Diffusion-weighted MRI: distinction of skull base chordoma from chondrosarcoma

BACKGROUND AND PURPOSE

Chordoma and chondrosarcoma of the skull base are rare tumors with overlapping presentations and anatomic imaging features but different prognoses. We hypothesized that these tumors might be distinguished by using diffusion-weighted MR imaging.

MATERIALS AND METHODS

We retrospectively reviewed 19 patients with pathologically confirmed chordoma or chondrosarcoma who underwent both conventional and diffusion-weighted MR imaging. Differences in distributions of ADC were assessed by the Kruskal-Wallis test. Associations between histopathologic diagnosis and conventional MR imaging features (T2 signal intensity, contrast enhancement, and tumor location) were assessed with the Fisher exact test.

RESULTS

Chondrosarcoma was associated with the highest mean ADC value (2051 ± 261 × 10(-6) mm(2)/s) and was significantly different from classic chordoma (1474 ± 117 × 10(-6) mm(2)/s) and poorly differentiated chordoma (875 ± 100 × 10(-6) mm(2)/s) (P < .001). Poorly differentiated chordoma was characterized by low T2 signal intensity (P = .001), but other conventional MR imaging features of enhancement and/or lesion location did not reliably distinguish these tumor types.

CONCLUSIONS

Diffusion-weighted MR imaging may be useful in assessing clival tumors, particularly in differentiating chordoma from chondrosarcoma. A prospective study of a larger cohort will be required to determine the value of ADC in predicting histopathologic diagnosis.

Role of IκBα as a negative regulator of EGFR and a molecular determinant of prognosis in glioblastoma multiforme

2028

Background: Glioblastoma multiforme is a complex disease that involves the deregulation of overlapping signaling pathways. Constitutive activation of the transcription factor nuclear factor-κB (NF-κB) has been broadly associated with various human cancers, including glioblastomas, and their therapy resistance and may be due to cross-coupling with other oncogenic pathways, such as epidermal growth factor signaling. Methods: Multidimensional analysis involving gene and transcript data for the endogenous NF-κB modulator IκBα/NFKBIA and clinical patient profiles of 482 glioblastomas/high-grade gliomas from multiple institutions in the United States and The Cancer Genome Atlas Pilot Project. Functional analyses using LN229, U87, and U118 glioblastoma cells, and human embryonic kidney 293T cells with transgene phenotypes for IκBα. IκBα promoter and coding sequence and promoter methylation analyses in a resistance model of 15 glioblastomas cell lines with in vitro and/or in vivo resistance to O6-alkylating agents. Results: We have identified a regulatory circuit between NF-κB and EGFR signaling in glioblastomas, where IκBα binds to EGFR and attenuates EGFR signaling by immobilizing its kinase domain into an inactive conformation. We found the NFKBIA gene at 14q13.2 deleted in 25% of glioblastomas and its occurrence mutually exclusive with EGFR amplification. Loss of NFKBIA associates independently with patient survival. Functional analyses uncover a bona fide tumor suppressor role for IκBα in glioblastoma cells, where it functions to constrain tumorigenic and migratory potential, and induce spontaneous cellular senescence, and apoptosis in response to treatment. IκBα expression is an independent predictor of patient prognosis in multiple glioblastoma populations. Glioblastomas with initially high IκBα expression significantly repress IκBα upon tumor recurrence, suggesting an acquired mechanism to evade its tumor-suppressive and/or chemo-sensitizing effects during tumor progression. Conclusions: IκBα is a molecular determinant of biological tumor behavior and patient survival in glioblastoma multiforme. Deletion of NFKBIA could present an alternate mechanism to activate EGFR signaling in EGFR non-amplified glioblastomas.

No significant financial relationships to disclose.

