Identification of isochromosome 1q as a recurring chromosome aberration in skull base chordomas: a new marker for aggressive tumors?

Presentation, Treatment, and Long-Term Outcome of Intrasellar Chordoma: A Pooled Analysis of Institutional, SEER (Surveillance Epidemiology and End Results), and Published Data

BACKGROUND

Chordoma that occurs primarily in the sella turcica is rare and presents unique treatment challenges.

OBJECTIVE

The purpose of this study was to determine common features, treatment approaches, and survival characteristics of intrasellar chordoma.

METHODS

Institutional databases, the SEER (Surveillance Epidemiology and End Results) database, and PubMed/EMBASE were queried for chordoma with a primarily intrasellar component. The SEER database was also queried for adult skull base chordoma. Patient-level data were extracted where available. Kaplan-Meier survival analyses were conducted.

RESULTS

Among 80 cases, the mean age at presentation was 55.6 (standard deviation, 15.9), with a female predominance (1.16:1.00). Patients experienced symptoms for a mean duration of 19.0 months, including cranial nerve deficits, hypopituitarism, and hyperprolactinemia. Among patients receiving treatment, 77.5% underwent surgery. In addition, less than half of the patients (n = 34, 47.3%) received adjuvant radiation therapy. The 5-year overall survival (OS) of intrasellar chordoma was 60.0% (standard error [SE], 6.9). Patients aged 40 years and younger had a 5-year OS of 80.8% (SE, 12.2), compared with patients older than 40 years, who had an OS of 55.4% (SE, 7.7) (Mantel-Cox, P = 0.044). Males experienced a lower 5-year OS (44.0; SE, 9.7) than did females (76.8; SE, 8.5), (Mantel-Cox, P = 0.003). Median OS was greater in patients with skull base chordoma than in patients with intrasellar chordoma (Mantel-Cox, P = 0.046).

CONCLUSIONS

Intrasellar chordoma presents frequently with visual disturbances and hyperprolactinemia and has a slightly higher incidence in females. Young age predicts a better prognosis. Intrasellar chordoma has a lower overall survival than has skull base chordoma.

Genetic aberrations and molecular biology of skull base chordoma and chondrosarcoma

Chordomas and chondrosarcomas are two major malignant bone neoplasms located at the skull base. These tumors are rarely metastatic, but can be locally invasive and resistant to conventional chemotherapies and radiotherapies. Accordingly, therapeutic approaches for the treatment of these tumors can be difficult. Additionally, their location at the skull base makes them problematic. Although accurate diagnosis of these tumors is important because of their distinct prognoses, distinguishing between these tumor types is difficult due to overlapping radiological and histopathological findings. However, recent accumulation of molecular and genetic studies, including extracranial location analysis, has provided us clues for accurate diagnosis. In this report, we review the genetic aberrations and molecular biology of these two tumor types. Among the abundant genetic features of these tumors, brachyury immunohistochemistry and direct sequencing of IDH1/2 are simple and useful techniques that can be used to distinguish between these tumors. Although it is still unclear why these tumors, which have such distinct genetic backgrounds, show similar histopathological findings, comparison of their genetic backgrounds could provide essential information.

Establishment of clival chordoma cell line MUG-CC1 and lymphoblastoid cells as a model for potential new treatment strategies

Chordomas are rare malignant tumors that develop from embryonic remnants of the notochord and arise only in the midline from the clivus to the sacrum. Surgery followed by radiotherapy is the standard treatment. As chordomas are resistant to standard chemotherapy, further treatment options are urgently needed. We describe the establishment of a clivus chordoma cell line, MUG-CC1. The cell line is characterized according to its morphology, immunohistochemistry, and growth kinetics. During establishment, cell culture supernatants were collected, and the growth factors HGF, SDF-1, FGF2, and PDGF analyzed using xMAP^® technology. A spontaneous lymphoblastoid EBV-positive cell line was also developed and characterized. MUG-CC1 is strongly positive for brachyury, cytokeratin, and S100. The cell line showed gains of the entire chromosomes 7, 8, 12, 13, 16, 18, and 20, and high level gains on chromosomes 1q21–1q24 and 17q21–17q25. During cultivation, there was significant expression of HGF and SDF-1 compared to continuous chordoma cell lines. A new, well-characterized clival chordoma cell line, as well as a non-tumorigenic lymphoblastoid cell line should serve as an in vitro model for the development of potential new treatment strategies for patients suffering from this disease.

