injected with 740 MBq 99Tcm-hydrazinonicotinamide derivative (HYNIC)-IgG. Blood samples, urine and feces were collected. Whole-body gamma camera imaging studies were performed. The activity in source organs was quantified using the conjugate view counting method and a partial background subtraction technique. Dosimetric calculations were performed using the MIRD technique. For 111In-IgG, the mean biological half-times in the blood were 0.90 and 46 h for the a- and b-phase, respectively. For 99Tcm-HYNIC-IgG, these half times were 0.46 and 45 h. For 111In-IgG, the mean cumulative urinary excretion in the first 48 h was 18% of the injected dose, while excretion in the feces was less than 2% of the injected dose. For 99Tcm-HYNIC-IgG, the whole-body retention was always 100% up to 24 h. The mean absorbed doses in the liver, spleen, kidneys, red marrow and testes from 111In-IgG were 0.8, 0.7, 1.2, 0.3 and 0.4 mGy MBq-1 respectively. The mean absorbed doses for 99Tcm-HYNIC-IgG to these organs were 16, 24, 15, 10 and 22 mu Gy MBq-1 respectively. The mean effective dose was 0.25 mSv MBq-1 and 8.4 mu Sv MBq-1 for 111In-IgG and 99Tcm-HYNIC-IgG respectively. In conclusion, the radiation absorbed doses for both 111In-IgG and 99Tcm-HYNIC-IgG are low and, therefore, these radiopharmaceuticals can be administered safely from a radiation risk perspective.

111Indium-diethylenetriamine pentaacetic acid cerebrospinal fluid flow studies predict distribution of intrathecally administered chemotherapy and outcome in patients with leptomeningeal metastases

Abnormal CSF flow can impair the distribution of intrathecally administered drugs. We examined the relationship between 111indium-diethylenetriamine pentaacetic acid (111In-DTPA) CSF flow studies and methotrexate levels in ventricular and lumbar CSF and correlated these findings with outcome in patients with leptomeningeal metastases (LM). Seven men and 10 women with LM (10 solid tumors, 6 lymphoma, 1 leukemia) received 12 mg methotrexate and 0.5 mCi 111In-DTPA by intra-Ommaya injection; images were obtained immediately and after 4, 24, and 48 hours. Ventricular and lumbar CSF methotrexate and radioactivity levels were measured 6 hours after injection. Thirteen patients had abnormal CSF flow studies, 9 with multiple sites of obstruction. CSF flow obstruction was observed at ventricular outlets in 13 patients, cerebral convexities in 9 and in the spine in 2. With one exception, all obstructions were explicable by tumor deposits on MRIs. For all patients, ventricular and lumbar methotrexate and radioactivity levels correlated closely. Three patients with a normal CSF flow study are alive at 15+, 7.5+, and 3.9+ months from treatment. Of 12 with abnormal CSF flow studies, 11 are dead a median of 2 months from diagnosis. Two patients had diffusely delayed flow studies and both developed methotrexate leukoencephalopathy. CSF flow studies using 111In-DTPA reliably predict distribution of intrathecal methotrexate. Abnormal flow studies correlate with structural abnormalities, are an unfavorable prognostic factor, and may predict intrathecal chemotherapy toxicity.

Pre-clinical comparison of [DTPA0] octreotide, [DTPA0,Tyr3] octreotide and [DOTA0,Tyr3] octreotide as carriers for somatostatin receptor-targeted scintigraphy and radionuclide therapy

