Identification of genomic aberrations associated with shorter overall survival in patients with oligodendroglial tumors

Deletions on chromosomes 1p and 19q are associated with favorable prognosis in patients with oligodendroglial tumors. The aim of our study was to identify additional genomic aberrations linked to patient survival. We performed a genome-wide screen for genomic imbalances by comparative genomic hybridization on tumors from 70 patients, including 40 oligodendrogliomas, 30 oligoastrocytomas (21 WHO grade II tumors, 49 WHO grade III tumors). Data were correlated with overall patient survival (OS, median follow-up: 5.8 years). The most frequent aberrations were losses on chromosome 19q (64%), 1p (59%), 9p (26%), 4q (21%), 10q (19%), 18q (17%); gains on 7q (24%), 19p (19%), 7p (17%). In univariate analyses, combined 1p/19q and 19q loss were significantly associated with longer OS, and gains on 7, 8q, 19q, 20, losses on 9p, 10, 18q, Xp with shorter OS. Multivariate analyses showed the most significant prognostic factors for OS of patients with any oligodendroglial tumor to be WHO grade [odds ratio (OR) 8], 7p gain (OR 6), 9p loss (OR 3); for OS of patients with anaplastic tumors to be 7p gain (OR 10), 8q gain (OR 5), 18q loss (OR 3). Patients with anaplastic oligodendroglial tumors containing one or more prognostically unfavorable genomic aberration had a poor outcome independent of the 1p/19q status. In summary, we identified several independent genomic markers of shorter survival in patients with oligodendroglial tumors. Thus, molecular diagnostic testing, which is usually restricted to 1p/19q deletion analysis, may need to be refined by additionally assessing the prognostically unfavorable genomic aberrations identified.     

Correlation between genetic alteration and long-term clinical outcome of patients with oligodendroglial tumors,with identification of a consistent region of deletion on chromosome arm 1p

BACKGROUND: In oligodendroglial tumors, allelic losses on chromosome arms 1p and 19q are not only diagnostic molecular markers but also statistically significant predictors of both chemosensitivity and longer recurrence-free survival. In the current study, the authors attempted to analyze 21 patients genetically and clinically, with special emphasis on the correlation between genetic alterations and long-term therapeutic results. METHODS: The authors reviewed the clinical cases of 21 patients who had undergone surgery for oligodendroglial tumors (13 oligodendrogliomas, World Health Organization [WHO] Grade II; 3 anaplastic oligodendrogliomas, WHO Grade III; 3 oligoastrocytomas, WHO Grade II; and 2 anaplastic oligoastrocytomas, WHO Grade III). Genetic testing for 1p deletions was performed using fluorescence in situ hybridization, and testing for 1p, 17p, and 19q deletions was carried out by microsatellite analysis. Survival was analyzed with univariate and multivariate Cox regression models. In addition, a high-resolution deletion map of 1p, which led to the discovery of a new deleted region on 1p, was obtained. RESULTS: Statistical analysis revealed that both loss of 1p and loss of 19q independently and significantly predicted overall survival. A high-resolution deletion map, which displayed unusually narrow deletions, revealed a new region of deletion between D1S513 and D1S458 (1p34.3-36.11). CONCLUSIONS: One of the putative tumor suppressor loci exists more proximally than ever reported. Based on the observation that 1p and 19q deletions predicted survival, the authors suggest further use of diagnostic and prognostic genetic testing in the clinical setting.     

High expression of the stem cell marker nestin is an adverse prognostic factor in WHO grade II–III astrocytomas and oligoastrocytomas

