Recent guidelines for diagnostic and therapeutic management of accidentally detected adrenal tumours (incidentaloma) in adults.

At the end of 2023, the European Journal of Endocrinology published the latest guidelines of the European Society of Endocrinology (ESE) on the management of accidentally detected adrenal tumours (incidentalomas) in adults. Comparing them with the previous version of the ESE recommendations from 2016, a tendency towards far-reaching individualisation of the therapeutic and diagnostic approach in patients with adrenal incidentaloma can be seen - it is reflected by changes in the initial assessment of the malignancy of the lesion, in the scope of the proposed hormonal assessment, and qualification for surgery. The latest version of the guidelines includes 9 completely new recommendations, and 5 more recommendations have been significantly changed. Among the most important changes, the introduction of the term "mild autonomous cortisol secretion" (MACS) instead of the previously used term "autonomous cortisol secretion (ACS)" along with more precise recommendations regarding its management should be emphasised. An important novelty is also the modification of the criteria for benign adrenal adenoma, which does not require further imaging observation - due to the results of recent clinical studies, the authors have removed the criteria of size below 4 cm from the definition. Among others, the guidelines also encourage more proactive surgical treatment of indeterminate adrenal incidentaloma in people < 40 years of age and pregnant women. The authors of the recommendations repeatedly accentuate the importance of a multidisciplinary approach in making decisions regarding further management of patients with an unspecified adrenal tumour. Despite a few significant differences compared to the previous version of guidelines, the authors emphasise the presence of gaps in the current scientific evidence, which would not allow for the formulation of more unambiguous recommendations. The need to optimise ordered diagnostic tests, which generate additional socio-economic burdens without negative impact on patients' health, is also an important aspect of the latest guidelines.

Prevention and management of hypertensive crises in children with pheochromocytoma and paraganglioma.

Hypertensive crises in pediatric patients are rare conditions. However, determining their precise prevalence is more challenging than in adults due to the heterogeneity in the definition itself. These crises frequently occur without a prior diagnosis of hypertension and may indicate an underlying cause of secondary hypertension, including pheochromocytoma/paraganglioma (PPGL). The mechanisms of hypertensive crises in the pediatric population with PPGL are directly related to different types of catecholamine excess. Noradrenergic tumors typically present with sustained hypertension due to their predominant action on α1-adrenoceptors in the vasculature. Conversely, adrenergic tumors, through epinephrine binding to ß2-adrenoceptors in addition to stimulation of α1- and α2-adrenoceptors, more frequently cause paroxysmal hypertension. Furthermore, the biochemical phenotype also reflects the tumor localization and the presence of a genetic mutation. Recent evidence suggests that more than 80% of PPGL in pediatric cases have a hereditary background. PPGL susceptibility mutations are categorized into three clusters; mutations in cluster 1 are more frequently associated with a noradrenergic phenotype, whereas those in cluster 2 are associated with an adrenergic phenotype. Consequently, the treatment of hypertensive crises in pediatric patients with PPGL, reflecting the underlying pathophysiology, requires first-line therapy with alpha-blockers, potentially in combination with beta-blockers only in the case of tachyarrhythmia after adequate alpha-blockade. The route of administration for treatment depends on the context, such as intraoperative or pre-surgical settings, and whether it presents as a hypertensive emergency (elevated blood pressure with acute target organ damage), where intravenous administration of antihypertensive drugs is mandatory. Conversely, in cases of hypertensive urgency, if children can tolerate oral therapy, intravenous administration may initially be avoided. However, managing these cases is complex and requires careful consideration of the selection and timing of therapy administration, particularly in pediatric patients. Therefore, facing these conditions in tertiary care centers through interdisciplinary collaboration is advisable to optimize therapeutic outcomes.

SDHA-related phaeochromocytoma and paraganglioma: review and clinical management.

