Tumor volume and growth kinetics in hypothalamic-chiasmatic pediatric low grade gliomas

Volumetric Growth and Growth Curve Analysis of Residual Intracranial Meningioma

BACKGROUND

After meningioma surgery, approximately 1 in 3 patients will have residual tumor that requires ongoing imaging surveillance. The precise volumetric growth rates of these tumors are unknown.

OBJECTIVE

To identify the volumetric growth rates of residual meningioma, growth trajectory, and factors associated with progression.

METHODS

Patients with residual meningioma identified at a tertiary neurosurgery center between 2004 and 2020 were retrospectively reviewed. Tumor volume was measured using manual segmentation, after surgery and at every follow-up MRI scan. Growth rates were ascertained using a linear mixed-effects model and nonlinear regression analysis of growth trajectories. Progression was defined according to the Response Assessment in Neuro-Oncology (RANO) criteria (40% volume increase).

RESULTS

There were 236 patients with residual meningioma. One hundred and thirty-two patients (56.0%) progressed according to the RANO criteria, with 86 patients being conservatively managed (65.2%) after progression. Thirteen patients (5.5%) developed clinical progression. Over a median follow-up of 5.3 years (interquartile range, 3.5-8.6 years), the absolute growth rate was 0.11 cm 3 per year and the relative growth rate 4.3% per year. Factors associated with residual meningioma progression in multivariable Cox regression analysis were skull base location (hazard ratio [HR] 1.60, 95% CI 1.02-2.50) and increasing Ki-67 index (HR 3.43, 95% CI 1.19-9.90). Most meningioma exhibited exponential and logistic growth patterns (median R 2 value 0.84, 95% CI 0.60-0.90).

CONCLUSION

Absolute and relative growth rates of residual meningioma are low, but most meet the RANO criteria for progression. Location and Ki-67 index can be used to stratify adjuvant treatment and surveillance paradigms.

Anorexia: an early sign of fourth ventricle astrocytoma in children

INTRODUCTION

Paediatric low-grade astrocytomas of the fourth ventricle are rare tumours, generally revealed by hydrocephalus. However, some patients present with a history of severe anorexia. It might be a harbinger, which if recognized, could lead to earlier diagnosis. We decided to examine our database in order to evaluate the incidence and signification of anorexia in this context.

METHODS

Retrospective monocentric study of cases of low-grade astrocytomas of the fourth ventricle operated between 1991 and 2012 in our paediatric neurosurgery department. We particularly observed the clinical presentation and long-term clinical, oncological and radiological evolution. Non-parametrical tests were used (Mann-Whitney, Fisher).

RESULTS

We reviewed 34 cases, 31 pilocytic astrocytomas and 3 diffuse astrocytomas, 16 boys and 18 girls, (M/F ratio 0.89). Mean age at diagnosis was 8 years old. Seven presented with notable anorexia, the average BMI in this group was ≤2 standard deviation (SD); with clinical signs evolving for 11.5 months. Twenty-seven children had no anorexia; average BMI in this group was +1 SD, with clinical evolution for 6 months on an average of p < 0.05. We found no significant difference regarding hydrocephalus or tumour location. In all children with anorexia, body mass index improved markedly in the postoperative follow-up, which lasted, on average, for 6 years.

CONCLUSION

Anorexia with stunted body weight curve is a non-exceptional presentation in children with low-grade astrocytomas of the fourth ventricle. Unexplained or atypical anorexia with negative etiologic assessment should prompt cerebral imaging. Clinical improvement after surgical resection, could suggest a possible interaction between tumour tissue and appetite-suppressing peptide secretion.

