Radioiodinated metaiodobenzylguanidine treatment of neuroendocrine tumors in adults

THE ROLE OF CONVENTIONAL ECHOENDOSCOPY (EUS) IN THERAPEUTIC DECISIONS IN PATIENTS WITH NEUROENDOCRINE GASTROINTESTINAL TUMORS

Background:

Gastrointestinal neuroendocrine tumors are rare, usually presented as subepithelial or polypoid tumors. Accurate diagnosis and indication of the type of resection are still challenging.

Aim:

To determine the effectiveness of echoendoscopy in determining the depth of the lesions (T) identified by endoscopy in order to evaluate surgical and/or endoscopic indication, and to evaluate the results of endoscopic removal in the medium term.

Methods:

Twenty-seven patients were included, all of whom underwent echoendoscopy for TN tumor staging and the evaluation of possible endoscopic resection. The parameters were: lesion size, origin layer, depth of involvement and identified perilesional adenopathies. The inclusion criteria for endoscopic resection were: 1) high surgical risk; 2) those with NET <2 cm; 3) absence of impairment of the muscle itself; and 4) absence of perilesional adenopathies in echoendoscopy and in others without distant metastases. Exclusion criteria were TNE> 2 cm; those with infiltration of the muscle itself; with perilesional adenopathies and distant metastases. The techniques used were: resection with polypectomy loop; mucosectomy with saline injection; and mucosectomy after ligation with an elastic band. The anatomopathological study of the specimens included evaluation of the margins and immunohistochemistry (chromogranin, synaptophysin and Ki 67) to characterize the tumor. Follow-up was done at 1, 6 and 12 months.

Results:

Resections with polypectomy loop were performed in 15 patients; mucosectomy in five; mucosectomy and ligation with elastic band in three and the remaining four were referred for surgery. The anatomopathological specimens and immunohistochemical analyzes showed positive chromogranin and synaptophysin, while Ki 67 was less than 5% among all cases. The medium-term follow-up revealed three recurrences. The average size of tumors in the stomach was 7.6 mm and in the duodenum 7.2 mm. Well-demarcated, hypoechoic, homogeneous lesions occurred in 75%; mucous layer in 80%; and the deep and submucosal mucosa in 70%.

Conclusions:

Echoendoscopy proved to be a good method for the study of subepithelial lesions, being able to identify the layer affected by the neoplasm, degree of invasion, echogenicity, heterogeneity, size of the lesion and perilesional lymph node involvement and better indicate the treatment option.

Theranostic radiopharmaceuticals: established agents in current use

Although use of the term "theranostic" is relatively recent, the concept goes back to the earliest days of nuclear medicine, with the use of radioiodine for diagnosis and therapy of benign and malignant thyroid disease being arguably the most successful molecular radiotherapy in history. A diagnostic scan with ¹²³I-, ¹²⁴I-, or a low activity of ¹³¹I-iodide is followed by therapy with high activity ¹³¹I-iodide. Similarly, adrenergic tumours such as phaeochromocytoma and neuroblastoma can be imaged with ¹²³I-metaiodobenzylguanidine and treated with ¹³¹I-metaiodobenzylguanidine. Bone scintigraphy can be used to select patients with painful bone metastases from prostate cancer who may benefit from treatment with beta- or alpha-particle emitting bone seeking agents, the most recent and successful of which is ²²³Ra radium chloride. Anti-CD20 monoclonal antibodies can be used to image and treat non-Hodgkins lymphoma, though this has not been as commercially successful as initially predicted. More recently established theranostics include somatostatin receptor targeting peptides for diagnosis and treatment of neuroendocrine tumours with agents such as ⁶⁸Ga-DOTATATE and ¹⁷⁷Lu-DOTATATE, respectively. Finally, agents which target prostate-specific membrane antigen are becoming increasingly widely available, despite the current lack of a commercial product. With the recent licensing of the somatostatin peptides and the rapid adoption of ⁶⁸Ga- and ¹⁷⁷Lu-labelled prostate-specific membrane antigen targeting agents, we have built upon the experience of radioiodine and are already seeing a great expansion in the availability of widely accepted theranostic radiopharmaceuticals.