Phaeochromocytomas and paragangliomas (collectively termed PPGL) are rare yet highly heritable neuroendocrine tumours, with over one-third of cases associated with germline pathogenic variants (PVs) in numerous genes. PVs in the succinate dehydrogenase subunit-A gene (SDHA) were initially implicated in hereditary PPGL in 2010, and SDHA has since become an important susceptibility gene accounting for up to 2.8% of cases. However, it remains poorly understood, particularly regarding the clinical nature of SDHA PPGL, rates of recurrence and metastasis, and the nature of metastatic disease. We present a narrative review of SDHA-related PPGL, covering pathophysiology, relevance to current clinical practice, and considerations for clinical genetics. We analyse a pool of 107 previously reported cases of SDHA-associated PPGL to highlight the spectrum of SDHA-related PPGL. Our analysis demonstrates that SDHA PPGL occurs across a wide age range (11-81 years) and affects men and women equally. SDHA PPGL typically presents as single tumours (91%), usually occurring in the head and neck (46%) or abdomen (43%, including 15% with phaeochromocytomas). Metastatic disease was reported in 25.5% of cases, with bone (82%) and lymph nodes (71%) being the most common sites of metastasis, often identified many years after the initial diagnosis. A family history of SDHA-related neoplasia was rare, reported in only 4% of cases. Understanding the clinical nature and risks associated with SDHA PVs is essential for facilitating the optimal management of patients and their families.

Metastatic pheochromocytoma and paraganglioma: Integrating tumor biology in clinical practice.

Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors derived from chromaffin cells in the autonomic nervous system. Depending on their location, these tumors are capable of excessive catecholamine production, which may lead to uncontrolled hypertension and other life-threatening complications. They are associated with a significant risk of metastatic disease and are often caused by an inherited germline mutation. Although surgery can cure localized disease and lead to remission, treatments for metastatic PPGL (mPPGL)-including chemotherapy, radiopharmaceutical agents, multikinase inhibitors, and immunotherapy used alone or in combination- aim to control tumor growth and limit organ damage. Substantial advances have been made in understanding hereditary and somatic molecular signaling pathways that play a role in tumor growth and metastasis. Treatment options for metastatic disease are rapidly evolving, and this paper aims to provide a brief overview of the management of mPPGL with a focus on therapy options.

[Diagnosis and management of patients with pheochromocytoma/paraganglioma: Consensus of experts of the Russian Medical Society for Arterial Hypertension and the Multidisciplinary Group for the Diagnosis and Treatment of Neuroendocrine Tumors].

The understanding of the nature of catecholamine-secreting tumors has changed significantly in recent years, affecting terminology and classification. Phaeochromocytoma/paraganglioma (PCC/PG) is a rare neuroendocrine tumor from chromaffin tissue that produces and secretes catecholamines. The incidence of PCC/PG is relatively low, with 2-8 cases per 1 million population per year; among patients with arterial hypertension, their prevalence is 0.2-0.6%. However, delayed diagnosis of PCC/PG is associated with a high risk of cardiovascular complications and a high mortality rate. The consensus presents the clinical manifestations of the disease with an emphasis on the course of arterial hypertension as the most common symptom in PCC/PG; modern ideas about the features of diagnosis, aspects of preoperative preparation, treatment, and follow-up of patients with PCC/PG are considered.

Adrenal Pathologies.

Adrenal pathologies have variable clinical presentations and primary care providers should be aware of common and serious adrenal disorders. All adrenal masses require evaluation for malignancy, whether primary or metastatic, and all masses require evaluation for inappropriate hormonal secretion. In the event of adrenal insufficiency, the etiology of cortisol inadequacy must be identified and appropriately treated to prevent life-threatening complications.

Multiple Endocrine Neoplasia Type 1, Type 2A, and Type 2B.

Multiple endocrine neoplasia type 1 is a rare genetic neuroendocrine syndrome caused by over 1500 different germline mutations. It can cause 20 different endocrine tumors affecting primarily the parathyroid glands, gastroenteropancreatic tract, and the anterior pituitary gland. Multiple endocrine neoplasia type 2A (MEN2A) and Multiple endocrine neoplasia type 2B (MEN2B) are autosomal dominant genetic syndromes because of a germline variant in the 'rearranged during transfection' (RET) proto-oncogene. There are common RET mutations causing receptor hyperactivation and induction of downstream signals that cause oncogenesis. Common conditions with MEN2A are medullary thyroid cancer (MTC), pheochromocytoma, and primary hyperparathyroidism. Common conditions with MEN2B include MTC, pheochromocytomas, and benign ganglioneuromas.

