Location of adrenal medullary pheochromocytoma by I-123 metaiodobenzylguanidine SPECT

MIBG (metaiodobenzylguanidine) theranostics in pediatric and adult malignancies

Metaiodobenzylguanidine, a guanithidine analog, labeled with ¹²³I and ¹³¹I, is used for imaging and therapy of neuroblastomas and various neural crest tumors like paragangliomas, pheochromocytomas, medullary cancer of thyroid and carcinoids since the past three to four decades. In this review article, we shall revisit metaiodobenzylguanidine as a radiopharmaceutical and its various applications in neural crest tumors.

Pheochromocytoma Diagnosis After an Abnormal Stress Test: Case Report and Review of the Literature

Pheochromocytoma is a rare adrenal gland tumor that is often difficult for physicians to diagnose because of its general, nonspecific complaints. Diagnosis is particularly difficult in patients with neurofibromatosis 1, because pheochromocytoma in these patients will mimic other cardiovascular abnormalities. The authors report the case of a 60-year-old woman with an extensive history of hyperlipidemia, malignant hypertension, coronary artery disease, and neurofibromatosis 1 who was referred for an elective cardiac catheterization as a result of an abnormal stress test. The patient returned to the hospital 3 days after the procedure complaining of increased angina and palpitations. While hospitalized, she developed severe episodic hypertension. A computed tomographic scan revealed bilateral adrenal masses. Findings of biochemical and imaging evaluation confirmed the diagnosis of bilateral pheochromocytoma. Early screening of pheochromocytomas in high-risk populations is essential for prompt diagnosis and successful management.

The incremental benefit of functional imaging in pheochromocytoma/paraganglioma: a systematic review

Computed tomography (CT) and magnetic resonance imaging (MRI) are the major imaging modalities used for the localization of catecholamine-producing tumors (pheochromocytoma and paraganglioma). Functional imaging (FI) offers an alternative approach to localize, evaluate, and stage these tumors. Our objective was to describe the additive benefit of FI studies for patients with pheochromocytoma and paraganglioma (PPG) who have undergone MRI or CT scan evaluation. We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus from database inception through June 2012 for studies that included patients with biochemically proven PPGs who underwent CT or MRI and additional FI for the localization of PPGs. We included 32 studies enrolling a total of 1,264 patients with a mean age of 43-years old. The studies were uncontrolled and evaluated six FI modalities. FI tests provided small additive value to CT/MRI, aiding in the localization of only 24/1,445 primary cases (1.4 %) and 28/805 metastatic cases (3.5 %). In metastatic cases, 6-[F-18]fluoro-L-dihydroxyphenylalanine (DOPA) and fluorodopamine-PET (FDA) were the FI tests most successful at identifying disease missed by CT/MRI, providing additional benefit in 6/60 (10 %) and 5/78 (6.4 %) cases, respectively. No clinically significant findings were observed in any of the predefined subgroups. No study evaluated the impact of FI on the completeness of surgical resection or other patient-important outcomes. Observational evidence suggests that FI tests have a limited additional role in patients with PPGs who have undergone CT/MRI evaluation. However, the role of FI tests in specific subgroups of patients with atypical presentations (metastatic, extra-adrenal) as well as the use of hybrid FI tests should be explored. Further research should also evaluate the impact of FI tests on patient-important outcomes.

