Cell phones and brain cancer: Unlocking the controversy?

Faina Linkov, PhD

Assistant Professor, University of Pittsburgh Cancer Institute

Why is there a concern about cell phones and breast cancer?

• Interest in the media• New technology with rapid increase in

use in the past 10 years• Potential exposure to Radiofrequency

(RF) “radiation”• Limited information re: RF radiation

risks• Etiology of brain tumors largely

unknown

What is brain cancer

Most brain cancers can spread through the brain tissue but rarely spread to other areas of the body. But even so-called "benign" tumors can, as they grow, compress normal brain tissue, causing damage that is often disabling and sometimes fatal. For this reason, doctors usually speak of "brain tumors" rather than "brain cancers."

Glioma: Most common type of brain cancer

Gliomas are not a specific type of cancer. Glioma is a general term for a group of tumors that start in glial cells. A number of tumors can be considered gliomas, including glioblastoma multiforme, astrocytomas, oligodendrogliomas, and ependymomas. About 4 out of 10 of all brain tumors are gliomas. Counting only malignant tumors, about 8 out of 10 are gliomas.

Brain cancer statistics• The American Cancer Society estimates that 21,810

malignant tumors of the brain or spinal cord (11,780 in men and 10,030 in women) will be diagnosed during 2008 in the United States. These numbers would likely be much higher if benign tumors were also included. About 13,070 people (7,420 men and 5,650 women) will die from these tumors.

• This would account for about 1.5% of all cancers and 2.3% of all expected cancer-related deaths in 2008. Both adults and children are included in these statistics.

• Overall, the chance that a person will develop a malignant tumor of the brain or spinal cord in his or her lifetime is less than 1% (about 1 in 150 for a man and 1 in 182 for a woman).

Trends in Brain Cancer Incidence By Age, 1973-2005 (SEER)

1

10

100

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Ye a r of Dia g nosis

≥65 years

45-64 years

15-44 years

< 15 years

Cell phones

The following factors have been proposed as possible risk factors for primary brain tumors. Whether these factors actually increase the risk of a brain tumor is not known for sure.

• Genetic risk• Radiation to the head• HIV infection• Smoking• Toxins

Electromagnetic Spectrum

Early analog phones

(800-900 Mhz)

Digital phones(up to

1900 MHz)

Biological Effects of Radiofrequency Radiation

• Energy of a radiofrequency (RF) wave from a cellular telephone is billions of times lower than the energy of an x-ray photon

• RF radiation is insufficiently energetic to break molecular bonds or ionize molecules

• At high power levels, RF radiation can cause heating, but biological effect from cellular phone use unlikely to be thermal

• No consistent experimental evidence of carcinogenicity or genotoxicity

• Mechanism by which RF radiation might cause cancer?

NCI Study – MethodsNCI Study – Methods

• Hospital-based, case-control study

• 3 hospitals (Phoenix, Pittsburgh, Boston)

• 782 newly-diagnosed cases (489 glioma, 197 meningioma, 96 acoustic neuroma)

• 799 matched controls

• Interview about use of cellular phones

• Data collection from 1994 to 1998

Cell-Phone Use and Risk of Glioma

Cumulative

Use (hr) Controls Cases OR 95% CI

never/rarely 625 398 1.0

< 13 55 26 0.8 0.4 - 1.4

13 to 100 58 26 0.7 0.4 - 1.3

> 100 54 32 0.9 0.5 - 1.6

> 500 27 11 0.5 0.2 - 1.3

Cell-Phone Use and Risk of Glioma:

Laterality of Tumor and Phone Use

Phone Use*

Tumor Left Right P-value**

Left 8 18 0.77

Right 10 17

* Use for >= 6 months before tumor diagnosis* Use for >= 6 months before tumor diagnosis

** Test for independence** Test for independence

Main Findings

• No association between incidence of glioma and level of use of cell phone

• Laterality of cancer not related to laterality of phone use

• Similar findings for meningioma & acoustic neuroma

Strengths

• Incident, histologically-confirmed cases

• Rapid case ascertainment– Relatively few proxy interviews

• High participation rates (92% for cases, 86% for controls)

• Large sample size for glioma• Use of imaging and surgical reports to

determine tumor location

Limitations

• Small number of long-term, heavy users• Cannot rule out small risks• Reliance on interviews taken after tumor

diagnosis to assess cell phone use – potential for imperfect recall (as in all case-

control studies)

• Changes in cellular technology

Changes in Cellular Networks and Phones

• Analog versus digital– First cell phones were analog– Digital service began in the U.S. in 1992; earlier in

Europe– Current cell phones are digital– Digital phones emit less RF energy per unit time– Adaptive power control

• Higher density of base station antennas• Higher operating frequencies

Other studies

• Most existing studies found little or no association between cell phone use and brain cancer

• Existing studies are quite limited, therefore more studies are needed to establish cause and effect relationship

Summary• Brain cancer incidence trends for brain

cancer appears to be unrelated to cell phone use

• No consistent subgroup findings but need larger numbers of longer-term users to evaluate different exposure metrics, latency, laterality, etc.

• There is a a need to evaluate consistency within and among existing studies

• Further studies are needed to detect longer-term risks and risks to children