Infiltrating astrocytomas and oligoastrocytomas of low to anaplastic grade (WHO grades II and III), in spite of being associated with a wide range of clinical outcomes, can be difficult to subclassify and grade by the current histopathologic criteria. Unlike oligodendrogliomas and anaplastic oligodendrogliomas that can be identified by the 1p/19q codeletion and the more malignant glioblastomas (WHO grade IV astrocytomas) that can be diagnosed solely based on objective features on routine hematoxylin and eosin sections, no such objective criteria exist for the subclassification of grade II–III astrocytomas and oligoastrocytomas (A+OA II–III). In this study, we evaluated the prognostic and predictive value of the stem cell marker nestin in adult A+OA II–III (n = 50) using immunohistochemistry and computer-assisted analysis on tissue microarrays. In addition, the correlation between nestin mRNA level and total survival was analyzed in the NCI Rembrandt database. The results showed that high nestin expression is a strong adverse prognostic factor for total survival (p = 0.0004). The strength of the correlation was comparable to but independent of the isocitrate dehydrogenase 1/2 (IDH 1/2) mutation status. Histopathological grading and subclassification did not correlate significantly with outcome, although the interpretation of this finding is limited by the fact that grade III tumors were treated more aggressively than grade II tumors. These results suggest that nestin level and IDH 1/2 mutation status are strong prognostic features in A+OA II–III and possibly more helpful for treatment planning than routine histopathological variables such as oligodendroglial component (astrocytoma vs. oligoastrocytoma) and WHO grade (grade II vs. III).     

The prognostic impact of histology and 1p/19q status in anaplastic oligodendroglial tumors

BACKGROUND: It has been reported previously that the combined loss of chromosomal arms 1p and 19q is a significant predictor of outcome for patients with anaplastic oligodendroglial (AO) tumors and that such chromosomal loss correlates with classic histology in AO. The authors sought to determine whether histology was an equivalent or superior predictor of outcome compared with 1p/19q status in 131 patients with AO tumors. METHODS: The status of 1p and 19q was determined using real-time, quantitative polymerase chain reaction analysis and/or fluorescence in situ hybridization. Clinical features (response to adjuvant therapy and tumor location) and molecular genetic abnormalities (9p and 10q deletions, overexpression of p53 and epidermal growth factor receptor) were determined on available specimens. Histologic assessments for classic oligodendroglial features were performed by five neuropathologists. RESULTS: Classic histology was associated closely with 1p/19q loss, as reported previously. Patients who had tumors that were considered classic by at least four of the five neuropathologists showed significantly increased progression-free and overall survival compared with the patients who had less classic tumors. The authors also tested the correlation between 1p/19q status and outcome in subsets of patients stratified according to classic tumor features. The association of 1p/19q status with survival was related closely to the presence of classic histology. Loss of 1p/19q was predictive of improved outcome only among patients who had tumors with classic histologic features. CONCLUSIONS: The current results suggested that, in addition to 1p/19q status, histologic features contribute information to the prediction of outcome in patients with AO. Loss of 1p and 19q appeared to be a prognostic marker only in the subset of patients who had AO tumors with classic histologic features.     

Combined 1p/19q loss in oligodendroglial tumors: predictive or prognostic biomarker?

PURPOSE: The combined loss of genetic material on chromosomes 1p and 19q is strongly associated with favorable outcome in patients with WHO grade 3 anaplastic oligodendroglial tumors. The prognostic value of 1p/19q loss in WHO grade 2 oligodendroglial tumors is less well defined. Importantly, the possible effect of combined 1p/19q loss has not been studied in patients who were not treated with radiotherapy or chemotherapy. EXPERIMENTAL DESIGN: Seventy-six patients with oligodendroglioma (n = 33), oligoastrocytoma (n = 30), anaplastic oligodendroglioma (n = 6), or anaplastic oligoastrocytoma (n = 7) were identified who had not received radiotherapy or chemotherapy after their first operation until the end of follow-up or until the first progression and had tissue for 1p/19q status available. 1p/19q status was assessed by multiplex ligation-dependent probe amplification. RESULTS: After a median follow-up of 3.8 years, progressive disease was documented in 34 patients. The estimated median progression-free survival was 4.6 years. Fifty-eight of the 76 patients had a combined loss of 1p and 19q. The absence or presence of combined 1p/19q loss was not prognostic for progression-free survival using multivariate adjustment for histology, extent of resection, and gender. CONCLUSIONS: Combined 1p/19q loss is not a sensitive prognostic biomarker in patients with oligodendroglial tumors who do not receive radiotherapy or chemotherapy. The gene products lost as a consequence of this codeletion may include mediators of resistance to genotoxic therapies. Alternatively, 1p/19q loss might be an early oncogenic lesion promoting the formation of glial neoplasms, which retain high sensitivity to genotoxic stress.     