We have evaluated the potential usefulness of radiolabelled [DTPA0,Tyr3]octreotide and [DOTA0,Tyr3]octreotide as radiopharmaceuticals for somatostatin receptor-targeted scintigraphy and radiotherapy. In vitro somatostatin receptor binding and in vivo metabolism in rats of the compounds were investigated in comparison with [111In-DTPA0] octreotide. Comparing different peptide-chelator constructs, [DTPA0,Tyr3]octreotide and [DOTA0,Tyr3]octreotide were found to have a higher affinity than [DTPA0]octreotide for subtype 2 somatostatin receptors (sst2) in mouse AtT20 pituitary tumour cell membranes (all IC50 values obtained were in the low nanomolar range). In vivo studies in CA20948 tumor-bearing Lewis rats revealed a significantly higher uptake of both 111In-labelled [DOTA0,Tyr3]octreotide and [DTPA0,Tyr3]octreotide in sst2-expressing tissues than after injection of [111In-DTPA0]octreotide, showing that substitution of Tyr for Phe at position 3 in octreotide results in an increased affinity for its receptor and in a higher target tissue uptake. Uptake of 111In-labelled [DTPA0]octreotide, [DTPA0,Tyr3]octreotide and [DOTA0,Tyr3]octreotide in pituitary, pancreas, adrenals and tumour was decreased to less than 7% of control by pre-treatment with 0.5 mg unlabelled octreotide/rat, indicating specific binding to sst2. Comparing different radionuclides, [90Y-DOTA0,Tyr3]octreotide had the highest uptake in sst2-positive organs, followed by the [111In-DOTA0,Tyr3]octreotide, whereas [DOTA0,125I-Try3]octreotide uptake was low compared to that of the other radiopharmaceuticals, when measured 24 hr after injection. Renal uptake of 111In-labelled [DTPA0]octreotide, [DTPA0,Tyr3]octreotide and [DOTA0,Tyr3]octreotide was reduced over 50% by an i.v. injection of 400 mg/kg D-lysine, whereas radioactivity in blood, pancreas and adrenals was not affected.

Human bronchiolar deposition and retention of 6-, 8- and 10-micrograms particles

Three groups, each consisting of 6 healthy subjects, inhaled, respectively, 6-micrograms (aerodynamic diameter), 8-micrograms, and 10-micrograms Teflon particles, labeled with indium-111. The particles were inhaled at an extremely low flow rate, 0.05 L/s. Lung retention was measured after 0, 24, 48, and 72 h. Two models were used to calculate particle deposition in the lungs in the various generations: the Karolinska Institute model (KI model) and the University of Southampton model (US model). From the experimental clearance data and the theoretical deposition data, it was calculated that the average retention after 24 h was around 100% for particles deposited in generations 13-16 (ciliated bronchioles) and around 20% in generations 0-12 (both large and small ciliated airways). In these calculations, it was assumed that the retained fractions were independent of particle size. The depositions in the bronchial region (generations 0-8), bronchiolar region (generations 9-15 or 9-16), and the alveolar region were calculated using the two models and compared with the recent ICRP model. On the whole, the three models agreed fairly well.

Chronic interstitial infusion of protein to primate brain: determination of drug distribution and clearance with single-photon emission computerized tomography imaging

High-flow interstitial infusion into the brain, which uses bulk fluid flow to achieve a relatively homogeneous drug distribution in the extracellular space of the brain, has the potential to perfuse large volumes of brain. The authors report reproducible long-term delivery of 111In-diethylenetriamine pentaacetic acid-apotransferrin (111In-DTPA-Tf) (molecular mass 81 kD) to Macaca mulatta brain and monitoring with single-photon emission computerized tomography (SPECT). The 111In-DTPA-Tf was infused at 1.9 microl/minute over 87 hours into the frontal portion of the centrum semiovale using a telemetry-controlled, fully implanted pump. On Days 1, 3, 4, 8, 11, and 15 after beginning the infusion, planar and SPECT scans of 111In-DTPA-Tf were obtained. Spread of protein in the brain ranged from 2 to 3 cm and infusion volumes ranged from 3.9 to 6.7 cm3. Perfusion of over one-third of the white matter of the infused hemisphere was achieved. From brain SPECT images of (99m)Tc-hexamethylpropyleneamine oxime, which was administered intravenously before each 111In scan, the authors also found that blood perfusion in the infused region was reduced by less than 5% relative to corresponding noninfused regions. Histological examination at 30 days revealed only mild gliosis limited to the area immediately surrounding the needle tract. These findings indicate that long-term interstitial brain infusion is effective for the delivery of drugs on a multicentimeter scale in the primate brain. The results also indicate that it should be possible to perfuse targeted regions of the brain for extended intervals to investigate the potential utility of neurotrophic factors, antitumor agents, and other materials for the treatment of central nervous system disorders.

