ABCG2 and cancer: However, because its primary mode of excretion is through the hepatobiliary system, [18F]AVT-011 would not be useful in imaging tumors located in organs such as the liver and gastrointestinal tract (whose cancers have high ABCB1 and ABCG2 expressions) because the high baseline values of uptake in these organs would make it difficult to distinguish uptake in tumor versus normal tissue [1].