乳腺癌核素靶向诊疗一体化的研究进展

近年来,核医学仪器设备的发展以及新型特异性显像剂的出现和深入研究使乳腺癌特异性分子显像技术得以快速发展,这有利于乳腺癌的特异性诊断。同时,利用特定靶点进行的放射性核素靶向治疗还能逐步推进乳腺癌个体化治疗的发展。随着靶向分子探针的不断出现和分子靶向技术的不断完善,乳腺癌核素特异性显像和放射性核素靶向治疗将成为乳腺癌个体化诊疗的重要手段。笔者对受体、抗体和基因介导的乳腺癌核素靶向诊疗的研究进展进行综述,并介绍其诊疗一体化的改进策略和发展前景。     

靶向PD-1/PD-L1放射性核素分子探针及其在恶性肿瘤中的应用

程序性细胞死亡受体1（PD-1）及其配体（PD-L1）免疫治疗已成为一种治疗多种恶性肿瘤的重要方法,但仅有部分患者临床获益,其影响因素之一是恶性肿瘤PD-1/PD-L1的表达水平。使用放射性核素标记完整单克隆抗体和抗体片段等制成靶向PD-1/PD-L1放射性核素分子探针进行显像,可无创、实时、动态地监测肿瘤PD-1/PD-L1的表达并量化其表达水平,进而筛选适宜治疗的患者、全面评估治疗疗效和预后。笔者综述了靶向PD-1/PD-L1放射性核素分子探针及其在恶性肿瘤中的应用。     

表皮生长因子受体-酪氨酸激酶肿瘤分子显像剂的研究进展

目前治疗肿瘤最重要的分子靶向药物是以表皮生长因子受体（EGFR）为靶点的一类化合物,为了更好地实现靶向治疗效果,需要借助分子显像技术实现快速、定量地检测体内EGFR的分布及突变等情况。利用不同核素标记的分子探针实施PET或SPECT显像能够实现快速、无创地对患者进行遴选、疗效评价和监测EGFR靶向治疗,从而提高肿瘤治疗效果。该文介绍了EGFR-酪氨酸激酶小分子显像剂及其最新的研究进展。     

放射性核素治疗的发展与思考

放射性核素内照射治疗是近年来发展较快的领域之一，也是核医学主要的组成部分之一。学科之间的交叉融合和各种技术的综合应用是核素治疗的主要发展趋势。分子生物学的发展促进了分子核医学的发展，放射免疫显像、受体显像、反义显像和报告基因表达显像促使放射免疫治疗、受体介导放射性核素靶向治疗、     

放射性核素标记的成纤维细胞活化蛋白抑制剂在肿瘤诊疗一体化中的研究进展

癌相关成纤维细胞（CAFs）是实体瘤肿瘤微环境中的重要成分之一。成纤维细胞活化蛋白（FAP）特异性高表达于CAFs,在大多数正常组织中不表达或低表达,是一种很有前景的肿瘤诊断与治疗靶点。近年来,放射性核素标记靶向FAP的分子探针在肿瘤的诊断和治疗中已取得一系列研究进展。笔者对FAP抑制剂（FAPI）新型分子影像探针在肿瘤诊断、辅助临床治疗决策优化及核素靶向治疗等方面进行综述,以期更深入地了解FAPI探针在核医学肿瘤诊疗中的临床应用价值。     

肿瘤靶向核素内照射治疗载体的研究进展

核素内照射治疗是一种很有前景的肿瘤靶向治疗手段。与化疗和外照射放疗相比 ,内照射治疗具有独特的优点 ,它以能高度选择性聚集在肿瘤组织的物质作为载体 ,如单克隆抗体、生物活性肽等 ,将放射性核素靶向运送到病灶内 ,或某些肿瘤细胞能直接摄取放射性核素 (如13 1I治疗甲癌 )     

uPAR放射性核素靶向显像研究进展

尿激酶型纤溶酶原激活物及其特异性受体(uPA/uPAR)系统是肿瘤侵袭、转移和血管生成的核心环节之一, 且与肿瘤的不良预后密切相关。检测肿瘤组织中uPA/uPAR表达水平及其随病情的变化情况, 对于肿瘤预后判断、治疗方案的选择与疗效评价意义重大。放射性核素分子靶向显像方法在靶向受体表达水平测定上具有独特的优势, 近来年医学研究者使用多种放射性核素标记uPAR的特异性配体进行了动物显像研究, 并于2015年首次用于人体显像。笔者就近年来uPAR放射性核素靶向显像的研究进展作一综述。     