A vertebral extra dural chordoma at C5, possibly deriving from a clival chordoma

Background:

Clival chordomas are a rare type of cancer with low metastatic potential and primary metastasize to the lung or bones.

Case Description:

This case report describes a possible metastatic, paravertebral chordoma at level C4-C5 in a patient with a past medical history of a clival chordoma.

Conclusion:

Chordomas are unpredictable and may metastasise.

Chordoma: the entity

Chordomas are malignant tumors of the axial skeleton, characterized by their locally invasive and slow but aggressive growth. These neoplasms are presumed to be derived from notochordal remnants with a molecular alteration preceding their malignant transformation. As these tumors are most frequently observed on the skull base and sacrum, patients suffering from a chordoma present with debilitating neurological disease, and have an overall 5-year survival rate of 65%. Surgical resection with adjuvant radiotherapy is the first-choice treatment modality in these patients, since chordomas are resistant to conventional chemotherapy. Even so, management of chordomas can be challenging, as chordoma patients often present with recurrent disease. Recent advances in the understanding of the molecular events that contribute to the development of chordomas are promising; the most novel finding being the identification of brachyury in the disease process. Here we present an overview of the current paradigms and summarize relevant research findings.

High-resolution whole-genome analysis of skull base chordomas implicates FHIT loss in chordoma pathogenesis

Chordoma is a rare tumor arising in the sacrum, clivus, or vertebrae. It is often not completely resectable and shows a high incidence of recurrence and progression with shortened patient survival and impaired quality of life. Chemotherapeutic options are limited to investigational therapies at present. Therefore, adjuvant therapy for control of tumor recurrence and progression is of great interest, especially in skull base lesions where complete tumor resection is often not possible because of the proximity of cranial nerves. To understand the extent of genetic instability and associated chromosomal and gene losses or gains in skull base chordoma, we undertook whole-genome single-nucleotide polymorphism microarray analysis of flash frozen surgical chordoma specimens, 21 from the clivus and 1 from C1 to C2 vertebrae. We confirm the presence of a deletion at 9p involving CDKN2A, CDKN2B, and MTAP but at a much lower rate (22%) than previously reported for sacral chordoma. At a similar frequency (21%), we found aneuploidy of chromosome 3. Tissue microarray immunohistochemistry demonstrated absent or reduced fragile histidine triad (FHIT) protein expression in 98% of sacral chordomas and 67%of skull base chordomas. Our data suggest that chromosome 3 aneuploidy and epigenetic regulation of FHIT contribute to loss of the FHIT tumor suppressor in chordoma. The finding that FHIT is lost in a majority of chordomas provides new insight into chordoma pathogenesis and points to a potential new therapeutic target for this challenging neoplasm.

Frequent activation of EGFR in advanced chordomas

Background

Chordomas are rare neoplasms, arising from notochordal remnants in the midline skeletal axis, for which the current treatment is limited to surgery and radiotherapy. Recent reports suggest that receptor tyrosine kinases (RTK) might be essential for the survival or proliferation of chordoma cells, providing a rationale for RTK targeted therapy. Nevertheless, the reported data are conflicting, most likely due to the assorted tumor specimens used for the studies and the heterogeneous methodological approaches. In the present study, we performed a comprehensive characterization of this rare entity using a wide range of assays in search for relevant therapeutic targets.

Methods

Histopathological features of 42 chordoma specimens, 21 primary and 21 advanced, were assessed by immunohistochemistry and fluorescent in situ hybridization (FISH) using PDGFRB, CSF1R, and EGFR probes. Twenty-two of these cases, for which frozen material was available (nine primary and 13 advanced tumors), were selectively analyzed using the whole-genome 4.3 K TK-CGH-array, phospho-kinase antibody array or Western immunoblotting. The study was supplemented by direct sequencing of KIT, PDGFRB, CSF1R and EGFR.

