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Barker, Frederick

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Barker

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Frederick

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Barker, Frederick
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Now showing 1 - 10 of 11
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    Pregnancy complications in women with rare tumor suppressor syndromes affecting central and peripheral nervous system
    (Elsevier BV, 2015) Terry, Anna R.; Merker, Vanessa; Barker, Frederick; Leffert, Lisa; Bateman, Brian; Souter, Irene; Plotkin, Scott
    Neurofibromatosis type 2 (NF2), tuberous sclerosis (TS), and von Hippel-Lindau disease (VHL) are tumor suppressor syndromes characterized by multiple benign tumors of the peripheral and central nervous system.1 These tumors may lead to an enhanced obstetric risk in female patients, but it is currently unknown whether women with NF2, TS, or VHL experience increased rates of adverse pregnancy outcomes. Current data consist primarily of case series, even the largest of which may lack power because of the small sample sizes.
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    Bevacizumab for Progressive Vestibular Schwannoma in Neurofibromatosis Type 2
    (Ovid Technologies (Wolters Kluwer Health), 2012) Plotkin, Scott; Merker, Vanessa; Halpin, Chris; Jennings, Dominique; McKenna, Michael; Harris, Gordon; Barker, Frederick
    Objective: Early studies suggest that bevacizumab treatment can result in tumor shrinkage and hearing improvement for some patients with neurofibromatosis type 2 (NF2). The aim of this study was to report extended follow-up in a larger cohort of similarly treated patients. Study Design: Retrospective study. Setting: Tertiary referral center Patients: Thirty-one consecutive NF2 patients who received bevacizumab for progressive vestibular schwannomas. Main Outcome Measure: Hearing improvement, defined as an improvement in word recognition score above the 95% critical difference compared with baseline, and radiographic response, defined as a 20% or greater decrease in tumor volume compared with baseline. Results: The median age was 26 years (range, 12–73 yr). The median volumetric tumor growth rate before treatment was 64% per year. At the time of analysis, the median duration of treatment was 14 months (range, 6–41 mo) with a total of 47 patient-years of follow-up. A hearing response occurred in 57% (13/23) of evaluable patients and a radiographic response in 55% (17/31) of target vestibular schwannomas. The median time to response was 3 months for both end points. The only clinical or radiographic feature at baseline that correlated with change in tumor volume at 3 months was the mean apparent diffusion coefficient value, a radiologic marker of edema (p = 0.036). Ninety percent of patients had stable or improved hearing after 1 year of treatment and 61% at 3 years; 88% of patients had stable or decreased tumor size after 1 year of treatment and 54% at 3 years. Overall, treatment was well tolerated. Conclusion: Bevacizumab treatment was followed by hearing improvement and tumor shrinkage in more than 50% of progressive vestibular schwannomas in NF2 patients. Stable or improved hearing was retained in the majority of patients.
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    Natural History of Vestibular Schwannoma Growth and Hearing Decline in Newly Diagnosed Neurofibromatosis Type 2 Patients
    (Ovid Technologies (Wolters Kluwer Health), 2014) Plotkin, Scott; Merker, Vanessa; Muzikansky, Alona; Barker, Frederick; Slattery, William
    Objective: To determine the rate of growth in vestibular schwannomas and the rate of hearing decline in neurofibromatosis type 2 (NF2) patients not undergoing active treatment Study Design: Prospective study. Setting: Data were collected at 10 NF2 centers, including hospital-based, academic, and tertiary care centers. Patients: 120 NF2 patients with 200 vestibular schwannomas. Outcome Measures: Hearing decline, defined as a decrease in word recognition score outside the 95% critical difference compared with baseline, and radiographic progression, defined as a 20% or greater increase in tumor volume compared with baseline. Results: During a total of 313.4 patient-years of follow-up, the rate of hearing decline was 5% at 1 year, 13% at 2 years, and 16% at 3 years; the rate of tumor progression was 31% at 1 year, 64% at 2 years, and 79% at 3 years. For this cohort, the median time to tumor progression (14 mo) was significantly shorter than the median time to hearing decline (62.0 mo). Conclusion: These data provide potentially useful information for the design of clinical trials for NF2 vestibular schwannoma.
