Proliferative characteristics of juvenile pilocytic astrocytomas determined by bromodeoxyuridine labeling

Clinical, histopathological and molecular risk factors for recurrence of pilocytic astrocytomas: brainstem/spinal location, nestin expression and gain of 7q and 19 are associated with early tumor recurrence

Pilocytic astrocytomas (PAs) are benign tumors. However, clinically aggressive PAs despite benign histology have been reported, and histological and molecular risk factors for prognosis have not been elucidated. 38 PAs were studied for clinical, histological, and molecular factors, including tumor location, extent of resection, post-operative treatment, glioma-associated molecules (IDH1/2, ATRX, BRAF, FGFR1, PIK3CA, H3F3A, p53, VEGF, Nestin, PD-1/PD-L1), CDKN2A/B deletion, and chromosomal number aberrations, to see if there is any correlation with patient's progression-free survival (PFS). Brainstem/spinal location, extent of resection and post-operative treatment, and VEGF-A, Nestin and PD-L1 expression, copy number gain of chromosome 7q or 19, TP53 mutation were significantly associated with shorter PFS. None of the histological parameters was associated with PFS. Multivariate analyses demonstrated that high Nestin expression, gain of 7q or 19, and extent of removal were independently predictive for early tumor recurrence. The brainstem/spinal PAs appeared distinct from those in the other sites in terms of molecular characteristics. Clinically aggressive PAs despite benign histology exhibited high Nestin expression. Brainstem/spinal location, extent of resection and some molecular factors including Nestin expression and gains of 7q and 19, rather than histological parameters, may be associated with early tumor recurrence in PAs.

Neuronal signatures in cancer

Despite advances in the treatment of solid tumors, the prognosis of patients with many cancers remains poor, particularly of those with primary and metastatic brain tumors. In the last years, "Cancer Neuroscience" emerged as novel field of research at the crossroads of oncology and classical neuroscience. In primary brain tumors, including glioblastoma (GB), communicating networks that render tumor cells resistant against cytotoxic therapies were identified. To build these networks, GB cells extend neurite-like protrusions called tumor microtubes (TMs). Synapses on TMs allow tumor cells to retrieve neuronal input that fosters growth. Single cell sequencing further revealed that primary brain tumors recapitulate many steps of neurodevelopment. Interestingly, neuronal characteristics, including the ability to extend neurite-like protrusions, neuronal gene expression signatures and interactions with neurons, have now been found not only in brain and neuroendocrine tumors but also in some cancers of epithelial origin. In this review, we will provide an overview about neurite-like protrusions as well as neurodevelopmental origins, hierarchies and gene expression signatures in cancer. We will also discuss how "Cancer Neuroscience" might provide a framework for the development of novel therapies.

Biphasic response of a tecto-mesencephalic pilocytic astrocytoma after Gamma Knife surgery--A case report

Biphasic response (shrinkage-regrowth-shrinkage) of tumors has never previously been reported in the postoperative course, neither after microsurgery, nor after Gamma Knife surgery (GKS). We present the case of an adult with dorsal midbrain syndrome resulting from a pilocytic astrocytoma centered on the mesencephalic tectum. The tumor extended to the third ventricle and the thalamus. Initially, due to tumor growth, a biopsy was performed and histology established. Later, a ventriculocisternostomy for obstructive hydrocephalus was performed. Finally, GKS was performed, as the tumor continued to grow. After GKS, the lesion exhibited a biphasic response, with a major shrinkage at 3 months, regrowth within the target volume at 6 and 9 months and a second phase of important shrinkage at 12 months, which persisted for the next two years. The possible mechanisms for this particular response pattern are discussed.

Postoperative Surveillance Magnetic Resonance Imaging for Cerebellar Astrocytoma

Introduction:

Patients with low grade astrocytomas generally have good prognosis when total resection can be achieved, but surveillance neuroimaging is commonly performed to detect recurrence or progression. This study evaluated the utility and yield of such strategy for pilocytic and non-pilocytic cerebellar astrocytomas.

Methods:

A 20-year retrospective review was performed of patients undergoing resection of cerebellar astrocytoma at a single institution. A negative MRI string (NMS) ratio was computed as the fraction of total follow-up period over which surveillance neuroimaging was negative for recurrence or progression. Chi-squared analysis differentiated NMS ratio by resection extent and lesion histopathology.