Results

We demonstrated that EGFR is frequently and the most significantly activated RTK in chordomas. Furthermore, concurrent to EGFR activation, the tumors commonly reveal co-activation of alternative RTK. The consistent activation of AKT, the frequent loss of the tumor suppressor PTEN allele, the recurrent activation of upstream RTK and of downstream effectors like p70S6K and mTOR, all indicate the PI3K/AKT pathway as an important mediator of transformation in chordomas.

Conclusions

Given the complexity of the signaling in chordomas, combined treatment regimens targeting multiple RTK and downstream effectors are likely to be the most effective in these tumors. Personalized therapy with careful selection of the patients, based on the molecular profile of the specific tumor, is anticipated.

The prognostic value of Ki-67, p53, epidermal growth factor receptor, 1p36, 9p21, 10q23, and 17p13 in skull base chordomas

CONTEXT

Skull base chordomas are rare, locally aggressive, notochord-derived neoplasms for which prognostically relevant biomarkers are not well established.

OBJECTIVE

To evaluate whether newly discovered molecular alterations in chordomas have prognostic significance similar to what has been described regarding Ki-67 proliferation index.

DESIGN

We conducted a retrospective study of 28 cases of primary clival chordomas.

RESULTS

Ki-67 proliferation index 5% or more, p53 accumulation, and epidermal growth factor receptor expression were seen in 32%, 44%, and 8% of chordomas, respectively. 1p loss of heterozygosity (LOH) and/or 1p36 hemizygous deletion was seen in 30% of tumors, while 9p LOH and/or 9p21 homozygous deletion was seen in 21% of cases. Loss of heterozygosity at 10q23 and 17p13 were identified in 57% and 52% of cases, respectively. Ki-67 proliferation index 5% or more and 9p LOH were significantly associated with a shorter overall survival, while homozygous deletion at 9p21 via fluorescence in situ hybridization approached significance. No correlation with survival was found for p53 or epidermal growth factor receptor expression, 1p36 hemizygous deletion, or LOH at 1p, 10q23, or 17p13.

CONCLUSIONS

Chordomas with elevated Ki-67 proliferation index or deletion at 9p21 may be at risk for a more aggressive clinical course and shorter survival. These biomarkers may thus be used to improve therapeutic stratification.

The prognostic value of Ki-67, p53, epidermal growth factor receptor, 1p36, 9p21, 10q23, and 17p13 in skull base chordomas

CONTEXT

Skull base chordomas are rare, locally aggressive, notochord-derived neoplasms for which prognostically relevant biomarkers are not well established.

OBJECTIVE

To evaluate whether newly discovered molecular alterations in chordomas have prognostic significance similar to what has been described regarding Ki-67 proliferation index.

DESIGN

We conducted a retrospective study of 28 cases of primary clival chordomas.

RESULTS

Ki-67 proliferation index 5% or more, p53 accumulation, and epidermal growth factor receptor expression were seen in 32%, 44%, and 8% of chordomas, respectively. 1p loss of heterozygosity (LOH) and/or 1p36 hemizygous deletion was seen in 30% of tumors, while 9p LOH and/or 9p21 homozygous deletion was seen in 21% of cases. Loss of heterozygosity at 10q23 and 17p13 were identified in 57% and 52% of cases, respectively. Ki-67 proliferation index 5% or more and 9p LOH were significantly associated with a shorter overall survival, while homozygous deletion at 9p21 via fluorescence in situ hybridization approached significance. No correlation with survival was found for p53 or epidermal growth factor receptor expression, 1p36 hemizygous deletion, or LOH at 1p, 10q23, or 17p13.

CONCLUSIONS

Chordomas with elevated Ki-67 proliferation index or deletion at 9p21 may be at risk for a more aggressive clinical course and shorter survival. These biomarkers may thus be used to improve therapeutic stratification.

