Peptides and Receptors in Image-Guided Therapy: Theranostics for Neuroendocrine Neoplasms

Pancreatic Neuroendocrine Tumor Control: Durable Objective Response to Combination 177Lu-Octreotate-Capecitabine-Temozolomide Radiopeptide Chemotherapy

BACKGROUND/METHODS

Thirty patients with advanced progressive grade 1 or 2 pancreatic neuroendocrine tumors (pNETs), treated on a prospective phase II single-center study, were followed up for up to 4 years after 4 cycles of 7.9 GBq 177Lu-octreotate combined with chemotherapy. Each 8-week cycle of treatment combined radiopeptide therapy with 14 days of capecitabine at 1,500 mg/m2 and 5 days of temozolomide at 200 mg/m2.

RESULTS

The overall response rate was 80% (95% CI 66-93), and there was complete remission in 13% (95% CI 4-30) and partial response in 70% (95% CI 52-83) of the cases. No patient manifested progressive disease on treatment. Median progression-free survival was 48 months. Median overall survival had not been reached at a median follow-up of 33 months. No patient was lost to follow-up, all but 1 received 4 cycles of outpatient therapy, and all were evaluated for response and toxicity. No one required hospital admission. The treatment was well tolerated, and no serious dose-limiting toxicities were seen. The commonest toxicity was transient nausea of grade 2 (33%) or 3 (7%). Hematological toxicity was limited to grade 3 thrombocytopenia (10%) and anemia (10%). There were no grade 4 adverse events, and no renal functional impairment was evident.

CONCLUSION

Combined 177Lu-octreotate-capecitabine-temozolomide radiopeptide chemotherapy is a well-tolerated, highly effective outpatient regimen for control of advanced progressive pNETs, achieving a durable objective response.

Contribution of ¹¹¹In-pentetreotide SPECT/CT imaging to conventional somatostatin receptor scintigraphy in the detection of neuroendocrine tumours

AIM

The aim of the study was to assess the contribution of 111In-pentetreotide single-photon emission computed tomography/computed tomography (SPECT/CT) imaging to conventional somatostatin receptor scintigraphy (SRS) in terms of lesion characterization and localization in the detection of neuroendocrine tumours (NETs).

MATERIALS AND METHODS

A total of 107 patients with suspected or confirmed NET underwent SRS and SPECT/CT after the injection of 148-222 MBq of 111In-pentetreotide. SRS and SPECT/CT images were interpreted independently. Each site of abnormal tracer uptake was recorded according to the anatomical localization, and as being consistent or not with NET. The findings were confirmed with pathological and/or clinical/imaging follow-up data.

RESULTS

A final diagnosis of NET was achieved in 49/107 patients (45.8%). No evidence of NET was found in the rest. SPECT/CT resulted in a significant reduction of indeterminate cases [14/107 (13.1%) vs. 1/107 (0.9%); P<0.001] and correctly reclassified one patient as negative for NET and another as positive for NET. SPECT/CT had 87.8% sensitivity and 96.6% specificity on a patient-based analysis, statistically higher than SRS (P<0.001). A total of 160 foci were detected (108 NETs and 52 physiological/benign tumours). SRS correctly classified 105/160 foci (65.6%) and remained inaccurate for 55 lesions. These 55 included 31 indeterminate lesions, 12 lesions detected only by SPECT/CT and 12 false-positive lesions. The number of foci correctly classified on the SPECT/CT images was 151/160 (94.4%), whereas two remained indeterminate and seven were false-positive findings.

CONCLUSION

SPECT/CT provides incremental diagnostic value over SRS, mainly because of a precise anatomical localization that helps discriminate between tumour lesions and physiological uptake. SPECT/CT may detect unsuspected lesions in a small proportion of patients.

Application and Dosimetric Requirements for Gallium-68-labeled Somatostatin Analogues in Targeted Radionuclide Therapy for Gastroenteropancreatic Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are associated with variable prognosis, with grade 1 and 2 NETs having more favorable outcomes than grade 3. Patients with gastroenteropancreatic (GEP)-NET need individualized interdisciplinary evaluations and treatment. New treatment options have become available with significant improvements in progression-free survival. Peptide receptor radionuclide therapy (PRRT) using (90)Y or (177)Lu-labeled somatostatin analogues (SSTa) has also shown promise in the treatment of advanced progressive NETs. (68)Ga-1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid (DOTA)-SSTa can be used as companion imaging agents to assist in radionuclide therapy selection. (68)Ga-DOTA-SSTa PET/computed tomography might also provide information for prognosis, tumor response assessment to PRRT, and internal dosimetry.