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    Rapid Intraoperative Molecular Characterization of Glioma
    (American Medical Association (AMA), 2015) Shankar, Ganesh; Francis, Joshua M.; Rinne, Mikael; Ramkissoon, Shakti H.; Huang, Franklin; Venteicher, Andrew S; Akama-Garren, Elliot H.; Kang, Yun Jee; Lelic, Nina; Kim, James C.; Brown, Loreal E.; Charbonneau, Sarah K; Golby, Alexandra; Sekhar Pedamallu, Chandra; Hoang, Mai; Sullivan, Ryan; Cherniack, Andrew D.; Garraway, Levi; Stemmer-Rachamimov, Anat; Reardon, David; Wen, Patrick; Brastianos, Priscilla; Curry, William; Barker, Frederick; Hahn, William; Nahed, Brian; Ligon, Keith; Louis, David; Cahill, Daniel; Meyerson, Matthew
    IMPORTANCE: Conclusive intraoperative pathologic confirmation of diffuse infiltrative glioma guides the decision to pursue definitive neurosurgical resection. Establishing the intraoperative diagnosis by histologic analysis can be difficult in low-cellularity infiltrative gliomas. Therefore, we developed a rapid and sensitive genotyping assay to detect somatic single-nucleotide variants in the telomerase reverse transcriptase (TERT) promoter and isocitrate dehydrogenase 1 (IDH1). OBSERVATIONS: This assay was applied to tissue samples from 190 patients with diffuse gliomas, including archived fixed and frozen specimens and tissue obtained intraoperatively. Results demonstrated 96% sensitivity (95% CI, 90%–99%) and 100% specificity (95% CI, 95%–100%) for World Health Organization grades II and III gliomas. In a series of live cases, glioma-defining mutations could be identified within 60 minutes, which could facilitate the diagnosis in an intraoperative timeframe. CONCLUSIONS AND RELEVANCE: The genotyping method described herein can establish the diagnosis of low-cellularity tumors like glioma and could be adapted to the point-of-care diagnosis of other lesions that are similarly defined by highly recurrent somatic mutations.
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    Sporadic hemangioblastomas are characterized by cryptic VHL inactivation
    (Springer Nature, 2014) Shankar, Ganesh; Taylor-Weiner, Amaro; Lelic, Nina; Jones, Robert T; Kim, James C; Francis, Joshua M; Abedalthagafi, Malak; Borges, Lawrence; Coumans, Jean-Valery; Curry, William; Nahed, Brian; Shin, John; Paek, Sun Ha; Park, Sung-Hye; Stewart, Chip; Lawrence, Michael S; Cibulskis, Kristian; Thorner, Aaron R; Van Hummelen, Paul; Stemmer-Rachamimov, Anat; Batchelor, Tracy; Carter, Scott; Hoang, Mai; Santagata, Sandro; Louis, David; Barker, Frederick; Meyerson, Matthew; Getz, Gad; Brastianos, Priscilla; Cahill, Daniel
    Hemangioblastomas consist of 10-20% neoplastic “stromal” cells within a vascular tumor cell mass of reactive pericytes, endothelium and lymphocytes. Familial cases of central nervous system hemangioblastoma uniformly result from mutations in the Von Hippel-Lindau (VHL) gene. In contrast, inactivation of VHL has been previously observed in only a minority of sporadic hemangioblastomas, suggesting an alternative genetic etiology. We performed deep-coverage DNA sequencing on 32 sporadic hemangioblastomas (whole exome discovery cohort n = 10, validation n = 22), followed by analysis of clonality, copy number alteration, and somatic mutation. We identified somatic mutation, loss of heterozygosity and/or deletion of VHL in 8 of 10 discovery cohort tumors. VHL inactivating events were ultimately detected in 78% (25/32) of cases. No other gene was significantly mutated. Overall, deep-coverage sequence analysis techniques uncovered VHL alterations within the neoplastic fraction of these tumors at higher frequencies than previously reported. Our findings support the central role of VHL inactivation in the molecular pathogenesis of both familial and sporadic hemangioblastomas.