Gain of chromosome 7 by chromogenic in situ hybridization (CISH) in chordomas is correlated to c-MET expression

Chordomas are low to intermediate grade malignancies that arise from remnants of embryonic notochord. They often recur after surgery and are highly resistant to conventional adjuvant therapies. Recently, the development of effective targeted molecular therapy has been investigated in chordomas that show receptors for tyrosine kinase (RTKs) activation. Expression of specific RTKs such as Epidermal Growth Factor Receptor (EGFR) and Mesenchymal-epithelial transition factor (c-MET) in chordomas may offer valuable therapeutic options. We investigated changes in copy number of chromosome 7 and correlated it with EGFR gene status and EGFR and c-MET protein expression in 22 chordoma samples. Chromosome 7 copy number was evaluated by chromogenic in situ hybridization (CISH) and protein expression of EGFR and c-MET by immunohistochemistry. Tumors mostly showed conventional histopathologic features and were found mainly in sacral (41%) and cranial sites (54.5%). Aneusomy of chromosome 7 was seen in 73% of the samples, 62% of primary tumors and in all recurrent chordomas. EGFR and c-MET were both expressed, but only c-MET protein expression was significantly correlated with chromosome 7 aneusomy (P ≤ 0.001). c-MET overexpression may represent an early chromosome 7 alteration that could play an important role during chordoma pathogenesis. c-MET overexpression shows promise as a molecular marker of response to targeted molecular therapy in the treatment of chordomas.

A compendium of myeloma-associated chromosomal copy number abnormalities and their prognostic value

To obtain a comprehensive genomic profile of presenting multiple myeloma cases we performed high-resolution single nucleotide polymorphism mapping array analysis in 114 samples alongside 258 samples analyzed by U133 Plus 2.0 expression array (Affymetrix). We examined DNA copy number alterations and loss of heterozygosity (LOH) to define the spectrum of minimally deleted regions in which relevant genes of interest can be found. The most frequent deletions are located at 1p (30%), 6q (33%), 8p (25%), 12p (15%), 13q (59%), 14q (39%), 16q (35%), 17p (7%), 20 (12%), and 22 (18%). In addition, copy number-neutral LOH, or uniparental disomy, was also prevalent on 1q (8%), 16q (9%), and X (20%), and was associated with regions of gain and loss. Based on fluorescence in situ hybridization and expression quartile analysis, genes of prognostic importance were found to be located at 1p (FAF1, CDKN2C), 1q (ANP32E), and 17p (TP53). In addition, we identified common homozygously deleted genes that have functions relevant to myeloma biology. Taken together, these analyses indicate that the crucial pathways in myeloma pathogenesis include the nuclear factor-κB pathway, apoptosis, cell-cycle regulation, Wnt signaling, and histone modifications. This study was registered at http://isrctn.org as ISRCTN68454111.

Chordoma in the lateral medullary cistern in a patient with tuberous sclerosis: A case report and review of the literature

Background:

Chordomas are rare intracranial tumors. There are several reported cases of these tumors arising in patients with tuberous sclerosis (TSC), a neurocutaneous disorder inherited in autosomal dominant fashion that predisposes patients to hamartomatous and neoplastic lesions.

Case Description:

A 38-year-old man with the diagnosis of TSC presented with the complaint of dizziness and near syncope. Imaging revealed a mass in the lateral medullary cistern that was found at the time of surgery to be a chordoma. The patient underwent a left far lateral approach for removal of the tumor. Upon opening of the dura, the tumor could be seen under the arachnoid. The tumor was carefully debulked within the limits of safety. The patient did well postoperatively and was referred to the radiation oncology department at our institution for follow-up radiotherapy of the tumor bed.

Conclusion:

This study presents an unusual presentation and location for a chordoma and contributes to the growing literature associating chordomas with TSC.

Three genetic developmental stages of papillary renal cell tumors: duplication of chromosome 1q marks fatal progression

Papillary renal cell tumors (RCT) make up a cytomorphologically and biologically heterogeneous group of kidney cancers including renal cell adenomas (RCA) and renal cell carcinomas (RCC). To find genetic markers landmarking the tumor progression, we have evaluated the genetic alterations obtained by karyotyping, chromosomal and array-CGH and compared with the cytological characteristics and biological behavior of 60 papillary RCTs. Based on the genetic and clinical data, we have separated 3 groups of tumors and proposed 3 genetically defined developmental stages of papillary RCTs. Papillary RCAs are characterized by combined trisomy of chromosomes 7 and 17, whereas papillary RCCs displayed additional trisomies of 3q, 8q, 12q, 16q and 20q. In addition to the genetic changes occurring in the second group, the third group of tumors was characterized by 1q gain and 6q, 8p, 9p and 14q losses. Kaplan-Meier analysis revealed a significant association between chromosome 1q gain and deadly outcome of the disease. The cytomorphological variation and size of tumors in the second and third groups did not correlate with the clinical outcome. Therefore, we suggest that our genetic classification system landmarking papillary RCA, papillary RCC without and with progression offer a better system to characterize the tumor biology of clinical significance than a cellular/morphological classification.

