Use of m-[131I]iodobenzylguanidine in the treatment of malignant pheochromocytoma

Management of pheochromocytomas and paragangliomas: Review of current diagnosis and treatment options

Pheochromocytomas (PCCs) are rare neuroendocrine tumors derived from the chromaffin cells of the adrenal medulla. When these tumors have an extra-adrenal location, they are called paragangliomas (PGLs) and arise from sympathetic and parasympathetic ganglia, particularly of the para-aortic location. Up to 25% of PCCs/PGLs are associated with inherited genetic disorders. The majority of PCCs/PGLs exhibit indolent behavior. However, according to their affiliation to molecular clusters based on underlying genetic aberrations, their tumorigenesis, location, clinical symptomatology, and potential to metastasize are heterogenous. Thus, PCCs/PGLs are often associated with diagnostic difficulties. In recent years, extensive research revealed a broad genetic background and multiple signaling pathways leading to tumor development. Along with this, the diagnostic and therapeutic options were also expanded. In this review, we focus on the current knowledge and recent advancements in the diagnosis and treatment of PCCs/PGLs with respect to the underlying gene alterations while also discussing future perspectives in this field.

Systemic Radiopharmaceutical Therapy of Pheochromocytoma and Paraganglioma

Whereas benign pheochromocytomas and paragangliomas are often successfully cured by surgical resection, treatment of metastatic disease can be challenging in terms of both disease control and symptom control. Fortunately, several options are available, including chemotherapy, radiation therapy, and surgical debulking. Radiolabeled metaiodobenzylguanidine (MIBG) and somatostatin receptor imaging have laid the groundwork for use of these radiopharmaceuticals as theranostic agents. ¹³¹I-MIBG therapy of neuroendocrine tumors has a long history, and the recent approval of high-specific-activity ¹³¹I-MIBG for metastatic or inoperable pheochromocytoma or paraganglioma by the U.S. Food and Drug Administration has resulted in general availability of, and renewed interest in, this treatment. Although reports of peptide receptor radionuclide therapy of pheochromocytoma and paraganglioma with ⁹⁰Y- or ¹⁷⁷Lu-DOTA conjugated somatostatin analogs have appeared in the literature, the approval of ¹⁷⁷Lu-DOTATATE in the United States and Europe, together with National Comprehensive Cancer Network guidelines suggesting its use in patients with metastatic or inoperable pheochromocytoma and paraganglioma, has resulted in renewed interest. These agents have shown evidence of efficacy as palliative treatments in patients with metastatic or inoperable pheochromocytoma or paraganglioma. In this continuing medical education article, we discuss the therapy of pheochromocytoma and paraganglioma with ¹³¹I-MIBG and ⁹⁰Y- or ¹⁷⁷Lu-DOTA-somatostatin analogs.

Neuroendocrine and Adrenal Tumors, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Neuroendocrine and Adrenal Gland Tumors focus on the diagnosis, treatment, and management of patients with neuroendocrine tumors (NETs), adrenal tumors, pheochromocytomas, paragangliomas, and multiple endocrine neoplasia. NETs are generally subclassified by site of origin, stage, and histologic characteristics. Appropriate diagnosis and treatment of NETs often involves collaboration between specialists in multiple disciplines, using specific biochemical, radiologic, and surgical methods. Specialists include pathologists, endocrinologists, radiologists (including nuclear medicine specialists), and medical, radiation, and surgical oncologists. These guidelines discuss the diagnosis and management of both sporadic and hereditary neuroendocrine and adrenal tumors and are intended to assist with clinical decision-making. This article is focused on the 2021 NCCN Guidelines principles of genetic risk assessment and counseling and recommendations for well-differentiated grade 3 NETs, poorly differentiated neuroendocrine carcinomas, adrenal tumors, pheochromocytomas, and paragangliomas.

Effects of Repeated 131I-Meta-Iodobenzylguanidine Radiotherapy on Tumor Size and Tumor Metabolic Activity in Patients with Metastatic Neuroendocrine Tumors

¹³¹I-meta-iodobenzylguanidine (¹³¹I-MIBG) radiotherapy has shown some survival benefits in metastatic neuroendocrine tumors (NETs). European Association of Nuclear Medicine clinical guidelines for ¹³¹I-MIBG radiotherapy suggest a repeated treatment protocol, although none currently exists. The existing single-high-dose ¹³¹I-MIBG radiotherapy (444 MBq/kg) has been shown to have some benefits for patients with metastatic NETs. However, this protocol increases adverse effects and requires alternative therapeutic approaches. Therefore, the aim of this study was to evaluate the effects of repeated ¹³¹I-MIBG therapy on tumor size and tumor metabolic response in patients with metastatic NETs. Methods: Eleven patients with metastatic NETs (aged 49.2 ± 16.3 y) prospectively received repeated 5,550-MBq doses of ¹³¹I-MIBG therapy at 6-mo intervals. In total, 31 treatments were performed. The mean number of treatments was 2.8 ± 0.4, and the cumulative ¹³¹I-MIBG dose was 15,640.9 ± 2,245.1 MBq (286.01 MBq/kg). Tumor response was observed by CT and ¹⁸F-FDG PET or by ¹⁸F-FDG PET/CT before and 3-6 mo after the final ¹³¹I-MIBG treatment. Results: On the basis of the CT findings with RECIST, 3 patients showed a partial response and 6 patients showed stable disease. The remaining 2 patients showed progressive disease. Although there were 2 progressive-disease patients, analysis of all patients showed no increase in summed length diameter (median, 228.7 mm [interquartile range (IQR), 37.0-336.0 mm] to 171.0 mm [IQR, 38.0-270.0 mm]; P = 0.563). In tumor region-based analysis with partial-response and stable-disease patients (n = 9), ¹³¹I-MIBG therapy significantly reduced tumor diameter (79 lesions; median, 16 mm [IQR, 12-22 mm] to 11 mm [IQR, 6-16 mm]; P < 0.001). Among 5 patients with hypertension, there was a strong trend toward systolic blood pressure reduction (P = 0.058), and diastolic blood pressure was significantly reduced (P = 0.006). Conclusion: Eighty-two percent of metastatic NET patients effectively achieved inhibition of disease progression, with reduced tumor size and reduced metabolic activity, through repeated ¹³¹I-MIBG therapy. Therefore, this relatively short-term repeated ¹³¹I-MIBG treatment may have potential as one option in the therapeutic protocol for metastatic NETs. Larger prospective studies with control groups are warranted.