Uptake of In-111 pentetreotide by normally functioning nodular goiters

After the intravenous administration of a radiolabeled somatostatin analogue (octreotide), normal thyroid and neoplastic and nonneoplastic thyroid lesions can be visualized. The authors present the cases of two patients who underwent somatostatin receptor scintigraphy (SSRS) using In-111 pentetreotide: one for the study of suspected paraneoplastic ACTH hypersecretion, and the other for a restaging of breast carcinoma with neuroendocrine features. In both patients, SSRS revealed increased uptake in the thyroid, corresponding to "cold" nodules on Tc-99m pertechnetate imaging. Cytologic and histologic examinations showed the typical features of thyroid goiters without lymphocytic infiltration.

Treatment of lymphoid cell malignancy with In-114m labelled autologous lymphocytes

This paper is a preliminary report of a clinical trial for the treatment of patients with refractory chronic lymphocytic leukaemia, using autologous In-114m-labelled lymphocytes. Fourteen patients have been treated so far with doses ranging from 69 to 211 MBq. All patients had progressive low grade NHL, resistant to chemotherapy and conventional radiotherapy. Following the intravenous administration of radiolabelled autologous lymphocytes 53% (range 33-92%) of the activity accumulated in the spleen, 35% (21-64%) in the liver and 5% in the bone marrow. The initial response in all patients was a rapid decrease in lymphocyte count in peripheral blood. 10 of the 14 (72%) patients showed a response to the treatment. In 2 patients, there was a complete response which lasted 24 and 36 months respectively, 8 patients showed a partial response of 2 to 17 months duration. None of the patients experienced any subjective toxicity although myelosuppression was seen in all patients. This is a novel concept for the administration of therapeutic radiation in a selective way for the treatment of lymphoid cell malignancy and has produced significant antitumour effect in patients with highly resistant disease. The trial is ongoing and a full report will be published on its completion.

Scintigraphic evaluation of four dogs with protein-losing enteropathy using 111indium-labeled transferrin

The purpose of this study was to determine the clinical utility of 111In-labeled transferrin (111In-TF) scintigraphy for evaluating dogs suspected of having protein-losing enteropathies. Four dogs were injected intravenously with autologous 111In-TF after 30 min incubation (at 37 degrees C) of 18.5 MBq (0.5 mCi) 111InCl3 with one ml of autologous plasma. Serial right lateral, left lateral and dorsal images were obtained 2, 4, and 24 hours post 111In-TF administration. Images were subjectively evaluated for the presence or absence of 111In-TF within the gastrointestinal tract. The results of total protein, albumin and globulin levels and results from gastrointestinal biopsies were recorded. In one dog, a follow-up scintigraphic study was done six months after initial evaluation and initiation of treatment for plasmocytic-lymphocytic enteritis. Gastrointestinal activity was noted by two hours in two dogs, while all four dogs had gastrointestinal activity on the 24 hour images. The mean (+/-std dev) plasma protein, albumin and globulin levels were 3.5 (+/-0.9), 1.7 (+/-1) and 1.8 (+/-0.3) respectively at the time of initial presentation. In the one dog that was evaluated after therapy, faint visualization of radioactivity within the colon was noted on the 24 hour image. Based on this study, 111In-TF appears to be a viable scintigraphic method for evaluating dogs with suspected protein-losing enteropathies. Potential limitations of this radiopharmaceutical include cost and prolonged isolation of the animal prior to release to the client due to the long physical half-life (T1/2 = 2.82 days).

Simultaneous administration of 99Tcm-HMPAO-labelled autologous leukocytes and 111In-labelled non-specific polyclonal human immunoglobulin G in bone and joint infections

The aim of this study was to investigate the ability of 111In-labelled human polyclonal immunoglobulin G (111In-IgG) to localize bone and joint infections compared with 99Tcm-HMAPO-labelled leukocytes (99Tcm-WBC). Thirty-four patients routinely referred for investigation of bone and joint infections were studied. In all patients, a bone scan using 99Tcm-MDP was initially obtained. Subsequently, 99Tcm-WBC and 111In-IgG were simultaneously injected and images obtained at 30 min, 4 h and 24 h post-injection. Diagnostic accuracy was established by bacteriology of specimens obtained by needle aspiration and/or surgery, other imaging methods and clinical follow-up. The images were read by three experienced observers blinded to any other information; the clinical suspicion of infection and the diagnosis were established when two observers agreed. Infection was confirmed in 11 patients. The 99Tcm-WBC scans gave 8 true-positive, 5 false-positive, 18 true-negative and 3 false-negative results. With 111In-IgG, the figures were 7, 6, 17 and 4, respectively. The sensitivity, specificity and accuracy were 72.7%, 78.2% and 76.4% respectively for the labelled leukocytes and 63.6%, 73.9% and 70.6% respectively for 111In-IgG. There was greater agreement between the observers with 99Tcm-WBC than 111In-IgG. In this study, 111In-IgG was less sensitive and less specific than 99Tcm-WBC scintigraphy for the diagnosis of chronic infections, but these differences were not significant. Both tracers appear to be useful in the diagnosis of bone and joint infections. However, our results were less reliable for the diagnosis of an infected prosthesis.