Impact of cytogenetic abnormalities on the management of skull base chordomas

Object

Cytogenetic studies of chordomas are scarce and show multiple changes involving different chromosomes. These abnormalities are implicated in the pathogenesis of chordoma, but the clinical significance of these changes is yet to be determined. In this study, the authors discuss the cytogenetic changes in a large series of skull base chordomas with long-term follow-up and focus on the impact of these changes on the prognosis, progression, and management of the disease.

Methods

The karyotypes of chordomas in 64 patients (36 men and 28 women) were studied in relation to survival and recurrence or progression over a mean follow-up period of 48 ± 37.5 months. The standard G-banding technique was used for karyotype analysis. Statistical analysis was performed with the Fisher exact test and ORs, and Kaplan-Meier curves were generated for survival and recurrence/progression of disease.

Results

Seventy-four percent of de novo chordomas had normal karyotypes and a 3% recurrence rate; there was a 45% recurrence rate in de novo tumors with abnormal karyotypes (p < 0.01). Recurrent tumors were associated with a high incidence of abnormal karyotype (75%). The OR for recurrence in lesions with an abnormal versus a normal karyotype was 12. Aberrations in chromosomes 3, 4, 12, 13, and 14 were associated with frequent recurrence and decreased survival time. Ninety-five percent of cases with progression involved chromosome 3 and/or 13. The median survival time was 4 months when both of these chromosomes had aberrations (p = 0.02).

Conclusions

Chordomas with normal karyotypes were associated with a low rate of recurrence and a long patient survival, and recurrent chordomas were associated with an abnormal karyotype, disease progression, and poor survival. De novo chordomas with normal karyotypes may be amenable to radical resection and adjunctive proton beam therapy. Recurrent and de novo chordomas with abnormal karyotypes were associated with complex cytogenetic abnormalities and a poor prognosis, particularly in the presence of aberrations underlying tumor progression in chromosomes 3, 4, 12, 13, and 14.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

Evaluation of 1p36 markers and clinical outcome in a skull base chordoma study

Chordomas are rare embryogenetic tumors, arising from remnants of the notochord, characterized by local invasiveness and variable tendency for recurrence. No molecular markers are currently used in a clinical setting to distinguish chordomas with an indolent or an aggressive pattern. Among the genetic lesions observed in this tumor, one of the most commonly detected is 1p loss. In a previous study we observed 1p36 loss of heterozygosity (LOH) in 85% of the analyzed chordomas. We studied a group of 16 homogeneously treated skull base chordomas (SBCs), reporting 1p36 LOH in 75% of them and determining the expression pattern of eight apoptotic genes mapped at 1p36. No tumors shared a common expression profile with nucleus pulposus, which is considered the only adult normal tissue deriving from notochord. In particular, tumor necrosis factor receptor superfamily genes TNFRSF8, TNFRSF9, and TNFRSF14 were differently expressed compared with control in a higher percentage of tumors (40%-53%) than were the remaining analyzed genes, suggesting that the deregulation of these three genes might have a role in chordoma tumorigenesis. The presence/absence of LOH and the expression/nonexpression of each apoptotic gene were studied in a survival analysis. Our results suggest that the lack of 1p36 LOH or the presence of TNFRSF8 expression might be associated with a better prognosis in patients with SBCs.

Frequent deletion of the CDKN2A locus in chordoma: analysis of chromosomal imbalances using array comparative genomic hybridisation

The initiating somatic genetic events in chordoma development have not yet been identified. Most cytogenetically investigated chordomas have displayed near-diploid or moderately hypodiploid karyotypes, with several numerical and structural rearrangements. However, no consistent structural chromosome aberration has been reported. This is the first array-based study characterising DNA copy number changes in chordoma. Array comparative genomic hybridisation (aCGH) identified copy number alterations in all samples and imbalances affecting 5 or more out of the 21 investigated tumours were seen on all chromosomes. In general, deletions were more common than gains and no high-level amplification was found, supporting previous findings of primarily losses of large chromosomal regions as an important mechanism in chordoma development. Although small imbalances were commonly found, the vast majority of these were detected in single cases; no small deletion affecting all tumours could be discerned. However, the CDKN2A and CDKN2B loci in 9p21 were homo- or heterozygously lost in 70% of the tumours, a finding corroborated by fluorescence in situ hybridisation, suggesting that inactivation of these genes constitute an important step in chordoma development.