The New Age of -omics in Urothelial Cancer - Re-wording Its Diagnosis and Treatment

Unmet needs in urothelial cancer management represent an important challenge in our effort to improve long-term overall and disease-free survival rates with no significant compromise in quality of life. Radical cystectomy with pelvic lymph node dissection is the standard for the management of muscle-invasive, non-metastatic cancers. In spite of a 90% local disease control, up to 50% of patients ultimately die of distant metastasis. Bladder preservation using chemo-radiation is an acceptable alternative, but optimal patient selection remains elusive. Recent research is focused on the employment of tailored-made strategies in urothelial cancer exploiting the potential of theranostics in patient selection for specific therapies. Herein, we review the current knowledge on molecular theranostics in urothelial cancer and we suggest that this is the time to move toward imaging theranostics, if tailored-made disease management and patient stratification is envisaged.

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Urothelial cancer management represents an important challenge.

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Optimum patient stratification and tailored-made theranostics remain elusive.

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Imaging theranostics is envisaged as a cancer roadmap.

131I-MIBG Therapy in a Metastatic Small Bowel Neuroendocrine Tumor Patient Undergoing Hemodialysis

Systemic radioisotope therapy with I-metaiodobenzylguanidine (I-MIBG) is an effective form of targeted therapy for neuroendocrine tumors. One of the absolute contraindications to administering I-MIBG therapy listed in the 2008 European Association of Nuclear Medicine guidelines is renal insufficiency requiring dialysis, although this contraindication is not evidence based. We describe a 68-year-old woman with a metastatic small bowel neuroendocrine tumor who developed renal insufficiency requiring hemodialysis. Imaging and dosimetry with I-MIBG were performed and showed that the radiation doses to the whole body and lungs were within safe limits. She was treated with 1820 MBq of I-MIBG with no short-term adverse reactions.

Medical imaging in personalised medicine: a white paper of the research committee of the European Society of Radiology (ESR)

The future of medicine lies in early diagnosis and individually tailored treatments, a concept that has been designated 'personalised medicine' (PM), which aims to deliver the right treatment to the right patient at the right time. Medical imaging has always been personalised and is fundamental to almost all aspects of PM. It is instrumental in solving clinical differential diagnoses. Imaging procedures are tailored to the clinical problem and patient characteristics. Screening for preclinical disease is done with imaging. Stratification based on imaging biomarkers can help identify individuals suited for preventive intervention. Treatment decisions are based on the in vivo visualisation of the location and extent of an abnormality, as well as the loco-regional physiological, biochemical and biological processes using structural and molecular imaging. Image-guided biopsy provides relevant tissue specimens for genetic/molecular characterisation. In addition, radiogenomics relate imaging biomarkers to these genetic and molecular features. Furthermore, imaging is essential to patient-tailored therapy planning, therapy monitoring and follow-up of disease, as well as targeting non-invasive or minimally invasive treatments, especially with the rise of theranostics. Radiologists need to be prepared for this new paradigm as it will mean changes in training, clinical practice and in research. Key Points • Medical imaging is a key component in personalised medicine • Personalised prevention will rely on image-based screening programmes • Anatomical, functional and molecular imaging biomarkers affect decisions on the type and intensity of treatment • Treatment response assessment with imaging will improve personalised treatment • Image-based invasive intervention integrates personalised diagnosis and personalised treatment.

Long-term outcome and toxicity after dose-intensified treatment with 131I-MIBG for advanced metastatic carcinoid tumors

Reported experience with systemic (131)I-metaiodobenzylguanidine ((131)I-MIBG) therapy of neuroendocrine tumors comprises different dosing schemes. The aim of this study was to assess the long-term outcome and toxicity of treatment with 11.1 GBq (300 mCi) of (131)I-MIBG per cycle.