肿瘤受体显像及介导靶向治疗的研究进展

肿瘤细胞上某些受体常常超量表达,放射性核素标记的配体可与肿瘤细胞上的相应受体特异性结合而使肿瘤得以显像。利用受体的介导作用,使放射性配体进入并杀死肿瘤细胞而行靶向药物治疗。肿瘤受体显像及受体介导靶向治疗得到广泛的研究,在肿瘤的诊断和治疗中有很高价值。     

肿瘤受体显像及介导靶向治疗的研究进展

肿瘤细胞上某些受体常常超量表达，放射性核素标记的配体可与肿瘤细胞上的相应受体特异性结合而使肿瘤得以显像。利用受体的介导作用，使放射性配体进入并杀死肿瘤细胞而行靶向药物治疗。肿瘤受体显像及受体介导靶向治疗得到广泛的研究，在肿瘤的诊断和治疗中有很高价值。     

核素标记的生长抑素受体拮抗剂在神经内分泌肿瘤显像和治疗中的研究进展

生长抑素受体（SSTR）特别是SSTR2过表达是神经内分泌肿瘤（NEN）的共同特征,也是NEN分子显像和核素靶向治疗的理想靶点。过去,研究者们一直致力于核素标记的SSTR激动剂的研究,并成功将其应用于NEN的临床显像和治疗。近年来的研究结果表明,核素标记的SSTR拮抗剂比激动剂具有更好的药代动力学特性,其肿瘤摄取率更高、滞留时间更长,且所获得的影像对比度更高,故其在NEN的分子显像和核素靶向治疗中更具优越性。笔者就核素标记的SSTR拮抗剂在NEN显像和治疗中的研究进展进行综述,以期为NEN的临床诊疗提供参考。     

Dosimetric aspects of radiolabeled antibodies for tumor therapy

Radioimmunotherapy (RIT) is rapidly attracting interest as a potential new weapon in the arsenal for cancer therapy. This article concentrates on some of the dosimetric aspects affecting the potential success of RIT, and examines factors which influence the choice of a radiolabel for RIT. No radionuclide is likely to give an optimum tumor/nontumor insult for all tumor types; therefore, the concept of matching the source to tumor morphology is introduced. Lists of candidate radionuclides are given, classified according to the type of decay, range, and energy of the emission. The article examines how the choice of radionuclide for radiolabeling the antibody affects the local energy deposition in the tumor. Both the effect of tumor size on the energy absorbed fraction and the problem of antibody binding heterogeneity are discussed. The approach to RIT is to relate the choice of radionuclide to the physical properties of the tumor.     

Treatment of non-Hodgkin's lymphoma (NHL) with radiolabeled antibodies (mAbs)

Most patients with non-Hodgkin's lymphoma (NHL) achieve remission but, despite newer drugs, the natural history of this disease has not improved during the last 20 years. Less than one half of patients with aggressive NHL are cured, and few of those with low-grade NHL are curable. Furthermore, NHL becomes progressively more chemoresistant while remaining responsive to external beam radiation therapy. Radioimmunotherapy (RIT) is a logical strategy for the treatment of NHL because this disease is multifocal and radiosensitive. Because of their remarkable effectiveness for RIT, 2 anti-CD20 monoclonal antibodies (mAbs), one labeled with (111)In for imaging or (90)Y for therapy and a second labeled with (131)I for imaging and therapy, have been approved for use in patients with NHL. These drugs have proven remarkably effective and safe. Evidence for the importance of the radionuclide is manifested by the data in the randomized pivotal phase III trial of (90)Y-ibritumomab that revealed response rates were several times greater in the (90)Y-ibritumomab arm than in the rituximab arm. A second drug for RIT, (131)I-tositumomab, was compared in a pivotal trial with the efficacy of the last chemotherapy received by each patient. Once again, response rates were much higher for RIT. Both (90)Y-ibritumomab and (131)I-tositumomab require preinfusion of several hundred milligrams of unlabeled anti-CD20 mAb to obtain "favorable" biodistribution, that is, targeting of NHL. Response rates for other mAbs and radionuclides in NHL also have been high but these drugs have not reached the approval stage. These drugs can be used safely by physicians who have suitable training and judgment. Unlike chemotherapy, RIT is not associated with mucositis, hair loss, or persistent nausea or vomiting. Although hematologic toxicity is dose limiting, hospitalization for febrile neutropenia is uncommon. Randomized trials of RIT in different formulations have not been conducted, but there is evidence to suggest that the mAb, antigen, radionuclide, chelator, linker, and dosing strategy may make a difference in the outcome.     

