The largest study to examine a potential link between cellphone use and cancer is already stirring up controversy, two days ahead of its actual release. After many years of ambiguous and sometimes conflicting results, the Interphone study was an attempt to provide a definitive measure of any risks associated with heavy cellphone use. But even the studys authors spent several years arguing over how to interpret the data that came in, before finally producing a report thats due to be published Monday evening, US time.