Results:

Twenty-eight patients with pilocytic (n=15) and non-pilocytic (n=13) astrocytoma underwent 34 craniotomies, with total resection in 19 cases. Surveillance MRIs (n=167) among total resection patients were uniformly negative for recurrent disease at average seven years follow-up (NMS ratio = 1.0). The 43 surveillance MRIs among subtotal resection patients revealed disease progression in two patients within six months of operation (NMS ratio = 0.78, p<0.05). No differences in NMS ratio were observed between pilocytic and non-pilocytic astrocytoma subtypes.

Discussion:

This study illustrates pediatric patients with low-grade cerebellar astrocytomas undergoing total resection may not benefit from routine surveillance neuroimaging, primarily because of low recurrence likelihood. Patients with subtotal resection may benefit from surveillance of residual disease, with further work aimed at exploring the schedule of such follow-up.

Development, characterization, and reversal of acquired resistance to the MEK1 inhibitor selumetinib (AZD6244) in an in vivo model of childhood astrocytoma

PURPOSE

The BT-40 low-grade childhood astrocytoma xenograft model expresses mutated BRAF(V600E) and is highly sensitive to the MEK inhibitor selumetinib (AZD6244). In this study, we developed and characterized selumetinib resistance and explored approaches to circumventing the mechanisms of acquired resistance.

EXPERIMENTAL DESIGN

BT-40 xenografts were selected in vivo for selumetinib resistance. Resistant tumors were obtained and characterized, as were tumors that reverted to sensitivity. Characterization included expression profiling, assessment of MEK signature and compensatory pathways, MEK inhibition, BRAF expression, and cytokine levels. Combination treatment of BT-40/AZD-resistant tumors with the MEK inhibitor and a STAT3 inhibitor (LLL12) was assessed.

RESULTS

Resistance was unstable, tumors reverting to selumetinib sensitivity when passaged in untreated mice, and MEK was equally inhibited in sensitive and resistant tumors by selumetinib. Drug resistance was associated with an enhanced MEK signature and increased interleukin (IL)-6 and IL-8 expression. Selumetinib treatment induced phosphorylation of STAT3 (Y705) only in resistant xenografts, and similar results were observed in BRAF(V600E) astrocytic cell lines intrinsically resistant to selumetinib. Treatment of BT-40-resistant tumors with selumetinib or LLL12 had no significant effect, whereas combined treatment induced complete regressions of BT-40/AZD-resistant xenografts.

CONCLUSIONS

Resistance to selumetinib selected in vivo in BT-40 tumor xenografts was unstable. In resistant tumors, selumetinib activated STAT3, and combined treatment with selumetinib and LLL12 induced complete responses in resistant BT-40 tumors. These results suggest dual targeting BRAF (V600E) signaling and STAT3 signaling may be effective in selumetinib-resistant tumors or may retard or prevent onset of resistance.

Primary neurosurgery for pediatric low-grade gliomas: a prospective multi-institutional study from the Children's Oncology Group

BACKGROUND

Central nervous system neoplasms are the most common solid tumors in children, and more than 40% are low-grade gliomas. Variable locations, extent of resection, postoperative neurodiagnostic evaluation, and histology have confounded therapy and outcome.

OBJECTIVES

To investigate disease control and survival after surgery.

METHODS

A prospective natural history trial from 1991 to 1996 produced a subset of patients with low-grade gliomas managed by primary surgery and subsequent observation. Patients were evaluable if eligibility, tumor location, and extent of resection were confirmed by pathological diagnosis, preoperative and postoperative imaging, and the surgeon's report. Primary end points were overall survival (OS), progression-free survival (PFS), and postprogression survival.

RESULTS

Of 726 patients enrolled, 518 were fully evaluable for analysis. The 5- and 8-year OS rates were 97% ± 0.8% and 96% ± 0.9%, respectively, and PFS rates were 80% ± 1.8% and 78% ± 2.0%. In univariate analyses, histological type, extent of residual tumor, and disease site were significantly associated with PFS and OS. In multivariate analysis, gross total resection (GTR) without residual disease was the predominant predictor of PFS. In patients with limited residual disease, 56% were free of progression at 5 years.