Neuroendocrine Neoplasms.

Neuroendocrine neoplasms (NENs), also known as neuroendocrine tumors (NETs), are rare tumors derived from cells with characteristics of both nerve and endocrine cells. The clinical presentation, diagnosis, and treatment of NENs vary significantly depending on the type, location, whether the neoplasm is hormonally functional, how aggressive it is, and whether it has metastasized to other parts of the body. This article provides an overview of specific types of NETs, clinical presentations and related syndromes, diagnosis, and approach to management of common NENs.

Management of metastatic pheochromocytomas and paragangliomas: when and what.

Recently, the treatment landscape for metastatic pheochromocytomas and paragangliomas (MPPGL) has seen both progress and setbacks. We provide an up-to-date review of the multimodality management of MPPGL and discuss novel opportunities and current challenges in the treatment landscape. Given the unique clinical presentation of MPPGL, we discuss the management of hormone-related clinical sequelae and traditional modalities of therapy. Advances in the understanding of the molecular biology of these diverse tumors have enabled novel strategies such as augmenting DNA damage by targeted delivery of radionuclides such as 131I and 177Lu, abrogating tumor angiogenesis, hypoxia resistance, and DNA damage repair. Despite progress, we address the significant challenges still faced by patients and researchers engaged in efforts to improve outcomes in these rare cancers.

Adverse skeletal related events in patients with bone-metastatic pheochromocytoma/paraganglioma.

Metastatic pheochromocytomas and paragangliomas (PPGLs) are frequently associated with skeletal complications. Primary objective: to describe the frequency of adverse skeletal related events (SREs) in PPGL patients with bone metastases (BMs). Secondary objectives: to 1) identify predictive and prognostic factors for SREs and 2) obtain information on the effectiveness of bone resorption inhibitors in reducing SRE risk and improving outcomes in term of survival and SREs time onset. In this retrospective multicenter, multinational study, 294 PPGL patients were enrolled. SREs occurred in 90 patients (31 %). Fifty-five patients (19 %) had bone fractures, 47 (16 %) had spinal cord compression, and 11 (4 %) had hypercalcemia. Twenty-two patients (7 %) had more than one SRE. Sixty-four patients (22 %) underwent surgery, and 136 (46 %) underwent radiotherapy. SREs occurred a median of 4.4 months after diagnosis of BM (range, 0-246.6 months). Independent factors associated with reduced risk of SREs in multivariable analysis were I-131-MIBG radionuclide therapy (hazard ratio [HR], 0.536 [95 % CI, 0.309-0.932]; P = .027) and absence of liver metastases (HR, 0.638 [95 % CI, 0.410-0.992]; P = .046). The median overall survival duration was 5.3 year. In multivariable analysis, age younger than 48 years at PPGL diagnosis (HR, 0.558 [95 % CI, 0.3877-0.806]; P = .002), absence of liver metastases (HR, 0.618 [95 % CI, 0.396-0.965]; P = .034), treatment with bisphosphonates or denosumab (HR, 0.598 [95 % CI, 0.405-0.884]; P = .010), and MIBG radionuclide therapy (HR, 0.444 [95 % CI, 0.274-0.718]; P = .001) were associated with a reduced risk of death. SREs occur frequently and early in bone-metastatic PPGL patients but do not negatively impact survival. MIBG radionuclide therapy and treatment with bone resorption inhibitors are associated with favorable outcome.

Management of Pheochromocytomas and Paragangliomas.