Targeted Radionuclide Therapy for Patients with Metastatic Pheochromocytoma and Paraganglioma: From Low-Specific-Activity to High-Specific-Activity Iodine-131 Metaiodobenzylguanidine

Low-specific-activity iodine-131–radiolabeled metaiodobenzylguanidine (I-131-MIBG) was introduced last century as a potential systemic therapy for patients with malignant pheochromocytomas and paragangliomas. Collective information derived from mainly retrospective studies has suggested that 30–40% of patients with these tumors benefit from this treatment. A low index of radioactivity, lack of therapeutic standardization, and toxicity associated with intermediate to high activities (absorbed radiation doses) has prevented the implementation of I-131-MIBG’s in clinical practice. High-specific-activity, carrier-free I-131-MIBG has been developed over the past two decades as a novel therapy for patients with metastatic pheochromocytomas and paragangliomas that express the norepinephrine transporter. This drug allows for a high level of radioactivity, and as yet is not associated with cardiovascular toxicity. In a pivotal phase two clinical trial, more than 90% of patients achieved partial responses and disease stabilization with the improvement of hypertension. Furthermore, many patients exhibited long-term persistent antineoplastic effects. Currently, the high-specific-activity I-131-MIBG is the only approved therapy in the US for patients with metastatic pheochromocytomas and paragangliomas. This review will discuss the historical development of high-specific-activity I-131-MIBG, its benefits and adverse events, and future directions for clinical practice applicability and trial development.

Complete remission of metastatic pheochromocytoma in 123I-metaiodobenzylguanidine scintigraphy after a single session of 131I-metaiodobenzylguanidine therapy: a case report

Background

Pheochromocytomas are rare neuroendocrine tumors, with a malignancy frequency of approximately 10%. The treatment of malignant pheochromocytoma is palliative, and the traditional management strategy has limited efficacy. Furthermore, no clear criteria exist for the treatment of metastatic pheochromocytoma, especially for unresectable lesions. We report a case of complete remission of metastatic pheochromocytoma in ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy after a single session of ¹³¹I-MIBG therapy.

Case presentation

A 61-year-old woman had a right adrenal grand tumor and lymph node metastasis on the hilum of the right kidney, both of which incorporated MIBG. After surgery, immunostaining of a tumor specimen showed expression of the tumor makers chromogranin and synaptophysin. One year postoperatively, abdominal computed tomography revealed a local recurrence and retroperitoneal lymph node swelling. The local recurrence was positive for MIBG uptake, whereas the swollen retroperitoneal lymph nodes were negative. She underwent surgery again, but the local recurrence was unresectable because of rigid adhesion to the surrounding tissue. Immunostaining of an intraoperatively extracted swollen retroperitoneal lymph node showed expression of tumor markers. The patient then underwent a single session of ¹³¹I-MIBG therapy (7.4 GBq, 200 mCi), after which the residual lesions no longer incorporated MIBG, and a complete response in ¹²³I- metaiodobenzylguanidine (MIBG) scintigraphy was achieved. The ¹³¹I-MIBG treatment was repeated 6 months later. None of the lesions were positive for MIBG uptake.

Conclusions

¹³¹I-MIBG therapy efficaciously treats unresectable lesions that are positive for MIBG uptake.

I-131 Metaiodobenzylguanidine Therapy of Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas are rare tumors arising from chromaffin cells. Available therapeutic modalities consist of chemotherapy, tyrosine kinase inhibitors, and I-131 metaiodobenzylguanidine (MIBG). I-131 MIBG is taken up via specific receptors and localizes into many but not all pheochromocytomas and paragangliomas. Because these tumors are rare, most therapy studies are retrospective presentations of clinical experience. Numerous retrospective studies and a few prospective studies have shown favorable responses in this disease, including symptomatic, biochemical, and objective responses. In this report, we review the experience of using I-131 MIBG therapy for targeting pheochromocytoma and paragangliomas.

Therapy of endocrine disease: treatment of malignant pheochromocytoma and paraganglioma

Metastatic pheochromocytomas and paragangliomas (MPPs) present clinicians with three major challenges: scarcity, complexity of characterization, and heterogeneous behavior and prognosis. As with the treatment for all neuroendocrine tumors, the control of hormonal symptoms and tumor growth is the main therapeutic objective in MPP patients. A significant number of MPP patients still die from uncontrolled hormone secretion. In addition, the management of MPPs remains palliative. Steps forward include proper characterization of MPP patients at large cancer referral centers with multidisciplinary teams; improved strategies to stratify patients prognostically; and implementation of trials within national and international networks. Progress in the molecular characterization and staging of MPPs constitutes the basis for significant treatment breakthroughs.

(131)I-MIBG therapy for malignant paraganglioma and phaeochromocytoma: systematic review and meta-analysis

BACKGROUND

(131)I-MIBG therapy can be used for palliative treatment of malignant paraganglioma and phaeochromocytoma. The main objective of this study was to perform a systematic review and meta-analysis assessing the effect of (131)I-MIBG therapy on tumour volume in patients with malignant paraganglioma/phaeochromocytoma.

