Sarah C. Jost

Application of novel response/progression measures for surgically delivered therapies for gliomas: Response Assessment in Neuro-Oncology (RANO) working group

BACKGROUND The Response Assessment in Neuro-Oncology (RANO) Working Group is an international, multidisciplinary effort to develop new standardized response criteria for clinical trials in brain tumors. The RANO group identified knowledge gaps relating to the definitions of tumor response and progression after the use of surgical or surgically based treatments. OBJECTIVE To outline a proposal for new response and progression criteria for the assessment of the effects of surgery and surgically delivered therapies for patients with gliomas. METHODS The Surgery Working Group of RANO identified surgically related end-point evaluation problems that were not addressed in the original Macdonald criteria, performed an extensive literature review, and used a consensus-building process to develop recommendations for how to address these issues in the setting of clinical trials. RESULTS Recommendations were formulated for surgically related issues, including imaging changes associated with surgical resection or surgically mediated adjuvant local therapies, the determination of progression in the setting where all enhancing tumor has been removed, and how new enhancement should be interpreted in the setting where local therapies that are known to produce nonspecific enhancement have been used. Additionally, the terminology used to describe the completeness of surgical resections has been recognized to be inconsistently applied to enhancing vs nonenhancing tumors, and a new set of descriptors is proposed. CONCLUSION The RANO process is intended to produce end-point criteria for clinical trials that take into account the effects of prior and ongoing therapies. The RANO criteria will continue to evolve as new therapies and technologies are introduced into clinical trial and/or practice.

FK506 promotes functional recovery in crushed rat sciatic nerve

In this study we examine whether the systemic administration of FK506 or Cyclosporin A (CsA) expedited functional recovery following an axonotmetic nerve injury, and compared their effects in a rat model. Seventy‐five adult Buffalo rats received a crush injury to the right posterior tibial nerve and subsequently underwent either no treatment (group I), daily injections of FK506 (group II), or daily injections of CsA (group III). Walking track analysis demonstrated return of hindlimb function by 20 days postoperatively in group I, 14 days in group II, and 18 days in group III. The blood–nerve barrier (BNB) was reconstituted by postoperative day (POD) 7 in both FK506‐ and CsA‐treated animals and by POD 13 in control animals. These results suggest that recovery of function is more rapid with daily administration of FK506 than with CsA or no treatment, perhaps because of earlier restoration of the blood–nerve barrier. Agents that facilitate nerve regeneration have the potential to limit the extent of motor endplate loss and muscle atrophy seen with prolonged denervation, thereby limiting permanent functional loss.

Malignant gliomas with primitive neuroectodermal tumor-like components: A clinicopathologic and genetic study of 53 cases

Central nervous system neoplasms with combined features of malignant glioma and primitive neuroectodermal tumor (MG‐PNET) are rare, poorly characterized, and pose diagnostic as well as treatment dilemmas. We studied 53 MG‐PNETs in patients from 12 to 80 years of age (median = 54 years). The PNET‐like component consisted of sharply demarcated hypercellular nodules with evidence of neuronal differentiation. Anaplasia, as seen in medulloblastomas, was noted in 70%. Within the primitive element, N‐myc or c‐myc gene amplifications were seen in 43%. In contrast, glioma‐associated alterations involved both components, 10q loss (50%) being most common. Therapy included radiation (78%), temozolomide (63%) and platinum‐based chemotherapy (31%). Cerebrospinal fluid (CSF) dissemination developed in eight patients, with response to PNET‐like therapy occurring in at least three. At last follow‐up, 27 patients died, their median survival being 9.1 months. We conclude that the primitive component of the MG‐PNET: (i) arises within a pre‐existing MG, most often a secondary glioblastoma; (ii) may represent a metaplastic process or expansion of a tumor stem/progenitor cell clone; (iii) often shows histologic anaplasia and N‐myc (or c‐myc) amplification; (iv) has the capacity to seed the CSF; and (v) may respond to platinum‐based chemotherapy regimens.

