Bone mineral density and body composition in adolescents with childhood-onset growth hormone deficiency

BACKGROUND/AIMS

The aim of the present study was to evaluate bone mineral density (BMD) and body composition of patients with childhood-onset growth hormone (GH) deficiency (GHD) treated with GH during the transition period.

METHODS

BMD and body composition, measured by dual-energy X-ray absorptiometry, were evaluated at final height and yearly thereafter during 2 years. Twenty-nine of the 40 patients had also been measured before start and during GH therapy.

RESULTS

Mean lumbar spine BMD and bone mineral apparent density (BMAD) as well as total body BMD and lean body mass (LBM) SD score (SDS) were significantly lower than normal at final height and during the 2 years thereafter for all patients. Final-height SDS was related to the change in height SDS as well as in LBM SDS during the first year of GH treatment. LBM SDS decreased significantly in the group of patients with GHD without GH treatment (p < 0.01, n = 19). Fat mass SDS increased in all patients.

CONCLUSION

Mean BMD, BMAD and LBM SDS were significantly lower than normal in adolescents with childhood-onset GHD at and 2 years after the attainment of final height.

Bone mineral density, growth, and thyroid function in long-term survivors of pediatric Hodgkin's lymphoma treated with chemotherapy only

BACKGROUND

The aim of this study was to investigate the long-term side effects of treatment for childhood Hodgkin's lymphoma with chemotherapy only on growth, bone mineral density (BMD), body composition, and thyroid function.

PROCEDURE

A total of 88 patients (56 male, 32 female; 17.6-42.6 yr), treated for childhood Hodgkin's lymphoma from 1974-1998 with combination chemotherapy adriamycin (doxorubicin), bleomycin, vinblastine, and dacarbazine or epirubicin, bleomycin, vinblastine, dacarbazine with or without mechlorethamine, oncovin (vincristine), procarbazine, and prednisone (MOPP) with the intention to avoid radiotherapy, participated in this study. Median follow-up was 15.5 yr (range 5.6-30.2). BMD of lumbar spine and total body (BMD-TB), and body composition were measured using dual-energy x-ray absorptiometry. Bone mineral apparent density of the lumbar spine was calculated to correct for bone size. Free T4 and TSH were measured.

RESULTS

Men treated with MOPP had a significantly reduced height with normal body proportions. Women treated with MOPP had decreased BMD-TB and bone mineral apparent density of the lumbar spine as compared with healthy controls. Percent body fat was significantly increased in female patients treated without MOPP. Body mass index was significantly increased in male patients treated without MOPP, whereas lean body mass was normal in all patients. All patients, except one, treated with chemotherapy only had normal thyroid function. However, five patients who received additional radiation to the thyroid either had abnormal levels of TSH or free T4, or used thyroid hormones.

CONCLUSIONS

Lean body mass was normal in all patients; thyroid function was normal in all but one patient. The use of MOPP leads to decreased height and increased body mass index in men and decreased BMD-TB in women.

Effects of therapy with [177Lu-DOTA 0,Tyr 3]octreotate on endocrine function

Purpose

Peptide receptor radionuclide therapy (PRRT) with radiolabelled somatostatin analogues is a novel therapy for patients with somatostatin receptor-positive tumours. We determined the effects of PRRT with [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-octreotate) on glucose homeostasis and the pituitary-gonadal, pituitary-thyroid and pituitary-adrenal axes.

Methods

Hormone levels were measured and adrenal function assessed at baseline and up to 24 months of follow-up.

Results

In 35 men, mean serum inhibin B levels were decreased at 3 months post-therapy (205 ± 16 to 25 ± 4 ng/l, p < 0.05) and follicle-stimulating hormone (FSH) levels increased (5.9 ± 0.5 to 22.7 ± 1.4 IU/l, p < 0.05). These levels returned to near baseline levels. Total testosterone and sex hormone binding globulin (SHBG) levels decreased (15.0 ± 0.9 to 10.6 ± 1.0 nmol/l, p < 0.05 and 61.8 ± 8.7 to 33.2 ± 3.7 nmol, p < 0.05), respectively, whereas non-SHBG-bound T did not change. An increase (5.2 ± 0.6 to 7.7 ± 0.7 IU/l, p < 0.05) of luteinizing hormone (LH) levels was found at 3 months of follow-up returning to baseline levels thereafter. In 21 postmenopausal women, a decrease in levels of FSH (74.4 ± 5.6 to 62.4 ± 7.7 IU/l, p < 0.05) and LH (26.8 ± 2.1 to 21.1 ± 3.0 IU/l, p < 0.05) was found. Of 66 patients, 2 developed persistent primary hypothyroidism. Free thyroxine (FT₄) levels decreased (17.7 ± 0.4 to 15.6 ± 0.6 pmol/l, p < 0.05), whereas thyroid-stimulating hormone (TSH) and triiodothyronine (T₃) levels did not change. Reverse triiodothyronine (rT₃) levels decreased (0.38 ± 0.03 to 0.30 ± 0.01 nmol/l, p < 0.05). Before and after therapy adrenocorticotropic hormone (ACTH) stimulation tests showed an adequate response of serum cortisol (> 550 nmol/l, n = 18). Five patients developed elevated HbA_1c levels (> 6.5%).