Growth curve analysis of asymptomatic and symptomatic meningiomas

Meningiomas sometimes appear to stop growing after attaining a large size. Commonly used exponential growth models do not reflect this phenomenon. We attempted to find the best curve to simulate their growth. Fifty-two patients with meningioma were followed up for 3.1-21.7 years (mean 7.5 years) with four or more imaging studies each. Thirty-one patients had asymptomatic tumors. The other 21 patients with residual or recurrent tumor were followed up after surgery. Time-volume curves for each tumor were plotted. Nonlinear regression analyses were performed against power, exponential, logistic, and Gompertzian curves. Time-volume curves corresponded to the Gompertzian and logistic growth curves better than to power or exponential curves. When simulating time-volume curves with Gompertzian curves, the majority of benign meningiomas began to slow their growth before patient age of 80 years. Twenty-three of 31 asymptomatic meningiomas had already passed the inflection point before diagnosis. In contrast, this happened less frequently in symptomatic tumors. Especially, all six atypical meningiomas continued to grow quasi-exponentially. Sigmoid curves that approach a plateau were better descriptors of the growth of benign meningiomas than were curves of unlimited growth. However, atypical meningiomas were unlikely to slow their growth.

Alendronate binds to tooth root surfaces and inhibits progression of feline tooth resorption: a pilot proof-of-concept study

Tissue distribution, bioavailability, and efficacy of alendronate in preventing progression of resorption of teeth were evaluated in cats. [Butyl-4-14C-]-alendronate accumulates on subgingival tooth and alveolar bone surfaces adjacent to vascularized tissue resulting in concentration of the drug around tooth roots. Three cats were treated with a 0.03 mg/kg i.v. bolus of [butyl-4-14C-]-alendronate followed by blood, urine, and feces collection and euthanasia 24-hours later. Drug tissue distribution was accessed by autoradiography and sample combustion. To assess bioavailability, 12 cats were administered alendronate orally (3.0 or 9.0 mg/kg in water or 9.0 mg/kg in tuna water) and urine was collected for 24-hours. In these formulations, alendronate oral bioavailability in cats was approximately 3%. In addition, 10 cats with radiographic evidence of pre-existing tooth resorption (14 affected teeth) were treated with vehicle or 3.0 mg/kg alendronate per os once weekly for 22-weeks and, then, 9.0 mg/kg per os twice weekly for 27-weeks in a random, masked study. Radiographic area of resorption was measured and progression scored every 3 to 4-months. In placebo-treated cats, resorption progressed in five of six teeth (+ 97% average increase in area of resorption), whereas progression of resorption was seen in only three of eight affected teeth in alendronate-treated cats with a -22% average change (decrease) in area (P < 0.01 difference in number of teeth showing progression; P < 0.001 difference in area of resorption). Alendronate accumulated preferentially on subgingival tooth surfaces and adjacent alveolar bone and, at a dose of 9 mg/kg twice weekly, effectively slowed or arrested the progression of resorption.

Management of optic-hypothalamic gliomas in children: still a challenging problem

Optic pathway-hypothalamic gliomas (OPHGs) are rare, often unresectable tumors that mostly occur in childhood. Their biological behavior is unpredictable, although they tend to follow an aggressive clinical course in infants and a benign course in children with neurofibromatosis type 1. Optimal management is still controversial. Nonprogressing OPHGs are usually followed by surveillance alone. Surgery is advocated for progressing tumors to decompress the optic pathways, obtain a quick relief from intracranial hypertension and allow histologic examination (when needed). The current trend is in favor of conservative surgical behavior, except for resectable tumors. Chemotherapy is increasingly used in the management of OPHGs, especially in infants, to delay radiotherapy. Carboplatin and vincristine are the most frequently used drugs, although several chemotherapeutic agents in different combinations are currently employed with good results. Radiotherapy is utilized in children over 5 years of age as an adjuvant or as an alternative to surgery. The prognosis of OPHGs is quite good, with regard to the overall survival rate (70-100% at 5 years), but less favorable in terms of late morbidity.

