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The anatomical distribution of cerebral gliomas in mobile phone users   Back Bookmark and Share
A Ali Kahn

We analysed the association between mobile phone use and the anatomical distribution of glial brain tumours in Irish neurosurgical patients. All patients with unilateral histologically proven glioma were enrolled over a 12 month period. We hypothesised that were a cellular phone to cause a glioma then it would do so on the dominant hand side. Fifty mobile phone users and twenty three non-users were identified. The vast majority of patients (69/73) were right handed and the right side of the brain was more common as the tumour site (48/73). Fisher’s exact test revealed no statistical significance for glioma location based on the handedness of the patient in the mobile phone user group and location of the tumour in both user and non-user groups. We discuss our findings and the stable trend in the incidence of reported glioma cases.

Author : A Ali Kahn, DF OBrien, P Kelly

Abstract

We analysed the association between mobile phone use and the anatomical distribution of glial brain tumours in Irish neurosurgical patients. All patients with unilateral histologically proven glioma were enrolled over a 12 month period. We hypothesised that were a cellular phone to cause a glioma then it would do so on the dominant hand side. Fifty mobile phone users and twenty three non-users were identified. The vast majority of patients (69/73) were right handed and the right side of the brain was more common as the tumour site (48/73). Fishers exact test revealed no statistical significance for glioma location based on the handedness of the patient in the mobile phone user group and location of the tumour in both user and non-user groups. We discuss our findings and the stable trend in the incidence of reported glioma cases.

Introduction
Over the last number of years patients presenting to the Beaumont Neurosurgical Unit with cerebral tumours have expressed concern regarding the possible role of mobile (cell) phones in the pathogenesis of such lesions. Their concerns have mainly been fuelled by various media reports on the subject. News and health websites have reported on this issue as have websites for the electronic industries (Figure 1). The frequent malignant nature of such tumours elevates anxiety levels amongst patients and their relatives. Discussion in the public domain leads to many queries concerning the scientific basis for such claims and counter-claims.

BBC News Online: Health Monday, May 24, 1999. Mobile phone cancer study flawed.

Spectrum Online. Foster, K.R. August, 2000, 37,8,1-10. Are mobile phones safe?

Moulder, J.E. Written evidence to the independent expert group on mobile phones. An assessment of the evidence relating to radiofrequency radiation and cancer. Mobile phones home page, October, 1999.

Irish Times Supplement, EL, Smyth, J. page 9, January 15, 2002. The mobile generation: are they too young to txt?

PC World.Com Mobile phones linked to brain cancer. Peter Sayer, IDG News Service May 8,2000.

Figure 1
A sample of media and website comment on mobile phones and heath.

Mobile phones operate at several frequencies in the electromagnetic system. European systems use the Global System of Mobile Communications (GSM) with frequencies near 900MHz.1 Energy in this range is non-ionizing because the photon energy from it is insufficient to displace electrons from atoms in living tissue, a source of serious biological damage from other electromagnetic radiation sources such as X-rays. The most apparent biological effects of radiofrequency energy at mobile phone frequencies are due to heating. No deleterious biological effects have been noted in extensive in vitro and in vivo studies using animals and humans.2,3

As the Beaumont Neurosurgical Unit is a large neurosurgical center and as no such data exists for Irish patients we felt it important out to address the concerns of our patients and their families by undertaking a retrospective study of mobile phone use in patients presenting with cerebral glioma. Gliomas are the largest class of CNS tumour operated upon at Beaumont per annum and provide a large cohort of patients which can be easily assessed for such an association.

Methods
The study was carried out between October 2000 and September 2001 at the Beaumont Neurosurgical Unit. Adult patients who had a histological diagnosis of a supratentorial glioma were visited when comfortable in the post-operative period. Informed consent for entry to the study was obtained from all patients able to participate. Confused patients next of kin assented to the study in all other cases. The data collected consisted of the age, sex, clinical features, handedness, duration of mobile phone use, daily hours of use of mobile phone, the antenna specifications and the type of mobile phone used.

Certain cases were excluded from the study. These included patients with centrally located tumours and those with tumours involving both cerebral hemispheres as the laterality or side of the tumour in such cases is difficult to establish. Tumours not involving the cerebral cortex were also excluded as it is felt that radio-frequency waves have a minimal depth of penetration and that deep (non-cortex) tumours are outside the depth of radiowave penetration.