Clinical management of paragangliomas

Paragangliomas (PGLs) are rare vascular, neuroendocrine tumors of paraganglia, which are associated with either sympathetic tissue in adrenal (pheochromocytomas (PCCs)) and extraadrenal (sympathetic paraganglioma (sPGLs)) locations or parasympathetic tissue of the head and neck paragangliomas (HNPGLs). As HNPGLs are usually benign and most tumors grow slowly, a wait-and-scan policy is often advised. However, their location in the close proximity to cranial nerves and vasculature may result in considerable morbidity due to compression or infiltration of the adjacent structures, necessitating balanced decisions between a wait-and-see policy and active treatment. The main treatment options for HNPGL are surgery and radiotherapy. In contrast to HNPGLs, the majority of sPGL/PCCs produces catecholamines, in advanced cases resulting in typical symptoms and signs such as palpitations, headache, diaphoresis, and hypertension. The state-of-the-art diagnosis and localization of sPGL/PCCs are based on measurement of plasma and/or 24-h urinary excretion of (fractionated) metanephrines and methoxytyramine (MT). sPGL/PCCs can subsequently be localized by anatomical (computed tomography and/or magnetic resonance imaging) and functional imaging studies (123I-metaiodobenzylguanidine-scintigraphy, 111In-pentetreotide scintigraphy, or positron emission tomography with radiolabeled dopamine or dihydroxyphenylalanine). Although most PGL/PCCs are benign, factors such as genetic background, tumor size, tumor location, and high MT levels are associated with higher rates of metastatic disease. Surgery is the only curative treatment. Treatment options for patients with metastatic disease are limited. PGL/PCCs have a strong genetic background, with at least one-third of all cases linked with germline mutations in 11 susceptibility genes. As genetic testing becomes more widely available, the diagnosis of PGL/PCCs will be made earlier due to routine screening of at-risk patients. Early detection of a familial PGL allows early detection of potentially malignant PGLs and early surgical treatment, reducing the complication rates of this operation.

(11)C-hydroxyephedrine positron emission tomography in the postoperative management of pheochromocytoma and paraganglioma

AIM

Accurate detection of recurrent disease and restaging are essential in the postoperative surveillance of many patients with pheochromocytomas (PHEOs) and paragangliomas (PGLs). In this study, the impact of positron emission tomography (PET) and PET/computed tomography (CT) with (11)C-hydroxyephedrine (HED) was evaluated for the postoperative surveillance and diagnosis of recurrent disease and for functional monitoring of locoregional and systemic therapy.

METHODS

One hundred and eleven HED-PET and PET/CT examinations performed in 48 patients after surgical intervention for PHEO/PGL were analyzed retrospectively. In a subgroup of 16 patients who underwent systemic and locoregional therapies, the tracer uptake in tumors was also measured as the functional volume (FV), maximum standardized uptake value (SUVmax), mean SUV (SUVmean) and as the total catecholamine transporter tumor volume (TCTTV) calculated as TCTTV = FV × SUVmean. The PET imaging results were correlated with CT/magnetic resonance imaging findings and biochemical and clinical follow-up data.

RESULTS

In the first postoperative examination, HED-PET was positive in 24/48 and negative in 24/48 patients with no false-positive results, yielding 92.3% sensitivity and 100% specificity. For the 16 patients, there was a significant correlation between FV and SUVmax and SUVmax and TCTTV. TCTTV correlated significantly with plasma and urinary catecholamines. In 11/16 patients, SUVmax and TCTTV increased/decreased in parallel but not in the remaining 5 patients.

CONCLUSION

HED-PET and PET/CT were found to be valuable in the postoperative follow-up in detecting recurrent and metastatic disease. In a subgroup of patients, functional monitoring of systemic and locoregional therapies was feasible by assessing the changes of the TCTTV, and therefore warrants further prospective evaluation.

Improved Benefit of SPECT/CT Compared to SPECT Alone for the Accurate Localization of Endocrine and Neuroendocrine Tumors

Objective: To assess the clinical utility of SPECT/ CT in subjects with endocrine and neuroendocrine tumors compared to SPECT alone.

Material and Methods: 48 subjects (31 women;17 men; mean age 54±11) with clinical suspicion or diagnosis of endocrine and neuroendocrine tumor had 50 SPECT/CT scans (32 Tc-99m MIBI, 5 post treatment I-131, 8 In-111 Pentetreotide, and 5 I-123 MIBG). SPECT alone findings were compared to SPECT/CT and to pathology or radiological follow up.

Results: From the 32 Tc-99m MIBI scans, SPECT accurately localized the lesion in 22 positive subjects while SPECT/CT did in 31 subjects. Parathyroid lesions not seen on SPECT alone were smaller than 10 mm. In five post treatment I-131 scans, SPECT alone neither characterized, nor localized any lesions accurately. SPECT/CT revealed 3 benign etiologies, a metastatic lymph node, and one equivocal lesion. In 8 In-111 Pentetreotide scans, SPECT alone could not localize primary or metastatic lesions in 6 subjects all of which were localized with SPECT/CT. In five I-123 MIBG scans, SPECT alone could not detect a 1.1 cm adrenal lesion or correctly characterize normal physiologic adrenal uptake in consecutive scans of the same patient with prior history of adrenelectomy, all of which were correctly localized and characterized with SPECT/CT.