New candidate chromosomal regions for chordoma development

BACKGROUND

Chordomas are rare, slow growing, infiltrative tumors thought to arise from vestigial or ectopic notochord. Chordoma can occur along the axial skeleton, predominantly in the sphenooccipital, vertebral, and sacrococcygeal regions. Although most chordomas are sporadic, familial cases have also been reported. The most common molecular cytogenetic abnormalities in these tumors are monosomy of chromosome 1 and gain of chromosome 7. In addition, a variety of other chromosomal changes, which are associated with losses and gains of different chromosomes, have also been described in chordomas, such as 1q, 2p, 3p, 5q, 9p, 10, 12q, 13q, 17, and 20q.

METHODS

In this study, using molecular cytogenetics (iFISH), we have studied 1p36, 1q25, 3p13-p14, 7q33, 17p13.1 (p53 gene locus), 2p13 (TGF-alpha locus), 6p12 (VEGF locus), and 4q26-q27 (bFGF/FGF2 locus) loci in chordoma tissues from seven patients with 7 primary tumors and 11 recurrences.

RESULTS

We found that chromosomes 1p36, 1q25, 2p13, and 7q33 are affected in primary chordomas, and these aberrations persist in recurrences. However, the chromosome 6p12 aberration was seen only in primary chordomas, but not in recurrences, indicating that this locus may be associated with chordoma genesis.

CONCLUSIONS

Our descriptive data from interphase FISH analyses suggest that future studies should incorporate a larger number of patients and should focus on identifying the candidate genes in chordoma pathogenesis. Such studies may use a whole-genomic approach, in addition to the regions identified in this study and others.

Familial chordoma

We have treated 175 patients with a chordoma over a ten-year period. Only two had a family history of the condition and we describe these in this paper. In one patient the tumour was at the craniocervical junction and in the other the lesion affected the sacrum. We have undertaken a literature review of familial chordoma and have identified chromosomal abnormalities associated with the condition.

Chromosome 7 abnormalities are common in chordomas

Chordomas are malignant bone tumors most often located in the axial skeleton. The estimated 5-year patient survival rate is between 50 and 80%. The cytogenetic and molecular genetic features of chordomas are largely unknown but, from what can be seen, appear to be complex. Near-diploid karyotypes have been detected by G-banding analysis, and comparative genomic hybridization (CGH) has revealed losses of or from chromosome arms 1p and 3p, as well as partial or whole copy number gains of chromosomes 7 and 20. We provide additional molecular cytogenetic information about six sacral chordomas examined by CGH and interphase fluorescence in situ hybridization (IP-FISH). By CGH, gains of chromosomal areas 1q23 approximately q24 (three tumors), 7p21 approximately p22 (three tumors), 7q (four tumors), and 19p13 (three tumors), as well as loss of chromosomal segment 9p22 approximately p23 (three tumors), were the most frequently observed imbalances. These results are concordant with earlier CGH data, although loss of or from chromosome arms 1p and 3p was not found as frequently in this series; both were detected in only one tumor. IP-FISH confirmed the CGH findings and showed that chromosome 7 was polysomic in four of the tumors. All these samples had trisomic and tetrasomic clones for chromosome 7, and two of them had pentasomic clones as well.

Les chordomes de la base du crâne et du rachis cervical haut. À propos d'une série de 100 patients irradiés selon une technique conformationnelle 3D par une association de faisceaux de photons et de protons

OBJECTIVE

To define prognostic factors for local control and survival in 100 consecutive patients treated by fractionated photon and proton radiation for chordoma of the skull base and upper cervical spine.

