Eruption of Metastatic Paraganglioma After Successful Therapy with 177Lu/90Y-DOTATOC and 177Lu-DOTATATE

The heterobivalent (SSTR2/albumin) radioligand [67Cu]Cu-NODAGA-cLAB4-TATE enables efficient somatostatin receptor radionuclide theranostics

Somatostatin type 2 receptor (SSTR2) radionuclide therapy using β- particle-emitting radioligands has entered clinical practice for the treatment of neuroendocrine neoplasms (NENs). Despite the initial success of [177Lu]Lu‑DOTA-TATE, theranostic SSTR2 radioligands require improved pharmacokinetics and enhanced compatibility with alternative radionuclides. Consequently, this study evaluates the pharmacokinetic effects of the albumin-binding domain cLAB4 on theranostic performance of copper‑67-labeled NODAGA-TATE variants in an SSTR2-positive mouse pheochromocytoma (MPC) model. Methods: Binding, uptake, and release of radioligands as well as growth-inhibiting effects were characterized in cells grown as monolayers and spheroids. Tissue pharmacokinetics, absorbed tumor doses, and projected human organ doses were determined from quantitative SPECT imaging in a subcutaneous tumor allograft mouse model. Treatment effects on tumor growth, leukocyte numbers, and renal albumin excretion were assessed. Results: Both copper‑64- and copper‑67-labeled versions of NODAGA-TATE and NODAGA-cLAB4‑TATE showed similar SSTR2 binding affinity, but faster release from tumor cells compared to the clinical reference [177Lu]Lu‑DOTA-TATE. The bifunctional SSTR2/albumin-binding radioligand [67Cu]Cu‑NODAGA-cLAB4‑TATE showed both an improved uptake and prolonged residence time in tumors resulting in equivalent treatment efficacy to [177Lu]Lu‑DOTA-TATE. Absorbed doses were well tolerated in terms of leukocyte counts and kidney function. Conclusion: This preclinical study demonstrates therapeutic efficacy of [67Cu]Cu‑NODAGA-cLAB4‑TATE in SSTR2-positive tumors. As an intrinsic radionuclide theranostic agent, the radioligand provides stable radiocopper complexes and high sensitivity in SPECT imaging for prospective determination and monitoring of therapeutic doses in vivo. Beyond that, copper‑64- and copper‑61-labeled versions offer possibilities for pre- and post-therapeutic PET. Therefore, NODAGA-cLAB4-TATE has the potential to advance clinical use of radiocopper in SSTR2-targeted cancer theranostics.

Approach to the Patient: Concept and Application of Targeted Radiotherapy in the Paraganglioma Patient

Paragangliomas can metastasize, posing potential challenges both in symptomatic management and disease control. Systemic targeted radiotherapies using 131I-MIBG and 177Lu-DOTATATE are a mainstay in the treatment of metastatic paragangliomas. This clinical scenario and discussion aim to enhance physicians' knowledge of the stepwise approach to treat these patients with paraganglioma-targeted radiotherapies. It comprehensively discusses current approaches to selecting paraganglioma patients for targeted radiotherapies and how to choose between the two radiotherapies based on specific patient and tumor characteristics, when either therapy is feasible, or one is superior to another. The safety, efficacy, toxicity profiles, and optimization of these radiotherapies are also discussed, along with other therapeutic options including radiotherapies, available for patients besides these two therapies. Perspectives in radiotherapies of paraganglioma patients are outlined since they hold promising approaches in the near future that can improve patient outcomes.