Patient selection for personalized peptide receptor radionuclide therapy using Ga-68 somatostatin receptor PET/CT

Neuroendocrine tumors are malignant solid tumors originating from neuroendocrine cells dispersed throughout the body. Differentiated neuroendocrine tumors overexpress somatostatin receptors (SSTRs), which enable the diagnosis using radiolabeled somatostatin analogues. Internalization and retention within the tumor cell are important for peptide receptor radionuclide therapy using the same peptide. The use of the same DOTA-peptide for SSTR PET/CT using (68)Ga and for peptide receptor radionuclide therapy using therapeutic radionuclides like (177)Lu and (90)Y offers a unique theranostic advantage.

Comparison of immunoreactive score, HER2/neu score and H score for the immunohistochemical evaluation of somatostatin receptors in bronchopulmonary neuroendocrine neoplasms

AIMS

Due to the growing number of somatostatin receptor (SSTR) targeting analogues and radiopeptides used for the diagnosis and therapy of neuroendocrine neoplasms (NEN), the assessment of SSTR subtype status has increasingly gained predictive value. In pathology, the SSTR protein levels are detected routinely by immunohistochemistry (IHC); however, a lack of a standardized evaluation system persists. Thus, in the present investigation, three well-established semi-quantitative scoring systems [immunoreactive score (IRS), human epidermal growth factor receptor 2 (HER2)/neu score, H score] used commonly for SSTR-IHC evaluation in NEN were compared.

METHODS AND RESULTS

A total of 240 formalin-fixed, paraffin-embedded tumour samples from 90 patients with bronchopulmonary NEN were examined by IHC and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for SSTR1, 2A, 3, 4 and 5 expression. Using both methods, SSTR1, 2A and 5 were the most frequently expressed subtypes. For all SSTR subtypes, all three scores correlated well with each other and with qRT-PCR data. However, the IRS was the most meaningful score with the best correlation to mRNA levels.

CONCLUSIONS

Because a unified IHC scoring system for SSTR analysis is needed urgently to optimize the theranostics of NEN, among the scores tested, the IRS seems to be the most suitable according to our results. It provides sufficient accuracy combined with high practicability.

Somatostatin receptors in bronchopulmonary neuroendocrine neoplasms: new diagnostic, prognostic, and therapeutic markers

CONTEXT AND OBJECTIVES

Gastroenteropancreatic neuroendocrine neoplasms are known for their overexpression of somatostatin receptors (SSTRs), which provide the molecular basis for diagnostic and therapeutic interventions. In contrast, few data on the SSTR expression profile exist for bronchopulmonary neuroendocrine neoplasms (BP-NEN).

DESIGN AND SETTINGS

A total of 240 formalin-fixed, paraffin-embedded specimens from 26 typical carcinoid (TC), 30 atypical carcinoid (AC), and 34 small cell lung cancer (SCLC) patients were examined retrospectively by immunohistochemistry (IHC) using specific rabbit monoclonal antibodies and evaluated by the immunoreactive score. Adjacent slides from 20 samples of each tumor type were subjected to additional RT-quantitative PCR mRNA analysis.

RESULTS

With different expression patterns, SSTRs were present in most of the tumor sections, at both the protein and mRNA levels. The RT-quantitative PCR data correlated with the IHC scores. SSTR1 was detected in approximately 65% of the TC and AC, but hardly in the SCLC, whereas both SSTR2A and SSTR5 were present in approximately 45% of each entity. Furthermore, the SSTR1 expression level was positively correlated with patient survival.

CONCLUSIONS

Our results suggest that SSTRs can be used as novel diagnostic, prognostic, and therapeutic markers of BP-NEN. The differences in the SSTR expression profile between the three types of BP-NEN may help to set a diagnostic cutoff and predict patient prognosis. Similar to TC and AC, our results also revealed a previously unappreciated high level of SSTR2A expression in SCLC within a subgroup of patients. However, in most cases, pan-somatostatin analogs may represent an additional therapeutic option.