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    Suggested response criteria for phase II antitumor drug studies for neurofibromatosis type 2 related vestibular schwannoma
    (Springer Nature, 2009) Plotkin, Scott; Halpin, Chris; Blakeley, Jaishri O.; Slattery, William H.; Welling, Duane; Chang, Susan M.; Loeffler, Jay; Harris, Gordon; Sorensen, Alma Gregory; McKenna, Michael; Barker, Frederick
    Neurofibromatosis type 2 (NF2) is a tumor suppressor gene syndrome characterized by multiple schwannomas, especially vestibular schwannomas (VS), and meningiomas. Anticancer drug trials are now being explored, but there are no standardized endpoints in NF2. We review the challenges of NF2 clinical trials and suggest possible response criteria for use in initial phase II studies. We suggest two main response criteria in such trials. Objective radiographic response is defined as a durable 20% or greater reduction in VS volume based on postcontrast T1-weighted MRI images collected with 3 mm or finer cuts through the internal auditory canal. Hearing response is defined as a statistically significant improvement in word recognition scores using 50-word recorded lists in audiology. A possible composite endpoint incorporating both radiographic response and hearing response is outlined. We emphasize pitfalls in response assessment and suggest guidelines to minimize misinterpretations of response. We also identify research goals in NF2 to facilitate future trial conduct, such as identifying the expectations for time to tumor progression and time to measurable hearing loss in untreated NF2-related VS, and the relation of both endpoints to patient prognostic factors (such as age, baseline tumor volume, and measures of disease severity). These data would facilitate future use of endpoints based on stability of tumor size and hearing, which might be more appropriate for testing certain drugs. We encourage adoption of standardized endpoints early in the development of phase II trials for this population to facilitate comparison of results across trials of different agents.
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    Hearing Improvement after Bevacizumab in Patients with Neurofibromatosis Type 2
    (New England Journal of Medicine (NEJM/MMS), 2009) Plotkin, Scott; Stemmer-Rachamimov, Anat; Barker, Frederick; Halpin, Chris; Padera, Timothy; Tyrrell, Alex; Sorensen, Alma Gregory; Jain, Rakesh; di Tomaso, Emmanuelle
    Background Profound hearing loss is a serious complication of neurofibromatosis type 2, a genetic condition associated with bilateral vestibular schwannomas, benign tumors that arise from the eighth cranial nerve. There is no medical treatment for such tumors. Methods We determined the expression pattern of vascular endothelial growth factor (VEGF) and three of its receptors, VEGFR-2, neuropilin-1, and neuropilin-2, in paraffinembedded samples from 21 vestibular schwannomas associated with neurofibromatosis type 2 and from 22 sporadic schwannomas. Ten consecutive patients with neurofibromatosis type 2 and progressive vestibular schwannomas who were not candidates for standard treatment were treated with bevacizumab, an anti-VEGF monoclonal antibody. An imaging response was defined as a decrease of at least 20% in tumor volume, as compared with baseline. A hearing response was defined as a significant increase in the word-recognition score, as compared with baseline. Results VEGF was expressed in 100% of vestibular schwannomas and VEGFR-2 in 32% of tumor vessels on immunohistochemical analysis. Before treatment, the median annual volumetric growth rate for 10 index tumors was 62%. After bevacizumab treatment in the 10 patients, tumors shrank in 9 patients, and 6 patients had an imaging response, which was maintained in 4 patients during 11 to 16 months of follow-up. The median best response to treatment was a volumetric reduction of 26%. Three patients were not eligible for a hearing response; of the remaining seven patients, four had a hearing response, two had stable hearing, and one had progressive hearing loss. There were 21 adverse events of grade 1 or 2. Conclusions VEGF blockade with bevacizumab improved hearing in some, but not all, patients with neurofibromatosis type 2 and was associated with a reduction in the volume of most growing vestibular schwannomas.