Identification of serum markers of glioblastoma multiforme patients using image-guided genomic and proteomic analysis

20008

Background: Biomarkers in serum has been demonstrated to play a critical role in caner diagnostics. Glioblastoma multiforme (GBM) is a primary brain tumor with poor prognosis and low survival rate, which often has significant heterogeneity in morphology and increased vascular permeability and vessel density. In this study we identified molecules related to angiogenesis and vasculature development for GBM using a combination of contrast enhanced MR imaging, genomic and proteomic analysis, and enzyme immunoassay (ELISA). Methods: GBM patient without any prior procedures were scanned on a GE 1.5T MRI scanner using standard T1- and T2-weighted pulse sequences and gadopentetate dimeglumine as contrast agent. Samples from regions with contrast agent accumulation (contrast-enhancing, CE) and no uptake (non-enhancing, NE) were collected for microarray, Mass spectroscopic analysis and immunochemical staining. Patient serum samples were collected for protein expression quantification using ELISA assay. Results: Tissue samples from the CE and NE regions of 13 patients reveal significantly distinct gene expression patterns. Mass spectroscopy using MALDI system will also be examined. Growth factors such as laminin receptor, IGFBP-2, IGFBP-3, IGFBP-5, aFGF were all up-regulated in the CE regions, and immunohistochemical staining confirmed their protein expression. The presence of proteins with MW < 30 kD in the serum were examined using ELISA. IGFBP-2 showed to have a higher mean value (86.1 ± 29.1 ng/ml) in GBM serum as compared to healthy individuals (55.7 ± 9.9 ng/ml). Other potential markers such as IGFBP-3 and aFGF do not exhibit significant difference. Conclusions: CE-MRI using the clinical MRI agent Gd(DTPA) can reveal imaging features associated with increased vascular permeability and vessel density, and areas of fluid accumulation and necrosis. We have observed that differences in spatial resolution in the tumor correlate to changes in gene expression profiles, resulting in potential molecules that have high gene and protein expression levels in tumor area with high vascular activity and in serum. These targets can be used for diagnostic and clinical monitoring of the patient before and after therapeutic intervention.

No significant financial relationships to disclose.

Identification of integrin as potential molecular markers in human glioblastoma multiforme: Microarray analysis guided by contrast-enhanced MRI

10007

Background: Glioblastoma multiforme (GBM) is a primary brain tumor with poor prognosis and low survival rate. It is characterized as a highly infiltrative and vascular tumor, with morphologic heterogeneity including necrosis regions. We have used contrast enhanced (CE)-MRI to identify regions that differ in vascular permeability as delineated by the small molecule contrast agent Magnevist. Non-necrotic areas with and without contrast enhancement were sampled in the OR. The expression profiles for integrin family genes were investigated and validated using IHC. Genes encoding for integrin subunits with high expression levels in these regions of the tumor were identified and are presented here. Methods: Patients diagnosed with GBM, without any prior procedures were scanned on a GE 1.5T MRI scanner using standard T1- and T2-weighted pulse sequences and Gd(DTPA) as contrast agent. Samples from regions with vascular permeability to the contrast agent (contrast-enhancing, CE) and vascular regions that are not permeable to the contrast agent (non-enhancing, NE) were collected for gene expression profiling using the Affymatrix oligonucleotide microarray system. Genomic data was normalized at probe-level, and analyzed using a modified t-test, Significance Analysis of Microarray (SAM). Significant expression levels were identified. Immunohistochemical staining was used to validate protein expression of selected genes of interest. Results: Tissue samples from the CE and NE regions of 13 patients reveal significantly distinct gene expression patterns. In specific, genes in the integrin family such as integrin αIIb, αV and β3 show high expression levels in the CE region. Immunohistochemical staining confirmed correlation of protein expression patterns with the observed genomic profile. Conclusions: Combination of CE-MRI using the clinical contrast agent and microarray analysis can reveal spatial genomic profiles correlated with imaging features associated with increased vascular permeability, vessel density, and areas of fluid accumulation. The identified genes from the integrin family can be potential molecular targets, and can be used for molecular imaging and therapeutic purposes.