High rate of deletion of chromosomes 1p and 19q in insular oligodendroglial tumors

It has been reported recently that oligodendroglial tumors arising in the insula rarely harbor co-deletions of chromosomes 1p and 19q, a molecular signature which is associated with a good prognosis and increased responsiveness to radiation and chemotherapy compared with tumors in which 1p and/or 19q is intact. In the context of this claim, we analyzed a series of insular oligodendroglial tumors in order to determine the frequency of 1p/19q co-deletion in tumors arising in this region. We identified 14 insular cases operated on after 2003 in which testing for losses of 1p and 19q was performed. Of these cases, co-deletion of 1p and 19q occurred in eight (57%). Four (50%) of eight oligodendrogliomas and four (67%) of six oligoastrocytomas demonstrated 1p/19q co-deletions. Seven of the eight tumors with co-deletion of 1p/19q were WHO grade II gliomas. There were no statistical differences between tumors with 1p/19q co-deletion compared to those with 1p and/or 19q intact in terms of age, preoperative KPS, presenting symptoms, left versus right lateralization, tumor location (purely insular versus extension into frontal or temporal lobe), preoperative tumor size. There was a preponderance of females in the co-deletion group, and a greater average extent of resection. In contradistinction to previous reports, loss of 1p/19q occurs commonly in insular oligodendroglial tumors. With respect to 1p/19q, insular gliomas do not appear to be distinct from gliomas arising elsewhere in the brain.     

Evidence for a tumor suppressor gene on chromosome 19q associated with human astrocytomas, oligodendrogliomas, and mixed gliomas.

Previous studies have shown frequent allelic losses of chromosomes 9p, 10, 17p, and 22q in glial tumors. Other researchers have briefly reported that glial tumors may also show allelic losses of chromosome 19, suggesting a putative tumor suppressor gene locus on this chromosome (D. T. Ransom et al., Proc. Am. Assoc. Cancer Res., 32:302, 1991). To evaluate whether loss of chromosome 19 alleles is common in glial tumors of different types and grades, we performed Southern blot restriction fragment length polymorphism analysis for multiple chromosome 19 loci in 122 gliomas from 116 patients. Twenty-nine tumors had loss of constitutional heterozygosity of 19q, and four tumors had partial deletions of 19q. Allelic losses on 19q were restricted to grade III anaplastic astrocytomas (4/9) and grade IV glioblastomas (11/46), grade II oligodendrogliomas (2/5) and grade III anaplastic oligodendrogliomas (2/2), and grade II (5/8) and grade III (5/7) mixed oligoastrocytomas. These data demonstrate genetic similarities between astrocytomas, oligodendrogliomas, and mixed glial tumors and indicate the presence of a glial tumor suppressor gene on chromosome 19q.     

Deletion mapping of chromosome 19 in human gliomas

There is evidence that a putative glioma tumor suppressor locus resides on the long arm of chromosome 19. We present data on 161 gliomas from IS6 patients, which were studied by microsatellite analysis for loss of heterozygosity (LOH) on chromosome 19. Eight loci on the long arm and 2 loci on the short arm of chromosome IV were examined. LOH on I9qwas observed in 3/19 astrocytomas (WHO grade II), 12/27 anaplastic astrocytomas (WHO grade III), 16/76 cases of glioblastoma multiforme WHO (grade IV), 4/9 oligodendrogliomas (WHO grade II), 3/5 anaplastic oligodendrogliomas (WHO grade III), 5/9 mixed oligo-astrocytomas (WHO grade II) and 8/10 anaplastic oligo-astrocytomas (WHO grade III). While 31 of the tumors with LOH on chromosomal arm I9q exhibited allelic loss at every informative locus, 20 tumors showed terminal or interstitial deletions. In contrast to astrocytomas and glioblastomas, tumors with an oligodendroglial component had predominantly lost the entire long arm of chromosome 19. The common region of overlap in gliomas was located on 19q 13.2-q 13.4 between the markers D 19S 178 and D 19S 180. Our data confirm the involvement of a putative tumor suppressor gene on chromosomal arm 19q in gliomas and assign this gene to 19q 13.2-q 13.4.     