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    Erlotinib for Progressive Vestibular Schwannoma in Neurofibromatosis 2 Patients
    (Ovid Technologies (Wolters Kluwer Health), 2010) Plotkin, Scott; Halpin, Chris; McKenna, Michael; Loeffler, Jay; Batchelor, Tracy; Barker, Frederick
    In vitro treatment of Nf2-deficient cells with epidermal growth factor receptor (EGFR) inhibitors can inhibit cellular proliferation. We retrospectively assessed the effect of erlotinib (150 mg daily) on eleven consecutive NF2 patients with progressive VS who were poor candidates for standard therapy. A radiographic response was defined as ≥ 20% decrease in tumor volume compared to baseline. A hearing response was defined as a statistically significant increase in word recognition score (WRS) compared to baseline; a minor hearing response was defined as a 10 dB improvement in pure-tone average with stable WRS. Before treatment, the median and mean annual volumetric growth rate for eleven index VS were 26% and 46%, respectively. Among 10 evaluable patients, the median time-to-tumor progression was 9.2 months. Three patients with stable disease experienced maximum tumor shrinkage of 4%, 13%, and 14%. Nine patients underwent audiologic evaluations. One experienced a transient hearing response, two experienced minor hearing responses, three remained stable, and two developed progressive hearing loss. The median time-to-progressive hearing loss was 9.2 months and to either tumor growth or progressive hearing loss was 7.1 months. Adverse treatment effects included mild-to-moderate rash, diarrhea, and hair thinning, with 2 episodes of grade 3 toxicity. Erlotinib treatment was not associated with radiographic or hearing responses in NF2 patients with progressive VS. Because a subset of patients experienced prolonged stable disease, time-to-progression may be more appropriate than radiographic or hearing response for anti-EGFR agents in NF2-associated VS.
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    Bevacizumab Treatment for Meningiomas in NF2: A Retrospective Analysis of 15 Patients
    (Public Library of Science (PLoS), 2013) Nunes, Fabio Pereira; Merker, Vanessa L.; Jennings, Dominique; Caruso, Paul; di Tomaso, Emmanuelle; Muzikansky, Alona; Barker, Frederick; Stemmer-Rachamimov, Anat; Plotkin, Scott
    Bevacizumab treatment can result in tumor shrinkage of progressive vestibular schwannomas in some neurofibromatosis 2 (NF2) patients but its effect on meningiomas has not been defined. To determine the clinical activity of bevacizumab against NF2-related meningiomas, we measured changes in volume of meningiomas in NF2 patients who received bevacizumab for treatment of progressive vestibular schwannomas. A radiographic response was defined as a 20% decrease in tumor size by volumetric MRI analysis. In addition, we determined the expression pattern of growth factors associated with tumor angiogenesis in paraffin-embedded tissues from 26 unrelated meningiomas. A total of 48 meningiomas in 15 NF2 patients were included in this study with a median follow up time of 18 months. A volumetric radiographic response was seen in 29% of the meningiomas (14/48). Tumor shrinkage was not durable: the median duration of response was 3.7 months and the median time to progression was 15 months. There was no significant correlation between pre-treatment growth rate and meningioma response in regression models. Tissue analysis showed no correlation between tumor microvascular density and expression of VEGF pathway components. This data suggests that, in contrast to schwannomas, activation of VEGF pathway is not the primary driver of angiogenesis in meningiomas. Our results suggest that a minority of NF2-associated meningiomas shrink during bevacizumab therapy and that these responses were of short duration. These results are comparable to previous studies of bevacizumab in sporadic meningiomas.
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    Hearing and facial function outcomes for neurofibromatosis 2 clinical trials
    (Ovid Technologies (Wolters Kluwer Health), 2013) Plotkin, Scott; Ardern-Holmes, S. L.; Barker, Frederick; Blakeley, Jaishri O.; Evans, D. G.; Ferner, R. E.; Hadlock, Tessa; Halpin, C.
    Objectives: Vestibular schwannomas are the hallmark of neurofibromatosis 2 (NF2), occurring in >95% of patients. These tumors develop on the vestibulocochlear nerve and are associated with significant morbidity due to hearing loss, tinnitus, imbalance, facial weakness, and risk of early mortality from brainstem compression. Although hearing loss and facial weakness have been identified as important functional outcomes for patients with NF2, there is a lack of consensus regarding appropriate endpoints in clinical trials. Methods: The functional outcomes group reviewed existing endpoints for hearing and facial function and developed consensus recommendations for response evaluation in NF2 clinical trials. Results: For hearing endpoints, the functional group endorsed the use of maximum word recognition score as a primary endpoint, with the 95% critical difference as primary hearing outcomes. The group recommended use of the scaled measurement of improvement in lip excursion (SMILE) system for studies of facial function. Conclusions: These recommendations are intended to provide researchers with a common set of endpoints for use in clinical trials of patients with NF2. The use of common endpoints should improve the quality of clinical trials and foster comparison among studies for hearing loss and facial weakness.