A Durable Response With the Combination of Nivolumab and Cabozantinib in a Patient With Metastatic Paraganglioma: A Case Report and Review of the Current Literature

The Immune Landscape of Pheochromocytoma and Paraganglioma: Current Advances and Perspectives

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from neural crest cells from adrenal medullary chromaffin tissues and extra-adrenal paraganglia, respectively. Although the current treatment for PPGLs is surgery, optimal treatment options for advanced and metastatic cases have been limited. Hence, understanding the role of the immune system in PPGL tumorigenesis can provide essential knowledge for the development of better therapeutic and tumor management strategies, especially for those with advanced and metastatic PPGLs. The first part of this review outlines the fundamental principles of the immune system and tumor microenvironment, and their role in cancer immunoediting, particularly emphasizing PPGLs. We focus on how the unique pathophysiology of PPGLs, such as their high molecular, biochemical, and imaging heterogeneity and production of several oncometabolites, creates a tumor-specific microenvironment and immunologically "cold" tumors. Thereafter, we discuss recently published studies related to the reclustering of PPGLs based on their immune signature. The second part of this review discusses future perspectives in PPGL management, including immunodiagnostic and promising immunotherapeutic approaches for converting "cold" tumors into immunologically active or "hot" tumors known for their better immunotherapy response and patient outcomes. Special emphasis is placed on potent immune-related imaging strategies and immune signatures that could be used for the reclassification, prognostication, and management of these tumors to improve patient care and prognosis. Furthermore, we introduce currently available immunotherapies and their possible combinations with other available therapies as an emerging treatment for PPGLs that targets hostile tumor environments.

Anlotinib for Metastatic Progressed Pheochromocytoma and Paraganglioma: A Retrospective Study of Real-World Data

Introduction

Pheochromocytomas (PCC) and paragangliomas (PGL) (collectively PPGL) are a type of rare hypervascular neuroendocrine tumors that are very challenging to treat. This study aimed to determine the efficacy and safety of the multi-tyrosine kinase inhibitor anlotinib for the treatment of locally advanced or metastatic (LA/M) PPGL.

Methods

A total of 37 eligible patients with unresectable or progressive LA/M PPGL were enrolled. Of them, 27 patients received anlotinib alone (n = 19) or in combination (n = 8) with radionuclide therapies, including peptide receptor radionuclide therapy (PRRT) and iodine 131 meta-iodobenzylguanidine (131I-MIBG). The primary endpoints included objective response rate (ORR), defined as partial response (PR) or complete response (CR), and disease-control rate, defined as PR, CR, or stable disease (SD). The secondary endpoints were progression-free survival (PFS), duration of response, and drug safety.

Results

In the efficacy evaluation for all 27 patients, the ORR was 44.44% (95% CI: 24.4%-64.5%) and disease-control rate was 96.29% (95% CI: 88.7%-100%). Twelve cases (44.44%) achieved PR, 14 (51.85%) SD. The median PFS was 25.2 months (95% CI: 17.2 months to not reached). PFS was shorter in the anlotinib monotherapy group than in the group receiving anlotinib in combination with radionuclide therapy (P = .2). There were no serious treatment-related AEs.

Conclusion

Anlotinib monotherapy or in combination with radionuclide therapies shows promising efficacy and safety for the treatment of LA/M PCC and PGL. Multi-tyrosine kinase inhibitors might represent a novel therapeutic strategy for patients with PPGL; however, large-scale prospective randomized, blinded, controlled clinical research studies are required.

Cabozantinib for different endocrine tumours: killing two birds with one stone. A systematic review of the literature

PURPOSE

Cabozantinib is an oral multi-tyrosine kinase inhibitor (TKI) that has been approved in Europe for advanced renal cell carcinoma, hepatocellular carcinoma, locally advanced and metastatic medullary thyroid carcinoma (MTC) and radioiodine-refractory differentiated thyroid cancer. Merkel cell carcinoma (MCC) is a rare and highly aggressive cutaneous malignant neuroendocrine tumour that usually presents in sun-exposed skin areas of immunosuppressed patients. Conflicting data exist about cabozantinib for MCC and this TKI is currently under investigation in several onco-endocrine frameworks.

METHODS

We herein report a case of an 83-year-old man who was diagnosed with MCC during the treatment of an advanced metastatic MTC. The diagnosis of MCC was established based on clinical, histopathologic evaluation and immunohistochemistry. A systematic review of the literature on cabozantinib use for advanced endocrine and neuroendocrine tumours has been performed.

RESULTS

The patient was initially treated with surgery and adjuvant radiotherapy. Cabozantinib was therefore started to control both MTC and MCC. After 24 months, no sign of local or metastatic MCC relapse was evidenced.