Conclusion

In men ¹⁷⁷Lu-octreotate therapy induced transient inhibitory effects on spermatogenesis, but non-SHBG-bound T levels remained unaffected. In the long term, gonadotropin levels decreased significantly in postmenopausal women. Only a few patients developed hypothyroidism or elevated levels of HbA_1c. Therefore, PRRT with ¹⁷⁷Lu-octreotate can be regarded as a safe treatment modality with respect to short- and long-term endocrine function.

Peptide receptor imaging of prostate cancer with radiolabelled bombesin analogues

Prostate Cancer (PC) is a type of cancer that is often diagnosed at very early stages due to improved detection among man in the Western world. Current imaging techniques are not optimal to determine extent of minimal early stage PC even though this is of great clinical importance. Human PC and high-grade PIN have shown high Gastrin-Releasing Peptide Receptor (GRPR) expression, while normal prostate tissue and BPH revealed to be predominantly GRPR-negative. Radiolabelled Gastrin-Releasing Peptide (GRP) or bombesin (BN) analogues targeting the GRPR can be used as non-invasive tools to diagnose, monitor and potentially treat PC. These BN analogues have already proven to be able to image PC in both tumour-bearing mice and clinical patients showing no important side effects. It's desirable that new peptides require fast-track standardised comparative testing in relevant PC models to select the best performing BN analogues for further evaluation in patients. Although knowledge about GRPR expression and development of new BN analogues can be extended, it is time to study performance of BN analogues for peptide receptor based imaging in patients validating results of PC imaging using histopathology as a golden standard.

Optimised labeling, preclinical and initial clinical aspects of CCK-2 receptor-targeting with 3 radiolabeled peptides

Medullary thyroid carcinoma (MTC) expresses CCK-2 receptors. (111)In-labeled DOTA-DGlu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH(2) (DOTA-MG11), DOTA-DAsp-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH(2) (DOTA-CCK), and (99m)Tc-labeled N(4)-Gly-DGlu-(Glu)(5)-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH(2) ((99m)Tc-Demogastrin 2) are analogs developed for CCK-2 receptor-targeted scintigraphy. All 3 radiolabeled analogs were selected on the basis of their high CCK-2 receptor affinity and their good in vitro serum stability, with in vitro serum t(1/2) values of several hours. Radiolabeling of DOTA-peptides with (111)In requires a heating procedure, typically in the range of 80 degrees -100 degrees C up to 30 min. Following this procedure with DOTA-MG11 resulted in a >98 % incorporation of (111)In, however, with a radiochemical purity (RCP) of <50 %. The decrease in RCP was found to be due to oxidation of the methionine residue in the molecule. Moreover, this oxidized compound lost its CCK-2 receptor affinity. Therefore, conditions during radiolabeling were optimised: labeling of DOTA-MG11 and DOTA-CCK with (111)In involved 5 min heating at 80 degrees C and led to an incorporation of (111)In of >98 %. In addition, all analogs were radiolabeled in the presence of quenchers to prevent radiolysis and oxidation resulting in a RCP of >90 %. All 3 radiolabeled analogs were i.v. administered to 6 MTC patients: radioactivity cleared rapidly by the kidneys, with no significant differences in the excretion pattern of the 3 radiotracers. All 3 radiolabeled analogs exhibited a low in vivo stability in patients, as revealed during analysis of blood samples, with the respective t(1/2) found in the order of minutes. In patient blood, the rank of radiopeptide in vivo stability was: (99m)Tc-Demogastrin 2 (t(1/2) 10-15 min)>(111)In-DOTA-CCK (t(1/2) approximately 5-10 min)>(111)In-DOTA-MG11 (t(1/2)<5 min).

Comparison of three radiolabelled peptide analogues for CCK-2 receptor scintigraphy in medullary thyroid carcinoma

Purpose

Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in a high percentage of medullary thyroid carcinomas (MTC). Analogous to somatostatin receptors, CCK-2 receptors might be viable targets for radionuclide scintigraphy and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed, and some have been carried through into clinical studies. However, these studies are mostly limited and difficult to compare. The aim of this study was to evaluate the diagnostic and therapeutic potential of three promising CCK-2 receptor-binding radiopeptides in patients with MTC.