Morphologic and molecular genetic aspects of oligodendroglial neoplasms

Morphologic criteria for diagnosing oligodendrogliomas and for classifying them as well-differentiated (World Health Organization grade II) and anaplastic (World Health Organization grade III) are well recognized. Nevertheless, applying these guidelines to specific cases often reveals discrepancies among different observers. In addition, whether a given tumor also contains an astrocytic component may be debatable. Loss of heterozygosity studies have demonstrated that oligodendroglial neoplasms have a high incidence of loss of the 1p and 19q chromosomal arms. Although loss of heterozygosity for portions of 19q are sometimes seen in astrocytic neoplasms, these tumors seldom show complete loss of 19q accompanied by loss of 1p. Loss of 9p or homozygous deletion of the CDKN2 gene or both are associated with anaplastic oligodendrogliomas, whereas loss of 17p or TP53 gene mutations or both are frequent in astrocytomas, but rare in oligodendrogliomas. These observations suggest that molecular genetic parameters could provide an objective, reproducible framework for classifying oligodendroglial neoplasms.     

Prognostic significance of multiple genetic lesions on chromosomes 19, 10, and 17 in oligodendrogliomas

Patients diagnosed with oligodendrogliomas/oligoastrocytomas and with somatic loss of genes on chromosome 19q13.2-q13.3 survived for >5-6 years, a survival period typical of the tumors of oligodendroglial origin. One patient with oligoastrocytoma, harboring allelic loss on chromosome 10p in the tumor DNA, had a recurrence five years later with progression to anaplastic astrocytoma. However, another patient with oligoastrocytoma, whose tumor suffered multiple genetic lesions on chromosomes 19q13.2-13.3, 10q22-24, and 17p13.1 (a point mutation in the p53 gene), had two subsequent recurrences as anaplastic astrocytomas and a survival period of 29 months. Our data suggest that in tumors of oligodendroglial origin the inactivation of a tumor suppressor gene on chromosome 10, especially in conjunction with other genetic aberrations, is indicative of aggressive clinical course.     

Alterations of chromosome arms 1p and 19q as predictors of survival in oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas.

PURPOSE: A recent report suggests that alterations of chromosome arms 1p and 19q are associated with chemotherapeutic response and overall survival in anaplastic oligodendroglioma patients treated with procarbazine, lomustine, and vincristine chemotherapy. We set out to further clarify the diagnostic and prognostic implications of these alterations in a broader set of diffuse gliomas, including astrocytic neoplasms and low-grade oligodendrogliomas. PATIENTS AND METHODS: Fluorescence in situ hybridization (FISH) signals from DNA probes mapping to 1p and 19q common deletion regions were enumerated in 162 diffuse gliomas (79 astrocytomas, 52 oligodendrogliomas, and 31 mixed oligoastrocytomas), collected as part of an ongoing prospective investigation of CNS tumors. RESULTS: The oligodendroglial phenotype was highly associated with loss of 1p (P =.0002), loss of 19q (P <.0001), and combined loss of 1p and 19q (P <.0001). Combined loss of 1p and 19q was identified as a univariate predictor of prolonged overall survival among patients with pure oligodendroglioma (log-rank, P =.03) and remained a significant predictor after adjusting for the effects of patient age and tumor grade (P <.01). This favorable association was not evident in patients with astrocytoma or mixed oligoastrocytoma. CONCLUSION: Combined loss of 1p and 19q is a statistically significant predictor of prolonged survival in patients with pure oligodendroglioma, independent of tumor grade. Given the lack of this association in patients with astrocytic neoplasms and the previously demonstrated chemosensitivity of oligodendrogliomas, a combined approach of histologic and genotypic assessment could potentially improve existing strategies for patient stratification and management.     