Conclusion: SPECT/CT is superior to SPECT alone in the assessment of endocrine and neuroendocrine tumors. It is better in lesion localization and lesion characterization leading to a decrease in the number of equivocal findings. SPECT/CT should be included in the clinical work up of all patients with diagnosis or suspicion of endocrine and neuroendocrine tumors.

Conflict of interest:None declared.

Nuclear medicine imaging in the evaluation of endocrine hypertension

Endocrine hypertension forms a small (< 5%) but curable subset of patients with hypertension. Common endocrine causes of hypertension include pheochromocytoma, Cushing's syndrome, primary hyperaldosteronism, and thyroid disorders. Nuclear medicine imaging plays an important role in evaluation of patients with endocrine hypertension. It has established role in patients of pheochromocytoma/paraganglioma, Cushing's syndrome, aldosteronism, and thyroid disorders. We present a brief overview of role of nuclear medicine imaging in endocrine hypertension. Development of newer radiotracers might further broaden the role of nuclear medicine in these patients.

Current role of metaiodobenzylguanidine in the diagnosis of pheochromocytoma and medullary thyroid cancer

Despite early reports of excellent diagnostic characteristics of [(131)I]/[(123)I]-metaiodobenzylguanidine (MIBG) in the evaluation of pheochromocytomas/paragangliomas (PHEOs/PGLs) or medullary thyroid cancer as experience with it was accumulated, the sensitivity dropped. Nevertheless, this modality is still useful in the diagnostic work-up of PHEOs/PGLs because it is widely available, and in case of positive scans it might indicate patients who are potential candidates for [(131)I]MIBG therapy.

123I-meta-iodobenzylguanidine scintigraphy for the detection of neuroblastoma and pheochromocytoma: results of a meta-analysis

CONTEXT

(123)I-mIBG scintigraphy has been in clinical use for more than 20 yr for diagnostic assessment of patients with neural crest and neuroendocrine tumors. Prospective validation of the performance characteristics of this method has recently been published.

OBJECTIVE

A meta-analysis was performed to obtain best estimates of performance characteristics of (123)I-mIBG imaging for the two most common applications, evaluation of patients with neuroblastoma and pheochromocytoma.

DATA SOURCES

Articles published between 1980 and 2007 were identified from searches of multiple computer databases, including MEDLINE, BIOSIS, EMBASE, and SciSearch.

STUDY SELECTION

Primary inclusion criteria were: acceptable reference standard(s) for confirming subjects with disease (histopathology and/or a combination of imaging and catecholamine results); reference standards applied to all subjects who received (123)I-mIBG; and data on a minimum of 16 patients confirmed to have or not have the disease(s) under consideration. Two physician reviewers independently evaluated all articles against the inclusion/exclusion criteria. Twenty-two of 100 articles reviewed were included in the final analysis.

DATA EXTRACTION

The two reviewers extracted the data from eligible articles using a standardized form, capturing both study quality and efficacy information. Disagreements were resolved by consensus.

DATA SYNTHESIS

Sensitivity of (123)I-mIBG scans for detection of neuroblastoma was 97% [95% confidence interval (CI), 95 to 99%]; data were insufficient to estimate specificity. For pheochromocytoma, with application of the random-effects model, sensitivity and specificity were 94% (95% CI, 91-97%) and 92% (95% CI, 87-98%), respectively.

CONCLUSION

Based upon the literature, (123)I-mIBG scintigraphy has sensitivity and specificity greater than 90% for detection of neuroblastoma and pheochromocytoma.

