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  • Is the Increasing Incidence of Glioblastoma Related to Agricultural Chemicals? A Large Database Analysis of Iowa Tumor Incidence

    Final Number:

    Manu K Arul BA; Hal Starnes BA; Satish Krishnamurthy MD MCh

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2018 Annual Meeting

    Introduction: The incidence of Glioblastoma (GBM), the most aggressive primary brain tumor, has increased over 30 years. Agricultural chemicals have been questioned for their role, as some are known to be neurotoxic, yet are commonplace items. Various organizations, including the IARC, have conflicting conclusions on these chemicals and their carcinogenicity. Furthermore, previous studies in this topic use investigative techniques that are subject to bias. This study aims to improve these investigations and arguments by using the SEER database and NWIS Water Quality database to examine potential associations between agricultural chemicals and glioblastoma incidence in a moderate Iowa population size.

    Methods: The NCI SEER database was queried using SEER*stat, for all glioblastoma cases from 2004 – 2014 (age: 0 to 85+ years). All counties in Iowa were included. The incidence of tumor cases per year for each county using population census data was calculated. A geographic heat map of Iowa was created to visualize “GBM clusters” within the state (Fig. 1). Average water pollutant measurements for Atrazine, Chlorpyrifos, Glyphosate, and Imidacloprid were obtained for the same years from the NWIS. These were interpreted as a proxy for chemical usage. Statistical analyses was conducted for significance and association, using Spearman’s Rho for nonparametric data.

    Results: N=1100 patient cases from 99 counties were identified for analysis; males = 650 and females =450. Atrazine measurements(n=62), Chlorpyrifos (n=52), and Imidacloprid (n=18) did not show a significant association with tumor incidence (Rho=0.064, 0.018, -0.01231; P>.05, respectively). Glyphosate showed a moderate positive association with incidence, but this was not statistically significant (n=21, rho=0.58, P=.99).

    Conclusions: Of the four mainstream agricultural chemicals, atrazine, chlorpyrifos, and imidacloprid showed non-significant non-associations with tumor incidence. Glyphosate, a known neuro-toxic pesticide, showed moderate association with tumor incidence, but was statistically insignificant.

    Patient Care: This research aims to make associations between environmental pollutants and the development of Glioblastoma. We hope that this information helps guide the future research of carcinogens and directs attention to the cause of primary brain tumors, the mechanism of pathogenesis, and possibly toward preventive health measures to reduce the risk of developing glial tumors, especially Glioblastoma.

    Learning Objectives: 1-Analyze the Incidence of GBM in Iowa Counties from 2004-2010 2-Compare the varying levels of agricultural water pollutants to GBM incidence 3-Describe a possible association between agricultural water pollutants and GBM incidence

    References: 1)Deorah S, Lynch CF, Sibenaller ZA, Ryken TC. Trends in brain cancer incidence and survival in the United States: surveillance, epidemiology, and end results program, 1973 to 2001. Neurosurg. Focus 2006; 20:E1. 2) Gomes J, Zayadi AA, Guzman A. Occupational and Environmental Risk Factors of Adult Primary Brain Cancers: A Systematic Review. The Journal of Occupational and Environmental Medicine 2011; 2:82-111. 3) Portier CJ, Armstrong BK, Baguley BC, et al. Differences in the carcinogenic evaluation of glyphosate between the International Agency for Research on Cancer (IARC) and the European Food Safety Authority (EFSA) J Epidemiol Community Health 2016;70:741-745. 4) Xu H, Chen J, Xu H and Qin Z. Geographic Variations in the Incidence of Glioblastoma and Prognostic Factors Predictive of Overall Survival in US Adults from 2004–2013. Front. Aging Neurosci. 2017. 9:352.

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