No significant financial relationships to disclose.

Dose-escalation with proton/photon irradiation for Daumas-Duport lower-grade glioma: results of an institutional phase I/II trial

PURPOSE

The role of dose escalation with proton/photon radiotherapy in lower-grade gliomas was assessed in a prospective Phase I/II trial. We report the results in terms of local control, toxicity, and survival.

MATERIALS AND METHODS

Twenty patients with Grade 2/4 (n = 7) and Grade 3/4 (n = 13) gliomas according to the Daumas-Duport classification were treated on a prospective institutional protocol at Massachusetts General Hospital/Harvard Cyclotron Laboratory between 1993 and 1996. Doses prescribed to the target volumes were 68.2 cobalt Gray equivalent (CGE, 1 proton Gray = 1.1 CGE) to gross tumor in Grade 2 lesions and 79.7 CGE in Grade 3 lesions. Fractionation was conventional, with 1.8 to 1.92 CGE once per day. Eligibility criteria included age between 18 and 70 years, biopsy-proven Daumas-Duport Grade 2/4 or 3/4 malignant glioma, Karnofsky performance score of 70 or greater, and supratentorial tumor. Median age of the patient population at diagnosis was 35.9 years (range 19-49). Ten tumors were mixed gliomas, one an oligodendroglioma.

RESULTS

Five patients underwent biopsy, 12 a subtotal resection, and 3 a gross total resection. Median interval from surgery to first radiation treatment was 2.9 months. Actuarial 5-year survival rate for Grade 2 lesions was 71% as calculated from diagnosis (median survival not yet reached); actuarial 5-year survival for Grade 3 lesions was 23% (median 29 months). Median follow-up is 61 months and 55 months for 4 patients alive with Grade 2 and 3 patients alive with Grade 3 lesions, respectively. Three patients with Grade 2 lesions died from tumor recurrence, whereas 2 of the 4 survivors have evidence of radiation necrosis. Eight of 10 patients who have died with Grade 3 lesions died from tumor recurrence, 1 from pulmonary embolus, and 1 most likely from radiation necrosis. One of 3 survivors in this group has evidence of radiation necrosis.

CONCLUSION

Tumor recurrence was neither prevented nor noticeably delayed in our patients relative to published series on photon irradiation. Dose escalation using this fractionation scheme and total dose delivered failed to improve outcome for patients with Grade 2 and 3 gliomas.

Daily low-dose carboplatin as a radiation sensitizer for newly diagnosed malignant glioma

Surgical resection followed by local field radiotherapy is currently our most effective approach to treatment for most patients with malignant glioma. Carboplatin chemotherapy has direct cytotoxic effects on glioma cells and acts as a radiation sensitizer to enhance cell killing. Its demonstrated efficacy as a sensitizer in other solid tumors led to this clinical trial of carboplatin as a radiation sensitizer in the treatment of newly diagnosed glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA). Fourteen patients (nine GBM and five AA) were treated with daily low-dose carboplatin 25 mg/m2 intravenously within 2 h of their fractionated radiotherapy to a total dose of 600 mg/m2. No significant toxicities attributable to this combined therapy were observed. All patients have progressed, with median time to progression of 16 weeks. Eleven patients have died, with median survival of 38 weeks for the entire cohort. Although this regimen appeared safe, there was no benefit in survival time compared to historical patients treated with radiotherapy. The limitations and future potential for the strategy of radiation sensitization are discussed.

Pedicled rhinotomy for clival chordomas invaginating the brainstem

Object

Clival chordomas are frequently midline lesions whose posterior growth may breach the dura and invaginate the brainstem. This precludes safe delivery of potentially curative high-dose fractionated proton radiotherapy. To avoid this problem, the authors performed pedicled rhinotomy to resect chordomas in 10 patients.