METHODS

We performed a retrospective review of 31 patients with advanced metastatic neuroendocrine tumors (20 with carcinoid tumors and 11 with other tumors) treated with (131)I-MIBG. Treatment outcome was analyzed for patients with carcinoid tumors (the most common tumors in this study), and toxicity was analyzed for the entire patient cohort (n = 31). Treatment comprised 11.1 GBq (300 mCi) per course and minimum intervals of 3 mo. The radiographic response was classified according to modified Response Evaluation Criteria in Solid Tumors. Toxicity was determined according to Common Terminology Criteria for Adverse Events (version 3.0) for all laboratory data at regular follow-up visits and during outpatient care, including complete blood counts and hepatic and renal function tests. Survival analysis was performed with the Kaplan-Meier curve method (log rank test; P < 0.05).

RESULTS

The radiographic responses in patients with carcinoid tumors comprised a minor response in 2 patients (10%), stable disease in 16 patients (80%; median time to progression, 34 mo), and progressive disease in 2 patients (10%). The symptomatic responses in patients with functioning carcinoid tumors comprised complete resolution in 3 of the 11 evaluable symptomatic patients (27%), partial resolution in 6 patients (55%), and no significant change in 11 patients. The median overall survival in patients with carcinoid tumors was 47 mo (95% confidence interval, 32-62), and the median progression-free survival was 34 mo (95% confidence interval, 13-55). Relevant treatment toxicities were confined to transient myelosuppression of grade 3 or 4 in 15.3% (leukopenia) and 7.6% (thrombocytopenia) of applied cycles and a suspected late adverse event (3% of patients), myelodysplastic syndrome, after a cumulative administered activity of 66.6 GBq. The most frequent nonhematologic side effect was mild nausea (grade 1 or 2), which was observed in 28% of administered cycles. No hepatic or renal toxicities were noted.

CONCLUSION

Dose-intensified treatment with (131)I-MIBG at a fixed dose of 11.1 GBq (300 mCi) per cycle is safe and offers effective palliation of symptoms and disease stabilization in patients with advanced carcinoid tumors. The favorable survival and limited toxicity suggest that high cycle activities are suitable and that this modality may be used for targeted carcinoid treatment--either as an alternative or as an adjunct to other existing therapeutic options.

131I-MIBG targeting of neuroblastoma cells is acutely enhanced by KCl stimulation through the calcium/calmodulin-dependent kinase pathway

The efficacy of (131)I-metaiodobenzylguanidine (MIBG) therapy relies on norepinephrine transporter (NET) function. The ionic make-up of the extracellular fluid critically controls neuronal cell activity and can also affect substrate transport. In this study, we explored the effect of treatment with elevated KCl concentration on MIBG uptake in SK-N-SH neuroblastoma cells. KCl stimulation caused a rapid increase of (131)I-MIBG uptake in a manner that was calcium-dependent and accompanied by activation of calcium/calmodulin-dependent protein kinase (CaMK)II. The effect was completely abolished by KN93, an inhibitor of CaMKI, II, and IV. STO609, a selective inhibitor of CaMK kinase required for activation of CaMKI and IV, but not CaMKII, only modestly attenuated the response. The KCl effect was also completely abrogated by ML7, a selective inhibitor of myosin light chain kinase (MLCK). This restricted form of CaMK activates myosin, which is required for vesicle trafficking. Saturation kinetic analysis revealed KCl stimulation to increase maximal transport velocity without affecting substrate affinity. In conclusion, KCl stimulation rapidly upregulates NET function through the CaMK pathway via activation of CaMKII and MLCK. These findings allow a better understanding of how NET function is acutely modulated by the ionic environment, which in turn may ultimately help improve the efficacy of (131)I-MIBG therapy.