In vivo imaging in a murine model of glioblastoma

OBJECTIVETo use in vivo imaging methods in mice to quantify intracranial glioma growth, to correlate images and histopathological findings, to explore tumor marker specificity, to assess effects on cortical function, and to monitor effects of chemotherapy. METHODSMice with DBT glioma cell tumors implanted intracranially were imaged serially with a 4.7-T small-animal magnetic resonance imaging (MRI) scanner. MRI tumor volumes were measured and correlated with postmortem histological findings. Different nonspecific and specific positron emission tomography radiopharmaceuticals, [18F]2-fluoro-2-deoxy-d-glucose, [18F]3′-deoxy-3′-fluorothymidine, or [11C]RHM-I, a σ2-receptor ligand, were visualized with microPET (CTI-Concorde MicroSystems LLC, Knoxville, TN). Intrinsic optical signals were imaged serially during contralateral whisker stimulation to study the impact of tumor growth on cortical function. Other groups of mice were imaged serially with MRI after one or two doses of the antimitotic N,N′-bis(2-chloroethyl)-N-nitrosourea (BCNU). RESULTSMRI and histological tumor volumes were highly correlated (r2 = 0.85). Significant binding of [11C]RHM-I was observed in growing tumors. Over time, tumors reduced and displaced (P # 0.001) whisker-activated intrinsic optical signals but did not change intrinsic optical signals in the contralateral hemisphere. Tumor growth was delayed 7 days after a single dose of BCNU and 18 days after two doses of BCNU. Mean tumor volume 15 days after DBT implantation was significantly smaller for treated mice (1- and 2-dose BCNU) compared with controls (P = 0.0026). CONCLUSIONMouse MRI, positron emission tomography, and optical imaging provide quantitative and qualitative in vivo assessments of intracranial tumors that correlate directly with tumor histological findings. The combined imaging approach provides powerful multimodality assessments of tumor progression, effects on brain function, and responses to therapy.

Feasibility of small animal cranial irradiation with the microRT system

PURPOSE To develop and validate methods for small-animal CNS radiotherapy using the microRT system. MATERIALS AND METHODS A custom head immobilizer was designed and built to integrate with a pre-existing microRT animal couch. The Delrin couch-immobilizer assembly, compatible with multiple imaging modalities (CT, microCT, microMR, microPET, microSPECT, optical), was first imaged via CT in order to verify the safety and reproducibility of the immobilization method. Once verified, the subject animals were CT-scanned while positioned within the couch-immobilizer assembly for treatment planning purposes. The resultant images were then imported into CERR, an in-house-developed research treatment planning system, and registered to the microRTP treatment planning space using rigid registration. The targeted brain was then contoured and conformal radiotherapy plans were constructed for two separate studies: (1) a whole-brain irradiation comprised of two lateral beams at the 90 degree and 270 degree microRT treatment positions and (2) a hemispheric (left-brain) irradiation comprised of a single A-P vertex beam at the 0 degree microRT treatment position. During treatment, subject animals (n=48) were positioned to the CERR-generated treatment coordinates using the three-axis microRT motor positioning system and were irradiated using a clinical Ir-192 high-dose-rate remote after-loading system. The radiation treatment course consisted of 5 Gy fractions, 3 days per week. 90% of the subjects received a total dose of 30 Gy and 10% received a dose of 60 Gy. RESULTS Image analysis verified the safety and reproducibility of the immobilizer. CT scans generated from repeated reloading and repositioning of the same subject animal in the couch-immobilizer assembly were fused to a baseline CT. The resultant analysis revealed a 0.09 mm average, center-of-mass translocation and negligible volumetric error in the contoured, murine brain. The experimental use of the head immobilizer added 0.1 mm to microRT spatial uncertainty along each axis. Overall, the total spatial uncertainty for the prescribed treatments was +/-0.3 mm in all three axes, a 0.2 mm functional improvement over the original version of microRT. Subject tolerance was good, with minimal observed side effects and a low procedure-induced mortality rate. Throughput was high, with average treatment times of 7.72 and 3.13 min/animal for the whole-brain and hemispheric plans, respectively (dependent on source strength). CONCLUSIONS The method described exhibits conformality more in line with the size differential between human and animal patients than provided by previous prevalent approaches. Using pretreatment imaging and microRT-specific treatment planning, our method can deliver an accurate, conformal dose distribution to the targeted murine brain (or a subregion of the brain) while minimizing excess dose to the surrounding tissue. Thus, preclinical animal studies assessing the radiotherapeutic response of both normal and malignant CNS tissue to complex dose distributions, which closer resemble human-type radiotherapy, are better enabled. The procedural and mechanistic framework for this method logically provides for future adaptation into other murine target organs or regions.