Multispectral tissue characterization in a RIF-1 tumor model: monitoring the ADC and T2 responses to single-dose radiotherapy. Part II

A multispectral (MS) approach that combines apparent diffusion coefficient (ADC) and T(2) parameter maps with k-means (KM) clustering was employed to distinguish multiple compartments within viable tumor tissue (V1 and V2) and necrosis (N1 and N2) following single-dose (1000 cGy) radiotherapy in a radiation-induced fibrosarcoma (RIF-1) tumor model. The contributions of cell kill and tumor growth kinetics to the radiotherapy-induced response were investigated. A larger pretreatment V1 volume was correlated with decreased tumor growth delay (TGD) (r = 0.68) and cell kill (r = 0.71). There was no correlation for the pretreatment V2 volume. These results suggest that V1 tissue is well oxygenated and radiosensitive, whereas V2 tissue is hypoxic and therefore radioresistant. The relationship between an early ADC response and vasogenic edema and formation of necrosis was investigated. A trend for increased ADC was observed prior to an increase in the necrotic fraction (NF). Because there were no changes in T(2), these observations suggest that the early increase in ADC is more likely based on a slight reduction in cell density, rather than radiation-induced vasogenic edema. Quantitative assessments of individual tissue regions, tumor growth kinetics, and cell kill should provide a more accurate means of monitoring therapy in preclinical animal models because such assessments can minimize the issue of intertumor variability.

Realistic simulation of the 3-D growth of brain tumors in MR images coupling diffusion with biomechanical deformation

We propose a new model to simulate the three-dimensional (3-D) growth of glioblastomas multiforma (GBMs), the most aggressive glial tumors. The GBM speed of growth depends on the invaded tissue: faster in white than in gray matter, it is stopped by the dura or the ventricles. These different structures are introduced into the model using an atlas matching technique. The atlas includes both the segmentations of anatomical structures and diffusion information in white matter fibers. We use the finite element method (FEM) to simulate the invasion of the GBM in the brain parenchyma and its mechanical interaction with the invaded structures (mass effect). Depending on the considered tissue, the former effect is modeled with a reaction-diffusion or a Gompertz equation, while the latter is based on a linear elastic brain constitutive equation. In addition, we propose a new coupling equation taking into account the mechanical influence of the tumor cells on the invaded tissues. The tumor growth simulation is assessed by comparing the in-silico GBM growth with the real growth observed on two magnetic resonance images (MRIs) of a patient acquired with 6 mo difference. Results show the feasibility of this new conceptual approach and justifies its further evaluation.

On the role of endothelial progenitor cells in tumor neovascularization

The exact role that bone marrow (BM)-derived endothelial progenitor cells (EPCs) play in tumor neovascularization is heavily debated. We develop a quantitative three-compartment model with predictive power regarding the dynamics of tumorigenesis. There are two distinct processes by which tumor neovasculature can be built: angiogenesis is the formation of new blood vessels from preexisting vessels; vasculogenesis is the formation of new vessels by recruiting circulating EPCs. We show that vasculogenesis-driven and angiogenesis-driven tumors grow in different ways. (i) If angiogenesis is the prevailing process, then the tumor mass (and volume) will grow as a cubic power of time, and BM-derived EPCs will stay at a constant level. (ii) If vasculogenesis is the dominant process, then the tumor mass will be characterized by a linear growth in time, and the number of circulating EPCs (after possibly increasing to a maximum) will decrease to low levels. With this information, one can identify the "signature" of each of the processes in the observations of tumor growth and the dynamics of the relevant characteristics, such as the level of BM-derived EPCs. We show how our results can help explain some apparently contradictory experimental data. We also propose ways to couple this study with directed experiments to identify the exact role of vasculogenesis in tumor progression.