Methods

Pedicled rhinotomy is a midface transnasal route to the intercarotid sella and clivus from the tuberculum sellae to the mid-C-2 level. It involves a lateral rhinotomy incision, osteotomies of nasal bones and cartilage, lateral rotation of the nose, removal of the nasal septum and medial maxillary walls, opening of ethmoid and sphenoid sinuses, and dissection of nasopharynx and oropharynx to expose the clivus and craniovertebral junction. Tumors involving the sella, medial cavernous sinuses, middle and lower clivus, and C-1 arch and dens can be removed even if they traverse the dura. Closure involves dural repair, grafting of fat and split-thickness skin, rotation of a vascularized mucosal pedicle, and reattachment of nasal cartilage.

Ten clival chordomas in adult patients were surgically removed via a pedicled rhinotomy approach. Seven patients had previously undergone a total of nine skull base procedures. In eight of the 10 patients, tumors compressing the brainstem were completely removed using this technique. One patient required an additional subtemporal resection of a suprasellar tumor before definitive radiotherapy could be undertaken. No patient sustained any new neurological deficit; in eight patients headache, diplopia, or hemiparesis improved. One patient developed postoperative cerebrospinal fluid leakage and meningitis that were successfully treated with antibiotic agents and shunt placement.

Conclusions

Pedicled rhinotomy provides excellent shallow-field exposure of midline clival chordomas and permits relief of brainstem compression and the postoperative administration of potentially curative proton beam irradiation.

Cranial reconstruction for metastatic breast cancer

All women with advanced breast cancer who are medically stable despite their disease are candidates for tumor extirpation and reconstruction. Advanced breast cancer today is incurable, and many prognostic factors can be used to try to predict a clinical course and response to therapy; however, no guidelines are available. Our case report most likely represents a metastasis to the calvarium with intracranial extension, reported to occur in about 3 percent of primary breast cancer patients. As demonstrated here, tumor ablation with immediate, one-stage reconstruction of large scalp defects is possible without the need for free tissue transfer or a delay in adjuvant therapy. Local tissue rearrangement has been employed for coverage of defects up to 50 percent of the cranium. The resulting donor defects can be closed with split-thickness skin grafts over pericranium. Serial tissue expansion and rearrangement can be used secondarily to replace skin grafts with hair-bearing scalp. Bony defects can be managed with either autogenous or alloplastic materials. Split-calvarial bone grafts can be harvested from the same operative field and cover small to medium-sized defects. Other sources of autogenous grafts include split ribs and iliac bone. Metals, calcium ceramics, and polymers such as methylmethacrylate can be used to cover intracranial contents and restore calvarial contour when defects are large or when autogenous material is not available. Palliation from tumor burden, prevention of pathologic fracture and oncologic emergencies, controlling pain, and enhancing quality of life are the goals of the oncologic and reconstructive surgeons in cases of advanced breast cancer. These goals are becoming even more important as new forms and combinations of chemotherapy, radiation, and gene therapy are extending the life expectancy of women with breast carcinoma.

Stereotactic proton radiosurgery

The technique of stereotactic proton radiosurgery is discussed in depth in this article. The physics of the proton beam in radiosurgery is explained, and the different factors of beam delivery are examined. These key factors (correspondence to shape, accuracy of delineation of volume, correspondence to volume, and accuracy of delivery vary) with each of the radiosurgical techniques, from Gamma Knife surgery to linear accelerator therapy. Clinical series in the use of proton radiosurgery are also presented, with an emphasis on efficacy and uses.

