Pharmacogenetic impact of UGT1A1 polymorphisms on pulmonary neuroendocrine tumours treated with metronomic irinotecan‐based chemotherapy in Chinese populations

OBJECTIVES To evaluate the effects of UGT1A1*6 and UGT1A1*28 polymorphisms on the safety and efficacy of metronomic irinotecan-based chemotherapy (IBC) in Chinese patients with pulmonary neuroendocrine tumours (PNTs). METHODS Sixty-eight PNT patients who received metronomic IBC were observed. The quantitative fluorescent polymerase chain reaction was used to detect UGT1A1*6 and UGT1A1*28 polymorphisms. The follow-up data were collected to investigate the relationship between different genotypes and adverse drug reactions. The clinical outcomes of metronomic IBC were also evaluated. KEY FINDINGS In the genotype-toxicity association analysis, patients with homozygous UGT1A1*6 had the highest incidence of grade 3-4 diarrhoea (P = 0.010). Compared to other groups, patients with the haplotype of UGT1A1*28 showed a trend towards an increased incidence of grade 4 neutropaenia (P = 0.047). A higher incidence of grade 3-4 leucopaenia was found in groups with UGT1A1*1/*28 (P = 0.023) and UGT1A1*28/*28 (P = 0.022). Grade 1 total bilirubin elevation was associated with the homozygous UGT1A1*6 mutation (P = 0.027) or any UGT1A1*6 variants (P = 0.047). However, neither UGTA1A*28 nor UGT1A1*6 showed any significant association with tumour response or clinical outcomes. CONCLUSIONS The impact of UGT1A1 polymorphisms varies in different irinotecan-based chemotherapies. UGT1A1*6 and UGTA1A*28 were useful for the prediction of irinotecan-related severe toxicity in Chinese PNT patients treated with metronomic IBC.