Safety and efficacy of peptide receptor radionuclide therapy in neuroendocrine tumors: A single center experience

Peptide receptor radionucleotide therapy (PRRT) with 177Lu-dotatate is widely used for the treatment of patients with neuroendocrine tumors (NETs). We analyzed data from 104 patients with NETs treated with 177Lu -dotatate at a US academic center between December 2017 and October 2020 to better understand patterns of long-term efficacy, safety, and toxicity in the real-world setting. 177Lu-dotatate (200 mCi) was administered every eight weeks for four doses. The most common sites of primary disease were small intestine NETs (n = 49, 47%), pancreatic NETs (n = 32, 31%), and lung NETs (n = 7, 7%). Twenty-seven percent had Ki-67 <3%, 49% had Ki-67 between 3-20%, and 13.5% had Ki-67 >20%. The cohort had been pretreated with a median of two prior lines of treatment. Forty percent had received prior liver-directed treatment. Seventy-four percent of patients completed all four doses of treatment. The objective response rate was 18%. The median time-to-treatment failure/death was significantly longer for small-bowel NETs when compared to pancreatic NETs (37.3 months vs. 13.2 months, p = 0.001). In a multivariate model, Ki-67, primary site, and liver tumor burden ≥50% were found to independently predict time-to-treatment failure/death. Around 40% of patients experienced adverse events of ≥grade 3 severity. Treatment-related adverse events leading to discontinuation of therapy happened in 10% of patients. Preexisting mesenteric/peritoneal disease was present in 33 patients; seven of these patients developed bowel-related toxicities including two grade 5 events. We also report two cases of delayed-onset minimal change nephrotic syndrome, which occurred 14 and 27 months after the last dose of PRRT. Lastly, we describe six patients who developed rapid tumor progression in the liver leading to terminal liver failure within 7.3 months from the start of PRRT, and identify potential risk factors associated with this occurrence, which will need further study.

Improving susceptibility of neuroendocrine tumors to radionuclide therapies: personalized approaches towards complementary treatments

Radionuclide therapies are an important tool for the management of patients with neuroendocrine neoplasms (NENs). Especially [131I]MIBG and [177Lu]Lu-DOTA-TATE are routinely used for the treatment of a subset of NENs, including pheochromocytomas, paragangliomas and gastroenteropancreatic tumors. Some patients suffering from other forms of NENs, such as medullary thyroid carcinoma or neuroblastoma, were shown to respond to radionuclide therapy; however, no general recommendations exist. Although [131I]MIBG and [177Lu]Lu-DOTA-TATE can delay disease progression and improve quality of life, complete remissions are achieved rarely. Hence, better individually tailored combination regimes are required. This review summarizes currently applied radionuclide therapies in the context of NENs and informs about recent advances in the development of theranostic agents that might enable targeting subgroups of NENs that previously did not respond to [131I]MIBG or [177Lu]Lu-DOTA-TATE. Moreover, molecular pathways involved in NEN tumorigenesis and progression that mediate features of radioresistance and are particularly related to the stemness of cancer cells are discussed. Pharmacological inhibition of such pathways might result in radiosensitization or general complementary antitumor effects in patients with certain genetic, transcriptomic, or metabolic characteristics. Finally, we provide an overview of approved targeted agents that might be beneficial in combination with radionuclide therapies in the context of a personalized molecular profiling approach.

Case Report: Octreotide plus CVD chemotherapy for the treatment of multiple metastatic paragangliomas after double resection for functional bladder paraganglioma and urothelial papilloma

Background

Metastatic pheochromocytomas and paragangliomas are rare neuroendocrine tumors with a poor prognosis. Bladder paraganglioma concomitant with urothelial papilloma is even rarer. However, the rate of tumor response to cyclophosphamide-vincristine-dacarbazine (CVD) chemotherapy and 5-year overall survival for patients with metastatic PPGLs remained lower. We described, for the first time, a case of a patient with multiple metastatic bladder PGL who received octreotide LAR combined with CVD chemotherapy after urological surgery and then octreotide therapy was continued during follow-up.