Diagnostic accuracy of antimyosin scintigraphy in suspected myocarditis

BACKGROUND

Radiolabeled antibody specific for cardiac myosin administered intravenously has been used to define noninvasively regions of myocardial necrosis. Inflammatory heart disorders such as myocarditis and heart transplant rejection demonstrate diffuse and often faint myocardial uptake of antimyosin antibody. This study was undertaken to evaluate the reproducibility and diagnostic accuracy of antimyosin antibody imaging for the detection of patients with suspected myocarditis.

METHODS AND RESULTS

Fifty antimyosin scans, performed consecutively in patients with suspected myocarditis, were evaluated by one independent observer and two panels of observers. Antimyosin scan interpretations were compared with endomyocardial biopsy results and also with serial changes in left ventricular function. An independent observer (A) and a panel of five observers (A through E) interpreted the antimyosin scans as positive or negative on the basis of both planar images and tomographic reconstructions. Three of the five observers (A through C) again interpreted the scans but based interpretation only on planar images. Blinded random sequence evaluation of antimyosin scans based on the planar and tomographic interpretations revealed moderate agreement between the independent observer (A) and the group of observers (A through E) (kappa = 0.58). There was also moderate agreement between interpretations based on planar images alone and interpretations based on both planar and tomographic images (kappa [A through E]/[A through C] = 0.57; kappa [A through C]/A = 0.48). Comparison of antimyosin scan results with histologic evidence of myocarditis in endomyocardial biopsy specimens demonstrated that all scan results obtained from the individual or the panels of observers had a very high sensitivity (91% to 100%) and a high negative predictive value (93% to 100%). The specificity (31% to 44%) and positive predictive value (28% to 33%) were less impressive. We also compared the scan and biopsy results with the composite clinical standard of significant left ventricular functional improvement. Endomyocardial biopsy demonstrated poor sensitivity (35%) compared with antimyosin scans (82% to 94%) but had superior specificity (endomyocardial biopsy, 79%; antimyosin scan, 25% to 42%). The specificity of interpretations based on planar and tomographic interpretations (38% to 42%) was better than the planar images alone (25%). If reversible left ventricular dysfunction is considered clinical evidence of myocarditis, this study suggests that a negative endomyocardial biopsy significantly misses the presence of the disease. On the other hand, a negative antimyosin scan almost invariably excludes myocarditis.

CONCLUSIONS

This study demonstrates a high degree of interobserver reproducibility of antimyosin interpretation. Comparison of the scintigraphic results with histologic and clinical standards indicates a high sensitivity of antimyosin scans for the detection of myocarditis. The antimyosin scan is also not likely to miss clinically or pathologically diagnosed myocarditis, in contrast to the endomyocardial biopsy, which missed clinically validated myocarditis 65% of time. The combination of high sensitivity and negative predictive value suggests that antimyosin scintigraphy may be an effective screening procedure for obviating biopsies in patients with suspected myocarditis.