Methods

¹¹¹In-DOTA-(D)Asp-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH₂ (¹¹¹In-DOTA-CCK), a CCK analogue, and the gastrin-based ligands ^99mTc-N₄-Gly-(D)Glu-(Glu)₅-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH₂ (^99mTc-demogastrin 2) and ¹¹¹In-DOTA-(D)Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH₂ (¹¹¹In-DOTA-MG11) were each administered to the same group of six patients. Planar images made at 3–5, 7 and 24 h p.i. were used for comparison of tumour visualisation and renal uptake.

Results

^99mTc-demogastrin 2 scintigraphy visualised all known lesions and new lesions in four of six patients. ¹¹¹In-DOTA-CCK and ¹¹¹In-DOTA-MG11 on the other hand missed several lesions; tumour uptake of these two radiopharmaceuticals was quite low. Comparison of retention of renal activity showed no major differences between the three radiopeptides.

Conclusion

^99mTc-demogastrin 2 scintigraphy appeared most promising as a diagnostic tool in patients with MTC. Further studies are required to evaluate its value in patient management. Direct comparisons of the compounds studied strongly suggests that ¹¹¹In-DOTA-CCK and ¹¹¹In-DOTA-MG11 have less potential as imaging agents than ^99mTc-demogastrin 2. These DOTA-linked compounds are considered unlikely to be useful for radionuclide therapy because of low tumour uptake.

ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: peptide receptor radionuclide therapy with radiolabeled somatostatin analogs

The purpose of this guideline is to assist physicians caring for patients with neuroendocrine tumors in considering eligibility criteria for peptide receptor radionuclide therapy (PRRT), and in defining the minimum requirements for PRRT. This guideline also makes recommendations on what minimal patient, tumor, and treatment outcome characteristics should be reported for PRRT in order to make comparisons between studies possible. It is not this guideline's aim to give specific recommendations on the use of specific radiolabeled somatostatin analogs for PRRT because different analogs are being used, and their availability depends on national law and local permissions.

Molecular imaging of reduced renal uptake of radiolabelled [DOTA0,Tyr3]octreotate by the combination of lysine and Gelofusine in rats

AIM

In peptide receptor radionuclide therapy (PRRT) using radiolabelled somatostatin analogues, kidney uptake of radiolabelled compound is the major dose-limiting factor. We studied the effects of Gelofusine (20 mg) and lysine (100 mg) and the combination of both after injection of therapeutic doses of radiolabelled [DOTA0,Tyr3]octreotate (60 MBq 111In or 555 MBq 177Lu labelled to 15 microg peptide) in male Lewis rats.

METHODS

Kidney uptake was measured by single photon emission computed tomography (SPECT) scans with a four-headed multi-pinhole camera (NanoSPECT) at 24 h, 5 and 7 days p. i. and was quantified by volume of interest analysis. For validation the activity concentration in the dissected kidneys was also determined ex vivo using a gamma counter and a dose calibrator.

RESULTS

Gelofusine and lysine both reduced kidney uptake of [177Lu-DOTA0,Tyr3]octreotate significantly by about 40% at all time points. The combination of Gelofusine and lysine resulted in a 62% inhibition of kidney uptake (p < 0.01 vs. lysine alone). A weak but significant dose-response relationship for Gelofusine, but not for lysine, was found. In a study with [111In-DOTA0,Tyr3]octreotate, conclusions drawn from NanoSPECT data were confirmed by biodistribution data.

CONCLUSIONS

We conclude that rat kidney uptake of radiolabelled somatostatin analogues can be monitored for a longer period in the same animal using animal SPECT. Gelofusine and lysine had equal potential to reduce kidney uptake of therapeutic doses of [177Lu-DOTA0,Tyr3]octreotate. The combination of these compounds caused a significantly larger reduction than lysine or Gelofusine alone and may therefore offer new possibilities in PRRT. The NanoSPECT data were validated by standard biodistribution experiments.

Treatment with the radiolabeled somatostatin analog [177 Lu-DOTA 0,Tyr3]octreotate: toxicity, efficacy, and survival

PURPOSE

Despite the fact that most gastroenteropancreatic neuroendocrine tumors (GEPNETs) are slow-growing, median overall survival (OS) in patients with liver metastases is 2 to 4 years. In metastatic disease, cytoreductive therapeutic options are limited. A relatively new therapy is peptide receptor radionuclide therapy with the radiolabeled somatostatin analog [(177)Lu-DOTA(0),Tyr(3)]octreotate. Here we report on the toxicity and efficacy of this treatment, performed in over 500 patients.

