On the assumption that more than one molecular resistance mechanism is involved in irinotecan resistance [5], we now combined ABCG2 and TOP1 expression status in a single dichotomous parameter and hypothesized that patients with a tumor with a high ABCG2 and a low TOP1 expression level might represent those with a low response to irinotecan added to adjuvant 5FUL treatment. This evidence concerns the gene ABCG2 and neoplasm.