Pheochromocytomas and paragangliomas are distinctive neuroendocrine tumors which frequently produce excess catecholamines with resultant cardiovascular morbidity. These tumors have a strong genetic component, with up to 40% linked to hereditary pathogenic variants; therefore, germline genetic testing is recommended for all patients. Surgical resection offers the only potential cure in the case of localized disease. Given the potential for catecholaminergic crises, appropriate perioperative management is crucial, and all patients should undergo alpha-adrenergic blockade before resection. Therapeutic options for metastatic disease are limited and include surgical debulking, radiopharmaceutical therapies, and conventional chemotherapy.

[Adrenal tumors: current standards in clinical management]. / Nebennierentumoren ­ aktuelle Standards im klinischen Management.

Adrenal tumors are among the most common tumors in humans. They are most frequently discovered incidentally during abdominal imaging for other reasons or due to clinical symptoms (e.g. Conn's or Cushing's syndrome, pheochromocytoma or androgen excess). Although over 80% of adrenal tumors are benign, in cases of hormone excess, they are associated with significantly increased morbidity. In highly malignant adrenocortical carcinoma (ACC), early diagnosis is of particular prognostic relevance. Therefore, this review presents the diagnostic procedure for what are referred to as adrenal incidentalomas and provide recommendations for the management of ACC and pheochromocytomas/paragangliomas (PPGL). In primary diagnosis, sufficient hormone diagnostics is required for all adrenal tumors, as this is the only way to identify all patients with relevant hormone excess. Imaging has increasingly improved in recent years and allows a reliable assessment of the tumor's malignancy in most cases. Imaging of first choice is unenhanced computed tomography (CT), while magnetic resonance imaging (MRI) and fluorodeoxyglucose-18 positron emission tomography (FDG-PET/CT) are reserved for special situations, as published evidence on these procedures is more limited. The treatment of ACC and PPGL is complex and is carried out on an interdisciplinary basis at specialized centers. In the case of localized disease, surgery is the only curative treatment option. There are now clear recommendations for individualized adjuvant therapy for ACC. In metastatic disease, mitotane with or without platinum-containing chemotherapy is the standard. Other lines of therapy should be discussed with a reference center. Over 35% of PPGL have a germline mutation; therefore, genetic testing should be offered. In metastatic PPGL, an individual decision is required between active surveillance, radionuclide therapy, sunitinib or chemotherapy.

Comparison of adrenalectomy with conservative treatment on mild autonomous cortisol secretion: a systematic review and meta-analysis.

Objective: This systematic review and meta-analysis was conducted to compare the benefits of adrenalectomy and conservative treatment for comorbidities associated with mild autonomous cortisol secretion (MACS) in patients diagnosed with MACS. Background: MACS is the most common benign hormone-secreting functional adrenal incidentaloma. Overproduction of cortisol is observed in MACS patients, resulting in a variety of long-term health issues, including arterial hypertension (HTN), diabetes mellitus (DM), dyslipidemia, obesity, and osteoporosis; however, the classic clinical manifestations of Cushing's syndrome (CS) are not present. Methods: A systematic search was conducted using MEDLINE, Embase, Web of Sciences, and Scopus databases on December, 2023. Two reviewers independently extracted data and assessed the quality of the included articles. A meta-analysis was performed to compare the beneficial effects of adrenalectomy versus conservative management for MACS-related comorbidities. Results: Fifteen articles were included in this study, which evaluated 933 MACS patients (384 Adrenalectomy and 501 Conservative treatment, and 48 excluded due to incomplete follow-up duration). MACS diagnosis criteria were different among the included articles. All studies, however, stated that there must be no overt CS symptoms. Meta-analysis demonstrates the overall advantage of adrenalectomy over conservative treatment for MACS-related comorbidities (Cohen's d = -0.49, 95% CI [-0.64, -0.34], p = 0.00). Subgroup analysis indicated that the systolic blood pressure (pooled effect size = -0.81, 95% CI [-1.19, -0.42], p = 0.03), diastolic blood pressure (pooled effect size = -0.63, 95% CI [-1.05, -0.21], p = 0.01), and BMD (pooled effect size = -0.40, 95% CI [-0.73, -0.07], p = 0.02) were significantly in favor of adrenalectomy group rather than conservative treatment but no significant differences between the two treatment groups in other MACS-related comorbidities were reported. Conclusion: Despite the limited and diverse data, this study demonstrates the advantage of adrenalectomy over conservative treatment for MACS-related comorbidities.