PATIENTS AND METHODS

Patients were treated up to a cumulative dose of 750 to 800 mCi (27.8-29.6 GBq), usually in four treatment cycles, with treatment intervals of 6 to 10 weeks. Toxicity analysis was done in 504 patients, and efficacy analysis in 310 patients.

RESULTS

Any hematologic toxicity grade 3 or 4 occurred after 3.6% of administrations. Serious adverse events that were likely attributable to the treatment were myelodysplastic syndrome in three patients, and temporary, nonfatal, liver toxicity in two patients. Complete and partial tumor remissions occurred in 2% and 28% of 310 GEPNET patients, respectively. Minor tumor response (decrease in size > 25% and < 50%) occurred in 16%. Median time to progression was 40 months. Median OS from start of treatment was 46 months, median OS from diagnosis was 128 months. Compared with historical controls, there was a survival benefit of 40 to 72 months from diagnosis.

CONCLUSION

Treatment with [(177)Lu-DOTA(0),Tyr(3)]octreotate has few adverse effects. Tumor response rates and progression-free survival compare favorably to the limited number of alternative treatment modalities. Compared with historical controls, there is a benefit in OS from time of diagnosis of several years.

Gastroenteropancreatic neuroendocrine tumours

Gastroenteropancreatic (GEP) neuroendocrine tumours (NETs) are fairly rare neoplasms that present many clinical challenges. They secrete peptides and neuroamines that cause distinct clinical syndromes, including carcinoid syndrome. However, many are clinically silent until late presentation with mass effects. Investigation and management should be highly individualised for a patient, taking into consideration the likely natural history of the tumour and general health of the patient. Management strategies include surgery for cure (which is achieved rarely) or for cytoreduction, radiological intervention (by chemoembolisation and radiofrequency ablation), chemotherapy, and somatostatin analogues to control symptoms that result from release of peptides and neuroamines. New biological agents and somatostatin-tagged radionuclides are under investigation. The complexity, heterogeneity, and rarity of GEP NETs have contributed to a paucity of relevant randomised trials and little or no survival increase over the past 30 years. To improve outcome from GEP NETs, a better understanding of their biology is needed, with emphasis on molecular genetics and disease modeling. More-reliable serum markers, better tumour localisation and identification of small lesions, and histological grading systems and classifications with prognostic application are needed. Comparison between treatments is currently very difficult. Progress is unlikely to occur without development of centers of excellence, with dedicated combined clinical teams to coordinate multicentre studies, maintain clinical and tissue databases, and refine molecularly targeted therapeutics.

Hormonal crises following receptor radionuclide therapy with the radiolabeled somatostatin analogue [177Lu-DOTA0,Tyr3]octreotate

Introduction

Receptor radionuclide therapy is a promising treatment modality for patients with neuroendocrine tumors for whom alternative treatments are limited. The aim of this study was to investigate the incidence of hormonal crises after therapy with the radiolabeled somatostatin analogue [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-octreotate).

Materials and methods

All ¹⁷⁷Lu-octreotate treatments between January 2000 and January 2007 were investigated. Four hundred seventy-six patients with gastroenteropancreatic neuroendocrine tumors and three patients with metastatic pheochromocytoma were included for analysis.

Results

Four hundred seventy-nine patients received a total of 1,693 administrations of ¹⁷⁷Lu-octreotate. Six of 479 patients (1%) developed severe symptoms because of massive release of bioactive substances after the first cycle of ¹⁷⁷Lu-octreotate. One patient had a metastatic hormone-producing small intestinal carcinoid; two patients had metastatic, hormone-producing bronchial carcinoids; two patients had vasoactive intestinal polypeptide-producing pancreatic endocrine tumors (VIPomas); and one patient had a metastatic pheochromocytoma. With adequate treatment, all patients eventually recovered.

Conclusion

Hormonal crises after ¹⁷⁷Lu-octreotate therapy occur in 1% of patients. Generally, ¹⁷⁷Lu-octreotate therapy is well tolerated.

Up-regulation of somatostatin receptor density on rat CA20948 tumors escaped from low dose [177Lu-DOTA0,Tyr3]octreotate therapy

AIM

Peptide receptor radionuclide therapy using the somatostatin analogue [(177)Lu-DOTA(0),Tyr(3)]octreotate is a convincing treatment modality for metastasized neuroendocrine tumors. Therapeutic doses are administered in 4 cycles with 6-10 week intervals. A high somatostatin receptor density on tumor cells is a prerequisite at every administration to enable effective therapy. In this study, the density of the somatostatin receptor subtype 2 (sst2) was investigated in the rat CA20948 pancreatic tumor model after low dose [(177)Lu-DOTA(0), Tyr(3)]octreotate administration resulting in approximately 20 Gy tumor radiation absorbed dose, whereas 60 Gy is needed to induce complete tumor regression in these and the majority of tumors.