Theranostics: evolution of the radiopharmaceutical meta-iodobenzylguanidine in endocrine tumors

Since 1981, meta-iodobenzylguanidine (MIBG), labeled with (131)I and later (123)I, has become a valuable agent in the diagnosis and therapy of a number of endocrine tumors. Initially, the agent located pheochromocytomas and paragangliomas (PGLs), both sporadic and familial, in multiple anatomic sites; surgeons were thereby guided to excisional therapies, which were previously difficult and sometimes impossible. The specificity in diagnosis has remained above 95%, but sensitivity has varied with the nature of the tumor: close to 90% for intra-adrenal pheochromocytomas but 70% or less for PGLs. For patients with neuroblastoma, carcinoid tumors, and medullary thyroid carcinoma, imaging with radiolabeled MIBG portrays important diagnostic evidence, but for these neoplasms, use has been primarily as an adjunct to therapy. Although diagnosis by radiolabeled MIBG has been supplemented and sometimes surpassed by newer scintigraphic agents, searches by this radiopharmaceutical remain indispensable for optimal care of some patients. The radiation imparted by concentrations of (131)I-MIBG in malignant pheochromocytomas, PGLs, carcinoid tumors, and medullary thyroid carcinoma has reduced tumor volumes and lessened excretions of symptom-inflicting hormones, but its value as a therapeutic agent is being fulfilled primarily in attacks on neuroblastomas, which are scourges of children. Much promise has been found in tumor disappearance and prolonged survival of treated patients. The experiences with therapeutic (131)I-MIBG have led to development of new tactics and strategies and to well-founded hopes for elimination of cancers. Radiolabeled MIBG is an exemplar of theranostics and remains a worthy agent for both diagnosis and therapy of endocrine tumors.

Targeted systemic radiotherapy of pheochromocytoma and medullary thyroid cancer

Targeted systemic radiotherapy constitutes the systemic administration of a radioactive agent that targets a molecule expressed preferentially on cancer cells. The archetypal such therapy is 131-iodine ((131)I) therapy for differentiated thyroid cancers. Radiotherapy typically delivers a calculated radiation-absorbed dose to tumor that takes into account (contiguous) normal tissue. Systemic radiotherapy development currently uses schema more analogous to chemotherapy--a radioactivity estimate that does not cause any irreversible toxicity. Historically, arbitrary amounts of radioactivity shown to be effective, on the basis of retrospective review, were used for thyroid cancer therapy with (131)I as well as for neuroendocrine tumor therapy with (131)I-labeled meta-iodo-benzylguanidine (MIBG). Their established safety record has led to adaptations that include repeat therapies with nontoxic amounts of radioactivity. There remains, however, a lack of clear understanding of the safety limits of systemic targeted radiotherapy. This is probably most true in systemic therapy with MIBG in adult neuroendocrine tumors. Bone marrow is the primary critical organ for most targeted systemic radiotherapy; second organ involvement may be renal, as with MIBG and targeted radiopeptide therapy, or pulmonary, as with radioimmunotherapy. Most therapies have tended toward multiple administrations of subtoxic amounts of radioactivity. Therapy with MIBG in pheochromococytoma as well as targeted radiopeptide therapy in medullary thyroid cancer has followed this model. Radioimmunotherapy appears very promising; a definitive Phase 2 study needs completion. All therapy has shown promise in extending disease survival (as compared with historical controls), with few major structural (or biochemical) responses. This review will attempt to compliment the excellent existing literature by providing an overall systemic therapeutic approach to this promising endeavor.

Molecular theranostics: a primer for the imaging professional

OBJECTIVE

A theranostic system integrates some form of diagnostic testing to determine the presence of a molecular target for which a specific drug is intended. Molecular imaging serves this diagnostic function and provides powerful means for noninvasively detecting disease. We briefly review the paradigms rooted in nuclear medicine and highlight recent advances in this field. We also explore how nanometer-sized complexes, called nanomedicines, present an excellent theranostic platform applicable to both drug discovery and clinical use.

CONCLUSION

For imagers, molecular theranostics represents a powerful emerging platform that intimately couples targeted therapeatic entities with noninvasive imaging that yields information on the presence of defined molecular targets before, during, and after cognate therapy.