Improved delineation of human brain tumors on MR images using a long-circulating, superparamagnetic iron oxide agent

The purpose of this study was to corroborate experimental findings that long-circulating, superparamagnetic iron oxide contrast agents accumulate at the margins of human brain tumors, thereby improving their delineation on magnetic resonance (MR) images. This limited clinical study examined a total of four patients with brain tumors (three with primary gliomas and one with metastatic melanoma; n = 8 lesions) who were given a pharmaceutical formulation of a superparamagnetic, ultra-small-particulate iron oxide (USPIO, intravenous dose of 1.1 mg Fe/kg). The agent has a characteristically long plasma half-life and is currently undergoing Phase III clinical trials for liver disease (AMI-227, Advanced Magnetics, Cambridge, MA). MR (conventional spin-echo and gradient-echo) images of the brain were obtained before and 12, 24, and/or 36 hours after administration of the agent, with follow-up several weeks later. Twelve to 36 hours after IV administration of the USPIO, both primary and metastatic brain tumors showed readily detectable increases in signal intensity on T1-weighted spin-echo images. Unlike the pattern of enhancement with a gadolinium (Gd) chelate, which occurred immediately and decreased within hours, that with the USPIO occurred gradually, with a peak at 24 hours, and decreased over several days. Whereas the enhancing tumor margin with the Gd chelate blurred with time due to diffusion of the agent, the margin with the USPIO remained sharp, presumably due to the much lower diffusion coefficient (large size) of the particles and partly because of local endocytosis by tumor cells. Compared with Gd chelates, long-circulating, superparamagnetic iron oxide contrast agents can provide prolonged delineation of the margins of human brain tumors on MR images, which has implications for the targeting of diagnostic biopsies and the planning of surgical resections.

Selective delivery of herpes virus vectors to experimental brain tumors using RMP-7

RMP-7, a bradykinin analog, has been shown to selectively open the blood-tumor barrier for the delivery of chemotherapeutic drugs to brain tumors. In contrast to bradykinin, RMP-7 has no hypotensive effects and has been approved for human use. This study was initiated to determine whether RMP-7 would open the blood-tumor barrier to virus vectors encoding tumor-killing genes in an experimental model. The herpes virus vector used, hrR3, which encodes virus thymidine kinase gene and the lacZ reporter gene, is defective in a gene encoding ribonucleotide reductase, replicates selectively in dividing tumor cells and not in postmitotic neural cells. It was determined that an optimum dose of RMP-7 (1.5-3.0 microg/kg over 10-15 minutes) enhanced viral delivery to brain tumors in rats bearing intracranial 9 L gliosarcomas when infused through the carotid artery immediately prior to virus vector application. Maximum expression of the lacZ reporter gene occurred at 3 days after intracarotid infusion. By 8 days, transgene expression was largely confined to tumor foci away from the main tumor mass. Viral delivery was essentially specific to tumor cells, with little transgene expression elsewhere in the brain. Minimal uptake and pathology was noted in the kidney, spleen, and liver. These findings indicate that intracarotid delivery of RMP-7 can augment the selective delivery of virus vectors to brain tumors in an experimental rat model, with the potential for application to human brain tumors.

The protein tyrosine phosphatase SHP-2 is expressed in glial and neuronal progenitor cells, postmitotic neurons and reactive astrocytes

In this study we examined the distribution and developmental profile of the src homology 2 (SH2) domain-containing protein tyrosine phosphatase SHP-2 in the mouse brain. We found that SHP-2 is present in both mitotically active and postmitotic cells in the forebrains of embryonic day 12 (E12) mice. In a developmental study extending from embryonic day 12 to adulthood, Western blotting analysis demonstrated equivalent levels of SHP-2 protein at all of the ages examined. Expression of SHP-2 paralleled the level of enzymatic activity at the different developmental periods. In the adult brain SHP-2 was restricted to diverse classes of neurons, while the majority of glial cells did not express detectable levels of protein. However, reactive astrocytes in response to an ischemic brain injury showed SHP-2 immunolabelling. Our data suggest that SHP-2 may play a role in pathways of neuronal and glial progenitor cells, in a broad spectrum of neuronal responses in the adult brain and in the gliotic response to the injury.