Indium-111 bleomycin complex for radiochemotherapy of head and neck cancer--dosimetric and biokinetic aspects

Bleomycin (BLM) is used for the treatment of head and neck cancer. In order to improve the effectiveness of this chemotherapeutic drug, BLM was combined with indium-111. A complex of these agents (111In-BLMC), formed at low pH, was injected intravenously into ten head and neck cancer patients in escalating activities of 75, 175 and 375 MBq. The internally delivered dose to the tumours varied from 0.20 to 2.73 mGy at 75 MBq, from 0.33 to 2.51 mGy at 175 MBq, and from 0.87 to 31.3 mGy at the 375 MBq activity level. Uptake of radioactivity was 0.45+/-0.24x10(-3)% ID/g in primary tumours and 0. 52+/-0.20x10(-3)% ID/g in metastases (at 48 h). Tumour volumes varied from 0.51 to 49.0 cm3. The radioactivity half-lives in the tumours were 30+/-7 h. The activity distribution and penetration into tumour tissue were not affected by increasing the injected activity. There was a positive correlation between BLMC uptake and Ki-67/Mib activity as well as number of mitoses in tumour tissue. These data indicate that 111In-BLMC has potential as a radiochemotherapeutic agent in head and neck cancer and that adjuvant Auger-electron therapy is possible using 114mIn-labelled BLMC.

111In-DTPA-D-Phe-1-octreotide scintigraphy of small cell lung cancer

Twenty-one patients with small cell lung cancer (SCLC) were investigated with 111in-octreotide (111-In-OCT) scintigraphs, 5 hours after the i.v. injection of 111 MBq of the radiotracer. Whole-body and planar scintigraphy as well as SPECT of the thorax were required. The scintigraphic results were compared to those of other conventional diagnostic procedures used for the staging and follow-up of SCLC patients. 111In-OCT detected 86% (48/56) of the lesions already known at the time of scintigraphy, being positive for all 20 SCLC lesions and negative for one lung adenocarcinoma. 111In-OCT showed a high sensitivity for mediastinal metastases (94%) and good sensitivity for bone (75%) and abdominal lymph node metastases (71%). It did not detect 2 liver metastases but revealed 5 unknown lesions which were then confirmed by other diagnostic examinations. 111In-OCT was also effective in patients with low levels of NSE. Three patients received cold octreotide for seven days to investigate whether this treatment might affect SCLC imaging. Scans were performed before and after treatment. The 111In-OCT uptake increased in the cancer lesions while the fixation in normal tissues decreased, demonstrating enhancement of SCLC imaging following cold octreotide administration.

The role of 111In-octreotide scintigraphy in the detection of APUD tumours: our experience in eighteen patients

111In-Octreotide scintigraphy has been recently proposed as a sensitive technique for the detection of neuroendocrine tumours, based on the high radiotracer affinity towards the somatostatin receptors expressed by the APUD-system cells. In the present study, a group of 18 patients with carcinoid tumours and gastrointestinal (GI) apudomas was investigated to assess the accuracy of Octreotide scintigraphy in localizing primitive, recurrent or metastatic lesions. Both planar and SPECT studies were obtained 4 hours after the i.v. injection of 111In-Octreotide (111 MBq); planar images were also carried out 24 hours later. In accordance with other authors, the sensitivity of the method was found to be very high (94%) in our group of patients; only in one case of nesidioblastosis was the scintigraphy negative. No differences in sensitivity were observed between the planar and SPECT studies, but the latter provided a better topographic localization of the neoplastic foci. It should be pointed out that in 7 cases (3 primitive, 1 recurrent and 3 metastatic lesions) scintigraphy correctly localized the tumour, when the other morphological techniques, such as echography, computed tomography or magnetic resonance, failed. On the basis of our data, we believe that Octreotide scintigraphy should be the first study performed in the evaluation of patients affected by APUD tumours.

111In-octreotide in the evaluation of autoimmune thyroid diseases

Aim of our study was to evaluate the uptake of Indium-111 Octreotide (OCT) at the level of thyroid and orbits in autoimmune thyroid diseases. Nine patients with Graves' disease (GD) who were also affected with thyroid associated ophthalmopathy (TAO) and four patients with Hashimoto's thyroiditis (HT) were evaluated. A patient with lung cancer, presenting ophthalmopathy did not related to autoimmune dysthyroidism, was also studied. All patients with ophthalmopathy were evaluated by a Clinical Activity Score and an A-scan standardized echography. Multiple planar images were acquired over a 24-hour period after i.v. injection of 111 MBq of 111In-OCT. A SPECT study was also obtained in 7 patients five hours after the injection. A qualitative analysis was performed. Semiquantitative ratios comparing the counts on the thyroid with respect to background (T/BK) and on the orbits and brain with respect to the blood-pool were also obtained. Thyroid uptake of OCT was higher in GD with respect to HT, and was not related to the functional state of the gland. The highest T/BK ratio was observed at the 24 hour control. Intense orbital uptake was observed only in case where a clinically active ophthalmopathy was present.