CONCLUSION

GTR should be the goal when it can be achieved with an acceptable functional outcome. The variable rate of progression after incomplete resection highlights the need for new predictors of tumor behavior.

Activation of the Hedgehog pathway in pilocytic astrocytomas

Pilocytic astrocytoma is commonly viewed as a benign lesion. However, disease onset is most prevalent in the first two decades of life, and children are often left with residual or recurrent disease and significant morbidity. The Hedgehog (Hh) pathway regulates the growth of higher WHO grade gliomas, and in this study, we have evaluated the activation and operational status of this regulatory pathway in pilocytic astrocytomas. Expression levels of the Hh pathway transcriptional target PTCH were elevated in 45% of tumor specimens analyzed (ages 1–22 years) and correlated inversely with patient age. Evaluation of a tissue array revealed oligodendroglioma-like features, pilomyxoid features, infiltration, and necrosis more commonly in specimens from younger patients (below the median patient age of 10 years). Immunohistochemical staining for the Hh pathway components PTCH and GLI1 and the proliferation marker Ki67 demonstrated that patients diagnosed before the age of 10 had higher staining indices than those diagnosed after the age of 10. A significant correlation between Ki67 and PTCH and GLI1 staining indices was measured, and 86% of Ki67-positive cells also expressed PTCH. The operational status of the Hh pathway was confirmed in primary cell culture and could be modulated in a manner consistent with a ligand-dependent mechanism. Taken together, these findings suggest that Hh pathway activation is common in pediatric pilocytic astrocytomas and may be associated with younger age at diagnosis and tumor growth.

Les astrocytomes pilocytiques du diencéphale de l’enfant

BACKGROUND AND PURPOSE

Pilocytic astrocytoma (PA) is a WHO grade I tumor of the central nervous system mostly arising in children and young adults. Management of diencephalic PA is a difficult challenge. Surgical treatment has to cope with both the difficulties of deep location and eloquent area tumors.

MATERIALS AND METHODS

We retrospectively reviewed seven pediatric cases (female: 4, male: 3) of diencephalic PA. Opto-chiasmatic tumors were excluded from the series. Mean age at diagnosis was 108 months (9 years) (range: 4 month-18 years), median age was 111 months. Median follow-up for the series was 125 months. Tumor locations were as followed: right thalamus: 2, both thalami: 1, hypothalamus: 3, and right basal ganglia: 1. At the onset, the first symptom was mostly raised intracranial pressure. The delay in diagnosis ranged from 48 hours up to 6 years.

TREATMENT

a shunting procedure was performed in 3 patients, a direct surgical approach in 5 patients (gross total removal: 2; partial removal: 3) and one patient had only a biopsy. Three children were re-operated. Three patients were treated by radiationtherapy (RT) after surgery. Chemotherapy was delivered for 4 children.

RESULTS

The overall survival rate was 71.4 months (almost 6 years) (range: 3-184 months). Median survival rate was 42 months (3.5 years). Three children died, two by tumor progression and one death related to late side-effects of RT. Four patients have a good quality of life with GOS I (n = 3) or II (n = 1). We observed tumor regression in two patients at 1 and 17 years after the beginning of treatment. Correct diagnosis was only made for two cases at the initial pathological examination.

CONCLUSION

The course of diencephalic PA is still unpredictable. The tumor can be controlled by a partial surgical removal, and a residual tumor can sometimes decrease in size after surgery. Gross total removal of these tumors, although difficult, may be performed. With cranial navigation systems, the risk is low. Pathological diagnosis is sometimes difficult to assess.