New imaging approaches to phaeochromocytomas and paragangliomas

Formerly used concepts for phaeochromocytomas and paragangliomas have been challenged by recent discoveries that at least 24% of tumours are familial and thereby often multiple in various locations throughout the body. Furthermore, tumours are often malignant and perhaps more aggressive if associated with SDHB gene mutations. Some paragangliomas are clinically silent and may present only with dopamine hypersecretion. In the current era where CT and MRI are more commonly used, tumours are more often found as incidentalomas and MRI may be less specific for phaeochromocytoma and paraganglioma than previously thought. Because of unique tumour characteristics (e.g. the presence of cell membrane and intracellular vesicular norepinephrine transporters) these tumours were 'born' to be imaged by means of specific functional imaging approaches. Moreover, additional recent discoveries related to apoptosis, hypoxia, acidosis, anaerobic glycolysis and angiogenesis, often disturbed in tumour cells, open new options and challenges to specifically image phaeochromocytomas and paragangliomas and possibly link those results to their pathophysiology, genotypic alterations and metastatic potential. Functional imaging, especially represented by positron emission tomography (PET), offers an excellent approach by which tumour-specific processes can be detected, evaluated and seen in the context of tumour-specific behaviour and its genetic signature. In this review, we address the recent developments in new functional imaging modalities for phaeochromocytoma and paraganglioma and provide the reader with suggested imaging approaches in various phaeochromocytomas and paragangliomas of sympathetic origin. Current imaging algorithms of head and neck parasympathetic paragangliomas are not discussed. Finally, this review outlines some future perspectives of functional imaging of these tumours.

Update on pediatric pheochromocytoma

Pheochromocytomas are rare tumors in children arising from chromaffin cells of adrenal medullary or extra-adrenal paraganglionic tissue. The tumors are characterized by synthesis, metabolism, and secretion of catecholamines. The formerly used guidelines for pheochromocytoma have been changed by recent discoveries, implementation of new approaches, and understanding of biochemistry, genetics, imaging, pathophysiology, and nomenclature of these tumors. In children, pheochromocytomas are more frequently familial, extra-adrenal, bilateral, and multifocal than in adults. Because of a highly variable clinical presentation, pheochromocytoma is often referred to as the great mimic. Measurements of plasma or urinary fractionated metanephrines are recommended as first-line biochemical tests for diagnosis, with optimum diagnostic sensitivity to be preferred over specificity. In general, localization studies must be used secondary to clinical and biochemical evidence. Adequate preoperative treatment with alpha-blockade is mandatory, including for pheochromocytomas that do not secrete but only synthesize catecholamines. Because approximately 40% of pheochromocytomas in children have a hereditary basis, proper genetic testing should be performed, with appropriate implications for future follow-up and treatment options. The risk for development of malignant disease depends highly on the underlying mutation, which may also impact recommendations concerning screening and surgical or systemic treatment. This article reviews recent advances in biochemistry, genetics, and imaging and outlines recommendations for improved evaluation and treatment of children with benign or malignant pheochromocytomas.

Comparison of 6-18F-fluorodopamine PET with 123I-metaiodobenzylguanidine and 111in-pentetreotide scintigraphy in localization of nonmetastatic and metastatic pheochromocytoma

We compared functional imaging modalities including PET with 6-(18)F-fluorodopamine ((18)F-DA) with (123)I-metaiodobenzylguanidine ((123)I-MIBG) and somatostatin receptor scintigraphy (SRS) with (111)In-pentetreotide in nonmetastatic and metastatic pheochromocytoma (PHEO).

METHODS

We studied 25 men and 28 women (mean age +/- SD, 44.2 +/- 14.2 y) with biochemically proven nonmetastatic (n = 17) or metastatic (n = 36) PHEO. Evaluation included anatomic imaging with CT or MRI and functional imaging that included at least 2 nuclear medicine modalities: (18)F-DA PET, (123)I-MIBG scintigraphy, or SRS. Sensitivity of functional imaging versus anatomic imaging was assessed on a per-patient and a per-region basis.

RESULTS

For this available cohort, on a per-patient basis overall sensitivity (combined for nonmetastatic and metastatic PHEO) was 90.2% for (18)F-DA PET, 76.0% for (123)I-MIBG scintigraphy, and 22.0% for SRS. On a per-region basis, overall sensitivity was 75.4% for (18)F-DA PET, 63.4% for (123)I-MIBG scintigraphy, and 64.0% for SRS.

CONCLUSION

If available, (18)F-DA PET should be used in the evaluation of PHEO, because it is more sensitive than (123)I-MIBG scintigraphy or SRS. If (18)F-DA PET is not available, (123)I-MIBG scintigraphy (for nonmetastatic or adrenal PHEO) and SRS (for metastatic PHEO) should be the first alternative imaging methods to be used.