METHODS

A literature search was performed in December 2012 to identify potentially relevant studies. Main outcomes were the pooled proportions of complete response, partial response and stable disease after radionuclide therapy. A meta-analysis was performed with an exact likelihood approach using a logistic regression with a random effect at the study level. Pooled proportions with 95% confidence intervals (CI) were reported.

RESULTS

Seventeen studies concerning a total of 243 patients with malignant paraganglioma/phaeochromocytoma were treated with (131)I-MIBG therapy. The mean follow-up ranged from 24 to 62 months. A meta-analysis of the effect of (131)I-MIBG therapy on tumour volume showed pooled proportions of complete response, partial response and stable disease of, respectively, 0·03 (95% CI: 0·06-0·15), 0·27 (95% CI: 0·19-0·37) and 0·52 (95% CI: 0·41-0·62) and for hormonal response 0·11 (95% CI: 0·05-0·22), 0·40 (95% CI: 0·28-0·53) and 0·21 (95% CI: 0·10-0·40), respectively. Separate analyses resulted in better results in hormonal response for patients with paraganglioma than for patients with phaeochromocytoma.

CONCLUSIONS

Data on the effects of (131)I-MIBG therapy on malignant paraganglioma/phaeochromocytoma suggest that stable disease concerning tumour volume and a partial hormonal response can be achieved in over 50% and 40% of patients, respectively, treated with (131)I-MIBG therapy. It cannot be ruled out that stable disease reflects not only the effect of MIBG therapy, but also (partly) the natural course of the disease.

Repeated Radionuclide therapy in metastatic paraganglioma leading to the highest reported cumulative activity of 131I-MIBG

¹³¹I-MIBG therapy for neuroendocrine tumours may be dose limited. The common range of applied cumulative activities is 10-40 GBq. We report the uneventful cumulative administration of 111 GBq (= 3 Ci) ¹³¹I-MIBG in a patient with metastatic paraganglioma. Ten courses of ¹³¹I-MIBG therapy were given within six years, accomplishing symptomatic, hormonal and tumour responses with no serious adverse effects. Chemotherapy with cisplatin/vinblastine/dacarbazine was the final treatment modality with temporary control of disease, but eventually the patient died of progression. The observed cumulative activity of ¹³¹I-MIBG represents the highest value reported to our knowledge, and even though 12.6 GBq of ⁹⁰Y-DOTATOC were added intermediately, no associated relevant bone marrow, hepatic or other toxicity were observed. In an individual attempt to palliate metastatic disease high cumulative activity alone should not preclude the patient from repeat treatment.

An Unusual Case of Peritoneal Carcinomatosis

The peritoneal surface remains an important failure site for patients with gastrointestinal and gynecologic malignancies. In the past, oncologists regarded peritoneal carcinomatosis as an incurable component of an intra-abdominal malignancy. During the last two decades, novel therapeutic approaches have emerged for peritoneal carcinomatosis patients. We report the first case of peritoneal carcinomatosis emerging from an extra-adrenal, intra-abdominal paraganglioma. This 49-year-old male was treated with cytoreductive surgery and hyperthermic intraperitoneal perioperative chemotherapy. Paragangliomas are rare tumors of neural crest-derived chromaffin cells and can originate either from the sympathetic or from the parasympathetic ganglia. It has been estimated that as many as 10% of the paragangliomas arise outside the adrenal glands. This case represents an unreported presentation of paraganglioma. Two possible origins of this malignancy, and the applied therapy, are discussed. We report the feasibility of cytoreductive surgery plus hyperthermic intraperitoneal perioperative chemotherapy in the treatment of this malignancy.

Metachronous pheochromocytoma metastasis to the upper dorsal spine-6-year survival

BACKGROUND CONTEXT

Malignant pheochromocytoma is a rare neoplasm of chromaffin tissue. Very few cases of malignant adrenal pheochromocytoma metastatic to vertebrae exist.

PURPOSE

To determine the prognosis of a patient with an excised adrenal pheochromocytoma and a single metachronous metastasis to the upper dorsal spine.

STUDY DESIGN

Case report

METHODS

The authors report a patient who underwent total excision of an adrenal pheochromocytoma of the left adrenal gland in 2000 who developed a single metastasis to the second dorsal vertebra in 2002 with no evidence of abdominal recurrence.

RESULTS

Four-year survival is documented after the spinal metastasis was first detected after two attempts at excision and radiotherapy.

CONCLUSIONS

Patients with adrenal pheochromocytomas must be screened periodically with whole body imaging despite normal abdominal imaging as there is a definite risk of metachronous metastasis. Aggressive therapy may result in improving survival significantly in a subset of patients with isolated spinal metastases.

Scintigraphic imaging of body neuroendocrine tumors

Radionuclide imaging is often used in the diagnosis and work-up of a wide range of neoplasms, on the basis of the biologic behavior of the tumor. Neuroendocrine tumors are a subgroup of neoplasms that are generally small and slow growing, and consequently their identification with conventional anatomic imaging can be difficult. Depending on the physiologic properties of the tumor, functional images obtained with radionuclides are often complementary to anatomic images, not only in the localization of the tumor and its metastases, but also in the assessment of prognosis and response to therapy. Familiarity with the choice of the appropriate radiopharmaceutical, proper imaging protocols, and the wide range of imaging patterns will enable the radiologist to guide the clinician in case management.

Clinical review: Current treatment of malignant pheochromocytoma

CONTEXT

Pheochromocytomas are rare tumors of predominantly adrenal origin that often produce and secrete catecholamines. Malignancy occurs in a variable percentage of cases depending on genetic background and tumor location. Definitive diagnosis relies on the detection of distant metastases. Treatments for malignant pheochromocytoma include surgical debulking, pharmacological control of hormone-mediated symptoms, targeted methods such as external irradiation, and systemic antineoplastic therapy. Different agents and protocols for this purpose are reviewed, and their therapeutic potential is discussed.

EVIDENCE ACQUISITION

Literature on antineoplastic therapies for malignant pheochromocytoma was identified by searching the PubMed database with restriction to articles published in English during the past 30 yr.

