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.