Multi focal Pilocytic Astrocytomas With Ependymal Differentiation in the Bilateral Medial Temporal Lobes-Case Report-

A 7-year-old boy presented with headache, visual disturbance, and psychomotor seizures persisting for 7 months. He had mild hemiparesis and homonymous hemianopia on the left. Neuroimaging showed bilateral temporal lobe masses with calcification and cysts. The right temporal mass was subtotally resected. The histological diagnosis was pilocytic astrocytoma with ependymal differentiation and a MIB-1 staining index of up to 8.0%. Postoperatively his hemiparesis and psychomotor seizures disappeared. Adjuvant chemotherapy consisting of carboplatin and vincristine was given followed by radiotherapy. Neuroimaging showed that the bilateral tumors had disappeared and showed no recurrence for 29 months after the diagnosis. Pilocytic astrocytoma usually presents as a solitary mass in the cerebellum or optic pathway with low proliferative activity, but should be included in the differential diagnosis of multifocal tumors arising in the bilateral temporal lobes. Ependymal differentiation with extremely high proliferative activity might be related to this unusual clinical presentation. Intensive treatment is recommended for patients with such specific neuroimaging and histological features.

Prognosis-related histomorphological and immunohistochemical markers in central nervous system tumors of childhood and adolescence

Brain tumors account for approximately 20% of all childhood cancers, and are the leading cause of cancer morbidity and mortality among children. Although numerous demographic, clinical and therapeutic parameters have been identified over the past few years that have significant prognostic bearing for some pediatric brain tumors, predicting the clinical course and outcome among children with central nervous system tumors is still difficult. A survey of publications on prognosis-related histopathological and immunohistochemical features among pediatric brain tumors revealed 172 series, of which 91 presented statistically significant outcome-associated parameters as defined by a P value of less than 0.05. Most investigations revealing significant prognosis-related markers were performed on medulloblastomas (30 publications), ependymomas (25) and astrocytic tumors (18). In total, 16 cohorts consisted of more than 100 cases (5 on ependymomas, 3 each on medulloblastomas and astrocytic tumors). On the other hand, there were also 13 series with fewer than 20 cases (5 on medulloblastomas). Potentially prognostic histopathological markers vary among different entities and consist of assessment of necroses, mitoses, differentiation, vascular proliferation, and growth pattern, whereas immunohistochemical features include proliferation markers (Ki-67, MIB-1), expression of oncogenes/tumor suppressor genes and their proteins (TP53, c-erbB2), growth factor and hormonal receptors (VEGF, EGFR, HER2, HER4, ErbB-2), cell cycle genes (p27, p14ARF) and cell adhesion molecules, as well as factors potentially related to therapeutic resistance (DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the prognostic potential of histopathological and immunohistochemical markers that can be investigated by the practicing neuropathologist as part of the routine diagnostic workload, and scrutinizes their benefit for predicting therapy response and patient outcome among children with brain tumors.

Clinicopathological study of diffuse type brainstem gliomas: analysis of 40 autopsy cases

Diffuse type brainstem glioma is one of the most malignant types of brain tumors and the prognosis is extremely poor. The proliferative potential of these tumors is presumed to be very high, but there is little information about the cell kinetics of brainstem glioma because surgical resection is rarely performed. The histological grade, tumor spread, growth potential, and prognosis were evaluated in 40 autopsy cases of diffuse type brainstem glioma. To quantify the growth potentials of individual tumors, the proliferating cell indices of Ki-67 (MIB-1) and proliferating cell nuclear antigen (PCNA) monoclonal antibodies were measured. Mean MIB-1 and PCNA proliferating cell indices were 20.4% (24 cases) and 37.0% (28 cases), respectively, in 34 glioblastomas. The median survival time was 40 weeks in 22 treated patients. The mean PCNA proliferating cell index was 10.8% in four of five anaplastic astrocytomas and the median survival time in four treated patients was 91 weeks. The MIB-1 and PCNA proliferating cell indices of one astrocytoma were 2.9% and 20.3%, respectively, and the survival time was 56 weeks. The overall median survival time was 32 weeks. There was a significant difference in PCNA proliferating cell indices between glioblastomas and anaplastic astrocytomas (p < 0.05) and there was a significant difference in survival time between glioblastomas (40 weeks) and anaplastic astrocytomas plus astrocytoma (74 weeks) among the treated patients (p < 0.05). Supratentorial extension was more frequent in glioblastomas than in anaplastic astrocytomas (p < 0.05). Our results suggest that the majority of diffuse type brainstem gliomas are glioblastoma and the proliferative potential is probably as high as that of adult supratentorial glioblastoma. Supratentorial extension and dissemination are relatively frequent in the advanced stage. Anaplastic astrocytoma or astrocytoma is rarer and less infiltrative and proliferative, and carries a slightly better prognosis than glioblastoma.