Endocrine Fever.

Fever is usually thought to be of an infectious or inflammatory etiology. In this brief communication, we explore the multifaceted connections between fever and endocrine dysfunction. Impaired resistance to infection often leads to fever in conditions like diabetes and Cushing's syndrome. Additionally, several endocrine disorders, including hyperthyroidism, subacute thyroiditis, carcinoid syndrome, and pheochromocytoma, can manifest as fever. Furthermore, fever can be an adverse effect of various endocrine treatments, such as bisphosphonates and antithyroid drugs. We refer to these scenarios as 'endocrine fever.' Increased awareness of these clinical associations can aid in prompt diagnosis and management of these conditions.

Adolescent- and adult-onset neuroblastic tumor: A retrospective multicenter observational study of patients diagnosed in France between 2000 and 2020.

BACKGROUND: Adult- and adolescent-onset neuroblastomas are rare, with no established therapy. In addition, rare pheochromocytomas may harbor neuroblastic components. This study was designed to collect epidemiological, diagnostic and therapeutic data in order to better define the characteristics of malignant peripheral neuroblastic tumors (MPNT) and composite pheochromocytomas (CP) with MPNT. PROCEDURE: Fifty-nine adults and adolescents (aged over 15 years) diagnosed with a peripheral or composite neuroblastic tumor, who were treated in one of 17 institutions between 2000 and 2020, were retrospectively studied. RESULTS: Eighteen patients with neuroblastoma (NB) or ganglioneuroblastoma (GNB) had locoregional disease, and 28 patients had metastatic stage 4 NB. Among the 13 patients with CP, 12 had locoregional disease. Fifty-eight percent of the population were adolescents and young adults under 24 years of age. The probability of 5-year event-free survival (EFS) was 40% (confidence interval: 27%-53%). CONCLUSIONS: Outcomes were better for patients with localized tumor than for patients with metastases. For patients with localized tumor, in terms of survival, surgical treatment was the best therapeutic option. Multimodal treatment with chemotherapy, surgery, radiotherapy, and immunotherapy-based maintenance allowed long-term survival for some patients. Adolescent- and adult-onset neuroblastoma appeared to have specific characteristics associated with poorer outcomes compared to pediatric neuroblastoma. Nevertheless, complete disease control improved survival. The presence of a neuroblastic component in pheochromocytoma should be considered when making therapeutic management decisions. The development of specific tools/resources (Tumor Referral Board, Registry, biology, and trials with new agents or strategies) may help to improve outcomes for patients.

Mild autonomous cortisol secretion: pathophysiology, comorbidities and management approaches.

The majority of incidentally discovered adrenal tumours are benign adrenocortical adenomas and the prevalence of adrenocortical adenomas is around 1-7% on cross-sectional abdominal imaging. These can be non-functioning adrenal tumours or they can be associated with autonomous cortisol secretion on a spectrum that ranges from rare clinically overt adrenal Cushing syndrome to the much more prevalent mild autonomous cortisol secretion (MACS) without signs of Cushing syndrome. MACS is diagnosed (based on an abnormal overnight dexamethasone suppression test) in 20-50% of patients with adrenal adenomas. MACS is associated with cardiovascular morbidity, frailty, fragility fractures, decreased quality of life and increased mortality. Management of MACS should be individualized based on patient characteristics and includes adrenalectomy or conservative follow-up with treatment of associated comorbidities. Identifying patients with MACS who are most likely to benefit from adrenalectomy is challenging, as adrenalectomy results in improvement of cardiovascular morbidity in some, but not all, patients with MACS. Of note, diagnosis and management of patients with bilateral MACS is especially challenging. Current gaps in MACS clinical practice include a lack of specific biomarkers diagnostic of MACS-related health outcomes and a paucity of clinical trials demonstrating the efficacy of adrenalectomy on comorbidities associated with MACS. In addition, little evidence exists to demonstrate the efficacy and safety of long-term medical therapy in patients with MACS.