METHODS

Sixteen days after inoculation of the CA20948 tumor, male Lewis rats were injected with 185 MBq [(177)Lu-DOTA(0),Tyr(3)]octreotate to initiate a decline in tumor size. Approximately 40 days after injection, tumors re-grew progressively after initial response. Quantification of sst2 expression was performed using in vitro autoradiography on frozen sections of three groups: control (not-treated) tumors, tumors in regression and tumors in re-growth. Histology and proliferation were determined using HE- and anti-Ki-67-staining.

RESULTS

The sst2 expression on CA20948 tumor cells decreased significantly after therapy to 5% of control level. However, tumors escaping from therapy showed an up-regulated sst2 level of 2-5 times higher sst2 density compared to control tumors.

CONCLUSION

After a suboptimal therapeutic dose of [(177)Lu-DOTA(0),Tyr(3)]octreotate, escape of tumors is likely to occur. Since these cells show an up-regulated sst2 receptor density, a next therapeutic administration of radiolabelled sst2 analogue can be expected to be highly effective.

Renal uptake and retention of radiolabeled somatostatin, bombesin, neurotensin, minigastrin and CCK analogues: species and gender differences

INTRODUCTION

During therapy with radiolabeled peptides, the kidney is most often the critical organ. Newly developed peptides are evaluated preclinically in different animal models before their application in humans. In this study, the renal retention of several radiolabeled peptides was compared in male and female rats and mice.

METHODS

After intravenous injection of radiolabeled peptides [somatostatin, cholecystokinin (CCK), minigastrin, bombesin and neurotensin analogues], renal uptake was determined in both male and female Lewis rats and C57Bl mice. In addition, ex vivo autoradiography of renal sections was performed to localize accumulated radioactivity.

RESULTS

An equal distribution pattern of renal radioactivity was found for all peptides: high accumulation in the cortex, lower accumulation in the outer medulla and no radioactivity in the inner medulla of the kidneys. In both male rats and mice, an increasing renal uptake was found: [(111)In-DTPA]CCK8<[(111)In-DTPA-Pro(1),Tyr(4)]bombesin approximately [(111)In-DTPA]neurotensin<[(111)In-DTPA]octreotide<<[(111)In-DTPA]MG0. Renal uptake of [(111)In-DTPA]octreotide in rats showed no gender difference, and renal radioactivity was about constant over time. In mice, however, renal uptake in females was significantly higher than that in males and decreased rapidly over time in both genders. Moreover, renal radioactivity in female mice injected with [(111)In-DTPA]octreotide showed a different localization pattern.

CONCLUSIONS

Regarding the renal uptake of different radiolabeled peptides, both species showed the same ranking order. Similar to findings in patients, rats showed comparable and constant renal retention of radioactivity in both genders, in contrast to mice. Therefore, rats appear to be the more favorable species for the study of the renal retention of radioactivity.

Dose-dependent effects of (anti)folate preinjection on 99mTc-radiofolate uptake in tumors and kidneys

INTRODUCTION

The folate receptor (FR) is frequently overexpressed in tumors and can be targeted with folate-based (radio)pharmaceuticals. However, significant accumulation of radiofolates in FR-positive kidneys represents a drawback. We have shown that preadministration of the antifolate pemetrexed (PMX) significantly improved the tumor-to-kidney ratio of radiofolates in mice. The aim of this study was to investigate the dose dependence of these effects and whether the same results could be achieved with folic acid (FA) or 5-methyl-tetrahydrofolate (5-Me-THF).

METHODS

Biodistribution was assessed 4 h postinjection of the organometallic (99m)Tc-picolylamine monoacetic acid folate in nude mice bearing FR-positive KB tumor xenografts. PMX (50-400 microg/mouse) was injected 1 h previous to radioactivity. The effects of FA and 5-Me-THF (0.5-50 microg/mouse) were investigated likewise. Tissues and organs were collected and counted for radioactivity and the values tabulated as percentage of injected dose per gram tissue (% ID/g).

RESULTS

PMX administration reduced renal retention (<1.6% ID/g vs. control: >10% ID/g), while the tumor uptake (average 1.35%+/-0.40% ID/g vs. control: 1.79%+/-0.49% ID/g) was only slightly affected independent of the PMX dose. Replacement of PMX by FA or 5-Me-THF (50 microg/mouse) resulted in a significant renal blockade (<0.1% ID/g) but at the same time in an undesired reduction of tumor uptake (<0.2% ID/g).

CONCLUSIONS

Selective reduction of radiofolate uptake in kidneys under retention of high tumor accumulation could be achieved in combination with PMX over a broad dose range but not with FA or 5-Me-THF.

