It is estimated that the vast majority of patients are potentially good candidates for catheter placement. This is the result of recent improvements in patient selection and improved technical skills in catheter placement. However, physicians and patients should be aware of potential problems that can occur if TheraSphere® is not correctly placed in the liver, which can lead to serious side effects in the gastrointestinal (GI) tract or lungs. These usually only occur in patients who have unusual or severely damaged liver blood vessels. Prior to TheraSphere administration, patients are screened to determine if they are at risk for the side effects in the GI tract or lungs.