EVIDENCE SYNTHESIS

Because of the rarity of the condition, no randomized clinical trials concerning the treatment of malignant pheochromocytoma have been performed. The strategy established best is [131I]meta-iodobenzylguanidine (MIBG) therapy, which is well tolerated. Similar to cytotoxic chemotherapy with cyclophosphamide, vincristine, and dacarbazine, MIBG can induce remission for a limited period in a significant proportion of patients. Octreotide as a single agent seems to be largely ineffective.

CONCLUSIONS

MIBG radiotherapy and cyclophosphamide, vincristine, and dacarbazine chemotherapy are comparable with respect to response rate and toxicity. It is unclear whether combining both can improve the outcome. Future developments may include new multimodal concepts with focus on inhibition of angiogenetic factors and heat shock protein 90. Any present or new therapeutic approach must take into account the highly variable natural course of the disease.

The diagnosis and medical management of advanced neuroendocrine tumors

Neuroendocrine tumors (NETs) constitute a heterogeneous group of neoplasms that originate from endocrine glands such as the pituitary, the parathyroids, and the (neuroendocrine) adrenal, as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells dispersed between exocrine cells, such as endocrine cells of the digestive (gastroenteropancreatic) and respiratory tracts. Conventionally, NETs may present with a wide variety of functional or nonfunctional endocrine syndromes and may be familial and have other associated tumors. Assessment of specific or general tumor markers offers high sensitivity in establishing the diagnosis and can also have prognostic significance. Imaging modalities include endoscopic ultrasonography, computed tomography and magnetic resonance imaging, and particularly, scintigraphy with somatostatin analogs and metaiodobenzylguanidine. Successful treatment of disseminated NETs requires a multimodal approach; radical tumor surgery may be curative but is rarely possible. Well-differentiated and slow-growing gastroenteropancreatic tumors should be treated with somatostatin analogs or alpha-interferon, with chemotherapy being reserved for poorly differentiated and progressive tumors. Therapy with radionuclides may be used for tumors exhibiting uptake to a diagnostic scan, either after surgery to eradicate microscopic residual disease or later if conventional treatment or biotherapy fails. Maintenance of the quality of life should be a priority, particularly because patients with disseminated disease may experience prolonged survival.

Iodine -131 metaiodobenzylguanidine is an effective treatment for malignant pheochromocytoma and paraganglioma

INTRODUCTION

Iodine 131-meta-iodobenzylguanidine ((131)I-MIBG) has been applied to the palliative treatment of metastatic pheochromocytoma in small studies. We report our institutional experience for the treatment of metastatic pheochromocytoma and paraganglioma.

METHODS

We performed a retrospective review of 33 patients with metastatic pheochromocytoma (n=22) and paraganglioma (n=11) treated at our institution with (131)I-MIBG over a 10-year period.

RESULTS

Patients received a mean dose of 388+/-131 mCi (131)I-MIBG. Median survival after treatment was 4.7 years. Most patients experienced a symptomatic response leading to an improved survival (4.7 years vs 1.8 years, P<.01). Patients with a measurable hormone response demonstrated an increased survival in comparison to those with no response (4.7 years vs 2.6 years, P=.01). Patients who received a high dose (>500 mCi) as their initial therapy also had improved survival (3.8 years vs 2.8 years, P=.02).

CONCLUSION

These data support (131)I-MIBG treatment for select patients with metastatic pheochromocytoma. In our experience, prolonged survival was best predicted by symptomatic and hormone response to (131)I-MIBG treatment. An initial dose of 500 mCi may be optimal. The benefit of (131)I-MIBG treatment for metastatic pheochromocytoma must also be weighed against its side effects.

High-dose 131I-metaiodobenzylguanidine therapy for 12 patients with malignant pheochromocytoma

BACKGROUND

131I-Metaiodobenzylguanidine (131I-MIBG) can be used systemically to treat malignant pheochromocytoma. To improve outcome, the authors used higher levels of activity of 131I-MIBG than previously reported. The authors reported the response rates and toxicity levels in patients with malignant pheochromocytoma or paraganglioma who were treated with high-dose 131I-MIBG.

METHODS

Following debulking surgery and stem cell harvest, 12 patients with malignant pheochromocytoma or paraganglioma were treated with 131I-MIBG. Five had received previous external beam radiation and/or chemotherapy. The median single treatment dose was 800 mCi (37 gigabecquerels; range, 386-866 mCi) or 11.5 mCi/kg (range, 5.6-18.3 mCi/kg). The median cumulative dose was 1015 mCi (range, 386-1690 mCi).

RESULTS

Three patients had a complete response, two of whom had soft tissue and skeletal metastases. Their median follow-up was 45 months (range, 23-101 months). Seven patients had a partial response (PR), with a median follow-up 43 months (range, 6-47 months). Two patients without a response died with progressive disease (PD) and 2 patients with an initial PR died of PD at 13 and 11 months, respectively. Grade 3 thrombocytopenia occurred after 79% (15 of 19) of treatments had been administered. Grade 3 and 4 neutropenia followed 53% (10 of 19) and 19% (4 of 19) of treatments, respectively. One patient required stem cell infusion, and one developed primary ovarian failure.

CONCLUSIONS

The single and cumulative doses of 131I-MIBG were approximately 2-3.5 times higher than those used at other centers. Unlike previous reports, two patients with both skeletal and soft tissue metastases had a complete response. Hematologic toxicity was significant but tolerable. High-dose 131I-MIBG may lead to long-term survival in patients with malignant pheochromocytoma.

The management of benign and malignant pheochromocytoma and abdominal paraganglioma

AIMS

To report treatment and outcome in patients with malignant and benign pheochromocytoma and abdominal paraganglioma.

METHODS

Review of clinical and therapeutic features in 85 patients with pheochromocytoma or abdominal paraganglioma between 1976 and 1999.