PATIENTS AND METHODS

Between December 1995 and August 2002, 100 patients (median age: 53 years, range: 8-85, M/F sex-ratio: 3/2), were treated by a combination of high-energy photons and protons. The proton component was delivered by the 201 MeV proton beam of the Centre de Protonthérapie d'Orsay (CPO). The median total dose delivered to the gross tumour volume was 67 Cobalt Gray Equivalent (CGE) (range: 60-71). A complete surgery, incomplete surgery or a biopsy was performed before the radiotherapy in 16, 75 and 9 cases, respectively.

RESULTS

With a median follow-up of 31 months (range: 1-87), 25 tumours failed locally. The 2 and 4-year local control rates were 86.3% (+/-3.9%) and 53.8% (+/-7.5%), respectively. According to multivariate analysis, less than 95% of the tumour volume encompassed by the 95% isodose line (P=0.048; RR: 3.4 IC95% [1.01-11.8]) and a minimal dose less than 56 CGE (p=0.042; RR: 2.3 IC95% [1.03-5.2]) were independent prognostic factors of local control. Ten patients died. The 2 and 5-year overall survival rates were 94.3% (+/-2.5%) and 80.5% (+/-7.2%). According to multivariate analysis, a controlled tumour (P=0.005; RR: 21 IC95% [2.2-200]) was the lonely independent favourable prognostic factor for overall survival.

CONCLUSION

In chordomas of the skull base and upper cervical spine treated by surgical resection followed by high-dose photon and proton irradiation, local control is mainly dependent on the quality of radiation, especially dose-uniformity within the gross tumour volume. Special attention must be paid to minimise underdosed areas due to the close proximity of critical structures and possibly escalate dose-constraints to tumour targets in future studies, in view of the low toxicity observed to date.

Update on the cytogenetics and molecular genetics of chordoma

Chordoma is a rare mesenchymal tumour of complex biology for which only histologic and immunohistochemical criteria have been defined, but no biomarkers predicting the clinical outcome and response to treatment have yet been recognised. We herein review the interdisciplinary information achieved by epidemiologists, neurosurgeons and basic scientists on chordoma, usually a sporadic tumour, which also includes a small fraction of familial cases. Main focus is on the current knowledge of the genetic alterations which might pinpoint candidate genes and molecular mechanisms shared by sporadic and familiar chordomas. Due to the scarcity of the investigated tumour specimens and the multiple chromosome abnormalities found in tumours with aberrant karyotypes, conventional cytogenetics and Fluorescence In Situ Hybridization failed to detect recurrent chordoma-specific chromosomal rearrangements. Genome-wide approaches such as Comparative Genomic Hybridization (CGH) are yet at an initial stage of application and should be implemented using BAC arrays either genome-wide or targeting selected genomic regions, disclosed by Loss of Heterozygosity (LOH) studies. An LOH region was shown by a systematic study on a consistent number of chordomas to encompass 1p36, a genomic interval where a candidate gene was suggested to reside. Despite the rarity of multiplex families with chordoma impaired linkage studies, a chordoma locus could be mapped to chromosome 7q33 by positive lod score in three independent families. The role in chordomagenesis of the Tuberous Sclerosis Complex (TSC) genes has been proved, but the extent of involvement of TSC1 and TSC2 oncosuppressors in chordoma remains to be assessed. In spite of the scarce knowledge on the genetics and molecular biology of chordoma, recent initiation of clinical trials using molecular-targeted therapy, should validate new molecular targets and predict the efficacy of a given therapy. Comparative genetic and biomolecular studies should enhance the molecular taxonomy of chordoma which might have a prognostic significance and better orient the therapeutic options.

Cytogenetic analysis of three variants of clival chordoma

Chordoma is an uncommon malignant neoplasm derived from remnants of the embryonal notochord. The tumor arises in the sacrococcygeal region in most cases. Cytogenetic information on clival chordomas is scarce due to the low incidence of these tumors. In this study, we applied the G-banding and spectral karyotyping techniques to compare the karyotypes of three variants of clival chordoma: conventional, chondroid, and dedifferentiated. We describe a normal karyotype of a chondroid chordoma and a complex karyotype of a conventional chordoma involving chromosomes 1, 2, 3, 5, 8, 9, 11, 15, 19, 20, and X. The cytogenetic analysis of the dedifferentiated chordoma showed a polyploid complex karyotype of 71-123 chromosomes with double minutes that originated from chromosome 17.