Somatostatin receptor imaging: a preliminary experience in forty-nine patients

We report our experience with the 111In-pentetreotide scanning of 47 adult patients presenting with neuroendocrine tumors (n = 38) or malignant pheochromocytomas or related tumors (n = 9), and 2 children with metastatic neuroblastomas. A dynamic study was performed after i.v. administration of 50-190 MBq of 111In-pentetreotide followed by a whole body scan at 1.5-4 hours and at 24 hours. Where indicated, tomoscintigraphy or a dual isotope bone, liver or kidney scan was performed in order to improve the anatomical definition. Lesions were visualized in the earliest phases of the examination but contrast was enhanced on delayed images due to an improved signal to background ratio. In 9/49 patients, octreotide scan (OS) detected unknown tumors sites. On the other hand, the lesion uptake of 111In-pentetreotide varied, and not all the sites shown by other imaging modalities were visualised, probably due to differences in membrane receptor expression. In conclusion, OS can be useful in the diagnosis, follow-up and therapeutic management of neuro-endocrine tumors. Further investigations are required to assess the role of OS in other pathologies. Short title: Somatostatin receptor imaging.

111In-octreotide scintigraphy in small cell lung cancer

Somatostatin receptors have been identified on the cellular surface of a subset of patients with small cell lung cancer (SCLC) and may be associated with a less aggressive evolution of the tumor. Moreover, medical therapy with somatostatin analogues holds promise for neoplastic growth control. We performed planar imaging in 22 patients with histologically proven SCLC at 2-4 and 24 hours after the injection of 111-185 MBq of 111In-DTPA-octreotide (Octreoscan, Byk-Gulden). Tumor uptake was observed in 19 patients in both early and late scans, while 2 patients previously treated with chemotherapy showed negative early and late scans. One patient had a positive early scan and a negative late scan. All the scintigraphic studies showed more extensive disease than expected by CT. No significant modification in tumor uptake of radiooctreotide was observed in three patients studied before and after chemotherapy. In conclusion, 111In-octreotide is a suitable radiopharmaceutical for the in vivo evaluation of the somatostatin receptors of small lung cancer. The prognostic and therapeutical implications of this nuclear technique must be further investigated, however.

Effect of dose and specific activity on tissue distribution of indium-111-pentetreotide in rats

To increase the target-to-background ratio in receptor scintigraphy, we hypothesized that receptor scintigraphy is best performed using the lowest possible mass with the highest possible specific radioactivity of the radioligand.

METHODS

Rats were injected with 2 or 10 micrograms of unlabeled octreotide or 2 or 10 micrograms of 111In-pentetreotide. Scintigraphic images were then obtained from 10 min before to 20 min after the 111In injection.

RESULTS

In some instances, there was a significant increase in 111In uptake in somatostatin receptor-positive organs. In others, there was a significant decrease. Since no significant differences were found in background radioactivity in the percent dose uptake of 111In in receptor-negative organs, these data indicate that target-to-background ratios can be increased by the administration of nonradiolabeled peptides under select conditions.

CONCLUSION

The uptake of 111In-pentetreotide in somatostatin receptor-positive organs results in a tissue-specific bell-shaped function of the injected mass of the radiopharmaceutical. This curve may also apply to somatostatin receptor-positive tumors, the visualization of which may be enhanced by optimizing the mass of 111In-pentetreotide.

A turnover study in the male rat of plasma-bound 59Fe, 114Inm and 109Cd with particular reference to the gonad

After intravenous doses of the plasma-bound radionuclides 59Fe, 114Inm and 109Cd, only a minute percentage localizes in the rat testis and remains largely unchanged with time. Intratesticular injection of appropriately reduced volumes led to much higher proportionate percentage retention of 14, 65 and 11 for 59Fe, 114Inm and 109Cd, respectively. By this route, significant feedback of the elements escaping initial binding was prevented. Distinct but different testicular turnovers were now discernible. As a receptor of fluid and spermatozoa from the testicular tubules, the epididymis provides an indication of entry into and interaction of the metals with spermatogenic cells. For 59Fe no measurable changes were detected, whereas a progressive increase in epididymal 114Inm occurred, which had not reached a plateau by 70 days. 109Cd, now demonstrated within the testicular tubules by autoradiography, remained at constant organ level for upwards of 16 days but had declined by 25% by 57 days. At this point, the epididymis showed a five-fold increase in the radionuclide, declining to one-half this value by 126 days. Since 109Cd is carrier free, the data reflect a body turnover of dietary cadmium. These results, overall, are compatible with the entry of a proportion of each radionuclide into the seminiferous tubules and reaction with spermatogenic cells. Possible interpretations of the observed differences are presented.