RESULTS

Thirty-nine of 85 patients presented with symptoms other than classical paroxysmal attacks. Paragangliomas were more often malignant (7/15) than pheochromocytomas (7/70). No recurrences have occurred in 71 patients with tumours initially classified as benign after a median follow-up time of 144 months (range 7-287). Nine of 14 patients with tumours classified as malignant have developed metastasis and/or local recurrence. Treatment of malignant tumours with cyclophosphamide, vincristine and dacarbazine (CVD) improved or stabilised the disease in three of four patients.

CONCLUSION

Life long follow-up of patients with benign pheochromocytoma is not necessary. Combination chemotherapy (CVD) is a valid option in the treatment of malignant pheochromocytomas and abdominal paragangliomas.

Radiopharmaceutical treatment of pheochromocytomas

Malignant pheochromocytomas, a group of tumors that include metastatic paragangliomas, often produce hypertension and episodic symptoms from secretion of norepinephrine and sometimes epinephrine. In addition, the tumors usually manifest progressive metastases. Blockade of alpha and beta adrenergic receptors will control blood pressure and symptoms, but reduction of the malignancy has been difficult to achieve. Meta-iodobenzylguanidine (MIBG) follows the pathways of norepinephrine and, when labeled with 131-I, will concentrate sufficiently in the pheochromocytoma to impart therapeutic radiation. More than 100 patients have received treatment with 131-I-labeled MIBG at multiple medical centers. Individual doses were 3.7 to 18.5 GBq (100 to >500 mCi), and many patients received several doses separated by a few months. Partial remissions, recorded as decreased tumor presence and tumor function, have been observed in one-third or more of the treated patients. However, complete remissions are rare, and recurrence/progression within two years is the rule. Toxicity was generally modest and temporary. Subsequent chemotherapy increased the benefits attained by 131-I MIBG, but, in a small series of patients, this combination did not further change the outcome. Nevertheless, selective radiation from 131-I MIBG or a similar radiopharmaceutical could play a valuable role in treatments that combine several types of attacks on this recalcitrant malignancy.

Radiation treatment of recurrent pheochromocytoma of the bladder: case report and review of literature

Secondary to the paucity of pheochromocytoma, very limited data exist regarding the optimal treatments of metastatic disease. Malignant pheochromocytomas are often considered unresponsive to radiotherapy, but this decision is based on the few case reports performed before 1970. There have been a handful of reports about metastatic resolution and palliation from radiation therapy. Nevertheless, radiotherapy is not considered a mainstay of pheochromocytoma treatment. In this case report, we describe a patient with a malignant extraadrenal pheochromocytoma, metastatic to the right humerus, and her treatment course of surgery and radiotherapy.

Pheochromocytoma

The only definitive therapy for patients with pheochromocytoma is surgical resection [1,2**]. Advances in preoperative medical management of hypertension/hypovolemia and improved intraoperative anesthetic care have reduced the operative mortality rate for pheochromocytoma to less than 5% in most series. In addition, accurate preoperative localization studies have eliminated the need for extensive exploratory laparotomy. Focused approach and laparoscopic resection have become the new "gold standard," with a reduced morbidity [4**]. Large or locally invasive pheochromocytomas may still require open resection.

Treatment of metastatic carcinoid tumours, phaeochromocytoma, paraganglioma and medullary carcinoma of the thyroid with (131)I-meta-iodobenzylguanidine [(131)I-mIBG]

OBJECTIVE

Meta-iodo-benzyl-guanidine labelled with 131-iodine [(131)I-mIBG] has been used extensively for imaging tumours originating from the neural crest but experience with its therapeutic use is limited, particularly for non-catecholamine secreting tumours. In order to assess the therapeutic response and potential adverse effects of the therapeutic administration of (131)I-mIBG, we have reviewed all patients who had received this form of treatment in our department.

DESIGN

Retrospective analysis of the case notes of patients with neuroendocrine tumours who received treatment with (131)I-mIBG and were followed-up according to a defined protocol in a given time frame.

PATIENTS

Thirty-seven patients (18 with metastatic carcinoid tumours, 8 metastatic phaeochromocytoma, 7 metastatic paraganglioma and 4 metastatic medullary carcinoma of the thyroid) treated with (131)I-mIBG over a 15-year period were included in this analysis.

MEASUREMENTS

The symptomatic, hormonal and tumoural responses before and after (131)I-mIBG therapy over a median follow-up duration of 32 months (range 5-180 months) were recorded. Of the 37 patients (22 males; median age 51 years, range 18-81 years), 15 were treated with (131)I-mIBG alone whereas the other 22 received additional therapy.

RESULTS

A total of 116 therapeutic (131)I-mIBG doses were administered [mean cumulative dose 592 mCi (21.9 GBq); range 200-1592 mCi (7.4-58.9 GBq)]. None of the patients showed a complete tumour response. However, 82% of patients treated with (131)I-mIBG alone and 84% who received additional therapy showed stable disease over the period of follow-up. Overall survival during the period of the study was 71%. The overall 5-year survival rate was 85% (95% confidence interval, 72-99%) for all patients and 78% (95% confidence interval, 55-100%) for the carcinoid group alone, according to Kaplan-Meier analysis. Symptomatic control was achieved in all the patients treated with (131)I-mIBG alone, and in 72% of those receiving additional therapy. Hormonal control was noted in 50% and 57% of patients, respectively. (131)I-mIBG therapy was safe and well tolerated. Serious side-effects necessitating the termination of (131)I-mIBG therapy were seen in only 2 of our patients.

CONCLUSIONS

(131)I-mIBG therapy produces symptomatic and hormonal improvement and moderate tumour regression/stabilization in patients with metastatic neuroendocrine tumours with minimal adverse effects. It may be a valuable alternative or additional therapeutic option to the currently available conventional treatment modalities.