123I-metaiodobenzylguanidine (MIBG) scintigraphy for the detection of adrenal and extra-adrenal phaeochromocytomas: CT and MRI correlation

CONTEXT

Evidence regarding the accuracy of [(123)I] metaiodobenzylguanidine (MIBG) imaging for phaeochromocytoma localization is currently limited to small series.

OBJECTIVE

We present the largest series of primary phaeochromocytomas in which the performance of [(123)I]MIBG has been evaluated and correlated with cross-sectional imaging.

DESIGN

We identified 76 patients with both preoperative [(123)I]MIBG and cross-sectional imaging for confirmed primary phaeochromocytoma between 1995 and 2005 at our institution. This comprised 60 adrenal tumours in 55 patients and 33 extra-adrenal tumours in 23 patients (2 patients had both adrenal and extra-adrenal tumours). Phaeochromocytoma metastases were not evaluated.

MAIN OUTCOME MEASURE(S)

[(123)I]MIBG studies were independently reviewed and correlated with CT and MRI examinations, as well as tumour functional status, to identify features that may predict a false negative [(123)I]MIBG result.

RESULTS

The overall sensitivity of [(123)I]MIBG was 75%. Tumour detection was lower for extra-adrenal (58%) vs. adrenal (85%) phaeochromocytomas (P = 0.005). For extra-adrenal tumours, [(123)I]MIBG demonstrated 8 of 14 carotid body, 2 of 2 intrathoracic, 8 of 14 retroperitoneal and 2 of 3 pelvic phaeochromocytomas. Overall, MRI and CT demonstrated 68 of 68 and 72 of 74 primary phaeochromocytomas, respectively. Tumour size correlated with [(123)I]MIBG uptake for adrenal (P = 0.009) but not extra-adrenal tumours. When tumours were adjusted for size, no other imaging feature or functional status correlated with [(123)I]MIBG negativity, although two large [(123)I]MIBG negative adrenal tumours contained large areas of necrosis or haemorrhage.

CONCLUSIONS

Extra-adrenal and small adrenal phaeochromocytomas are more likely to result in false negatives on [(123)I]MIBG. Tumoural necrosis or haemorrhage do not consistently relate to [(123)I]MIBG uptake, although adrenal phaeochromocytomas containing minimal solid tissue due to extensive necrosis may predict a negative [(123)I]MIBG result.

Pheochromocytoma as a catecholamine producing tumor: implications for clinical practice

Pheochromocytomas are catecholamine-producing tumors presenting with various clinical symptoms, but mostly with headache, sweating, palpitations and hypertension. If not properly diagnosed, secretion of catecholamines may lead to fatal cardiovascular consequences. Biochemical testing for pheochromocytoma should be performed not only in symptomatic subjects or in subjects with adrenal incidentaloma but also in subjects with a genetic predisposition for pheochromocytoma (multiple endocrine neoplasia type 2, Von Hippel-Lindau (VHL) syndrome, neurofibromatosis type 1 (NF 1)and mutations of succinate dehydrogenase (SDH) genes). Once a pheochromocytoma is proven, computed tomography (CT), magnetic resonance imaging (MRI) and functional imaging with [(123)I]-MIBG may be used for tumor localization. Adequate medical pre-treatment is essential for successful operation which is performed in most cases by laparoscopy. After tumor removal, further follow-up is necessary due to possible recurrence. Although prognosis after tumor resection is excellent, a significant proportion of pheochromocytomas recur, some as metastases. Thus, appropriate follow-up is mandatory.

Work-up of the functional adrenal mass

Evaluation of a functional adrenal mass may be initiated based on symptomatic presentation or the detection of an incidental adrenal mass. Recent literature suggests that 10% to 20% of adrenal incidentalomas demonstrate subclinical hormonal dysfunction, which may place patients at a higher risk for metabolic or cardiovascular disorders. Many diagnostic algorithms have been proposed for the evaluation of pheochromocytoma, Cushing's adenoma, aldosteronoma, and hormonally active adrenal cortical carcinoma. In this article, the available literature on functional adrenal masses is reviewed and up-to-date methods of efficient diagnosis are proposed.