Fishers exact test was used in the statistical analysis as a test of homogeneity of odds ratios for case control comparing left and right sided cerebral gliomas in relation to handedness of the patient and for the distribution of the tumours within the lobes of the brain.

Results
92 patients with supratentorial glioma were recruited to the study. All patients and their families answered a questionnaire whilst in-patients at the Beaumont Neurosurgical Unit. 19 were excluded as per above. There was an almost equal population of male and female patients (male 36: female 37). Ages ranged from 20 to 81 years with a mean of 51 years. In the patient population there were 50 regular mobile phone users and 23 non mobile phone users. 20% used a mobile phone for 30-60 minutes per day, 50% for 10-30 minutes per day and 30% for 5-10 minutes per day.

The vast majority of patients (69/73) were right handed and the right side of the brain was more common as the tumour site (48/73). Overall the frontal lobe was the most common site and the occipital lobe was the least common location. The location within the brain of gliomas in the mobile phone user and non user groups is shown in Table 1. The frontal lobe was the most common site in both groups. The handedness of mobile phone users versus tumour distribution (left or right sides of brain) is shown in Table 2. There were 43 cases of a high grade malignancy.

Table 1 Anatomical distribution of tumours in mobile phone user and non-user groups
Location
Mobile Phone Users
Non-Mobile Phone
Users  
 
Right
Left
Right
       Left
 
total
%
total
%
total
%
total
%
Frontal
14
28
7
14
3
13
1
4
Parietal
7
14
5
10
6
26
2
9
Temporal
9
18
1
2
3
13
2
9
Occipital
3
6
4
8
3
13
3
13
Total
33
17
15
8

Table 2 Handedness of mobile phone user patients versus laterality of glioma tumours
Handedness
Tumours on Right
Tumours on Left
Left 4
4
0
Right 46
29
17
%
66%
34%

Fishers exact test revealed no statistical difference at the 5% level of significance for tumour location based on the handedness of the patient in the user group and location of the tumour in both groups (Tables 3a and 3b).

Table 3a Statistical analysis of patient handedness and tumour laterality
 
Left sided tumours
Right sided tumours
Total
Left handed
0
4
4
Right handed
17
29
46
Fishers exact test =0.285 (correlation between handedness of patient and side of tumour: no significance). 0.05 is the minimum value to give a level of significance.

Table 3b Statistical analysis of mobile phone use and anatomical distribution
 
1
2
3
4
Total
Non user
4
8
5
6
23
User
21
12
10
7
50
Total
25
12
10
13
73
Fishers exact test =0.168 (correlation between use, non use of mobile phone and location of tumour: no significance)
Key: 1 frontal, 2 parietal, 3 temporal, 4 occipital.

Discussion
In 1992 in the case of Reynard versus the State of Florida it was alleged that mobile phone use had caused a fatal brain tumour. The case was defeated. In a major study published in the New England Journal of Medicine (2001) 782 patients with brain tumours from hospitals across the U.S., who were were frequent (> 60 minutes per day) mobile phone users, were compared to an age, sex and race controlled group of non brain tumour hospital in-patients.4 Data collected included the handedness of the patient and the duration of mobile phone use. The issue concerning handedness was felt to be important as it was hypothesised that were a cellular phone to cause a brain tumour then it would do so on the dominant hand side, i.e. a left handed person would generally hold a cell phone to his/her left ear. The specific absorption rate of the radiofrequency energy (SAR) from a mobile phone averages through the outer 1cm of brain tissue to be 20-30% of surface skin measurements.1 The SAR at a depth of 5cm is further attenuated by a factor of 90%. Hence the rationale for proposing the hypothesis that radiofrequency waves from mobile phones could only cause unilateral tumours.

There were 489 pateints with gliomas, 96 with acoustic neuromas and 197 with meningiomas in this study. The results did not support the hypothesis that the recent use of hand-held cellular telephones caused brain tumours. The authors added a cautionary note saying that the data were insufficient to evaluate the risks among long-term, heavy users and for potentially long induction periods. We hypothesized like the U.S. workers that were a mobile phone to cause a glioma it would do so on the patients dominant hand side and that if there was no association there would be no relationship between the handedness of the patient and the side or laterality of the tumour.