CONCLUSION

Promising data on cabozantinib treatment for endocrine and neuroendocrine neoplasms is recently emerging in the literature. In our clinical case, we reported that, besides the good response for the MTC, cabozantinib also seems to effectively control metastatic MCC, along with efficient surgery and adjuvant radiotherapy. Further investigations are needed to determine the efficacy and safety of cabozantinib in MCC patients and in off-label endocrine tumours.

Efficacy and Safety of Tyrosine Kinase Inhibitors in Patients with Metastatic Pheochromocytomas/Paragangliomas

CONTEXT

Tyrosine kinase inhibitors (TKIs) can be used to treat locally unresectable or distantly metastatic pheochromocytomas/paragangliomas (PPGLs), such as sunitinib, according to the National Comprehensive Cancer Network guidelines in 2022. However, the precise effect of different TKIs in metastatic PPGLs is still unclear.

OBJECTIVE

The aim of this meta-analysis is to assess the efficacy and safety of TKIs in metastatic PPGLs.

METHODS

The PubMed, Cochrane Library, Scopus, Clinical Trial, and Embase databases were searched by synonyms of 48 TKIs and metastatic PPGLs from inception up to August 2022. Outcomes were tumor response or survival data and the incidence of adverse events (AEs) after treatment. The MIONRS scale and the JBI's tools for case series were used for interventional and observational studies to assess risk of bias, respectively. The combined effects with fixed- or random-effect models, the combined median with the weighted median of medians method and their 95% CIs were reported.

RESULTS

A total of 7 studies with 160 patients were included. Tumor responses in metastatic PPGLs in 5 studies with available data showed the pooled proportion of partial response (PR), stable disease, and disease control rate (DCR) of, respectively, 0.320 (95% CI 0.155-0.486), 0.520 (95% CI 0.409-0.630), and 0.856 (95% CI 0.734-0.979). The combined median progressive-free survival in 6 studies was 8.9 months (95% CI 4.1-13.5) and the proportion of those who discontinued due to AEs in 5 studies was 0.143 (95% CI 0.077-0.209).

CONCLUSION

This meta-analysis suggests that patients with metastatic PPGLs can benefit from TKI therapy with PR and DCR up to more than 30% and 80%. However, because of restricted studies, larger clinical trials should be performed in the future.

Pseudohypoxia in paraganglioma and pheochromocytoma is associated with an immunosuppressive phenotype

Metastatic pheochromocytoma and paraganglioma (PPGL) have poor prognosis and limited therapeutic options. The recent advent of immunotherapies showing remarkable clinical efficacies against various cancer types offers the possibility of novel opportunities also for metastatic PPGL. Most PPGLs are pathogenically linked to inactivating mutations in genes encoding different succinate dehydrogenase (SDH) subunits. This causes activation of the hypoxia-inducible factor 2 (HIF2)-mediated transcriptional program in the absence of decreased intratumoral oxygen levels, a phenomenon known as pseudohypoxia. Genuine hypoxia in a tumor creates an immunosuppressive tumor microenvironment. However, the impact of pseudohypoxia in the immune landscape of tumors remains largely unexplored. In this study, tumoral expression of programmed death-ligand 1 (PD-L1) and HIF2α and tumor infiltration of CD8 T lymphocytes (CTLs) were examined in PPGL specimens from 102 patients. We assessed associations between PD-L1, CTL infiltration, HIF2α expression, and the mutational status of SDH genes. Our results show that high PD-L1 expression levels in tumor cells and CTL tumor infiltration were more frequent in metastatic than nonmetastatic PPGL. However, this phenotype was negatively associated with SDH mutations and high HIF2α protein expression. These data were validated by analysis of mRNA levels of genes expressing PD-L1, CD8, and HIF2α in PPGL included in The Cancer Genome Atlas database. Further, PD-L1 and CD8 expression was lower in norepinephrine than epinephrine-secreting PPGL. This in silico analysis also revealed the low PD-L1 or CD8 expression levels in tumors with inactivating mutations in VHL or activating mutations in the HIF2α-coding gene, EPAS1, which, together with SDH-mutated tumors, comprise the pseudohypoxic molecular subtype of PPGL. These findings suggest that pseudohypoxic tumor cells induce extrinsic signaling toward the immune cells promoting the development of an immunosuppressive environment. It also provides compelling support to explore the differential response of metastatic PPGL to immune checkpoint inhibitors. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Targeted Therapies in Pheochromocytoma and Paraganglioma