High-molecular-weight tropomyosins localize to the contractile rings of dividing CNS cells but are absent from malignant pediatric and adult CNS tumors

Tropomyosin has been implicated in the control of actin filament dynamics during cell migration, morphogenesis, and cytokinesis. In order to gain insight into the role of tropomyosins in cell division, we examined their expression in developing and neoplastic brain tissue. We found that the high-molecular-weight tropomyosins are downregulated at birth, which correlates with glial cell differentiation and withdrawal of most cells from the cell cycle. Expression of these isoforms was restricted to proliferative areas in the embryonic brain and was absent from the adult, where the majority of cells are quiescent. However, they were induced under conditions where glial cells became proliferative in response to injury. During cytokinesis, these tropomyosin isoforms were associated with the contractile ring. We also investigated tropomyosin expression in neoplastic CNS tissues. Low-grade astrocytic tumors expressed high-molecular-weight tropomyosins, while highly malignant CNS tumors of diverse origin did not (P </= 0.001). Furthermore, high-molecular-weight tropomyosins were absent from the contractile ring in highly malignant astrocytoma cells. Our findings suggest a role for high-molecular-weight tropomyosins in astrocyte cytokinesis, although highly malignant CNS tumors are still able to undergo cell division in their absence. Additionally, the correlation between high-molecular-weight tropomyosin expression and tumor grade suggests that tropomyosins are potentially useful as indicators of CNS tumor grade.

Malignant pilocytic astrocytoma in the medulla oblongata: case report

A 27-year-old woman visited our hospital with chief complaints of abducens nerve palsy and cerebellar symptoms. On computerized tomographic scanning and magnetic resonance imaging, a tumor with strong enhancement was found on the dorsal side of the medulla oblongata. A tumor was excised by suboccipital craniotomy and C1 laminectomy. Histologically, many Rosenthal fibers together with pilocytic tumor cells were found in some regions, but a very high Ki-67 labeling rate accompanied by cells with nuclei of irregular size and giant cells was observed in other regions. The tumor was diagnosed as malignant pilocytic astrocytoma originating from pilocytic astrocytoma by transformation. The biological behavior of pilocytic astrocytoma is obscure in several respects. We report our experience of a case of malignant pilocytic astrocytoma that developed in the brain stem and progressed extremely rapidly.

Spontaneous involution of pilocytic astrocytoma in a patient without neurofibromatosis type 1: case report

Serial magnetic resonance imaging findings are described in a patient with a sporadically occurring pilocytic astrocytoma that underwent spontaneous regression over 6 years. To the authors' knowledge, this is the first report in which spontaneous involution of a pilocytic astrocytoma not associated with neurofibromatosis type 1 has been described. A literature review regarding sporadic and syndrome-associated pilocytic astrocytoma was undertaken, with particular reference to treatment and natural history.

Proliferative activity as measured by MIB-1 labeling index and long-term outcome of visual pathway astrocytomas in children

Although most visual pathway tumors are low-grade gliomas their biologic behavior is highly unpredictable. In order to determine whether assessment of proliferative activity can assist in predicting tumor behavior, we studied the MIB-1 labeling indices (MIB-1 LIs) in surgical specimens and monitored tumor growth in 31 consecutive children operated on between 1978 and 1997. The MIB-1 LIs at diagnosis varied from 0-10.6% (mean +/- SD, 3.27 +/- 2.49%). Tumor progression occurred in 19 patients leading to death in seven, three of whom had neurofibromatosis type 1 (NF1). No association between MIB-1 LI at initial diagnosis and both progression free and overall survival was apparent. However, the MIB-1 LIs increased to 15.2% and 18% in two patients with NF1 who developed highly malignant gliomas 6 and 6.5 years after irradiation. In the remaining patients the MIB-1 LIs did not change significantly over time in a total of 17 repeat surgeries. Three patients with LIs of 6.8%, 10.6% and 8.8% are stable after 6, 4.5 and 3.5 years with partial resection, biopsy and subtotal resection, respectively, and no further therapy in the first two and chemotherapy in the latter. Three patients (10%) with LIs of 6.4%, 4.8% and 2.2% either presented with or developed leptomeningeal spread during follow-up. While MIB-1 LI does not appear to assist in clinical decision making patient numbers were too small to find out whether response to chemotherapy varies with proliferative potential.

