br The final results of a major international study of the potential link between cellphone use and cancer were published last week. The finding: Using a cellphone seems to protect against two types of brain tumors. br Even the researchers didn't quite believe it.br The apparent shield of cellphone radiation, most likely fictitious, illustrates how hard it is to analyze, let alone quantify, the potential for a small elevated risk in a rare disease from a widespread, mundane activity. br "They found that ever having used a cellphone appeared to be protective [against] brain cancer," says David O. Carpenter, director of the University at Albany's Institute for Health and the Environment, in Albany, N.Y. "And that just simply makes no sense." br The study was funded in part by the Mobile Manufacturers' Forum and GSM Association, two wireless industry groups.