Case presentation

A 43-year-old male patient was admitted to the urology department for frequent micturition syncope concomitant with malignant hypertension. Preoperative findings were elevated levels of normetanephrine in 24-h urine or plasma. CT and MRI indicated diagnosis of suspicious bladder paraganglioma. Transurethral resection of bladder tumor combined with laparoscopic partial cystectomy was performed successfully after preoperative phenoxybenzamine with aggressive volume repletion for 7 days. The result of postoperative pathology was immediate-risk functional bladder paraganglioma (T2N0M0, Stage II) concomitant with urothelial papilloma, and the immunohistochemistry results of PPGL were positive for Ki-67 (15%), SDHB, CgA, and SSTR2. The patient achieved enhanced recovery with normal urination and no syncope after surgery. However, the results of ¹⁸F-FDG and ¹⁸F-DOTATATE PET/CT found that the metastatic localizations of bladder PGLs were in the liver, lung, and bones at the 8th month after surgery. The patient received octreotide long-acting repeatable plus six courses of CVD chemotherapy for 6 months, and then octreotide therapy was continued every 3 months until now. Metastatic localizations were stable in CT scans, and vanillylmandelic acid in 24-h urine was maintained at lower levels during follow-up.

Conclusion

Octreotide long-acting repeatable plus CVD chemotherapy after surgery could achieve stable disease in the case with multiple metastatic bladder PGLs, and the following octreotide therapy could maintain a state of stable disease during the period of 6-month follow-up.

Performances of Functional and Anatomic Imaging Modalities in Succinate Dehydrogenase A-Related Metastatic Pheochromocytoma and Paraganglioma

Simple Summary

Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine cancers which carry the risk of metastatic disease. Pathogenic variants in the succinate dehydrogenase subunit A gene (SDHA) have been shown to cause metastatic disease, occurring in various regions of the body. Imaging is an early and vital step in the diagnosis and clinical care of these patients. The study here identifies which imaging modality among positron emission tomography (PET), computed tomography (CT), and magnetic resonance imaging (MRI) performs better in localizing metastatic PPGL lesions related to SDHA. The study identified that ⁶⁸Ga-DOTATATE PET/CT performed best at overall lesion detection; however, ¹⁸F-FDG PET/CT performed better in certain anatomic regions of the body. A combined approach with ⁶⁸Ga-DOTATATE and ¹⁸F-FDG would optimize care and guide clinicians in selecting the appropriate interventions and therapies.

Abstract

The study identifies the importance of positron emission tomographic (PET) and anatomic imaging modalities and their individual performances in detecting succinate dehydrogenase A (SDHA)-related metastatic pheochromocytoma and paraganglioma (PPGL). The detection rates of PET modalities—⁶⁸Ga-DOTATATE, ¹⁸F-FDG, and ¹⁸F-FDOPA—along with the combination of computed tomography (CT) and magnetic resonance imaging (MRI) are compared in a cohort of 11 patients with metastatic PPGL in the setting of a germline SDHA mutation. The imaging detection performances were evaluated at three levels: overall lesions, anatomic regions, and a patient-by-patient basis. ⁶⁸Ga-DOTATATE PET demonstrated a lesion-based detection rate of 88.6% [95% confidence interval (CI), 84.3–92.5%], while ¹⁸F-FDG, ¹⁸F-FDOPA, and CT/MRI showed detection rates of 82.9% (CI, 78.0–87.1%), 39.8% (CI, 30.2–50.2%), and 58.2% (CI, 52.0–64.1%), respectively. The study found that ⁶⁸Ga-DOTATATE best detects lesions in a subset of patients with SDHA-related metastatic PPGL. However, ¹⁸F-FDG did detect more lesions in the liver, mediastinum, and abdomen/pelvis anatomic regions, showing the importance of a combined approach using both PET modalities in evaluating SDHA-related PPGL.