Molecular targeted therapy plays an increasingly important role in the treatment of metastatic pheochromocytomas and paragangliomas (PPGLs), which are rare tumors but remain difficult to treat. This mini-review provides an overview of established molecular targeted therapies in present use, and perspectives on those currently under development and evaluation in clinical trials. Recently published research articles, guidelines, and expert views on molecular targeted therapies in PPGLs are systematically reviewed and summarized. Some tyrosine kinase inhibitors (sunitinib, cabozantinib) are already in clinical use with some promising results, but without formal approval for the treatment of PPGLs. Sunitinib is the only therapeutic option which has been investigated in a randomized placebo-controlled clinical trial. It is clinically used as a first-, second-, or third-line therapeutic option for the treatment of progressive metastatic PPGLs. Some other promising molecular targeted therapies (hypoxia-inducible factor 2 alpha [HIF2α] inhibitors, tumor vaccination together with checkpoint inhibitors, antiangiogenic therapies, kinase signaling inhibitors) are under evaluation in clinical trials. The HIF2α inhibitor belzutifan may prove to be particularly interesting for cluster 1B-/VHL/EPAS1-related PPGLs, whereas antiangiogenic therapies seem to be primarily effective in cluster 1A-/SDHx-related PPGLs. Some combination therapies currently being evaluated in clinical trials, such as temozolomide/olaparib, temozolomide/talazoparib, or cabozantinib/atezolizumab, will provide data for novel therapy for metastatic PPGLs. It is likely that advances in such molecular targeted therapies will play an essential role in the future treatment of these tumors, with more personalized therapy options paving the way towards improved therapeutic outcomes.

Endocrine and Neuroendocrine Tumors Special Issue—Checkpoint Inhibitors for Adrenocortical Carcinoma and Metastatic Pheochromocytoma and Paraganglioma: Do They Work?

Adrenocortical cancers and metastatic pheochromocytomas are the most common malignancies originating in the adrenal glands. Metastatic paragangliomas are extra-adrenal tumors that share similar genetic and molecular profiles with metastatic pheochromocytomas and, subsequently, these tumors are studied together. Adrenocortical cancers and metastatic pheochromocytomas and paragangliomas are orphan diseases with limited therapeutic options worldwide. As in any other cancers, adrenocortical cancers and metastatic pheochromocytomas and paragangliomas avoid the immune system. Hypoxia-pseudohypoxia, activation of the PD-1/PD-L1 pathway, and/or microsatellite instability suggest that immunotherapy with checkpoint inhibitors could be a therapeutic option for patients with these tumors. The results of clinical trials with checkpoint inhibitors for adrenocortical carcinoma or metastatic pheochromocytoma or paraganglioma demonstrate limited benefits; nevertheless, these results also suggest interesting mechanisms that might enhance clinical responses to checkpoint inhibitors. These mechanisms include the normalization of tumor vasculature, modification of the hormonal environment, and vaccination with specific tumor antigens. Combinations of checkpoint inhibitors with classical therapies, such as chemotherapy, tyrosine kinase inhibitors, radiopharmaceuticals, and/or novel therapies, such as vaccines, should be evaluated in clinical trials.

Mutational Profile and Potential Molecular Therapeutic Targets of Pheochromocytoma

PURPOSE

Pheochromocytoma/paraganglioma (PCC/PGL; collectively known as PPGL) can be driven by germline and somatic mutations in susceptibility genes. We aimed to investigate the mutation profile and clinical features of pathogenic genes in highly genetically heterogeneous PPGL and to preliminary explore molecular therapeutic targets in PPGL.

METHODS

We established a panel of 260 genes, including susceptibility genes of PPGL and other important tumorigenic genes to sequence 107 PPGL tissues.

RESULTS

Overall, 608 genomic mutations were identified in 107 PPGL tissues. Almost 57% of PPGL tissue samples exhibited pathogenic mutations, and the most frequently mutated gene was SDHB (15/107, 14%). SDHB and HRAS were the most commonly mutated genes in germline-mutated PPGL (25/107, 23%) and nongermline-mutated PPGL (36/107, 34%), respectively. In addition, novel pathogenic mutations were detected in sporadic PPGL. PPGL with mutations in the hypoxia pathway had an earlier onset and higher norepinephrine level than those in the kinase pathway. Receptor tyrosine kinase (RTK; 22%, 24/107), mitogen-activated protein kinase (MAPK; 14%, 15/107), and tyrosine kinase (TK; 2%, 2/107) pathways were the most frequently mutated pathways in PPGL.

CONCLUSION

Our results provided the genetic mutation profile in PPGL tissues. Genetic mutations in PPGL were mainly concentrated in the RTK, TK, and MAPK pathways, suggesting potential molecular therapeutic targets for PPGL.