Tumeurs oligodendrogliales anaplasiques

Oligodendroglial anaplastic tumors include oligodendrogliomas and anaplastic oligo-astrocytomas or mixed anaplastic gliomas. These tumors are relatively rare and their histological diagnosis is difficult, leading to frequent differences of opinion. The main genetic alteration is the codeletion of chromosomes 1p and 19q, which is observed in 50 to 90% of anaplastic oligodendrogliomas and in 10 to 20% of anaplastic oligoastrocytomas. This codeletion indicates both a slower evolution and better chemosensitivity of the tumour. Other favorable prognostic factors are a young age, a good performance index, a macroscopically complete surgical resection and a pure oligodendroglial phenotype. The treatment includes surgery, radiotherapy and chemotherapy. Maximum possible resection is universally accepted but the best sequence and possible association with radiotherapy and chemotherapy are as yet poorly codified. Several international clinical trials based on the 1p–19q molecular status are underway with the aim of identifying the best possible therapeutic sequence.     

IDH‐mutated astrocytomas with 19q‐loss constitute a subgroup that confers better prognosis

IDH‐mutant gliomas are classified into astrocytic or oligodendroglial tumors by 1p/19q status in the WHO 2016 classification, with the latter presenting with characteristic morphology and better prognosis in general. However, the morphological and genetic features within each category are varied, and there might be distinguishable subtypes. We analyzed 170 WHO grade II‐IV gliomas resected in our institution. 1p/19q status was analyzed by microsatellite analysis, and genetic mutations were analyzed by next‐generation sequencing and Sanger sequencing. For validation, the Brain Lower Grade Glioma dataset of The Cancer Genome Atlas was analyzed. Of the 42 grade III IDH‐mutated gliomas, 12 were 1p‐intact/19q‐intact (anaplastic astrocytomas [AA]), 7 were 1p‐intact/19q‐loss (AA), and 23 showed 1p/19q‐codeletion (anaplastic oligodendrogliomas). Of the 88 IDH‐wild type glioblastomas (GBMs), 14 showed 1p‐intact/19q‐loss status. All of the seven 1p‐intact/19q‐loss AAs harbored TP53 mutation, but no TERT promotor mutation. All 19q‐loss AAs had regions presenting oligodendroglioma‐like morphology, and were associated with significantly longer overall survival compared to 19q‐intact AAs (P = .001). This tendency was observed in The Cancer Genome Atlas Lower Grade Glioma dataset. In contrast, there was no difference in overall survival between the 19q‐loss GBM and 19q‐intact GBM (P = .4). In a case of 19q‐loss AA, both oligodendroglial morphology and 19q‐loss disappeared after recurrence, possibly indicating correlation between 19q‐loss and oligodendroglial morphology. We showed that there was a subgroup, although small, of IDH‐mutated astrocytomas harboring 19q‐loss that present oligodendroglial morphology, and also were associated with significantly better prognosis compared to other 19q‐intact astrocytomas.     

Molecular analysis of anaplastic oligodendroglial tumors in a prospective randomized study: A report from EORTC study 26951

Recent studies have shown that the clinical outcome of anaplastic oligodendroglial tumors is variable, but also that the histological diagnosis is subject to interobserver variation. We investigated whether the assessment of 1p/19q codeletion, polysomy of chromosome 7, epidermal growth factor receptor (EGFR) gene amplification (EGFR^amp), and loss of chromosome 10 or 10q offers additional prognostic information to the histological diagnosis and would allow molecular subtyping. For this study, we used the clinical data and tumor samples of the patients included in multicenter prospective phase III European Organisation for Research and Treatment of Cancer (EORTC) study 26951 on the effects of adjuvant procarbazine, chloroethyl cyclohexylnitrosourea (lomustine), and vincristine chemotherapy in anaplastic oligodendroglial tumors. Fluorescence in situ hybridization was used to assess copy number aberrations of chromosome 1p, 19q, 7, 10, and 10q and EGFR. Three different analyses were performed: on all included patients based on local pathology diagnosis, on the patients with confirmed anaplastic oligodendroglial tumors on central pathology review, and on this latter group but after excluding anaplastic oligoastrocytoma (AOA) with necrosis. As a reference set for glioblastoma multiforme (GBM), patients from the prospective randomized phase III study on GBM (EORTC 26981) were used as a benchmark. In 257 of 368 patients, central pathology review confirmed the presence of an anaplastic oligodendroglial tumor. Tumors with combined 1p and 19q loss (1p^loss19q^loss) were histopathologically diagnosed as anaplastic oligodendroglioma, were more frequently located in the frontal lobe, and had a better outcome. Anaplastic oligodendroglial tumors with EGFR^amp were more frequently AOA, were more often localized outside the frontal lobe, and had a survival similar to that for GBM. Survival of patients with AOA harboring necrosis was in a similar range as for GBM, while patients with AOA with only endothelial proliferation had better overall survival. In univariate analyses, all molecular factors except loss of 10q were of prognostic significance, but on multivariate analysis a histopathological diagnosis of AOA, necrosis, and 1p^loss19q^loss remained independent prognostic factors. AOA tumors with necrosis are to be considered WHO grade IV tumors (GBM). Of all molecular markers analyzed in this study, especially loss of 1p/19q carried prognostic significance, while the others contributed little prognostic value to classical histology.     