Familial SDHB gene mutation in disseminated non-hypoxia-related malignant paraganglioma treated with [90Y]Y/[177Lu]Lu- DOTATATE

Familial paraganglioma may be related to mutations in succinate dehydrogenase (SDH) enzyme complex genes. Among patients with hereditary paraganglioma, SDH subunit B (SDHB) gene mutations are associated with the highest morbidity and mortality related to a higher malignancy rate. We report a family with the c.689G>A (p.Arg230His) mutation in the SDHB gene identified in two family members, a father and his daughter. While the 14-year-old daughter had no evidence of clinical disease, recurrent and later disseminated [¹³¹I]metaiodobenzylguanidine uptake-negative head and neck paraganglioma with multiple bone metastases developed in the father who underwent peptide receptor radionuclide therapy with [⁹⁰Y]Y/[¹⁷⁷Lu]Lu-dodecane tetraacetic acid octreotate (DOTATATE) at the time of the genetic diagnosis. This treatment was repeated 6 years later due to disease progression and the patient, who is currently 49 years old, remains alive and in good overall clinical condition at 8 years of follow-up after the original presentation at our unit. The growing armamentarium of imaging methods available for such patients may inform decision making regarding choice of the optimal treatment approach, potentially contributing to improved outcomes.

HIF2alpha-Associated Pseudohypoxia Promotes Radioresistance in Pheochromocytoma: Insights from 3D Models

Pheochromocytomas and paragangliomas (PCCs/PGLs) are rare neuroendocrine tumors arising from chromaffin tissue located in the adrenal or ganglia of the sympathetic or parasympathetic nervous system. The treatment of non-resectable or metastatic PCCs/PGLs is still limited to palliative measures, including somatostatin type 2 receptor radionuclide therapy with [¹⁷⁷Lu]Lu-DOTA-TATE as one of the most effective approaches to date. Nevertheless, the metabolic and molecular determinants of radiation response in PCCs/PGLs have not yet been characterized. This study investigates the effects of hypoxia-inducible factor 2 alpha (HIF2α) on the susceptibility of PCCs/PGLs to radiation treatments using spheroids grown from genetically engineered mouse pheochromocytoma (MPC) cells. The expression of Hif2α was associated with the significantly increased resistance of MPC spheroids to external X-ray irradiation and exposure to beta particle-emitting [¹⁷⁷Lu]LuCl₃ compared to Hif2α-deficient controls. Exposure to [¹⁷⁷Lu]LuCl₃ provided an increased long-term control of MPC spheroids compared to single-dose external X-ray irradiation. This study provides the first experimental evidence that HIF2α-associated pseudohypoxia contributes to a radioresistant phenotype of PCCs/PGLs. Furthermore, the external irradiation and [¹⁷⁷Lu]LuCl₃ exposure of MPC spheroids provide surrogate models for radiation treatments to further investigate the metabolic and molecular determinants of radiation responses in PCCs/PGLs and evaluate the effects of neo-adjuvant-in particular, radiosensitizing-treatments in combination with targeted radionuclide therapies.

Somatostatin Receptors and Analogs in Pheochromocytoma and Paraganglioma: Old Players in a New Precision Medicine World

Neuroendocrine tumors overexpress somatostatin receptors, which serve as important and unique therapeutic targets for well-differentiated advanced disease. This overexpression is a well-established finding in gastroenteropancreatic neuroendocrine tumors which has guided new medical therapies in the administration of somatostatin analogs, both "cold", particularly octreotide and lanreotide, and "hot" analogs, chelated to radiolabeled isotopes. The binding of these analogs to somatostatin receptors effectively suppresses excess hormone secretion and tumor cell proliferation, leading to stabilization, and in some cases, tumor shrinkage. Radioisotope-labeled somatostatin analogs are utilized for both tumor localization and peptide radionuclide therapy, with ⁶⁸Ga-DOTATATE and ¹⁷⁷Lu-DOTATATE respectively. Benign and malignant pheochromocytomas and paragangliomas also overexpress somatostatin receptors, irrespective of embryological origin. The pattern of somatostatin receptor overexpression is more prominent in succinate dehydrogenase subunit B gene mutation, which is more aggressive than other subgroups of this disease. While the Food and Drug Administration has approved the use of ⁶⁸Ga-DOTATATE as a radiopharmaceutical for somatostatin receptor imaging, the use of its radiotherapeutic counterpart still needs approval beyond gastroenteropancreatic neuroendocrine tumors. Thus, patients with pheochromocytoma and paraganglioma, especially those with inoperable or metastatic diseases, depend on the clinical trials of somatostatin analogs. The review summarizes the advances in the utilization of somatostatin receptor for diagnostic and therapeutic approaches in the neuroendocrine tumor subset of pheochromocytoma and paraganglioma; we hope to provide a positive perspective in using these receptors as targets for treatment in this rare condition.