Measuring Brain Tumor Growth: Combined Bioluminescence Imaging-Magnetic Resonance Imaging Strategy

Small-animal tumor models are essential for developing translational therapeutic strategies in oncology research, with imaging having an increasingly important role. Magnetic resonance imaging (MRI) offers tumor localization, volumetric measurement, and the potential for advanced physiologic imaging but is less well suited to high-throughput studies and has limited capacity to assess early tumor growth. Bioluminescence imaging (BLI) identifies tumors early, monitors tumor growth, and efficiently measures response to therapeutic intervention. Generally, BLI signals have been found to correlate well with magnetic resonance measurements of tumor volume. However, in our studies of small-animal models of malignant brain tumors, we have observed specific instances in which BLI data do not correlate with corresponding MRIs. These observations led us to hypothesize that use of BLI and MRI together, rather than in isolation, would allow more effective and efficient measures of tumor growth in preclinical studies. Herein we describe combining BLI and MRI studies to characterize tumor growth in a mouse model of glioblastoma. The results led us to suggest a cost-effective, multimodality strategy for selecting cohorts of animals with similar tumor growth patterns that improves the accuracy of longitudinal in vivo measurements of tumor growth and treatment response in preclinical therapeutic studies.

A Novel Murine Model for Localized Radiation Necrosis and its Characterization using Advanced Magnetic Resonance Imaging

PURPOSE To develop a murine model of radiation necrosis using fractionated, subtotal cranial irradiation; and to investigate the imaging signature of radiation-induced tissue damage using advanced magnetic resonance imaging techniques. METHODS AND MATERIALS Twenty-four mice each received 60 Gy of hemispheric (left) irradiation in 10 equal fractions. Magnetic resonance images at 4.7 T were subsequently collected using T1-, T2-, and diffusion sequences at selected time points after irradiation. After imaging, animals were killed and their brains fixed for correlative histologic analysis. RESULTS Contrast-enhanced T1- and T2-weighted magnetic resonance images at months 2, 3, and 4 showed changes consistent with progressive radiation necrosis. Quantitatively, mean diffusivity was significantly higher (mean = 0.86, 1.13, and 1.24 microm(2)/ms at 2, 3, and 4 months, respectively) in radiated brain, compared with contralateral untreated brain tissue (mean = 0.78, 0.82, and 0.83 microm(2)/ms) (p < 0.0001). Histology reflected changes typically seen in radiation necrosis. CONCLUSIONS This murine model of radiation necrosis will facilitate investigation of imaging biomarkers that distinguish between radiation necrosis and tumor recurrence. In addition, this preclinical study supports clinical data suggesting that diffusion-weighted imaging may be helpful in answering this diagnostic question in clinical settings.

Glioblastomas with giant cell and sarcomatous features in patients with Turcot syndrome type 1: a clinicopathological study of 3 cases.