Anatomical and Functional Imaging of Metastatic Pheochromocytoma

Although in the majority of patients with pheochromocytoma the tumor is localized in the adrenal, up to 26% of patients have malignant/metastatic disease. Metastatic disease should be ruled out before initial surgery is attempted. Anatomical imaging modalities (computed tomography or magnetic resonance imaging) should be done first over the adrenals, and if negative over the abdomen and if no tumor is found, then the chest and neck should be covered. Regardless of the anatomical imaging results functional imaging with [123-I]- or [131-I]-metaiodobenzylguanidine (MIBG) scintigraphy should be done to corroborate the diagnosis. Negative MIBG scans should be followed by positron emission tomography (PET) studies with specific ligands like [18-F]-dopamine. Persistently negative evaluations should be followed by PET studies with non-specific ligands such as [18-F]-deoxyglucose or somatostatin receptor scintigraphy.

Primary diagnosis of multiple pheochromocytomas in the brother of a MEN-2 patient by simultaneous MIBG scintigraphy and low-dose computed tomography

Metaiodobenzylguanidine (MIBG) scintigraphy is a well-established functional imaging method for localizing pheochromocytomas. However, the morphologic information revealed on the scintigram is often too sparse and thus, accordingly, supplemental computed tomography (CT) or magnetic resonance imaging are often performed. Recently, gamma cameras with built-in low-dose CT were introduced. The authors describe a patient with a high likelihood of pheochromocytoma who had simultaneous MIBG scintigraphy and low-dose CT performed as the primary examinations. The scan revealed pheochromocytomas in both adrenal glands and one extra-adrenal pheochromocytoma located in the liver. The combined imaging ensured the final diagnosis without any need for further imaging. Based on the findings of this case, the authors believe that combined MIBG scintigraphy and low-dose CT is a promising future single imaging technique for pheochromocytomas.

I-123 MIBG imaging and intraoperative localization of metastatic pheochromocytoma: a case report

The authors describe the diagnostic use of I-123 MIBG scintigraphy in a 61-year-old man who was thought to have a recurrence 25 years after a left adrenalectomy for a pheochromocytoma. Preoperative I-123 MIBG scintigraphy was performed twice along with intraoperative gamma probe localization of the lesions. The preoperative MIBG scintigraphy revealed three pathologic processes in the upper left abdomen, whereas computed tomographic scanning identified only one site of involvement. All three metastatic lesions were removed successfully with the aid of a gamma probe. Preoperative I-123 MIBG scintigraphy, combined with intraoperative gamma probe identification of I-123 MIBG foci, is feasible and a valuable tool to detect malignant masses possibly overlooked by other imaging techniques.

Isotopic evaluation and therapy in patients with malignant endocrine disease

The contribution of nuclear medicine to the diagnosis and treatment of endocrine malignancy is increasing. Advances in molecular biology offer new opportunities for tumour targeting via surface receptor recognition and tumour-specific metabolic markers. Imaging the biodistribution of these markers allows quantitative, in vivo characterization of tumour function. There is growing interest in the therapeutic potential of nuclear medicine targeting, substituting therapeutic beta-emitting radionuclides for the gamma-emitters used in diagnostic imaging. Limited clinical experience supports the rationale of this approach in patients with inoperable or disseminated disease and controlled trials are in progress. This chapter outlines the place of nuclear medicine techniques in the routine management of endocrine malignancy and explores areas for further development.

Tc-99m MIBG imaging in a huge clinically silent pheochromocytoma with cystic degeneration and massive hemorrhage

I-131 metaiodobenzylguanidine scintigraphy showed marked accumulation in the walls of a clinically silent, huge cystic adrenal mass with a prominent hemorrhage in a 48-year-old man. Although a careful reexamination of the histologic specimen finally lead to a diagnosis of pheochromocytoma, the appearances of this mass on computed tomography and magnetic resonance imaging were not specific for this neoplasm, and even pathologic analysis initially indicated, incorrectly, that this lesion was a hemorrhagic hemangioma. This case shows that I-131 metaiodobenzylguanidine scintigraphy is useful for correctly diagnosing an adrenal mass with prominent cystic or hemorrhagic degeneration.