Sacrococcygeal chordomas in patients with tuberous sclerosis complex show somatic loss of TSC1 or TSC2

Chordomas are rare sacrococcygeal/sacral, sphenooccipital/clivus, and spinal tumors whose molecular etiology remains relatively understudied. As several anecdotal reports had described chordomas in individuals with tuberous sclerosis complex (TSC), a multisystem hamartoma syndrome, we hypothesized that the genes that cause TSC may have an etiological role in chordomas. In two cases of sacrococcygeal chordomas in individuals with TSC, one with a germ-line TSC2 mutation and the other with a germ-line TSC1 mutation, we confirmed somatic inactivation of the corresponding wild-type allele by loss of heterozygosity analysis and immunohistochemistry. These data provide the first evidence of a pathogenic role by TSC genes in sacrococcygeal chordomas.

Combined binary ratio labeling fluorescence in situ hybridization analysis of chordoma

Chordoma is a rare, low- to intermediate-grade malignant tumor involving the axial spine. Cytogenetic data on these tumors have been limited to 25 cases. The findings of clonal chromosome aberrations in five new cases are presented. One of these and two previously reported cases have been studied with multicolor combined binary ratio labeling fluorescence in situ hybridization (COBRA-FISH). The karyotypes were near-diploid, mostly with several numerical and structural aberrations. There were multiple imbalances, with loss of segments from 1p, 3p, 3q, 9p, and chromosome 10 seen in two to four of the seven cases. No clustering of breakpoints was seen and no recurrent recombination between chromosomes was detected. The findings are consistent with previous data and indicate that chordoma tumor development is associated with multiple, nonrandom losses including chromosome segments that are frequently involved in many other solid tumors.

Mapping of candidate region for chordoma development to 1p36.13 by LOH analysis

Various cytogenetic and molecular findings indicate 1p36 loss as a consistent change in sporadic and inherited chordoma, a rare embryogenetic neoplasm arising from notochord remnants. We studied 27 sporadic chordomas by means of loss of heterozygosity (LOH) of 31 microsatellites localized to the 1p36.32-36.11 region, and restricted the minimal LOH interval shared by 85% of the tumours to 1p36.13. We also used RT-PCR analysis to investigate the role of the candidate genes CASP9, EPH2A, PAX7, DAN and DVL1, which were selected on the basis of the physical mapping of the LOH region and their plausible oncosuppressor function. RT-PCR analysis showed the presence of DAN and PAX7 transcript fragments of the expected size in all of 8 chordoma samples, whereas the CASP9-specific fragment was observed in only 3 and EPH2A was absent in one. Smaller than expected DVL1 transcripts were found in 4 tumours as well as in their normal counterpart (nucleus pulposus), which also showed a typically sized transcript. Sequencing revealed the skipping of 3 exons in the smallest DVL1 fragment, thus leading to a frameshift and predicting a truncated DVL1 gene product. Our study of the largest cohort of chordoma patients recruited so far indicates a common molecular lesion at 1p36.13, and suggests that the CASP9, EPH2A and DVL1 genes may play an onco-suppressing role and be involved in the development of chordoma.

Familial chordoma, a tumor of notochordal remnants, is linked to chromosome 7q33

Chordoma is a rare tumor originating from notochordal remnants that is usually diagnosed during midlife. We performed a genomewide analysis for linkage in a family with 10 individuals affected by chordoma. The maximum two-point LOD score based on only the affected individuals was 2.21, at recombination fraction 0, at marker D7S2195 on chromosome 7q. Combined analysis of additional members of this family (11 affected individuals) and of two unrelated families (one with 2 affected individuals and the other with 3 affected individuals), with 20 markers on 7q, showed a maximum two-point LOD score of 4.05 at marker D7S500. Multipoint analysis based on only the affected individuals gave a maximum LOD score of 4.78, with an approximate 2-LOD support interval from marker D7S512 to marker D7S684. Haplotype analysis of the three families showed a minimal disease-gene region from D7S512 to D7S684, a distance of 11.1 cM and approximately 7.1 Mb. No loss of heterozygosity was found at markers D7S1804, D7S1824, and D7S2195 in four tumor samples from affected family members. These results map a locus for familial chordoma to 7q33. Further analysis of this region, to identify this gene, is ongoing.