It has been been shown that there is a maximum rise in brain temperature of 0.11 degree Celsius for an antenna with an average emitted power of 0.25 W, the maximum value in common mobile phones, and indefinite exposure.2 It is felt that these values are far too small to have any lasting effects. Newer digital phones in widespread use today have an even lower emitted power than the older analogue devices. In experimental studies on mammals it has been shown that there are no ill effects until brain temperature exceeded 41 degrees Celsius.2

Our analysis shows no association between the handedness of the patient and the side of the tumour. There is also no association between the use, non use of a mobile phone and the lobar location of the tumour (Tables 3a and 3b). The realization that all 4 left handed patients had right sided tumours is enough to appreciate the lack of statistical significance. Using the data of the National Cancer Registry of Ireland from the period 1994-1997 one can see no increasing trend during this period (Table 4). Allowing for additional cases from the Cork unit our figures are in line with this data. It is reasonable to speculate that upcoming data data from the National Cancer Registry may show a slight increase in numbers due to higher rates of detection caused by easier access to CT scanning by virtue of its greater availability. It is interesting to note that almost 10 years ago we published data, gathered in late eighties, in this journal from the Southern Tumour Registry which showed the frontal lobe also as the most common tumour site.5 Were mobile phones to have caused a proliferation of brain tumours one would have expected a greater preponderance in the temporal lobe given its proximity to the auditory apparatus.

Table 4 Number of glioma cases per annum as per National Cancer Registry of Ireland
Year
No. of Glioma cases
1994
78
1995
102
1996
92
1997
80
Beaumont Oct.2000-Sept. 2001
92

Several lengthy reviews of this topic show no harmful effects of mobile phones on the CNS.6 It has been suggested succinctly by our UK colleagues that the only harmful effects from mobile phones are brought about by using one while driving.7

An advice booklet for patients with brain tumours and their families has recently been published by Beaumont Hospital which offers support, explanations of the therapeutic options and excellent advice to patients and their families.8

Acknowledgements
The authors wish to thank Ms. Shona Beatty and Ms. Anne Lynch-Pope, Neuro-oncology Liaison Nurses, Sisters and Staff Nurses at Beaumont Hospital for their invaluable assistance with this study.

Declaration
The authors would like to state that at no time has any financial renumeration or gift been obtained from representatives or agents of mobile phone manufacturers in Ireland or abroad, or from representatives or agents of mobile phone licence holders in Ireland or abroad. No financial incentive has been received for the completion or publication of this clinical study. The authors have no vested interest of any kind in this papers publication.

Correspondence:
Donncha F. OBrien,
Department of Pediatric Neurological Surgery,
St. Louis Childrens Hospital,
Washington University School of Medicine,
One Childrens Place, St. Louis, Missouri, 63110, U.S.A.
Telephone: 00 1 314 4542814.
Fax: 00 1 314 4542818.
Email:[email protected]

References
  1. Rothman KJ, Chou CK, Morgan, R. Assessment of cellular telephones and other radio frequency exposure for epidemiologic research. Epidemiology 1996; 7:291-298.
  2. Van Leeuwen, GMJ, Lagendijk, JJW, Van Leersum, BJAM, Zwamborn, APM. Calculation of change in brain temperature due to exposure to a mobile phone. Phys.Med. Biol. 1999; 44:2367-2379.
  3. Hermann, D.M., Hossmann, K.A. Neurological effects of microwave exposure related to mobile communication. Journal of Neurological Sciences 1997; 152:1-14.
  4. Inskip, P.D., Tarone, R.E., Hatch, E.E. et al. Cellular-telephone use and brain tumours. The New England Journal of Medicine 2001; 344:79-86.
  5. Crowley, MJ, OBrien, DF. Epidemiology of tumours of the central nervous system in Ireland. Irish Medical Journal 1993; 86:87-88.
  6. Moulder, J.E., Erdreich, L.S., Malyapa, R.S., Merritt, J., Pickard, W.F. Cell phones and Cancer: What is the evidence for a connection? Radiation Research 1999; 151:513-531.
  7. Maier, M., Blakemore, C.and Koivisto, M. The health hazards of mobile phones-the only established risk is of using one while driving.BMJ 2000; 320:1288-1289.
  8. Coping with a Brain Tumour. Publication from the Department of Neurosciences, Beaumont Hospital, Dublin, 9, Ireland, 2001.
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