Cyclin D1 and MIB-1 immunohistochemistry in pilocytic astrocytomas: a study of 48 cases

Pilocytic astrocytoma is an infrequently encountered, generally low-grade neoplasm. No study has extensively looked at both cyclin D1 and MIB-1 labeling indices in pilocytic astrocytoma and their relation to clinical outcome. This study retrospectively examines the clinicopathologic features of 48 patients with pilocytic astrocytoma including MIB-1 (cell proliferation marker) and cyclin D1 (protein that regulates progression from G1 to S phase of the cell cycle) immunohistochemistry. Of 48 patients (27 females and 21 males; mean age, 12.7 years; age range, 2 to 57 years), 26 initially underwent gross total resection; 17, subtotal resection; four, biopsy alone; in one patient, the extent of tumor resection was unknown. Histological features observed included Rosenthal fibers (83.3%), granular bodies (75%), vascular sclerosis (56.2%), vascular proliferation (56.2%), prominent nuclear pleomorphism (14.6%), necrosis (10.4%), and identifiable mitotic figures (2.1%). MIB-1 labeling indices (n=45) (positive staining tumor nuclei per 1,000 nuclei evaluated) ranged from 0 to 3.5% (mean, 0.6%); seven tumors had a labeling index greater than 1.0%. Cyclin D1 labeling indices (n=45) ranged from 0 to 0.8% (mean, 0.1%). Most tumors (N=29, 66.7%) had no immunostaining. At last known follow-up, 27 patients were alive with no evidence of disease (mean, 49.2 months), 17 patients were alive with evidence of disease (mean, 36.8 months), three died with tumor at 2, 22, and 156 months, and one patient was lost to follow-up. Eight patients had at least one tumor recurrence requiring additional surgery; seven of these patients had an initial subtotal resection. In summary, MIB-1 labeling indices were generally low (mean, 0.6%) and are reflective of the slow growth of the tumors. Cyclin D1 immunostaining does not appear to be significantly increased in pilocytic astrocytoma. Adverse outcome in patients with pilocytic astrocytoma may be related to extent of surgical resection and does not seem to correlate with histology, MIB-1 labeling indices, or cyclin D1 immunoreactivity.

Pediatric low-grade gliomas: prognosis with proton magnetic resonance spectroscopic imaging

OBJECTIVE

Our aim was to assess the correlation between the low-grade glioma (LGG) metabolic profile and tumor progression. Using in vivo proton magnetic resonance spectroscopic imaging, we specifically asked whether and which metabolic features are associated with tumor regrowth or recurrence.

METHODS

Eleven pediatric patients with histologically proven partially resected (<20% resection) midline LGG were treated and followed up for a period of 2 years. All patients underwent proton magnetic resonance spectroscopic imaging studies before any management was determined. Tumor progression was defined as radiological evidence of mass enlargement (>25%) during the follow-up period. Proton magnetic resonance spectroscopic imaging was performed using a PRESS-CSI sequence on a General Electric 1.5-tesla scanner (General Electric Medical System, Waukesha, WI). The signal intensities of N-acetylaspartate, choline (CHO), and creatine from the tumor and the normal brain were used to calculate normalized metabolite intensities and metabolite ratios.

RESULTS

Tumors that progressed during a 2-year period displayed higher normalized CHO than those that remained stable (Mann-Whitney test, P < 0.03). The majority (five of six) of the rapidly growing LGG showed values of normalized CHO of at least 1, whereas the nonprogressors had a normalized CHO value of less than 1.

CONCLUSION

In association with pediatric LGG, high normalized CHO values seem to herald the potential for rapid tumor growth. These observations may be valuable for defining subsets of patients with LGG who may benefit from early therapeutic interventions.