Recursive partitioning analysis of prognostic variables in newly diagnosed anaplastic oligodendroglial tumors

Background

Anaplastic oligodendroglial tumors are rare, and median survival varies widely. Analysis of 1p19q deletion is performed commonly and is an important prognostic factor. However, age and other clinical variables also carry prognostic value, and it is unclear how to incorporate them into clinical decision making or to combine them for prognostication.

Methods

We compiled a retrospective database of 1013 patients with newly diagnosed anaplastic oligodendrogliomas or oligoastrocytomas and performed a recursive partitioning analysis to generate independent prognostic classes among 587 patients with informative 1p19q status. Variables included for survival classification were age (continuous), history of prior low-grade glioma, 1p19q deletion status, histology (presence or absence of an astrocytic component), tumor lobe, tumor hemisphere, gender, extent of resection, postresection treatment, and performance status at diagnosis.

Results

Recursive partitioning analysis identified 5 prognostic groups based on hazard similarity: class I (age <60 y, 1p19q codeleted), class II (age <43 y, not codeleted), class III (age 43–59 y, not codeleted, frontal lobe tumor or age ≥60 y, codeleted), class IV (age 43–59 y, not codeleted, not frontal lobe tumor or age 60–69 y, not codeleted), and class V (age ≥70 y, not codeleted). Survival differences were highly significant (P < .0001), with medians ranging from 9.3 years (95% CI: 8.4–16.0) for class I to 0.6 years (95% CI: 0.5–0.9) for class V.

Conclusions

These 5 distinct classification groups were defined using prognostic factors typically obtained during routine management of patients with anaplastic oligodendroglial tumors. Validation in a prospective clinical trial may better differentiate patients with respect to treatment outcome.     

Correlation among pathology,genetic and epigenetic profiles,and clinical outcome in oligodendroglial tumors

Recent studies have revealed a correlation between specific genetic changes, such as loss of chromosome 1p and 19q, and sensitivity of oligodendroglial neoplasm to radiotherapy and chemotherapy; epigenetic changes also play an important role in some tumors. In this retrospective study, we analyzed chromosomal alterations in 17 loci and promoter methylation status of 8 tumor‐related genes in 49 oligodendroglial tumors (29 WHO grade II and 11 WHO grade III oligodendrogliomas; 7 WHO grade II and 2 WHO grade III oligoastrocytomas) using quantitative microsatellite analysis and methylation‐specific polymerase chain reaction and correlated this information with clinical data. We also performed immunohistochemical stains for Ki‐67 and O (6)‐methyl guanine‐DNA methyl transferase. Our results showed that the frequency of deletions in regions on 1p, 9p, 10q, 17p and 19q were 71.4%, 26.5%, 6.1%, 69.4% and 89.8%, respectively. Promoter methylation was detected in p14, p15, p16, p53, p73, PTEN, MGMT and RASSF1A genes in 24.5%, 6.1%, 46.9%, 0%, 6.1%, 42.9%, 53.1% and 77.6% of tumors, respectively. Statistical analysis identified that 9p22 loss, p73 methylation and p15 methylation were independently associated with reduced overall survival, and Ki‐67 labeling index (LI) ≥ 5%, 9p22 loss, no loss of 19q, p73 methylation, p14 methylation and unmethylated MGMT predicted shorter progression‐free survival. Our findings suggest that the frequent deletion and hypermethylation of tumor‐related genes may represent a mechanism of tumor development and progression and emphasize the importance of defining new molecular markers for predicting prognosis, tumor recurrence and therapeutic response in cancer management. © 2009 UICC     