Radiopeptide imaging and therapy in Europe

Receptor targeting with radiolabeled peptides has become an important topic, particularly in nuclear oncology. Strong research efforts are under way in radiopharmaceutical science laboratories and in nuclear medicine departments in Europe. The target receptors belong to the large family of G-protein-coupled receptors. The prototypes of these radiopeptides are based on analogs of somatostatin targeting somatostatin receptor-positive tumors, particularly well-differentiated neuroendocrine tumors. These radiopeptides have an important impact not only on diagnosis but also on targeted radionuclide therapy of these tumors. Besides the registered radiopeptide (111)In-pentetreotide, efficient SPECT tracers labeled with (99m)Tc and PET agents based on generator-produced (68)Ga have been developed and used in the clinic. In parallel to the development of diagnostic agents, radiopeptides labeled with the β(-) emitters (90)Y and (177)Lu are also widely used. Because the same chelators and therefore the same conjugates can be used in diagnosis and therapy, they constitute ideal theranostic pairs. This progress is driven not only by scientists and clinicians but also by patient interest groups. New radiopeptides targeting other G-protein-coupled receptors are entering the clinic, among them glucagon-like peptide 1 receptor-targeting molecules. This receptor is overexpressed on literally all benign insulinomas. (111)In-labeled derivatives of the insulinotropic 39-mer peptide exendin-4 were beneficial in the pre- and perioperative localization of these benign lesions. In contrast, lack of localization may indicate malignant insulinoma. The bombesin- and gastrin-releasing peptide receptor family is potentially important because these receptors are overexpressed on major human tumors such as prostate tumors, breast tumors, gastrointestinal stromal tumors, and vessels of ovarian cancer. (99m)Tc-labeled peptides for SPECT and (68)Ga-, as well as (64)Cu-labeled agonists or antagonists, have been studied in breast tumors, prostate tumors, gastrointestinal stromal tumors, and gliomas with considerable success. A phase I therapeutic study with a (177)Lu-labeled agonist has been completed. There are not enough clinical data available to reveal the significance of these new modalities in patient care, but several phase I studies are under way in larger patient cohorts using PET agents. Another G-protein-coupled receptor with high overexpression on human tumors is the gastrin/cholecystokinin-2 receptor. It is overexpressed in more than 90% of cases of medullary thyroid cancer, in small cell lung cancer, and in a subgroup of neuroendocrine tumors. Correlating with in vitro receptor localization using autoradiography of 27 patients with metastasized medullary thyroid cancer, SPECT or planar imaging of these patients resulted in a 95% sensitivity of tumor localization. Finally, another G-protein-coupled receptor is found in brain tumors and peritumoral vessels. Literally all cases of glioblastoma multiforme overexpress the neurokinin type 1 receptor; the natural ligand is substance P, which was metabolically stabilized, labeled with (90)Y and (213)Bi, and injected into resection cavities or directly into tumors, which were critically located via a catheter system. The major advantage of this approach appeared to be the facilitated resectability of tumors, particularly in those patients who had been treated up front with the locoregional approach. It appears that neoadjuvant treatment before resection is a valid concept. Finally, another peptide family, the arginine-glycine-aspartate-based radiotracers, has made it to the clinic labeled with a variety of radioisotopes for monitoring the integrins α(v)β(3) overexpressed during tumor angiogenesis.     