The proliferative potential of the pilocytic astrocytoma: the relation between MIB-1 labeling and clinical and neuro-radiological follow-up

The proliferative potential of 39 pilocytic and 5 low grade astrocytomas was studied in relation to the Ki-67 activity as measured by the MIB-1 Labelings Index. The results were correlated to the biological behaviour of the tumor as measured by clinical and neuro-radiological (CT- or MRI-scans) follow-up of the patient. This study was undertaken to answer the question whether MIB-1 expression reflects differences in biological behaviour of these tumors, such as rapid progression of residual tumor or stable remaining tumor. MIB-1 LI values ranged from 0 to 19% in the group of pilocytic astrocytomas (mean 4.2%) and from 0 to 15% in the 5 low grade astrocytomas (mean 4,2%). All patients were operated and 23 of them had incomplete tumor resection as proven on postoperative neuro-imaging studies. Those 23 patients could be subdivided into two groups; one without progression of residual tumor during follow-up (n=12) and the other with tumor progression (n=11). mean MIB-1 LI in the group with 'quiescent' tumor tended to be lower than in the group with progressive tumor: 3,3% vs. 6,6%. Residual tumors which were negative for MIB-1 staining showed fewer progressions of residual tumor compared to those being positive for MIB-1 staining, however this difference was not significant (p=0, 15, Fisher exact test). Tumor samples of a second operation of the same patient had lower MIB-1 LI values than those of the samples taken at first operation. The proliferating potential seemed to be decreased after part of the tumor was resected. Pilocytic astrocytomas with a negative MIB-1 LI are unlikely to show progression of residual tumor after partial resection. MIB-1 staining might be an additional tool in determining the frequency and duration of follow-up and in making decisions regarding further treatment of a patient operated for a pilocytic astrocytoma with residual tumor.

Low grade gliomas: functional mapping resection strategies, extent of resection, and outcome

The impact of surgery on outcome of adult patients with low-grade gliomas is controversial. Without prospective randomized treatment trials, one is primarily dependent on retrospective studies to address this issue. This paper reviews the recent clinical series of low-grade gliomas in which the association between extent of resection (EOR) and outcome could be analyzed. Functional stimulation mapping methods will be described to point out their critical role in maximizing the extent of resection while minimizing the risk associated with radical resection of low-grade gliomas. Studies from the CT-era analyzed with multivariate statistical methods were emphasized. The analysis of these studies points out that, for astrocytomas, there is no clear consensus that a greater EOR improves survival, but in most series under review, greater EOR significantly extended the survival of patients with oligodendroglioma. Unfortunately, there is little data which specifically analyzes and stratifies the outcome for other end-points such as time to progression, malignant degeneration, mortality and morbidity, and duration of high quality survival by EOR.

Correlation between the bromodeoxyuridine labeling index and the MIB-1 and Ki-67 proliferating cell indices in cerebral gliomas

BACKGROUND

Recently, it has been shown that heating paraffin embedded tumor sections in a microwave oven can reactivate an epitope of Ki-67 protein that is recognized by the monoclonal antibody MIB-1. With this technique, a close correlation was shown between the bromodeoxyuridine labeling index (BUdR LI) and the MIB-1 proliferating cell index (PCI) in corresponding regions of glioblastomas.

METHODS

The reliability of the MIB-1 PCI as a marker of proliferation was evaluated in 90 cerebral gliomas. The MIB-1 immunostaining of ethanol-fixed, paraffin embedded sections of 23 moderately anaplastic astrocytomas, 22 highly anaplastic astrocytomas, 30 glioblastomas, and 15 mixed malignant gliomas was compared with the BUdR LI and, in some cases, the Ki-67 PCI.

RESULTS

MIB-1 positive cells were detected easily in the majority of the cases, and the MIB-1 immunostaining was often superior to that of Ki-67 in individual tumors. The MIB-1 PCI was significantly higher than the Ki-67 PCI and the BUdR LI. Linear-regression analysis showed significant correlations among the three indices. The MIB-1 PCI was correlated with the BUdR LI in each group of the astrocytic tumors and mixed malignant gliomas; the MIB-1 PCI was approximately 2.4-2.8 times higher than the BUdR LI.

CONCLUSIONS

The close correlation between the MIB-1 PCI and the in vivo BUdR LI in serial sections of glioma subtypes suggests that MIB-1 immunostaining is a useful technique for analyzing the proliferative potential of individual gliomas.