Nuclear endocrinology as a monitoring tool

Malignant endocrine disorders have been an enigma over the last few decades, from genetic, clinical, and imaging perspectives. The detection of the primary tumor and the identification of recurrent disease have been essentially based on various anatomic techniques, with localization procedures extensively developed for staging, follow-up, radio-guided surgery, and therapy. Frequently, the lesions are too small to cause anatomic alterations, or they are obscured by the changes in anatomic planes that occur after initial surgery. Small lesions, however, are the ones that can potentially be cured. Thus, every attempt should be made to localize these sites before further growth and dissemination occur beyond the scope of cure. Since the advent of iodine-131 for staging and follow-up of patients with differentiated thyroid carcinoma, the search has led to the use of radioiodinated metaiodobenzylguanidine (MIBG) for recurrent pheochromocytoma and neuroblastoma, to the development of antibodies to carcinoembryonic antigen for the staging and treatment of medullary thyroid carcinoma, and to the characterization of peptide receptors on neuroendocrine tumors. Additionally, there has been a breakthrough with the use of positron emitters in nuclear oncology, including F-18-fluorodeoxyglucose, for I-131-negative metastases of differentiated thyroid carcinoma, recurrent medullary thyroid carcinoma, malignant pheochromocytoma, and adrenocortical carcinoma. Undoubtedly, optimal care of the patient requires both the expertise of the treating endocrinologist and the use of various imaging techniques in the diagnosis, staging, and follow-up of these diseases.

[Recent progress in the diagnosis, prognostic evaluation and treatment of pheochromocytomas]

INTRODUCTION

Pheochromocytoma is a catecholamine-secreting neoplasm of chromaffin tissue. It is a rare disease. Biochemical tests should be performed only in patients at high risk of pheochromocytoma, and an imaging procedure only in those with positive biochemical tests.

CURRENT KNOWLEDGE AND KEY POINTS

The most specific and sensitive diagnostic test for the disease is the determination of plasma or urinary metanephrines. The tumor can be located by computerized tomography, magnetic resonance imaging, and specific scintigraphy. Ten to 20% of pheochromocytomas result from hereditary diseases, including multiple endocrine neoplasia type 2, von Hippel Lindau disease, and neurofibromatosis 1. Familial cases are diagnosed earlier, and are more frequently bilateral and recurring than sporadic cases. About 10% of the cases are malignant either at first operation or during follow-up, malignancy being diagnosed by the presence of lymph node, visceral or bone metastases. The probability of a recurrence is positively correlated with the urinary excretion of metanephrines and tumor size. Recurrences are more frequent in cases with ectopic tumors and in those with a low plasma epinephrine to total catecholamine ratio. Patients, especially those with familial tumors or low epinephrine secretion, should be followed-up indefinitely.

FUTURE PROSPECTS AND PROJECTS

Treatment for malignant recurrences includes surgery, therapeutic embolization, chemotherapy, and the application of therapeutic doses of metaiodobenzylguanidine. Metyrosine, phenoxybenzamine, or somatostatin analogs may help to control blood pressure and to alleviate symptoms in patients with malignant pheochromocytoma; however such a treatment has no antiproliferative effect.

Treatment of malignant pheochromocytomas with 131-I metaiodobenzylguanidine and chemotherapy

Malignant pheochromocytomas have exhibited partial responses to treatments with 131-I metaiodobenzylguanidine (MIBG) and with chemotherapy. The authors combined these two therapeutic methods to determine if beneficial effects from each would be additive. Patients with documented malignant pheochromocytomas were recruited with the intent of administering 131-I MIBG in three substantial amounts of radioactivity at 3-month intervals followed by a year of chemotherapy in which cyclophosphamide, dacarbazine, and vincristine were to be given in 21-day cycles. Six patients entered the protocol. After the 131-I MIBG treatments, three patients manifested declines in the presence of tumor (smaller tumor volume or abnormalities on bone and 131-I MIBG scans) and the function of tumor (decreased rate of normetanephrine excretion as the major index). Two patients completed at least 9 months of chemotherapy and showed further reductions in the presence and function of tumors and were classified as having partial responses. Progressive disease afflicted three of the other four subjects. Even though toxicity was minimal from 131-I MIBG, it was sufficient to force reduction in the dosages or duration of chemotherapy. A combination of 131-I MIBG treatments and chemotherapy produced additive effects in reducing malignant pheochromocytomas. Toxicity moderately curtailed the proposed chemotherapy protocol.

Carcinoid syndrome with unknown primary: a case report

Carcinoid syndrome usually is associated with a classic presentation, the diagnosis of which is supported by elevations in neuroendocrine substances such as 5-hydroxyindoleacetic acid and by localization and pathologic identification of a neuroendocrine tumor. The authors report a patient for whom there was a 7-year delay in diagnosis and even then a primary tumor could not be localized.

Pheochromocytomas: can malignant potential be predicted?

OBJECTIVES

The presence of metastatic lesions is the only acceptable fact to confirm malignant pheochromocytoma. Patients with malignant pheochromocytomas, however, have a very poor survival rate. The aim of our study was to postulate predictive values for malignant pheochromocytomas.

METHODS

We evaluated symptoms, diagnostic modalities, treatment, and long-term follow-up of 86 patients with 85 benign and 10 malignant pheochromocytomas. Parameters from the benign were compared with those of the malignant pheochromocytomas.