Brachytherapy for prostate cancer: real-time three-dimensional interactive seed implantation

A total of 71 men with clinical T1b-T2c carcinoma of the prostate underwent ultrasound-guided interactive seed implantation of the prostate. Sixty received 125I and II 103Pd implants. A laparoscopic lymph node dissection was performed in 58 patients. The patients have been followed a mean of 2 years (1-4.2 years). With use of a prostate specific antigen (PSA) value of 1 ng/ml, patients (n = 8) who presented with an initial PSA of < or = 4.0 ng/ml were all free from failure. This compared with those who presented with an initial PSA of 4.1-10, 10.1-20, and > or = 20 ng/ml, in whom the freedom from failure rates were 52, 32, and 22%, respectively. Patients (n = 49) who presented with an initial PSA of less than or equal to 15 ng/ml had a median PSA of 0.88 ng/ml at last follow-up compared with 2.25 ng/ml for those with an initial PSA of > 15 ng/ml. Prostate biopsies performed 18-24 months after implantation were negative in 82%. The median PSA for those with a negative biopsy was 0.7 ng/ml vs. 4.9 ng/ml for those with a positive biopsy. There were no long-term persistent urinary complaints. Grade 2 radiation proctitis occurred in three (4.2%). No cases of severe radiation proctitis or cystitis occurred. Urinary retention occurred in four patients (5.6%), one of whom required a transurethral resection of the prostate. No patients developed urinary incontinence. Potency was preserved in 94%. We conclude that the real-time ultrasound-guided transperineal seed implantation technique is an effective and safe method of treating prostate cancer. Longer follow-up is needed to substantiate these early encouraging results.

Indium-111 activity concentration in tissue samples after intravenous injection of indium-111-DTPA-D-Phe-1-octreotide

METHODS

Indium-111 activity concentrations in human tumor and normal tissue samples were determined at 24, 48 and 120 hr after i.v. injection of 111In-DTPA-D-Phe-1-octreotide. Fourteen patients were included in the study. Seven patients had medullary thyroid carcinoma, four had midgut carcinoid tumors, two had endocrine pancreatic tumors and one had chronic pancreatitis.

RESULTS

For midgut carcinoids, the tumor-to-blood ratio was 51:220, for medullary thyroid carcinoma 4:39, and for two endocrine pancreatic tumors 6 and 1500. Tumor-to-muscle ratios varied between 1 and 1200 and tumor-to-fat between 2 and 1500 depending on tumor type.

CONCLUSION

The sometimes extremely high tumor-to-normal tissue ratios present the possibility for use of radiolabeled octreotide for radiation therapy of somatostatin receptor positive tumors.

Successful in vivo immunolocalization of Langerhans cell histiocytosis with use of a monoclonal antibody, NA1/34

The antibody NA1/34 is a murine monoclonal antibody directed against the CD1a surface antigen expressed on normal Langerhans cells, cortical thymocytes, and on lesional cells in Langerhans cell histiocytosis (LCH). Our hypothesis was that NA1/34 would localize sites of disease activity in patients with multisystem LCH. To test this hypothesis, indium 111-labeled NA1/34 was administered to five patients with multisystem LCH and serial gamma scans were obtained for up to 120 hours. Serial serum samples were obtained from one patient for analysis of anti-mouse Ig antibody and NA1/34 levels. Direct and indirect immunofluorescence staining for CD1a and NA1/34 were performed on a tissue biopsy specimen from one patient after administration of the antibody. The 1- and 4-hour scans showed distribution of antibody in the blood pool, but in later scans localization of the antibody was noted in areas of known disease activity in all five patients. Bony lesions, previously seen on skeletal radiographs, were especially well identified. Serum kinetics studies showed clearance of the antibody from the blood pool within 12 hours of administration. Direct binding of NA1/34 to lesional cells was demonstrated by direct immunofluorescence. The only adverse effect was urticaria in one patient. We conclude that NA1/34 localizes disease activity in vivo in bones of patients with LCH with minimal toxic effects. An evaluation of its role in determining disease extent ("staging") and in treatment is now needed.