BACKGROUNDTurcot syndrome (TS) is a rare genetic disorder of DNA mismatch repair predisposing to glioblastoma (GBM) in the type 1 variant. OBJECTIVEWe report the clinicopathological and genetic features of 3 gliomas in TS type 1 patients. METHODSThree cases were reviewed from our clinical and pathology files at Washington University with the diagnosis of TS 1 and GBM over the past 14 years. All 3 had classic features of GBM, but also demonstrated bizarre multinucleated giant cells and remarkably high mitotic indices. Sarcomatous regions were found in 2. Despite these features, the patients had prolonged survival times of 44, 55, and >29 months (ie, currently alive). Demographic and clinical courses were abstracted from retrospective chart review. Histopathology was reviewed from all cases and reticulin histochemistry was added to identify possible foci of sarcomatous differentiation. RESULTSAll 3 had classic features of GBM, and Ki-67 labeling indices ranged from 18 to 45%. All 3 also showed strong nuclear p53 positivity. Two cases were negative for the isocitrate dehydrogenase 1 (IDH1) mutation, and O6-Methylguanine methyltransferase promoter methylation was seen in one. Fluorescence in situ hybridization was done using 1p/1q, 19p/19q, centromere 7/epithelial growth factor receptor (EGFR), and PTEN/DMBT1 probes. Focal EGFR amplification was seen in one case, although other common alterations of either primary GBMs or gliomas with prolonged survival (1p/19q codeletion) were lacking. CONCLUSIONWe conclude that 1) the giant cell variant of GBM is overrepresented in TS; 2) gliosarcomas may also be encountered; and 3) survival is often favorable, despite histological anaplasia and exuberant proliferation.

Transient Obstructive Hydrocephalus due to Intraventricular Hemorrhage: A Case Report and Review of Literature.

Background Acute transient obstructive hydrocephalus is rare in adults. We describe a patient with intraventricular hemorrhage (IVH) who experienced the delayed development of acute transient hydrocephalus. Case Report A 33-year-old man with a previously diagnosed Spetzler-Martin Grade 5 arteriovenous malformation presented with severe headache, which was found to be due to IVH. Forty hours after presentation he developed significant obstructive hydrocephalus due to the thrombus migrating to the cerebral aqueduct, and a ventriculostomy placement was planned. However, shortly thereafter his headache began to improve spontaneously. Within 4 hours after onset the headache had completely resolved, and an interval head CT scan revealed resolution of hydrocephalus. Conclusions In patients with IVH, acute obstructive hydrocephalus can develop at any time after the ictus. Though a delayed presentation of acute but transient obstructive hydrocephalus is unusual, it is important to be aware of this scenario and ensure that deterioration secondary to thrombus migration and subsequent obstructive hydrocephalus do not occur.

Neurofibromatosis and other genetic syndromes.

Tumors of the nervous system typically occur in a sporadic fashion without a pre-existing familial predisposition. The uncommon tumors that arise in the context of a tumor predisposition syndrome can provide valuable insights into the critical genetic events important for tumorigenesis in the nervous system. Such syndromes include neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), tuberous sclerosis complex (TSC), Von Hippel–Lindau syndrome (VHL), and Sturge–Weber syndrome (SWS). These syndromes are all autosomal dominant disorders characterized by an increased susceptibility to both benign and malignant nervous system tumors. The genetic syndromes described in this chapter are considered inherited cancer or tumor suppressor disorders. The genetic basis for these inherited cancer syndromes was first proposed by Alfred Knudson based on his studies of retinoblastoma (Knudson, 1971). The Knudson or ‘two hit’ hypothesis suggests that, in inherited cancers, patients begin life with a germline mutation (‘hit’) in a specific tumor suppressor gene (e.g., retinoblastoma gene). Cancer arises when the remaining normal gene undergoes somatic inactivation, leading to loss of function of both copies of that tumor suppressor gene (Figure 37.1). As patients with these inherited cancer syndromes need only one additional genetic change to promote tumorigenesis, they manifest a higher risk of tumor development than individuals in the general population who require two independent genetic changes (sequential loss of both copies of a specific tumor suppressor gene) for tumor formation.