RESULTS

Preoperative 24-hour urinary dopamine was in the normal range for benign pheochromocytomas but increased in malignant pheochromocytomas (P<0.0001). Vanillylmandelic acid was elevated in both benign and malignant pheochromocytomas but higher in malignant than in benign tumors (P = 0.01). No differences could be shown in urinary epinephrine and norepinephrine samplings. Tumor location was divided into 77 adrenal (81%) and 18 extra-adrenal (19%) sites. Malignant pheochromocytomas were located more often at extra-adrenal sites (P = 0.03). There was no increased incidence of malignancy in patients with familial bilateral pheochromocytomas or multiple endocrine neoplasia. Tumors greater than 80 g in weight corresponded to malignancy (P<0.0001). Dopamine tumor concentration was higher in malignant than in benign pheochromocytomas (P = 0.01). Persistent arterial hypertension occurred in 9 (13%) of 72 benign and 6 (60%) of 10 malignant pheochromocytomas (P = 0.001). The 10-year survival rate was 94% for benign pheochromocytomas. All patients with malignant pheochromocytomas died within this period (P = 0.0001).

CONCLUSIONS

High preoperative 24-hour urinary dopamine levels, extra-adrenal tumor location, high tumor weight, elevated tumor dopamine concentration, and postoperative persistent arterial hypertension are all factors that increase the likelihood of malignant pheochromocytoma. Patients with these characteristics should have more frequent follow-up evaluations to identify malignancy at earlier states.

The treatment of malignant pheochromocytoma with iodine-131 metaiodobenzylguanidine (131I-MIBG): a comprehensive review of 116 reported patients

Iodine-131 metaiodobenzylguanidine (131I-MIBG), a radiopharmaceutical agent used for scintigraphic localization of pheochromocytomas, has been employed to treat malignant pheochromocytomas since 1983 in a few specialized centers around the world. We review our clinical experience together with the published experience of 23 other centers in 10 countries, regarding the use of 1311-MIBG for treating patients with malignant adrenal pheochromocytomas or extra-adrenal paragangliomas. There were a total of 116 evaluable patients: 3 were from our current report and another 113 were reported in the literature from 1983 to 1996. A majority of the patients were selected for treatment based upon positive tracer uptake studies. The cumulative dose of 131I-MIBG administered ranged from 96 to 2,322 mCi (3.6 to 85.9 GBq), with a mean (+/-SD) of 490+/-350 mCi (18.1+/-13.0 GBq). The subjects received a mean single therapy dose of 158 mCi (5.8 GBq) and the number of doses administered ranged from 1 to 11, with a mean of 3.3+/-2.2 doses. Initial symptomatic improvement was achieved in 76% of patients, tumor responses in 30%, and hormonal responses in 45%. Five patients had complete tumor and hormonal responses, ranging from 16 to 58 months, which were sustained at the time of reporting. Patients with metastases to soft tissue had more favorable responses to treatment than those with metastases to bone. No difference was noted in the age between the responders and non-responders. Adverse effects, recorded in 41% of the treated patients, were generally mild except for one fatality from bone marrow aplasia. Among 89 patients with follow-up data, 45% of the responders had relapsed with recurrent or progressive disease after a mean interval of 29.3+/-31.1 months (median 19 months). Of patients with an initial response to 1311-MIBG, death was reported in 33% after a mean of 23.2+/-8.1 months (median 22 months) following treatment. Of non-responders, death was reported in 45% after a mean of 14.3+/-8.3 months (median 13 months). In conclusion, this review suggests that 131I-MIBG therapy may be a useful palliative adjunct in selected patients with malignant pheochromocytoma or paraganglioma. Although controlled studies are lacking, our review raises the hope that this therapeutic modality may prolong survival with an occasional sustained complete remission or possible cure.

Antiproliferative effect of suramin on primary cultures of human pheochromocytomas and rat PC12 pheochromocytoma cells

BACKGROUND

Suramin inhibits growth of neural crest-derived cells and is used to treat adrenocortical cancer and neuroblastoma in clinical trials. The antiproliferative effect of suramin was evaluated in primary cultures of human pheochromocytoma and the PC12 rat pheochromocytoma cell line in vitro and in vivo.

METHODS

Human pheochromocytoma and PC12 rat pheochromocytoma cells were grown in medium supplemented with suramin at concentrations of 1-1,000 micrograms/ml (1.43-1.43 mM) for up to five generations. Suramin did not induce neuronal differentiation, but inhibited growth of cultured human pheochromocytoma cells with IC50 (inhibitory concentration at which a 50% reduction of proliferation is observed) of 50-250 micrograms/ml. Also, suramin inhibited proliferation of PC12 cells with IC50 of 228 micrograms/ml after 5 days and 161 micrograms/ml at 10 days of treatment. Colony formation assays demonstrated these effects to be cytotoxic rather than cytostatic. Thus when reproductive integrity of PC12 cells was taken into account, IC50 was calculated with 118 micrograms/ml and 129 micrograms/ml, respectively. In vivo experiments were performed with subcutaneously xenotransplanted PC12 cells (BALB/c NCR-NU mice). Suramin did not alter tumorigenicity and did not inhibit local tumor growth.

RESULTS

These data determine for the first time an antiproliferative effect of suramin in pheochromocytoma cells. Suramin is cytotoxic to pheochromocytoma cells in vitro at levels that are clinically achievable.

CONCLUSIONS

Suramin may have potential as an antiproliferative drug in nonresectable pheochromocytoma.

Radiation therapy of metastatic pheochromocytoma: case report and review of the literature

Malignant pheochromocytomas are rare tumors, which are considered radioresistant on the basis of little information. We report a patient, with cranial nerve deficits from a pheochromocytoma metastatic to the parasellar region, who promptly responded to radiation therapy (2,500 cGy) with reversal of neurologic deficit. The disease recurred 2 years later and again promptly responded upon treatment to 2,000 cGy. Hepatic metastases were controlled for over 1 year with 3,240 cGy. The radiotherapy of pheochromocytoma and chemodectoma is reviewed, and the similarities between the two kinds of tumor are discussed. We speculate that a higher initial radiation dose might have resulted in a more sustained remission in our patient and recommend doses of 4,000-5,000 cGy if they can be safely administered, in 4-5 weeks for pheochromocytomas.