Control of human glioma cell growth, migration and invasion in vitro by transforming growth factor beta 1

Factors involved in the control of the biological properties of gliomas, the major form of brain tumour in man, are poorly documented. We investigated the role of transforming growth factor beta 1 (TGF-beta 1) in the control of proliferation of human glioma cell lines as well as normal human fetal brain cells. The data presented show that TGF-beta 1 exerts a growth-inhibitory action on both human fetal brain cells and three cell lines derived from human glioma of different grades of malignancy. In addition, this growth-inhibitory effect is dose dependent and serum independent. Since TGF-beta 1 is known to be involved in the control of cell migration during ontogenesis and oncogenesis, we investigated the role of this factor in the motile and invasive behaviour that characterises human gliomas in vivo. TGF-beta 1 was found to elicit a strong stimulation of migration and invasiveness of glioma cells in vitro. In combination with recent data showing an inverse correlation between TGF-beta 1 expression in human gliomas and survival, these findings may suggest that TGF-beta 1 plays an important role in the malignant progression of gliomas in man. A study of the molecular mechanisms involved in the antiproliferative action and the invasion-promoting action of TGF-beta 1 may help to identify new targets in therapy for brain tumours. A combined antiproliferative and anti-invasive therapy could be envisaged.

Regional differences in bromodeoxyuridine uptake, expression of Ki-67 protein, and nucleolar organizer region counts in glioblastoma multiforme

To investigate intratumoral differences in indices of tumor cell proliferation, we measured the bromodeoxyuridine labeling index (BrdUrd LI), the Ki-67 protein proliferating cell indices (PCIs) determined by monoclonal antibody MIB 1 in microwave-processed paraffin sections (MIB 1 PCI) and in some cases by monoclonal antibody in frozen sections (Ki-67 PCI), and counts of argyrophilic nucleolar organizer regions (AgNORs) in 20 glioblastomas. In the most actively proliferating areas, MIB 1 and Ki-67 PCIs correlated well with the BrdUrd LI and with each other, while AgNOR counts correlated less strongly with these indices. In less active areas, the MIB 1 PCI and BrdUrd LI changed concomitantly from one area to another within a tumor except in areas of pseudopalisading with necrosis; in these areas the BrdUrd LI decreased significantly compared with neighboring tumor tissue, while the MIB 1 PCI did not. There was very little staining of gemistocytic nuclei with either anti-BrdUrd or MIB 1 monoclonal antibodies; this supports the concept that gemistocytes are mainly quiescent cells. AgNORs in all of the above-mentioned areas varied from tumor to tumor, which suggests that they may indicate some cellular activity other than proliferation. The close correlation between the BrdUrd LI and Ki-67 protein PCIs in corresponding regions of glioblastomas suggests that MIB 1 staining of microwave-processed paraffin sections can be used to evaluate the growth potential of individual glioblastomas and possibly of other gliomas as well.

Proliferative potential and prognostic evaluation of low-grade astrocytomas

Despite their histological similarity, low-grade astrocytomas vary widely in their clinical behavior. To elucidate this variable behavior, we measured the proliferative potential of 69 primary and 18 recurrent low-grade astrocytomas and correlated the results with the clinical characteristics and outcome. Each patient received an intravenous infusion of bromodeoxyuridine (BUdR); BUdR-labeled nuclei in excised tumor specimens were identified by immunoperoxidase staining. The BUdR labeling index (LI), or S-phase fraction, ranged from < 1 to 9.3%; the LI was < 1% in 64 (74%) patients and > or = 1% in 23 patients (26%). The LI did not appear to be associated with age, sex, tumor location, or whether the tumor was primary or recurrent. A Cox proportional-hazards analysis of the influence of the LI and other variables (age, sex, tumor location, extent of surgery, primary versus recurrent tumor) on survival showed that the LI and extent of surgery (total resection, subtotal resection, biopsy) were significant in predicting both survival and progression-free survival for all patients and for patients with primary tumors. The LI was also significant in predicting progression-free survival for patients with recurrent tumors. The correlation between the BUdR LI and both survival and time to recurrence suggests that the outcome of low-grade astrocytomas varies according to the proliferative potential. The growth rate of these histologically similar tumors should be assessed individually in order to select specific treatment.