The results contradicted earlier studies including one Swedish study that showed mobile users in rural areas had an increased risk of tumors because base-stations are further apart, forcing the phone to operate at higher power. The UK study found no evidence to support this link. However, other past studies also pointed to increased risk on the side of the brain closest to where users hold their phones.
The UK study also observed a "significant excess risk" here. The results indicated a "significant reduction in risk" on the other side of the brain however, leading the researchers to conclude that there is insufficient evidence that such a phenomenon exists. The researchers also pointed out that widespread mobile phone usage hasn't been going on long enough to provide a proper risk assessment.
Source:
The Register