A meta-analysis in Caucasians was conducted to investigate the possible 
association of uridine diphosphate glucuronosyltransferase (UGT) 1A1 gene 
polymorphisms with irinotecan (IRI)-induced neutropenia and diarrhoea in 
colorectal cancer (CRC). We searched PubMed and Embase until May 2012 to 
identify eligible studies, extracted data, assessed methodological quality, and 
performed statistical analysis using REVMAN 5.1 and R software. Subgroups 
meta-analyses were performed in groups representing different IRI combination 
regimens and IRI doses. Sixteen trials were included. UGT1A1*28/*28 genotype was 
associated with more than fourfold (odds ratio (OR)=4.79, 95% confidence 
intervals (CI): 3.28-7.01; P<0.00001) and threefold (OR=3.44, 95% CI: 2.45-4.82; 
P<0.00001) increases in the risk of neutropenia when compared with wild type and 
with at least one UGT1A1*1 allele, respectively. UGT1A1*1/*28 genotype had an OR 
of 1.90 (95% CI: 1.44-2.51; P<0.00001) for an increased risk of neutropenia. A 
twofold increase in risk of diarrhoea was associated with UGT1A1*28/*28 genotype 
(OR=1.84, 95% CI: 1.24-2.72; P=0.002). In subgroup meta-analysis, the higher 
incidence of diarrhoea in UGT1A1*28/*28 patients was limited to studies where 
when IRI was given at higher doses (OR=2.37, 95% CI: 1.39-4.04; P=0.002) or 
combined with 5-fluorouracil (FU or analogue) (OR=1.78, 95% CI: 1.16-2.75; 
P=0.009). Genotyping of UGT1A1*28 polymorphism before treatment for CRC can 
tailor IRI therapy and reduce the IRI-related toxicities. IRI-combined 5-FU (or 
analogue) and a high-dose IRI therapy enhance IRI-induced diarrhoea among 
patients bearing the UGT1A1*28 allele. Although the toxicity relationships were 
much stronger with the UGT1A1*28 homozygous variant, associations were also 
found with the UGT1A1*28 heterozygous variant.