Metastatic phaeochromocytoma with a long-term response after iodine-131 metaiodobenzylguanidine therapy

Iodine-131 metaiodobenzylguanidine ([131I]MIBG), a radiopharmaceutical agent, is used for treating malignant phaeochromocytoma. [131I]MIBG therapy results in a hormone response rate of approximately 50%, but generally it yields only a partial or no tumour response. We present a case of a 46-year-old woman with a familial history of von Hippel-Lindau disease, who was treated with [131I]MIBG for a metastatic phaeochromocytoma involving the lungs, liver and bones. The patient received a cumulative dose of 33.3 GBq (900 mCi) and a complete hormone response was observed, as evaluated on the basis of catecholamine and metanephrine levels. Conventional radiography, computerized tomography and [131I]MIBG scintigraphy indicated that a near-complete tumour regression was achieved, with no evidence of relapse during a 4-year follow-up period. This case thus demonstrates that treatment with [131I]MIBG may lead to a dramatic tumour response in malignant phaeochromocytoma presenting both soft tissue and bone metastases.

Pheochromocytoma. Update on diagnosis, localization, and management

Pheochromocytoma, although rare, is associated with a high degree of morbidity and mortality if not recognized. A high degree of suspicion in patients with new-onset hypertension; hypertension with sudden worsening or development of diabetes mellitus; or a family history of MEN, neuroectodermal tumors, or simple pheochromocytoma should prompt biochemical confirmation with either 24-hour urine catecholamines (norepinephrine and epinephrine) or total MET (NMET plus MET). Following confirmation of the diagnosis, radiologic studies with CT and (if needed) MIBG are employed to localize the tumor. Surgical removal is the only definitive therapy. Medical management with alpha-blocking agents, to control symptoms and prevent a hypertensive crisis, is generally advocated for 2 weeks preoperatively and intraoperatively. Occasionally, beta-blockers, employed only after adequate alpha-blockade, are necessary to control tachycardia and tachyarrhythmias. High-dose MIBG and combination chemotherapy have been used adjunctively to treat malignant pheochromocytoma, although neither modality provides lasting satisfactory results. Normal urine assays performed 2 weeks postoperatively ensure the complete removal of all tumor. Additionally, lifelong follow-up (yearly initially) is necessary to detect any signs of benign recurrence or malignancy because these have been reported to occur as long as 41 years after the initial surgical resection. Biochemical evidence of excess catecholamine production usually precedes the clinical manifestations of catecholamine excess when these tumors recur.

Palliative treatment of neuroendocrine tumors

Effective palliation of patients with incurable neuroendocrine tumors requires both control of hormonal overproduction symptoms as well as control of tumor growth. Several important advances have been made in recent years toward these two goals. Octreotide and omeprazole have both been extremely effective in ameliorating hormonal symptoms of carcinoids, islet cell tumors and medullary thyroid carcinoma. Newer cytotoxic chemotherapy regimens and interferon have increased response rates over traditional therapy. More aggressive surgical extirpation of metastatic disease has also been beneficial.

Meta-iodobenzylguanidine in children

Meta-iodobenzylguanidine (MIBG) is an effective imaging agent for neuroblastoma and pheochromocytoma in children, MIBG is concentrated by the neurosecretory granules of normal and neoplastic tissues of neural crest origin. The typical normal scintigraphic uptake pattern of MIBG includes the salivary glands, lung, myocardium, liver, gastrointestinal tract, and contents of the urinary bladder. When MIBG is labeled with iodine-123 (123I), the adrenal glands often are seen. The sensitivity and specificity of MIBG imaging is extremely high in both neuroblastoma and pheochromocytoma. MIBG may detect extensive bone and bone marrow involvement in neuroblastoma, in the absence of findings on bone marrow aspiration and biopsy, plain radiographs, and bone scintigraphy. MIBG labeled with 131I has been used with moderate success in the palliation of advanced neuroblastoma and pheochromocytoma. Early therapeutic intervention in advanced neuroblastoma is promising. Current controversies in the application of MIBG include (1)131I versus 123I as a label for imaging studies: Although improved image quality and reduced absorbed radiation dose are achieved with [123I]MIBG imaging, is it actually more efficacious in the detection of neuroblastoma? (2) Use of bone scintigraphy in neuroblastoma: Given the small number of false-negative MIBG scans for bone involvement, can the bone scan be dropped as a routine study in the follow-up of neuroblastoma? (3) Other new imaging agents: Is there a role for labeled monoclonal antibodies, somatostatin analogs, and magnetic resonance imaging of marrow in the routine follow-up of neuroblastoma? (4) Iodine-125 MIBG therapy in neuroblastoma: Is the improved energy deposition of 125I at extremely short range useful in the ablation of micrometastases? (5) Early therapy with MIBG in neuroblastoma: Is there a role for MIBG therapy in the initial therapeutic regimens of children with advanced neuroblastoma? Twelve years after the initial report of its use in humans, MIBG has become an important imaging agent in pediatric neural tumors, one that is used routinely and efficaciously in many centers. In the next few years we will continue to learn more about its use, particularly in the therapy of advanced neural crest tumors.

Pheochromocytoma: 1926-1993

Pheochromocytoma is a tumor frequently sought and rarely found. It is associated with spectacular cardiovascular disturbances and, when correctly diagnosed and properly treated, it is curable; when undiagnosed or improperly treated, it can be fatal. Catecholamine-producing tumors that arise from chromaffin cells of the adrenal medulla and sympathetic ganglia are termed pheochromocytomas and paragangliomas, respectively. However, the term pheochromocytoma has become the generic name for all catecholamine-producing tumors. The biochemical diagnosis is straightforward. The localization of pheochromocytoma has been greatly facilitated by advances in computerized imaging and meta-iodobenzylguanidine scanning. Treatment with preoperative alpha- and beta-adrenergic blockade followed by surgical excision of the pheochromocytoma are associated with very low morbidity and mortality.