Decoding the Molecular and Mutational Ambiguities of Gastroenteropancreatic Neuroendocrine Neoplasm Pathobiology

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN), considered a heterogeneous neoplasia, exhibit ill-defined pathobiology and protean symptomatology and are ubiquitous in location. They are difficult to diagnose, challenging to manage, and outcome depends on cell type, secretory product, histopathologic grading, and organ of origin. A morphologic and molecular genomic review of these lesions highlights tumor characteristics that can be used clinically, such as somatostatin-receptor expression, and confirms features that set them outside the standard neoplasia paradigm. Their unique pathobiology is useful for developing diagnostics using somatostatin-receptor targeted imaging or uptake of radiolabeled amino acids specific to secretory products or metabolism. Therapy has evolved via targeting of protein kinase B signaling or somatostatin receptors with drugs or isotopes (peptide-receptor radiotherapy). With DNA sequencing, rarely identified activating mutations confirm that tumor suppressor genes are relevant. Genomic approaches focusing on cancer-associated genes and signaling pathways likely will remain uninformative. Their uniquely dissimilar molecular profiles mean individual tumors are unlikely to be easily or uniformly targeted by therapeutics currently linked to standard cancer genetic paradigms. The prevalence of menin mutations in pancreatic NEN and P27^KIP1 mutations in small intestinal NEN represents initial steps to identifying a regulatory commonality in GEP-NEN. Transcriptional profiling and network-based analyses may define the cellular toolkit. Multianalyte diagnostic tools facilitate more accurate molecular pathologic delineations of NEN for assessing prognosis and identifying strategies for individualized patient treatment. GEP-NEN remain unique, poorly understood entities, and insight into their pathobiology and molecular mechanisms of growth and metastasis will help identify the diagnostic and therapeutic weaknesses of this neoplasia.

Peptide receptor radionuclide therapy of differentiated thyroid cancer: efficacy and toxicity

In rare cases of differentiated thyroid carcinoma (DTC), radioiodine treatment is no longer effective due to cell dedifferentiation. Targeting somatostatin receptors in DTC cells by radiolabelled somatostatin analogues could provide an alternative therapy option. The aim of this study was to evaluate safety and efficacy of peptide receptor radionuclide therapy (PRRT) in patients with advanced, non-iodine avid DTC. Eleven patients aged 47–81 years (median: 65 years) with a history of several courses of radioiodine therapy, increasing thyroglobulin (Tg) and negative whole body scan, were qualified to the study. After confirming receptor expression by somatostatin receptor scintigraphy, PRRT with yttrium-90 labelled analogue was initiated. Fractionated treatment protocol was used with four doses of ⁹⁰Y-DOTA-TOC in 12-week intervals. Activity of each dose was 3.7 GBq (100 mCi). Of 11 patients, 5 died before receiving the fourth course of PRRT. In the remaining six patients, morphological response, evaluated 3 months after the last course using RECIST criteria showed partial remission (PR) in one patient, stable disease (SD) in two patients and progressive disease (PD) in three patients. Biochemical response based on Tg measurements before and after PRRT showed PR in one patient, SD in four patients and PD in one patient. Median survival was 21 months from the first course of PRRT. Only minor and transient hematological toxicity was observed in some patients. We conclude that PRRT is generally well-tolerated and may be a valuable option for some patients with radioiodine-refractory DTC.

The search for the primary tumor in metastasized gastroenteropancreatic neuroendocrine neoplasm