Loss of Heterozygosity for Loci on Chromosome Arms 1p and 10q in Oligodendroglial Tumors: Relationship to Outcome and Chemosensitivity

Oligodendroglial tumors frequently have deletions of chromosomal loci on 1p and 19q. Loss of heterozygosity (LOH) of chromosome 10 may be a negative prognostic factor. We reviewed 23 patients with oligodendroglial tumors, to evaluate the frequency of 1p and 10q LOH and correlate with clinical outcome. Three loci (D1S402, D1S1172, MCT118) on 1p and 2 loci (D10S520 and D10S521) on 10q were analyzed for LOH using PCR techniques. Sixteen oligodendrogliomas (6 low grade and 10 anaplastic) and 7 oligoastrocytomas (1 low grade and 6 anaplastic) were studied. Overall 14/22 (64%) showed 1p LOH and 7/23 (30%) showed 10q LOH. Of 7 patients with some response to chemotherapy, all showed 1p LOH and none had 10q LOH. Of 5 patients with stable or progressive disease, 1 had 1p LOH and 2 showed 10q LOH. The presence of 1p LOH was significantly associated with response to chemotherapy (p = 0.02). Median progression free survival (PFS) was 31 months for 1p intact patients and 118 months for the 1p LOH group (p = 0.014). Median PFS for 10q LOH patients was 31 and 118 months for patients with intact chromosome 10 (p = 0.016). 1p LOH is a predictor of response to chemotherapy and a good prognostic factor. 10q LOH is less common in oligodendroglial tumors but predicts for worse outcome. Molecular genotyping of oligodendroglial tumors is recommended as part of the standard diagnostic workup.     

Correlation of histology and molecular genetic analysis of 1p, 19q, 10q, TP53, EGFR, CDK4, and CDKN2A in 91 astrocytic and oligodendroglial tumors.

PURPOSE: The histological diagnosis of human gliomas is of great importance for estimating patient prognosis and guiding therapy but suffers from being subjective and, therefore, variable. We hypothesized that molecular genetic analysis could provide a more objective means to classify tumors and, thus, reduce diagnostic variability. EXPERIMENTAL DESIGN: We performed molecular genetic analysis on 91 nonselected gliomas for 1p, 19q, 10q, TP53, epidermal growth factor receptor, and cyclin-dependent kinase 4 abnormalities and compared with the consensus diagnoses established among four independent neuropathologists. RESULTS: There were six astrocytomas, seven anaplastic astrocytomas, 45 glioblastomas, 21 oligodendrogliomas, eight anaplastic oligodendrogliomas, three oligoastrocytomas, and one anaplastic oligoastrocytoma. Twenty-nine cases had either 1p or 19qloss of heterozygosity (LOH) while retaining both copies of 10q, of which 25 (86%) were histologically oligodendroglioma, anaplastic oligodendroglioma, oligoastrocytoma, or anaplastic oligoastrocytoma. As for the oligodendroglial tumors, unanimous agreement of the initial diagnoses was almost restricted to those cases with combined 1p/19qLOH, whereas all nine tumors without 1p loss initially received variable diagnoses. Interestingly, TP53 mutation was inversely related to 1pLOH in all gliomas (P = 0.0003) but not 19qLOH (P = 0.15). CONCLUSIONS: These data demonstrate that molecular genetic analysis of 1p/19q/10q/TP53 has significant diagnostic value, especially in detecting oligodendroglial tumors. In addition, 1pLOH and TP53 mutations in gliomas may be markers of oligodendroglial and astrocytic pathways, respectively, which may separate gliomas with the same histological diagnosis, especially oligodendroglial tumors and glioblastomas. Testing for those molecular genetic alterations would be essential to obtain more homogeneous sets of gliomas for the future clinical studies.