By ecancer reporter Clare Sansom

Mobile phones are now ubiquitous even in parts of the world where landline coverage is sparse and unreliable. Anecdotal reports suggest that there will be more phones than people on the planet by the mid-2010s. Although no biological mechanism through which the radio waves emitted by these phones could be carcinogenic is known, there is an ongoing public concern about this possibility and epidemiological studies have been recommended. Leukaemia is of particular interest because of the presence of bone marrow in the skull and mandible, close to the usual location of a phone in use, and because its induction period after carcinogen exposure is shorter than that of than solid tumours.

A group of researchers led by Rosie Cooke at the Institute of Cancer Research, London, UK has now conducted a large case-control study into the relation between mobile phone use and the risk of contracting leukaemia. Chronic lymphocytic leukaemia was excluded from the study as its aetiology is considered to be different from that of other types. A total of 1660 cases were identified, all of people who had been diagnosed with other types of leukaemia in South-East England between 2003 and 2009, and who were aged between 18 and 59 at the time of diagnosis. Of these, 806 were willing and able to take part in telephone interviews. The most common leukaemia diagnosis was AML, with 449 cases; 154 were diagnosed with CML, 125 with ALL, and the others with rarer or mixed type leukaemias. The 589 controls interviewed were non-blood relatives of the cases in the same age range who did not live with them and had never been diagnosed with leukaemia.

All cases and controls were interviewed in detail about their use of mobile phones. They were asked whether and for how long they had been regular mobile users; how intensively they had used the phones; and to specify the makes and models of phones used and how much of this use had been hands-free. Odds ratios for leukaemia risk were calculated in relation to several aspects of phone use and adjusted for a number of demographic variables and for smoking status. The analysis was repeated excluding participants who had been exposed to known or possible leukaemia risk factors (including telecommunication masts) or who had known cytogenetic abnormalities.

The results indicated broadly that regular users of mobile phones had similar risks of leukaemia to non-users, and that the risk was not increased with more intensive use. No significant trends were observed when the results were stratified by years of use, years since first use or leukaemia subtype, or when data for analogue and digital phone use was separated. There appeared to be a slight, but non-significant, increase in risk of AML after more than 15 years of use, and in risk of ALL after 10-14 years. All results were unchanged when people with a known environmental or genetic risk factor for leukaemia were excluded.

In general, these results have confirmed those of the few previous studies, that in general there is no statistically significant raised leukaemia risk associated with the regular use of mobile phones. The possibility of a slight increase in risk after long-term use remains and it will be useful to monitor this with further large scale case-control and cohort studies.

Reference

Cooke, R., Laing, S. and Swerdlow, A.J. (2010) A case–control study of risk of leukaemia in relation to mobile phone use British Journal of Cancer 103, 1729-1735 doi:10.1038/sj.bjc.6605948