Gastroenteropancreatic neuroendocrine tumors (NETs) often present as liver metastasis from a carcinoma of unknown primary. We recently showed that primary NETs from the pancreas, small intestine and stomach as well as their respective liver metastases differ from each other by the expression profile of the three genes CD302, PPWD1 and ABHB14B. The gene and protein expression of CD302, PPWD1, and ABHB14B was studied in abdominal NET metastases to identify the site of the respective primary tumors. Cryopreserved tissue from NET metastases collected in different institutions (group A: 29, group B: 50, group C: 132 specimens) were examined by comparative genomic hybridization (Agilent 105 K), gene expression analysis (Agilent 44 K) (groups A and B) and immunohistochemistry (group C). The data were blindly evaluated, i.e. without knowing the site of the primary. Gene expression analysis correctly revealed the primary in the ileum in 94 % of the cases of group A and in 58 % of group B. A pancreatic primary was predicted in 83 % (group A) and 20 % (group B), respectively. The combined sensitivity of group A and B was 75 % for ileal NETs and 38 % for pancreatic NETs. Immunohistochemical analysis of group C revealed an overall sensitivity of 80 %. Gene and protein expression analysis of CD302 and PPWD1 in NET metastases correctly identifies the primary in the pancreas or the ileum in 80 % of the cases, provided that the tissue is well preserved. Immunohistochemical profiling revealed CD302 as the best marker for ileal and PPWD1 for pancreatic detection.

Perspectives in molecular imaging through translational research, human medicine, and veterinary medicine

The concept of molecular imaging has taken off over the past 15 years to the point of the renaming of the Society of Nuclear Medicine (Society of Nuclear Medicine and Molecular Imaging) and Journals (European Journal of Nuclear Medicine and Molecular Imaging) and offering of medical fellowships specific to this area of study. Molecular imaging has always been at the core of functional imaging related to nuclear medicine. Even before the phrase molecular imaging came into vogue, radionuclides and radiopharmaceuticals were developed that targeted select physiological processes, proteins, receptor analogs, antibody-antigen interactions, metabolites and specific metabolic pathways. In addition, with the advent of genomic imaging, targeted genomic therapy, and theranostics, a number of novel radiopharmaceuticals for the detection and therapy of specific tumor types based on unique biological and cellular properties of the tumor itself have been realized. However, molecular imaging and therapeutics as well as the concept of theranostics are yet to be fully realized. The purpose of this review article is to present an overview of the translational approaches to targeted molecular imaging with application to some naturally occurring animal models of human disease.

Successful treatment of metastasized pancreatic vasoactive intestinal polypeptide-secreting tumor unresponsive to high-dose octreotide by peptide receptor radionuclide therapy using 90Y DOTATATE

We report a successful treatment of a patient with heavily metastasized pancreatic vasoactive intestinal polypeptide-secreting tumor, which was unresponsive to high doses of octreotide analog using peptide receptor radionuclide therapy applying a radiolabeled somatostatin analog. After the peptide receptor radionuclide therapy, there was a decrease in vasoactive intestinal polypeptide levels, a significant reduction in somatostatin receptor expression and in molecular tumor volume on 68Ga DOTANOC PET/CT scan, and a complete long-term resolution of symptoms of the patient.

Role of Ki-67 proliferation index in the assessment of patients with neuroendocrine neoplasias regarding the stage of disease

BACKGROUND

Neuroendocrine neoplasias (NEN) of the gastroenteropancreatic (GEP) system frequently present with metastatic deposits. The proliferation marker Ki-67 is used for diagnosis and to assess the prognosis of disease. The aim of our study was to evaluate the usefulness of Ki-67 % in the assessment of NEN patients with regard to their disease stage in clinical practice. Additionally, a comparative analysis of Ki-67 levels among different sites of disease was performed.

METHODS

This retrospective study included patients with GEP NEN referred to our center from 2010 to 2012. The NEN diagnosis was confirmed by standard histopathology. Ki-67 immunohistochemistry was done on paraffin-embedded sections using an automated Leica immunohistochemistry machine. NEN grading was carried out according to European Neuroendocrine Tumor Society recommendations (low grade [G1] to intermediate grade [G2], well to moderately differentiated neuroendocrine neoplasms; high-grade [G3], moderately to poorly differentiated neuroendocrine neoplasms). Results of tumor staging and grading were correlated. In a subgroup of cases, comparative analysis of Ki-67 levels in different sites of disease was carried out.