Lu-177-Based Peptide Receptor Radionuclide Therapy for Advanced Neuroendocrine Tumors

Peptide receptor radionuclide therapy (PRRT) is a systemic cytotoxic radiation therapy using a compound of β-emitting radionuclide chelated to a peptide for the treatment of tumor with overexpressed specific cell receptor such as somatostatin receptor subtype 2 (SSTR2) of neuroendocrine tumor (NET). Surgical resection should be performed for the curative treatment for NETs when it is feasible; however, a multi-disciplinary approach is needed when locally advanced or metastasized disease. PRRT with lutetium-177 (Lu-177)-labeled somatostatin analogues, as a new treatment modality targeting metastatic or inoperable NETs expressing the SSTR2, have been developed and successfully used for the past two decades. As Lu-177 emits both β- and γ-radiation, it has the ability as a theragnostic agent for NETs compared with only β-emitting yttrium-90 labeled PRRT. Several recent studies reported that Lu-177 gave an overall positive response and improved the patients’ quality of life. To fully exploit its potential, large comparative studies are needed for the assessment of distinct efficacies of Lu-177 labeled PRRT. Additionally, for extending the indications and developing new regimens of Lu-177-based PRRT, more dedicated clinical research is required.     

放射免疫治疗计划研究

放射免疫治疗(RIT)计划是通过收集治疗前病人的特定信息如活度分布等来指导具体治疗,它的目的是使病人的肿瘤灶得到治疗剂量的同时周围的重要器官在耐受量以内。要得到好的RIT疗效,必须知道以下三点:带有放射性核素的载体在病人体内的空间分布和定量;在这种分布下肿瘤灶和重要器官的吸收剂量;用CT或MRI、以及CT或MRI与其它放射影像结合来获得肿瘤和重要器官的体积。本文总结和探讨了目前使用的各种放射免疫治疗计划及这些治疗计划中使用的活度定量方法、体积确定方法和吸收剂量计算方法。     

Selection of radiolabeled gastrin analogs for peptide receptor-targeted radionuclide therapy.

The gastrin/cholecystokinin-2 (CCK-2) receptor has been identified as a possible target for peptide receptor radionuclide imaging and therapy. Several radiolabeled peptides binding to this receptor have been explored in animal models and clinical trials but either low tumor uptake or high renal retention has been found. The aim of this study was to identify a peptide with improved tumor-to-kidney pharmacodynamics when compared with current candidates. METHODS: A small peptide-chelator library of 34 compounds based on the C-terminal sequences of CCK-8 or minigastrin was constructed. The peptides were radiolabeled with (111)In with high labeling efficiency (>90%), as determined by high-performance liquid chromatographic analysis. The labeled peptides were screened by assessing tumor and kidney uptake in pancreatic xenograft nude mouse models, including AR42J. An extensive biodistribution analysis was performed on the lead candidate from the library. RESULTS: Minigastrin analogs containing a pentaglutamate sequence showed the highest tumor uptake but very high renal retention. CCK analogs showed the lowest tumor and renal uptake. Deletion of the pentaglutamate sequence in the gastrin analogs lowered the tumor uptake by a factor of 3 but decreased the kidney uptake by a factor of 20. Insertion of histidine residues in the sequence reduced kidney uptake by a further factor of almost 2-fold. In AR42J tumor-bearing mice, the peptide with the sequence DOTA-HHEAYGWMDF-NH(2) (DOTA is tetraazacyclododecane tetraacetic acid) showed the highest tumor-to-kidney ratio of all peptides studied, with saturable uptake in target organs and low uptake by nontarget tissues other than the kidney. CONCLUSION: This peptide is a worthwhile candidate for clinical studies to determine whether it is suitable for use in peptide receptor-targeted radionuclide therapy.     

Preclinical animal research on therapy dosimetry with dual isotopes

Preclinical research into radionuclide therapies based on radiation dosimetry will enable the use of any LET-equivalent radionuclide. Radiation dose and dose rate have significant influence on dose effects in the tumour depending on its radiation sensitivity, possibilities for repair of sublethal damage, and repopulation during or after the therapy. Models for radiation response of preclinical tumour models after peptide receptor radionuclide therapy based on the linear quadratic model are presented. The accuracy of the radiation dose is very important for observation of dose-effects. Uncertainties in the radiation dose estimation arise from incomplete assay of the kinetics, low accuracy in volume measurements and absorbed dose S-values for stylized models instead of the actual animal geometry. Normal dose uncertainties in the order of 20% might easily make the difference between seeing a dose-effect or missing it altogether. This is true for the theoretical case of a homogeneous tumour type behaving in vivo in the same way as its cells do in vitro. Heterogeneity of tumours induces variations in clonogenic cell density, radiation sensitivity, repopulation capacity and repair kinetics. The influence of these aspects are analysed within the linear quadratic model for tumour response to radionuclide therapy. Preclinical tumour models tend to be less heterogenic than the clinical conditions they should represent. The results of various preclinical radionuclide therapy experiments for peptide receptor radionuclide therapy are compared to the outcome of theoretical models and the influence of increased heterogeneity is analysed when the results of preclinical research is transferred to the clinic. When the radiation dose and radiobiology of the tumour response is known well enough it may be possible to leave the current phenomenological approach in preclinical radionuclide therapy and start basing these experiments on radiation dose. Then the use of a gamma ray-emitting radionuclides for a chemically comparable beta-particle-emitting paired isotope for therapy evaluation would be feasible.     

