UGT1A6 and neoplasm: This study was conducted in a small group of patients (four responders and eight non-responders), but the mRNA expression data are supported by immunohistochemical observations, with an average of 65% UGT1A6-positive cells in tumours from non-responders relative to 23% in tumours from responders.40 Expression was measured before treatment initiation, consistent with UGT1A6 being a predisposing resistance factor, as for patients with head and neck cancer or NSCLC.