Identification of three gene candidates for multicellular resistance in colon carcinoma

Solid tumours display elevated resistance to chemo- and radiotherapies compared to individual tumour derived cells. This so-called multicellular resistance (MCR) phenomenon can only be partly explained by reduced diffusion and altered cell cycle status; even fast growing cells on the surface of solid tumours display MCR. Multicellular spheroids (MCS) recapture this phenomenon ex vivo and here we compare gene expression in exponentially growing MCS with gene expression in monolayer culture. Using an 18,664 gene microarray, we identified 42 differentially expressed genes and three of these genes can be linked to potential mechanisms of MCR. A group of interferon response genes were also up-regulated in MCS, as were a number of genes that that are indicative of greater differentiation in three-dimensional cultures.

Improvement of visual acuity caused by opticochiasmal astrocytoma after treatment for associated hydrocephalus--case report

A 33-year-old male presented with syncopal attacks. He had a history of slowly progressive deterioration of visual acuity in both eyes. His visual deterioration began in the left eye at age 12 years and in the right eye at age 20 years. His left eye was completely blind by age 33 years. He had received no prior treatment for these visual disturbances. Magnetic resonance (MR) imaging on admission showed a large tumor with inhomogeneous intensity occupying the bilateral optic canals and orbital cavities, with extension to parasellar region. Arachnoid cysts were found in the left middle fossa and supracerebellar space, which had caused herniation of the cerebellar tonsils to the foramen magnum. Open biopsy and histology verified that the tumor was pilocytic astrocytoma. Arachnoid cysts associated with the hydrocephalus were treated with a ventriculoperitoneal shunt. Seven years after surgery, visual acuity of the right eye had improved although the left eye remained blind. Follow-up MR imaging demonstrated marked reduction in size of the ventricles and arachnoid cysts, but the tumor size did not change. This case illustrates the benign nature of low-grade glioma in this region in spite of the large size and long history. Deterioration of visual acuity may be reversible in some cases of opticochiasmal astrocytoma. In our case, the improvement in visual acuity probably resulted from growth arrest of the tumor and improvement in the dynamics of cerebrospinal fluid flow.

Hanging-drop multicellular spheroids as a model of tumour angiogenesis

The establishment of a vascular network within tumours is a key step in the progression towards an aggressive, metastatic state, with poor prognosis. We have developed a novel in vitro model to specifically capture the interaction between endothelial cells and solid tumours. Micro-vascularised in vitro tumour constructs were produced by introducing endothelial cells to multicellular spheroids formed in hanging drops. Upon introduction, the endothelial cells migrated into the tumour spheroid, establishing tubular networks and luminal structures. This system relies on the natural pro-angiogenic capacity of multicellular spheroids, and does not require the addition of exogenous angiogenic factors, or use of extracellular-matrix substitutes.

Virtual and real brain tumors: using mathematical modeling to quantify glioma growth and invasion

Over the last 10 years increasingly complex mathematical models of cancerous growths have been developed, especially on solid tumors, in which growth primarily comes from cellular proliferation. The invasiveness of gliomas, however, requires a change in the concept to include cellular motility in addition to proliferative growth. In this article we review some of the recent developments in mathematical modeling of gliomas. We begin with a model of untreated gliomas and continue with models of polyclonal gliomas following chemotherapy or surgical resection. From relatively simple assumptions involving homogeneous brain tissue bounded by a few gross anatomical landmarks (ventricles and skull) the models have recently been expanded to include heterogeneous brain tissue with different motilities of glioma cells in grey and white matter on a geometrically complex brain domain, including sulcal boundaries, with a resolution of 1 mm(3) voxels. We conclude that the velocity of expansion is linear with time and varies about 10-fold, from about 4 mm/year for low-grade gliomas to about 3 mm/month for high-grade ones.

Pediatric brain tumors

Brain tumors in children vary with regard to histology, location, gender distribution, and age of onset. The past several decades have witnessed substantial improvements in the diagnosis and treatment. As a result, the number of long-term survivors also has increased continuously. Recent advances in neuroimaging facilitate tumor localization and mapping of brain function by noninvasive techniques and are becoming important in preoperative assessment for brain tumors. Surgery remains the mainstay of treatment of many tumor types. A role for chemotherapy is emerging, particularly for nonresectable tumors and in infants, for whom the adverse effects of radiation therapy are severe. Despite the improved treatments and prognostic data, however, many long-term survivors experience significant neurocognitive and developmental deficits.