Five Stabilized 111In-labeled neurotensin analogs in nude mice bearing HT29 tumors

Neurotensin (NT) receptors are overexpressed in different human tumors, such as human ductal pancreatic adenocarcinoma. New stable neurotensin analogs with high receptor affinity have been synthesized by replacing arginine residues with lysine and arginine derivatives. The aim of this study was to explore the biodistribution, tumor uptake, kidney localization, and stability characteristics of these new analogs in order to develop new diagnostic tools for exocrine pancreatic cancer. Four (111)In-labeled DTPA-chelated NT analogs and one (111)In-labeled DOTA-chelated NT analog were evaluated in NMRI nude mice bearing NT receptor-positive HT29 tumors. Experiments with a coinjection of unlabeled NT or lysine were performed to investigate receptor-mediated uptake and kidney protection, respectively. In addition, the in vivo serum stability of the most promising analog was analyzed. In the biodistribution study in mice, at 4 hours postinjection, a low percentage of the injected dose per gram (%ID/g) of tissue for all compounds was found in NT receptor-negative organs, such as the blood, spleen, pancreas, liver, muscle, and femur. A high uptake was found in the colon, intestine, kidneys, and in implanted HT29 tumors. The coinjection of excess unlabeled neurotensin significantly reduced tumor uptake, showing tumor uptake to be receptor-mediated. To a lesser extent, this was also observed for the colon, but not for other tissues. We concluded that DTPA-(Pip)Gly-Pro-(PipAm)Gly-Arg-Pro-Tyr-tBuGly-Leu-OH and the DOTA-linked counterpart have the most favorable biodistribution properties regarding tumor uptake.

Peptide Receptor Radionuclide Therapy with radiolabelled somatostatin analogues in patients with somatostatin receptor positive tumours

Peptide Receptor Radionuclide Therapy (PRRT) with radiolabelled somatostatin analogues is a promising treatment option for patients with inoperable or metastasised neuroendocrine tumours. Symptomatic improvement may occur with all of the various (111)In, (90)Y, or (177)Lu-labelled somatostatin analogues that have been used. Since tumour size reduction was seldom achieved with (111)Indium labelled somatostatin analogues, radiolabelled somatostatin analogues with beta-emitting isotopes like (90)Y and (177)Lu were developed. Reported anti-tumour effects of [(90)Y-DOTA(0),Tyr(3)]octreotide vary considerably between various studies: Tumour regression of 50% or more was achieved in 9 to 33% (mean 22%). With [(177)Lu-DOTA(0),Tyr(3)]octreotate treatments, tumour regression of 50% or more was achieved in 28% of patients and tumour regression of 25 to 50% in 19% of patients, stable disease was demonstrated in 35% and progressive disease in 18%. Predictive factors for tumour remission were high tumour uptake on somatostatin receptor scintigraphy and limited amount of liver metastases. The side-effects of PRRT are few and mostly mild, certainly when using renal protective agents: Serious side-effects like myelodysplastic syndrome or renal failure are rare. The median duration of the therapy response for [(90)Y-DOTA(0),Tyr(3)]octreotide and [(177)Lu-DOTA(0),Tyr(3)]octreotate is 30 months and more than 36 months respectively. Lastly, quality of life improves significantly after treatment with [(177)Lu-DOTA(0),Tyr(3)]octreotate. These data compare favourably with the limited number of alternative treatment approaches, like chemotherapy. If more widespread use of PRRT is possible, such therapy might become the therapy of first choice in patients with metastasised or inoperable gastroenteropancreatic neuroendocrine tumours. Also the role in somatostatin receptor expressing non-GEP tumours, like metastasised paraganglioma/pheochromocytoma and non-radioiodine-avid differentiated thyroid carcinoma might become more important.

Treatment of patients who have endocrine gastroenteropancreatic tumors with radiolabeled somatostatin analogues

Treatment with radiolabeled somatostatin analogs is a promising new tool in the management of patients who have inoperable or metastasized endocrine tumors. Symptomatic improvement may occur with all (111)In-, (90)Y-, or (177)Lu-labeled somatostatin analogs that have been used for peptide receptor radionuclide therapy. The results that were obtained with [(90)Y-DOTA degrees ,Tyr(3)]octreotide and [(177)Lu-DOTA degrees ,Tyr(3)]octreotate are encouraging in tumor regression. Also, if kidney-protective agents are used, the side effects of this therapy are few and mild. These data compare favorably with the limited number of alternative treatment approaches.

From outside to inside? Dose-dependent renal tubular damage after high-dose peptide receptor radionuclide therapy in rats measured with in vivo (99m)Tc-DMSA-SPECT and molecular imaging

In peptide receptor radionuclide therapy (PRRT), the dose-limiting organ is, most often, the kidney. However, the precise mechanism as well as the exact localization of kidney damage during PRRT have not been fully elucidated. We studied renal damage in rats after therapy with different amounts of [(177)Lu-DOTA(0), Tyr(3)]octreotate and investigated (99m)Tc-DMSA (dimercaptosuccinic acid) as a tool to quantify renal damage after PRRT.