[111In]-DTPA-labeled analogues of alpha-melanocyte-stimulating hormone for melanoma targeting: receptor binding in vitro and in vivo

Six alpha-MSH(4-10) [Nle-Asp-His-D-Phe-Arg-Trp-Lys-amide] derivatives carrying 2 or 1 or no 2,3-dihydroxy-(2S)-propyl (DHP) groups on the Lys10 amino side chain were coupled to diethylene-triaminopentaacetic acid (DTPA, a chelator for 111In) in monomeric and dimeric forms and tested for their binding activity and bioactivity in vitro with mouse and human melanoma cell lines and by receptor autoradiography to tumor sections, as well as in vivo with normal and melanoma-bearing mice: DTPA-[Nle4,Asp5,D-Phe7,Lys(bis-DHP)10]-alpha-MSH(4-10),DTPA-[Nle4, Asp5, D-Phe7,Lys(mono-DHP)10]-alpha-MSH(4-10), DTPA[Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH(4-10), DTPA-bis-([Nle4,Asp5,D-Phe7,Lys(bis-DHP)10]-alpha-MSH(4-10)), DTPA-bis[([Nle4,Asp5,D-Phe7,Lys(mono-DHP)10]-alpha-MSH(4-10)) and DTPA-bis-([Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH(4-10)). In the receptor-binding assays with B16-F1 mouse and D10 human melanoma cells, the KD values ranged between 0.76 and 31.17 nM and in the melanin bioassay the results were similar (EC50 values between 0.15 and 4.40 nM). The tissue distribution of the 111In-labeled compounds in C57Bl/6J mice showed that the dimeric [111In]-DTPA-bis([Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH(4-10)) and the monomeric [111In]-DTPA-[Nle4,Asp5,D-Phe7,Lys(bis-DHP)10]-alpha-MSH(4-10) exhibited the lowest non-specific binding. In mice carrying B16-F1 melanoma tumors, the monomeric compound displayed 2-fold higher 111In uptake by the tumor and a much lower non-specific uptake by the liver (12-fold) and the kidneys (2.5-fold) than the dimeric derivative. This demonstrates that modification of the Lys10 side chain by DHP is a promising lead for new MSH radiopharmaceuticals for melanoma targeting.

Total and segmental colon transit time in constipated children assessed by scintigraphy with 111In-DTPA given orally

Serial colon scintigraphy using 111In-DTPA (2 MBq) given orally was performed in 39 children referred for constipation, and the total and segmental colon transit times were measured. The bowel movements during the study were recorded and the intervals between defecations (ID) were calculated. This method proved able to identify children with normal colon morphology (no. = 32) and those with dolichocolon (no. = 7). Normal children were not included for ethical reasons and we used the normal range determined by others using x-ray methods (29 +/- 4 hours). Total and segmental colon transit times were found to be prolonged in all children with dolichocolon (TC: 113.55 +/- 41.20 hours; RC: 39.85 +/- 26.39 hours; LC: 43.05 +/- 18.30 hours; RS: 30.66 +/- 26.89 hours). In the group of children with a normal colon shape, 13 presented total and segmental colon transit times within the referred normal value (TC: 27.79 +/- 4.10 hours; RC: 9.11 +/- 2.53 hours; LC: 9.80 +/- 3.50 hours; RS: 8.88 +/- 4.09 hours) and normal bowel function (ID: 23.37 +/- 5.93 hours). In the remaining children, 5 presented prolonged retention in the rectum (RS: 53.36 +/- 29.66 hours), and 14 a prolonged transit time in all segments. A good correlation was found between the transit time and bowel function. From the point of view of radiation dosimetry, the most heavily irradiated organs were the lower large intestine and the ovaries, and the level of radiation burden depended on the colon transit time. We can conclude that the described method results safe, accurate and fully diagnostic.