Radiopharmaceutical development of radiolabelled peptides

Receptor targeting with radiolabelled peptides has become very important in nuclear medicine and oncology in the past few years. The overexpression of many peptide receptors in numerous cancers, compared to their relatively low density in physiological organs, represents the molecular basis for in vivo imaging and targeted radionuclide therapy with radiolabelled peptide-based probes. The prototypes are analogs of somatostatin which are routinely used in the clinic. More recent developments include somatostatin analogs with a broader receptor subtype profile or with antagonistic properties. Many other peptide families such as bombesin, cholecystokinin/gastrin, glucagon-like peptide-1 (GLP-1)/exendin, arginine-glycine-aspartic acid (RGD) etc. have been explored during the last few years and quite a number of potential radiolabelled probes have been derived from them. On the other hand, a variety of strategies and optimized protocols for efficient labelling of peptides with clinically relevant radionuclides such as (99m)Tc, M(3+) radiometals ((111)In, (86/90)Y, (177)Lu, (67/68)Ga), (64/67)Cu, (18)F or radioisotopes of iodine have been developed. The labelling approaches include direct labelling, the use of bifunctional chelators or prosthetic groups. The choice of the labelling approach is driven by the nature and the chemical properties of the radionuclide. Additionally, chemical strategies, including modification of the amino acid sequence and introduction of linkers/spacers with different characteristics, have been explored for the improvement of the overall performance of the radiopeptides, e.g. metabolic stability and pharmacokinetics. Herein, we discuss the development of peptides as radiopharmaceuticals starting from the choice of the labelling method and the conditions to the design and optimization of the peptide probe, as well as some recent developments, focusing on a selected list of peptide families, including somatostatin, bombesin, cholecystokinin/gastrin, GLP-1/exendin and RGD.     

Radioactive iodine (<Superscript>131</Superscript>I) therapy for differentiated thyroid cancer in Japan: current issues with historical review and future perspective

Radioactive iodine (RAI, ¹³¹I) has been used as a therapeutic agent for differentiated thyroid cancer (DTC) with over 50 years of history. Recently, it is now attracting attention in medical fields as one of the molecular targeting therapies, which is known as targeted radionuclide therapy. Radioactive iodine therapy (RIT) for DTC, however, is now at stake in Japan, because Japan is confronting several problems, including the recent occurrence of the Great East Japan Disaster (GEJD) in March 2011. RIT for DTC is strictly limited in Japan and requires hospitalization. Because of strict regulations, severe lack of medical facilities for RIT has become one of the most important medical problems, which results in prolonged waiting time for Japanese patients with DTC, including those with distant metastasis, who wish to receive RIT immediately. This situation is also due to various other factors, such as prolonged economic recession, super-aging society, and subsequent rapidly changing medical environment. In addition, due to the experience of atomic bombings in Hiroshima and Nagasaki, Japanese people have strong feeling of “radiophobia”. There is fear that GEJD and related radiation contamination may worsen this feeling, which might be reflected in more severe regulation of RIT. To overcome these difficulties, it is essential to collect and disclose all information about the circumstances around this therapy in Japan. In this review, we would like to look at this therapy through several lenses, including historical, cultural, medical, and socio-economic points of view. We believe that clarifying the problems is sure to lead to the resolution of this complicated situation. We have also included several recommendations for future improvements.     

血管活性肠肽受体显像及治疗研究进展

血管活性肠肽(VIP)是由28个氨基酸组成的小分子多肽,属胰高血糖素-胰泌素家族,通过其受体( VIPR)介导,调节正常及肿瘤细胞的增殖与分化.多种类型的肿瘤细胞膜上表达高密度及高亲和力VIPR,为实现肿瘤放射性核素标记VIPR显像及靶向治疗提供了分子基础.新的VIPR放射性配体的研发极大地推动了肿瘤VIPR显像及治疗...