EXPERIMENTAL DESIGN

Twenty-nine (29) rats were divided into 3 groups and injected with either 0, 278, or 555 MBq [(177)Lu-DOTA(0), Tyr(3) ]octreotate, leading to approximately 0, 46, and 92 Gy to the renal cortex. More than 100 days after therapy, kidney damage was investigated using (99m)Tc-DMSA single-photon emission computed tomography (SPECT) autoradiography, histology, and blood analyses.

RESULTS

In vivo SPECT with (99m)Tc-DMSA resulted in high-resolution (<1.6-mm) images. The (99m)Tc-DMSA uptake in the rat kidneys was inversely related with the earlier injected activity of [(177)Lu-DOTA(0), Tyr(3)]octreotate and correlated inversely with serum creatinine values. Renal ex vivo autoradiograms showed a dose-dependent distribution pattern of (99m)Tc-DMSA. (99m)Tc-DMSA SPECT could distinguish between the rats that were injected with 278 or 555 MBq [(177)Lu-DOTA(0), Tyr(3) ]octreotate, whereas histologic damage grading of the kidneys was nearly identical for these 2 groups. Histologic analyses indicated that lower amounts of injected radioactivity caused damage mainly in the proximal tubules, whereas as well the distal tubules were damaged after high-dose radioactivity.

CONCLUSIONS

Renal damage in rats after PRRT appeared to start in a dose-dependent manner in the proximal tubules and continued to the more distal tubules with increasing amounts of injected activity. In vivo SPECT measurement of (99m)Tc-DMSA uptake was highly accurate to grade renal tubular damage after PRRT.

Diagnostic versus therapeutic doses of [(177)Lu-DOTA-Tyr(3)]-octreotate: uptake and dosimetry in somatostatin receptor-positive tumors and normal organs

AIM

The aim of this study was to investigate the influence of a diagnostic versus therapeutic dose of [(177)Lu-DOTA-Tyr(3)]octreotate on the uptake, effects, and dosimetry in somatostatin receptor subtype 2(sst2)-positive tumors and normal organs in a rat tumor model.

MATERIALS AND METHODS

Lewis rats bearing rat pancreatic CA20948-tumor grafts were injected intravenously with different amounts of radioactivity and peptide of [(177)Lu-DOTA-Tyr(3)]octreotate: 3 MBq/0.5 microg (group A), 3 MBq/15 microg (group B), 300 MBq/15 microg (group C), and 555 MBq/15 microg (group D). Biodistribution studies were performed at several time points between 3 and 13 days post injection. Ex vivo and in vitro autoradiography was performed with frozen tumor sections.

RESULTS

Normal sst2-positive tissues showed a significantly higher uptake of radioactivity [%IA/g] when a low peptide amount was injected. On the other hand, the radioactivity concentration [%IA/g] in sst2-negative tissues and organs (blood, muscles, kidney, and liver) were comparable (groups A and B), independent of the injected peptide amount. Initially, this held true for the tumors as well. Yet, over time, we found a decrease in the radioactivity concentration in the tumors of groups A and B, because of tumor growth. On the other hand, therapeutic amounts of radioactivity (groups C and D) resulted in a significant reduction of tumor size, where radioactivity concentration remained higher than in groups A and B, despite the use of the high peptide amounts. Ex vivo autoradiograms of tumor sections confirmed these results. In vitro autoradiography performed on adjacent tumor sections revealed a reduced density of sst2 in tumors from animals that received a therapeutic radioactivity dose. Ki67-antibody immunohistochemistry showed an absence of proliferating tumor cells after therapy.

CONCLUSIONS

The differences in radioactivity retention in tumors after diagnostic or therapeutic doses, depending on a change in tumor kinetics, have to be taken into account when calculating tumor-absorbed radiation doses.

Novel 111In-labelled bombesin analogues for molecular imaging of prostate tumours

PURPOSE

It has been shown that some primary human tumours and their metastases, including prostate and breast tumours, overexpress gastrin-releasing peptide (GRP) receptors. Bombesin (BN) is a neuropeptide with a high affinity for these GRP receptors. We demonstrated successful scintigraphic visualisation of BN receptor-positive tumours in preclinical studies using the radiolabelled BN analogue [(111)In-DTPA-Pro(1),Tyr(4)]BN. However, the receptor affinity as well as the serum stability of this analogue leave room for improvement. Therefore new (111)In-labelled BN analogues were synthesised and evaluated in vitro and in vivo.