Feocromocitoma y paraganglioma en un hospital pediátrico de Argentina. Serie de casos / Pheochromocytoma and paraganglioma at a children's hospital in Argentina. A case series

El feocromocitoma y el paraganglioma son tumores neuroendocrinos secretores de catecolaminas. Los feocromocitomas se originan en la médula suprarrenal, mientras que los paragangliomas son extraadrenales. Se describe una serie de casos de niños con diagnóstico anatomopatológico de feocromocitoma o paraganglioma que consultaron en un hospital pediátrico de alta complejidad de Argentina. Se incluyeron 21 pacientes, 14 varones, con una mediana de edad de 11,4 años; 8 casos con feocromocitoma y 13 casos con paraganglioma. Se presentaron con hipertensión arterial 14/21. La mayoría de los paragangliomas tuvieron localización paraaórtica (9/13). Debido a que representan una causa potencialmente curable de hipertensión arterial, la sospecha clínica es muy importante. El diagnóstico temprano y la instauración de un tratamiento antihipertensivo adecuado, que permita afrontar la cirugía con normotensión arterial, aseguran la curación en la mayoría de los casos si la resección tumoral es completa.

Pheochromocytomas and paragangliomas are neuroendocrine tumors producing catecholamines. Pheochromocytomas occur in the adrenal medulla, while paragangliomas are those that occur outside the adrenal gland. Here we describe a case series of children with a pathological diagnosis of pheochromocytoma or paraganglioma who consulted at a tertiary care children's hospital in Argentina. A total of 21 patients (14 males) were included; their median age was 11.4 years; 8 children had pheochromocytoma and 13, paraganglioma. Arterial hypertension was observed in 14/21. Most paragangliomas were para-aortic (9/13). Since they are a potentially curable cause of hypertension, clinical suspicion is very important. An early diagnosis and the initiation of an adequate antihypertensive treatment, which allows the patient to undergo surgery with normal blood pressure, ensure a cure in most cases if tumor resection is complete.

Phaeochromocytoma and paraganglioma.

Phaeochromocytomas and paragangliomas are rare catecholamine-producing neuroendocrine tumours which can potentially cause catastrophic crises with high morbidity and mortality. This best practice article considers the causes and presentation of such tumours, screening and diagnostic tests, management of these patients and consideration of family members at risk.

Clinical features and treatment options for pediatric adrenal incidentalomas: a retrospective single center study.

BACKGROUND: The aim of this study was to investigate the clinical features and treatment options for pediatric adrenal incidentalomas(AIs) to guide the diagnosis and treatment of these tumors. METHODS: The clinical data of AI patients admitted to our hospital between December 2016 and December 2022 were collected and retrospectively analyzed. All patients were divided into neonatal and nonneonatal groups according to their age at the time of the initial consultation. RESULTS: In the neonatal group, 13 patients were observed and followed up, and the masses completely disappeared in 8 patients and were significantly reduced in size in 5 patients compared with the previous findings. Four patients ultimately underwent surgery, and the postoperative pathological diagnosis was neuroblastoma in three patients and teratoma in one patient. In the nonneonatal group, there were 18 cases of benign tumors, including 9 cases of ganglioneuroma, 2 cases of adrenocortical adenoma, 2 cases of adrenal cyst, 2 cases of teratoma, 1 case of pheochromocytoma, 1 case of nerve sheath tumor, and 1 case of adrenal hemorrhage; and 20 cases of malignant tumors, including 10 cases of neuroblastoma, 9 cases of ganglioneuroblastoma, and 1 case of adrenocortical carcinoma. CONCLUSIONS: Neuroblastoma is the most common type of nonneonatal AI, and detailed laboratory investigations and imaging studies are recommended for aggressive evaluation and treatment in this population. The rate of spontaneous regression of AI is high in neonates, and close observation is feasible if the tumor is small, confined to the adrenal gland and has no distant metastasis.

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.