RESULTS

One hundred sixty-one GEP NEN patients were included in the study. Metastatic disease was seen in 46.1 % (53/115) of G1 tumors, 77.8 % (28/36) of G2 tumors, and 100 % of (10/10) G3 tumors (p = 0.0002). When stratified according to primary tumor site, metastatic disease was documented in 42.9 % (36/84) of patients with pancreatic NEN and in 91.9 % (34/37) of those with small intestinal primary. Stage IV metastatic disease was present in 27.8 % (32/115) and 72.2 % (26/36) of the G1 and G2 tumors, respectively, and in 90 % (9/10) of the G3 tumors. Assessment of the Ki-67 index for a subset of cases at metastatic sites as well as the primary tumor site showed discrepancies in 35.3 % cases. In 7/9 (77.8 %) patients with liver metastases, Ki-67 % was higher in the liver lesions than in the primary tumor.

CONCLUSIONS

Patients with GEP NEN exhibiting a high Ki-67 proliferation index present with metastatic disease in the vast majority of cases. Depending upon the primary tumor site, metastases are to be expected also in tumors with low Ki-67 %, although they are considered less aggressive. Different disease sites may express heterogeneous Ki-67 levels.

[The relevance of PET/CT for the surgical management of neuroendocrine neoplasms]

Neuroendocrine neoplasms (NEN) are rare malignancies with a wide spectrum of metastatic potential which originate from the endocrine cells of the body and express somatostatin receptors. The (68)gallium somatostatin receptor positron emission tomography-computed tomography (PET/CT) technique is the most sensitive method of assessment of well-differentiated NENs and for the detection of cancer of unknown primary (CUP syndrome) NENs. Imaging with 18F-fluorodeoxyglucose (18F-FDG PET/CT) is indicated in poorly differentiated neuroendocrine carcinomas. The receptor-dependent imaging of NENs has a decisive impact on further management.

Neuroendocrine tumors of the bronchopulmonary system (typical and atypical carcinoid tumors): current strategies in diagnosis and treatment. Conclusions of an expert meeting February 2011 in Weimar, Germany

Neuroendocrine tumors (NETs; syn. carcinoid tumors) are highly or moderately differentiated neoplasms. They comprise a large variety of rare and heterogeneous tumors with an estimated incidence of 3-5/100,000/year. They can arise in virtually every internal organ, but mainly occur in the gastroenteropancreatic and bronchopulmonary systems. Around 25% of the NETs are localized in the bronchopulmonary system. Approximately 2% of all lung tumors are NETs. According to the World Health Organization (WHO) classification of lung tumors, bronchopulmonary NETs are subdivided into typical carcinoids (TCs) and atypical carcinoids (ACs). The parameter with the highest impact on NET behavior and prognosis is the histological classification and staging according to the tumor/node/metastasis (TNM) system. The diagnosis of NETs is established by histological examination and the immunohistochemical detection of general neuroendocrine markers, such as chromogranin A (CgA) and synaptophysin. Serum markers and the use of functional imaging techniques are important additive tools to establish the diagnosis of a NET. The only curative option for lung NETs is complete surgical resection. Beyond that, the currently available interdisciplinary therapeutic options are local ablation, biotherapy (somatostatin analogues), or chemotherapy. New therapeutic options such as peptide receptor radionuclide therapy (PRRT) and molecularly targeted therapies achieve promising results and are under further evaluation. This report is a consensus summary of the interdisciplinary symposium 'Neuroendocrine Tumors of the Lung and of the Gastroenteropancreatic System (GEP NET) - Expert Dialogue' held on February 25-26, 2011 in Weimar, Germany. At this conference, a panel of 23 German experts shared their knowledge and exchanged their thoughts about research, diagnosis, and clinical management of NETs, whereby special attention was paid to NETs of the respiratory tract.

Targeted chemoradiation in metastatic colorectal cancer: a phase I trial of 131I-huA33 with concurrent capecitabine

huA33 is a humanized antibody that targets the A33 antigen, which is highly expressed in intestinal epithelium and more than 95% of human colon cancers but not other normal tissues. Previous studies have shown huA33 can target and be retained in a metastatic tumor for 6 wk but eliminated from normal colonocytes within days. This phase I study used radiolabeled huA33 in combination with capecitabine to target chemoradiation to metastatic colorectal cancer. The primary objective was safety and tolerability of the combination of capecitabine and (131)I-huA33. Pharmacokinetics, biodistribution, immunogenicity, and tumor response were also assessed.