METHODS AND RESULTS

The receptor affinity of the new BN analogues was tested on human GRP receptor-expressing prostate tumour xenografts and rat colon sections. Analogues with high receptor affinity (low nM range) were selected for further evaluation. Incubation in vitro of GRP receptor-expressing rat CA20948 and human PC3 tumour cells with the (111)In-labelled analogues resulted in rapid receptor-mediated uptake and internalisation. The BN analogue with the best receptor affinity and in vitro internalisation characteristics, Cmp 3 ([(111)In-DTPA-ACMpip(5),Tha(6),betaAla(11),Tha(13),Nle(14)]BN(5-14)), was tested in vivo in biodistribution studies using rats bearing GRP receptor-expressing CA20948 tumours, and nude mice bearing human PC3 xenografts. Injection of (111)In-labelled Cmp 3 in these animals showed high, receptor-mediated uptake in receptor-positive organs and tumours which could be visualised using planar gamma camera and microSPECT/CT imaging.

CONCLUSION

With their enhanced receptor affinity and their rapid receptor-mediated internalisation in vitro and in vivo, the new BN analogues, and especially Cmp 3, are promising candidates for use in diagnostic molecular imaging and targeted radionuclide therapy of GRP receptor-expressing cancers.

Peptide receptor radionuclide therapy with 177Lu-octreotate in patients with foregut carcinoid tumours of bronchial, gastric and thymic origin

PURPOSE

Foregut carcinoid tumours have a different embryological origin than other gastroenteropancreatic neuroendocrine tumours (GEP NETs). In the total group of GEP NETs (n = 131), treatment with (177)Lu-octreotate resulted in tumour remission in 47% of patients, with a median time to progression (TTP) of >36 months. As patients with foregut carcinoids may respond differently, we here present the effects of this treatment in a subgroup of patients with foregut carcinoids of bronchial, gastric or thymic origin.

METHODS

Nine patients with bronchial, five with gastric and two with thymic carcinoids were treated. All patients had metastasised disease. The intended cumulative dose of (177)Lu-octreotate was 22.2-29.6 GBq. Southwest Oncology Group criteria were used for response evaluation.

RESULTS

Bronchial carcinoids: Five patients had partial remission, one had minor response (MR, tumour size reduction: > or =25%, <50%), two had stable disease (SD) and one had progressive disease (PD). Median TTP was 31 months. Gastric carcinoids: One patient had complete remission, one had MR and two had SD, including one with PD at baseline. One patient developed PD. Thymic carcinoids: One patient had SD. In the other patient, disease remained progressive. All patients: Overall remission rate was 50%, including MR.

CONCLUSION

(177)Lu-octreotate treatment can be effective in patients with bronchial and gastric carcinoids. Its role in thymic carcinoids cannot be determined yet because of the limited number of patients. The overall remission rate of 50% in patients with the studied foregut carcinoids is comparable to that in the total group of GEP NETs.

Somatostatin receptor subtype 2-mediated uptake of radiolabelled somatostatin analogues in the human kidney

PURPOSE

Renal irradiation is a dose-limiting factor in peptide receptor radionuclide therapy using radiolabelled somatostatin analogues. This irradiation is mainly caused by reabsorption of radiolabelled peptides in the proximal tubule. In the human kidney, somatostatin receptors are expressed in the vasa recta, tubuli and glomeruli. It is not clear to what extent these receptors contribute to the total kidney radioactivity uptake.

METHODS

Retrospectively, [(111)In-DTPA(0)]octreotide scans of ten selected patients with carcinoids (well-differentiated gastrointestinal endocrine tumour) with liver metastases were evaluated. For each patient, two scans were obtained: one scan was performed without (control) and one during treatment with unlabelled octreotide. Kidney, tumour, spleen and liver uptake was measured in both scans.

RESULTS

The interval between the two scans per patient varied from 50 to 397 days. Octreotide treatment substantially lowered kidney [(111)In-DTPA(0)]octreotide uptake in eight out of ten patients. Kidney uptake in all patients was reduced to 82%+/-15% of control, (p < 0.01). A correlation between kidney uptake and spleen uptake was found (r=0.67, p < 0.05). Serum creatinine was unchanged. Surprisingly, tumour and liver [(111)In-DTPA(0)]octreotide uptake was not significantly influenced by unlabelled octreotide therapy, but spleen uptake was significantly lowered by treatment (30.6% of control, p < 0.002).

CONCLUSION

We conclude that the somatostatin receptor plays a role in the total renal uptake of radiolabelled somatostatin analogues. The long interval between scans might explain the finding that tumour and liver metastasis uptake of [(111)In-DTPA(0)]octreotide was unchanged. Further studies are needed to confirm and eludicate the results of this study.