A mathematical model for self-limiting brain tumors

It is puzzling that certain brain tumors exhibit arrested exponential growth. We have observed in pediatric low-grade astrocytomas (LGA) at a certain volume approximately 100-150 cm(3) that the tumor ceases to grow. This observation led us to develop a macroscopic mathematical model for LGA growth kinetics that assumes the flow through the surface of the astrocytoma of a triggering agent or "promoter" that is uniformly distributed throughout the tumor, thereby providing relatively homogeneous growth. The model relates the transport of the promoter by the electrochemical potential associated with the tumor and diffusion effects through the surface of the growth and its consumption throughout the tumor volume via a pair of ordinary differential equations. The model assumes a constant growth rate, if the promoter density is above some threshold, and is zero otherwise. We also develop equations for an electrochemical (Nernst) transport mechanism for the promoter, and describes the microscopic basis for the macroscopic evolution to the equilibrium state at a well-defined and universal size. The latter description is unstable to asymmetric perturbations and provides a "star-like" shape for emergent tumors and a spheroidal shape for fully developed ones. The underlying assumption in our hypothesis would also result in tumor growth remission beginning from the periphery and proceeding inwards, a feature that has now been validated clinically.

Pediatric tumors of the orbit and optic pathway

We present an overview of the treatment and clinical outcome of 30 pediatric patients with orbital and optic pathway tumors cared for in our center from 1991 to 2002. Follow-ups were available for 48 months on average. Eight of 14 gliomas of the optic nerve or pathway were subtotally resected via a pterional approach. Two were totally resected with transection of the optic nerve, 2 were only biopsied and 2 were observed. One of 4 optic nerve sheath meningiomas in patients with good visual acuity was subtotally resected with decompression of the optic canal. Two were totally resected with transection of the prechiasmal optic nerve and 1 was only biopsied. Four infectious intra-/extraconal lesions were biopsied (transconjunctival approach) and treated with antibiotics. Two vascular intra-/extraconal tumors (hemangiomas) were removed via a transconjunctival approach and a lateral orbitotomy. The following histologies only occurred once: dermoid cyst, aneurysmal bone cyst, eosinophilic granuloma, fibrous dysplasia, osteopetrosis and rhabdomyosarcoma. The spectrum of pathology in pediatric orbital tumors is wide and requires multidisciplinary treatment.

Advances in pediatric neuro-oncology

A number of exciting advances have been reported over the past few years in the understanding and treatment of children with brain tumors. The present review highlights many of the publications from this period, focusing on their relevance within the major diagnostic and treatment domains of pediatric oncology (surgery, radiation therapy, chemotherapy, neuropathology, and neuroradiology). Although many of the publications cited provide confirmation of previously reported work, when taken together they form a good framework of the state of the field from the past few years.

Treatment of low-grade pediatric gliomas

The prognosis of pediatric low-grade gliomas is relatively favorable, but residual or unresectable tumors remain a challenge. Conventional radiation therapy is effective but may be associated with unacceptable sequelae in young children. Chemotherapy can delay the need for radiation therapy in young children; however, its role in older children has yet to be established. New forms of radiation are being introduced that may be less toxic.

Spontaneous regression of low-grade astrocytomas in childhood

An 8-year-old boy with neurofibromatosis type 1 (NF1) and a biopsy-proven juvenile pilocytic astrocytoma of the hypothalamic/chiasmatic region was followed with serial MRIs over 4 years. Spontaneous tumor regression was followed by progression and biopsy; 6 months later, the tumor regressed again. This bimodal regression is rare, but highlights the variable natural history of low-grade gliomas in children with NF1 and the difficulty in evaluating response of such tumors to therapy.