Targeted Radionuclide Therapy in Patient-Derived Xenografts Using 177Lu-EB-RGD

Currently, most patients with non-small cell lung cancer (NSCLC) are diagnosed in advanced stages with a poor five-year survival rate. Therefore, intensive research aimed at finding novel therapeutic strategies has been ongoing; experimental models that reliably emulate NSCLC disease are greatly needed to predict responses to novel therapeutics. Therefore, we developed patient-derived xenograft (PDX) models of NSCLC, which we then used to evaluate the therapeutic efficacy of ¹⁷⁷Lu-EB-RGD, a peptide-based radiopharmaceutical with improved pharmacokinetics that targets integrin α_vβ₃ In this study, three different groups of NSCLC-PDXs were successfully established, all of which maintained the same IHC and genetic characteristics of the human primary tumor. The two NSCLC-PDX groups with intense and low expression of integrin α_vβ₃ (denoted as PDX_αvβ3+ and PDX_αvβ3-) were chosen as the experimental models to evaluate the in vivo biological behavior of ¹⁷⁷Lu-EB-RGD. In SPECT imaging and biodistribution studies, ¹⁷⁷Lu-EB-RGD showed significantly higher accumulation in PDX_αvβ3+ and PDX_αvβ3- models than its corresponding monomer ¹⁷⁷Lu-RGD. A single dose of 18.5 MBq ¹⁷⁷Lu-EB-RGD was enough to completely eradicate the tumors in PDX_αvβ3+, with no sign of tumor recurrence during the observation period. Such treatment was also efficacious in PDX_αvβ3-: a single dose of 29.6 MBq ¹⁷⁷Lu-EB-RGD led to a significant delay in tumor growth as compared with that in the control or ¹⁷⁷Lu-RGD group. The preclinical data from the use of this model suggest that ¹⁷⁷Lu-EB-RGD may be an effective treatment option for NSCLC and should be further evaluated in human trials.

Molecular imaging and radionuclide therapy of pheochromocytoma and paraganglioma in the era of genomic characterization of disease subgroups

In recent years, advancement in genetics has profoundly helped to gain a more comprehensive molecular, pathogenic, and prognostic picture of pheochromocytomas and paragangliomas (PPGLs). Newly discovered molecular targets, particularly those that target cell membranes or signaling pathways have helped move nuclear medicine in the forefront of PPGL precision medicine. This is mainly based on the introduction and increasing experience of various PET radiopharmaceuticals across PPGL genotypes quickly followed by implementation of novel radiotherapies and revised imaging algorithms. Particularly, 68Ga-labeled-SSAs have shown excellent results in the diagnosis and staging of PPGLs and in selecting patients for PRRT as a potential alternative to 123/131I-MIBG theranostics. PRRT using 90Y/177Lu-DOTA-SSAs has shown promise for treatment of PPGLs with improvement of clinical symptoms and/or disease control. However, more well-designed prospective studies are required to confirm these findings, in order to fully exploit PRRT's antitumoral properties to obtain the final FDA approval. Such an approval has recently been obtained for high-specific-activity 131I-MIBG for inoperable/metastatic PPGL. The increasing experience and encouraging preliminary results of these radiotherapeutic approaches in PPGLs now raises an important question of how to further integrate them into PPGL management (e.g. monotherapy or in combination with other systemic therapies), carefully taking into account the PPGLs locations, genotypes, and growth rate. Thus, targeted radionuclide therapy (TRT) should preferably be performed at specialized centers with an experienced interdisciplinary team. Future perspectives include the introduction of dosimetry and biomarkers for therapeutic responses for more individualized treatment plans, α-emitting isotopes, and the combination of TRT with other systemic therapies.