Is there friction within the Interphone study group?


April 18... Is there friction within the Interphone study group? An exchange of letters in today's issue of the Journal of the National Cancer Institute (JNCI) exposes a rift between the Swedish Interphone group led by Maria Feychting and the Danish and German Interphone groups led by Joachim Schüz and Christoffer Johansen, respectively. At issue is the nature and extent of a possible tumor risk among long-term mobile phone users.

Late last year, Schüz and Johansen
updated their analysis of a Danish cohort and concluded that it provides "evidence that any large association of risk of cancer and cellular telephone use can be excluded." (Schüz is now at the Danish Cancer Society in Copenhagen, where Johansen also works.)

In a
letter to the JNCI, Feychting and Anders Ahlbom, both of the Karolinska Institute in Stockholm, counter that "such a global conclusion is premature and not supported by the data." They go on: "Although results from this and other studies concerning short-term use are reassuring, we do not see how these data provide convincing evidence against an effect of long-term use which for some time has been the critical issue in evaluations of potential health risks related to mobile phone use."

In their
reply, Schüz and the other members of the Danish study team —including John Boice and Joseph McLaughlin of the International Epidemiology Institute in Bethesda, MD— appear to back off from their original conclusion, acknowledging that "further study is warranted to evaluate the possibility of an association between long-term cellular telephone use and brain tumor risk."

Elisabeth Cardis of IARC in Lyon, France, who is the principal investigator of the overall Interphone project, signed the letter from the Swedish team, as did Paul Elliott of Imperial College, London.

One additional comment: The Schüz letter could easily mislead the uninitiated reader into thinking that the Interphone results published so far do not show a link between long-term use and acoustic neuroma, a tumor of the acoustic nerve. In fact, they do. The Danish study did not find an association, but that may be because a cohort study offers no information about on which side of the head the phone was used (laterality) and therefore which side of the head was exposed to radiation. In their April 18 response, Schüz and coworkers write that "our acoustic neuroma results are overall consistent with the results of the pooled five-country study." That five-country
study is an analysis from five Interphone teams —Ahlbom, Cardis and Feychting are all among the authors— which does have data on laterality. While it does not show a general elevated risk of acoustic neuroma after ten or more years of cell phone use, the five-country analysis does when laterality is added to the mix. Then, a clear statistically significant tumor risk becomes apparent. This was a key finding of the five-country analysis and is included in the abstract of the published paper.





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