METHODS

Eligibility included measurable metastatic colorectal cancer, adequate hematologic and biochemical function, and informed consent. An outpatient scout (131)I-huA33 dose was followed by a single-therapy infusion 1 wk later, when capecitabine was commenced. Dose escalation occurred over 5 dose levels. Patients were evaluated weekly, with tumor response assessment at the end of the 12-wk trial. Tumor targeting was assessed using a γ camera and SPECT imaging.

RESULTS

Nineteen eligible patients were enrolled. The most frequently observed toxicity included myelosuppression, gastrointestinal symptoms, and asymptomatic hyperbilirubinemia. Biodistribution analysis demonstrated excellent tumor targeting of the known tumor sites, expected transient bowel uptake, but no other normal tissue uptake. (131)I-huA33 demonstrated a mean terminal half-life and serum clearance suited to radioimmunotherapy (T1/2β, 100.24 ± 20.92 h, and clearance, 36.72 ± 8.01 mL/h). The mean total tumor dose was 13.8 ± 7.6 Gy (range, 5.1-26.9 Gy). One patient had a partial response, and 10 patients had stable disease.

CONCLUSION

(131)I-huA33 achieves specific targeting of radiotherapy to colorectal cancer metastases and can be safely combined with chemotherapy, providing an opportunity to deliver chemoradiation specifically to metastatic disease in colorectal cancer patients.

Prospective of ⁶⁸Ga-radiopharmaceutical development

Positron Emission Tomography (PET) experienced accelerated development and has become an established method for medical research and clinical routine diagnostics on patient individualized basis. Development and availability of new radiopharmaceuticals specific for particular diseases is one of the driving forces of the expansion of clinical PET. The future development of the ⁶⁸Ga-radiopharmaceuticals must be put in the context of several aspects such as role of PET in nuclear medicine, unmet medical needs, identification of new biomarkers, targets and corresponding ligands, production and availability of ⁶⁸Ga, automation of the radiopharmaceutical production, progress of positron emission tomography technologies and image analysis methodologies for improved quantitation accuracy, PET radiopharmaceutical regulations as well as advances in radiopharmaceutical chemistry. The review presents the prospects of the ⁶⁸Ga-based radiopharmaceutical development on the basis of the current status of these aspects as well as wide range and variety of imaging agents.

Theranostics with Ga-68 somatostatin receptor PET/CT: monitoring response to peptide receptor radionuclide therapy

Peptide receptor radionuclide therapy involves selective targeting of neuroendocrine tumors through the somatostatin receptors, the aim being to increase radiation dose to the tumors and spare the normal tissue. The advantage of this internal radiation therapy is the ability to selectively target multiple metastases throughout the body. Early and accurate assessment of therapy response helps not only to identify the poor responders but also to personalize the treatment regimes with the aim of achieving maximum treatment benefit. This is the basis of theranostics.

Neuroendocrine tumours of the head and neck: anatomical, functional and molecular imaging and contemporary management

Neuroendocrine tumours (NETs) of the head and neck are rare neoplasms and can be of epithelial or non-epithelial differentiation. Although the natural history of NETs is variable, it is crucial to establish an early diagnosis of these tumours as they can be potentially curable. Conventional anatomical imaging and functional imaging using radionuclide scintigraphy and positron emission tomography/computed tomography can be complementary for the diagnosis, staging and monitoring of treatment response. This article describes and illustrates the imaging features of head and neck NETs, discusses the potential future role of novel positron-emitting tracers that are emerging into clinical practice and reviews contemporary management of these tumours. Familiarity with the choice of imaging techniques and the variety of imaging patterns and treatment options should help guide radiologists in the management of this rare but important subgroup of head and neck neoplasms.

Clinical applications of Gallium-68

Gallium-68 is a positron-emitting radioisotope that is produced from a (68)Ge/(68)Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. (68)Ga-DOTATOC, (8)Ga-DOTATATE, (68)Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with (68)Ga over the past few years around the world, including within the United States. An estimated ∼10,000 scans are being performed yearly in Europe at about 100 centers utilizing (68)Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied (68)Ga-labeled imaging agents used in nuclear medicine.