An alternative role for the src-homology-domain-containing phosphotyrosine phosphatase (SH-PTP2) in regulating epidermal-growth-factor-dependent cell growth

The association of the src homology 2 (SH2) domain-containing tyrosine phosphatase (SH-PTP2) with the activated epidermal growth factor (EGF) and platelet-derived growth factor receptors, as well as the insulin receptor substrate 1 and growth-factor-receptor-bound protein 2 and its intrinsic tyrosine phosphatase activity suggests an important role for this phosphatase in signal transduction. Previous studies have shown a positive role for SH-PTP2 in growth-factor-mediated cell signaling. We show here that SH-PTP2 can also function to negatively regulate EGF-mediated signal transduction in the human glioma cell line SNB19. We demonstrate this by showing that, in SNB19 cells, which lack the ability to proliferate in response to EGF but retain the ability to bind EGF and also activate the EGF receptor as well as allow for the association of SH-PTP2 with the phosphorylated receptor, stable overexpression of an interfering SH-PTP2 mutant can restore the ability of these cells to proliferate in response to EGF.

Beta test site report: gamma plan

We describe our preliminary experience with a beta-test version of the Leksell Gamma Plan (LGP) treatment planning system. During this testing phase we used the LGP system to find an acceptable treatment plan and then transferred coordinates to the KULA system for final calculation. We find that the LGP system offers a fast way of optimizing shot placement and weighting, especially for complex treatments. The ability to display many MR and CT images on screen and to superimpose isodose lines on these images, as soon as the dose distribution has been calculated, allows adjustments to be made more rapidly than with the plotting approach used by the KULA system. This software is in beta-test, and is undergoing modification. Problems relating to our hardware configuration have been addressed with a newer workstation specified for the production system.

Clinical characteristics of acromegalic patients whose pituitary tumors contain mutant Gs protein

Activating mutations in the gene for the alpha-chain of Gs, the stimulatory regulator of adenylyl cyclase, have been identified in human GH-secreting pituitary tumors. Using the polymerase chain reaction and allele-specific oligonucleotide hybridization, we screened 25 GH-secreting tumors for the presence of the activating mutations. We also reviewed the clinical charts of the patients from whom the tumors were removed. Of 25 tumors, 10 (40%) contained activating mutations. Patients in the mutation-positive group came to surgery with smaller tumors and had lower GH levels. The activating mutations identify a subgroup of GH-secreting pituitary tumors that probably arise from a shared oncogenic mechanism.

Two G protein oncogenes in human endocrine tumors

Somatic mutations in a subset of growth hormone (GH)-secreting pituitary tumors convert the gene for the alpha polypeptide chain (alpha s) of Gs into a putative oncogene, termed gsp. These mutations, which activate alpha s by inhibiting its guanosine triphosphatase (GTPase) activity, are found in codons for either of two amino acids, each of which is completely conserved in all known G protein alpha chains. The likelihood that similar mutations would activate other G proteins prompted a survey of human tumors for mutations that replace either of these two amino acids in other G protein alpha chain genes. The first gene so far tested, which encodes the alpha chain of Gi2, showed mutations that replaced arginine-179 with either cysteine or histidine in 3 of 11 tumors of the adrenal cortex and 3 of 10 endocrine tumors of the ovary. The mutant alpha i2 gene is a putative oncogene, referred to as gip2. In addition, gsp mutations were found in 18 of 42 GH-secreting pituitary tumors and in an autonomously functioning thyroid adenoma. These findings suggest that human tumors may harbor oncogenic mutations in various G protein alpha chain genes.

Evidence for rearrangement, amplification, and expression of c-myc in a human glioblastoma

Amplified cellular genes are frequently manifested in one of two cytologically recognizable forms, double minutes or homogeneously staining regions. Additionally, evidence is accumulating that aberrant expression of cellular genes (including oncogenes) may be mediated by gene amplification. We now describe the amplification and expression of the cellular oncogene c-myc in double-minute-containing cells from a patient with glioblastoma multiforme, and we have shown that the amplification is associated with rearrangement of the c-myc gene. This finding further supports the common association of the myc gene family in neurogenic tumors and provides evidence of myc gene amplification in human brain cancer.