Cell phones and glioma risk: a review of the evidence.

Recently cell phones have become the target of much controversy because they are increasingly being viewed as potential carcinogenic agents with a causal role in brain tumor development. The overall incidence of malignant brain tumors in the United States from 1992 to 2007 declined slightly from 6.8 to 6.2 per 100,000, while the incidence in children has risen slightly over the past three decades [1, 2]. According to the Central Brain Tumor Registry (CBTRUS) [3] in 1995 the incidence of both benign and malignant brain tumors was 13.4 per 100,000 and in 2004 it was 18.2 per 100,000. The cause of the clear increase in benign tumor incidence is unknown, but there is concern that cell phones can trigger biological effects and that several decades of cell phone use in an individual may significantly increase the risk of a malignant brain tumor. The potential public health problem is sizeable as the most common malignant brain tumors are highly lethal and cell phone use in the U.S. alone has escalated dramatically, with approximately 70 million new cell phone subscriptions between 2006 and 2010, and 250 million subscriptions overall in 2007 [4, 5]. The concern relating to cell phone use and brain cancer is underscored by the fact that teens and children are beginning to use cell phones at younger ages [6]. Moreover, greater than 4 of 5 children/teens 12 years and older sleep with a cell phone next to them, often under the pillow [7]. Children and young adults are more susceptible to the harmful effects of carcinogenic agents such as radiation [8]. Therefore, a shift in incidence of brain tumors in younger age groups may emerge as their exposure to cell phones reaches long-term status and attains the 10-year or greater mark. A recent study revealed that children exposed to 1,800 MHz cell phone electromagnetic fields (EMF) can experience significantly higher exposures to cortical regions, hippocampus, hypothalamus and the eye than adults, and that this difference can be greater than one order of magnitude [6]. The most feared brain tumors in adults and children are the gliomas, which include the astrocytomas and oligodendrogliomas. These tumors are graded on a progressive scale of malignancy, and astrocytomas that have progressed to the Grade IV World Health Organization (WHO) classification level are also known as glioblastomas [9]. Glioblastomas are common brain tumors and most frequently arise de novo as primary cancers. The gliomas as a whole comprise approximately 33% of all brain tumors and 79% of malignant brain tumors [3]. Cure is not typical and the therapy of even low grade gliomas can be challenging. The glioblastomas are highly lethal and despite aggressive treatment efforts patients are dead at a median of 14 months after diagnosis [10]. Five year survival is dismal, less than 10%. This review will focus specifically on glioma risk from cell phone use, and will begin with a brief overview of the state of the relevant cell phone—brain tumor risk literature. The two significant, comprehensive databases concerning cell phone use and brain cancer risk are the often cited Hardell (Sweden) and the multicenter European Interphone studies [11, 12]. These two groups each include multiple studies, and they comprise the major focus of the current review. Glioma risk data derived from Hardell and Interphone, as well as from some smaller studies, is partitioned Courtney Corle and Milan Makale are co-first authors.