Controlled release strategies for bone, cartilage, and osteochondral engineering--Part II: challenges on the evolution from single to multiple bioactive factor delivery

The development of controlled release systems for the regeneration of bone, cartilage, and osteochondral interface is one of the hot topics in the field of tissue engineering and regenerative medicine. However, the majority of the developed systems consider only the release of a single growth factor, which is a limiting step for the success of the therapy. More recent studies have been focused on the design and tailoring of appropriate combinations of bioactive factors to match the desired goals regarding tissue regeneration. In fact, considering the complexity of extracellular matrix and the diversity of growth factors and cytokines involved in each biological response, it is expected that an appropriate combination of bioactive factors could lead to more successful outcomes in tissue regeneration. In this review, the evolution on the development of dual and multiple bioactive factor release systems for bone, cartilage, and osteochondral interface is overviewed, specifically the relevance of parameters such as dosage and spatiotemporal distribution of bioactive factors. A comprehensive collection of studies focused on the delivery of bioactive factors is also presented while highlighting the increasing impact of platelet-rich plasma as an autologous source of multiple growth factors.

Molecular Imaging using PET/CT Applying 68Ga-Labeled Tracers and Targeted Radionuclide Therapy: Theranostics on the Way to Personalized Medicine

Theranostics is an acronym, which exemplifies the togetherness of diagnostics and therapeutics in the individualized management of disease. The key to personalized medicine in cancer is to determine the molecular phenotypes of neoplasms, so that specific probes can be selected to target the tumor and its microenvironment. Molecular imaging and radionuclide therapy using a particular probe is based on this premise. Neuroendocrine neoplasms express somatostatin receptors, enabling the use of somatostatin analogs for molecular imaging, when labeled with the positron-emitter 68Ga for receptor positron emission tomography/computed tomography (PET/CT), and targeted radionuclide therapy, when labeled with beta-emitters 90Y and 177Lu.

How to cite this article

Kulkarni HR, Baum RP. Molecular Imaging using PET/CT Applying 68Ga-Labeled Tracers and Targeted Radionuclide Therapy: Theranostics on the Way to Personalized Medicine. J Postgrad Med Edu Res 2013; 47(1):47-53.

Phase I-II study of radiopeptide 177Lu-octreotate in combination with capecitabine and temozolomide in advanced low-grade neuroendocrine tumors

Abstract We conducted a phase I-II clinical trial to assess the safety and efficacy of combining lutetium-177 ((177)Lu)-octreotate with capecitabine and temozolomide in treating advanced low-grade neuroendocrine tumors (NETs). All 35 patients received fixed activities of 7.8 GBq (177)Lu-octreotate each 8 weeks, with 14 days of capecitabine 1500 mg/m(2) for 4 cycles. In phase I, successive cohorts of patients received escalating doses of temozolomide in groupings of 100, 150, and 200 mg/m(2) in the last 5 days of each capecitabine cycle. In phase II, patients were treated with 200 mg/m(2) temozolomide. Treatment was well tolerated in all dosage groups. No dose-limiting grade 2, 3, or 4 toxicities were seen in cohorts 1 (100 mg/m(2)) or 2 (150 mg/m(2)). Twenty-eight patients completed treatment at the 200 mg/m(2) temozolomide level. Adverse events were mild to moderate. The commonest toxicities were transient nausea grade 2 (18%), grade 3 (3%), thrombocytopenia grade 2 (24%), and neutropenia grade 3 (6%). There were no grade 4 events. Thirty-four patients were evaluable for tumor response. Overall, complete response (CR) was achieved in 15% (95% CI 3-27); partial response (PR), in 38% (95% CI 22-55); stable disease (SD), in 38% (95% CI 22-55); and 3 patients failed to respond to treatment. Median progression free survival (PFS) was 31 months (95% CI 21-33), and median overall survival (OS) has not been reached with 90% surviving at 24 months follow-up (range 21-30). Overall objective response rate (ORR) in patients with gastroenteropancreatic NETs showed CR 16% (95% CI 3-28), PR 41% (95% CI 24-58), SD 37% (95% CI 21-54), and PD 6% (95% CI 0-15). Response rates were higher in patients with gastropancreatic NETs than in those with bowel primaries (enteric-NETs); CR 18% versus 13%, PR 64% versus 13%, SD 12% versus 67%. (177)Lu-octreotate, in combination with capecitabine and temozolomide, is well tolerated in patients with advanced low-grade NETs, and shows substantial tumor control rates.