Prevalence of UGT1A1 polymorphisms in gastrointestinal cancer: A single-institutional retrospective study.

Abstract

797 Background: UGT1A1 gene polymorphisms are heterogeneously distributed among ethnicities and varying geographical regions. Patients with UGT1A1*6 and UGT1A1*28 polymorphisms have an increased risk of grade 3-4 neutropenia and diarrhea from irinotecan due to poor metabolism. This study evaluated the prevalence of UGT1A1 polymorphisms in the cancer patients in a large tertiary cancer center in the Appalachian region, in order to develop individualized institutional guidelines on the utility of UGT1A1 testing in chemotherapy dose management. Methods: This retrospective study evaluated all patients with gastrointestinal (GI) malignancies who underwent UGT1A1 testing prior to chemotherapy initiation between 1/1/2020 and 6/30/2022 at West Virginia University. All patients within this disease sub-specialty who were eligible for chemotherapy were tested for UGT1A1 *6 and UTG1A1*28 polymorphism via PCR based pharmacogenomic evaluation using OneOme RightMed comprehensive testing. Patients were excluded if they were tested for genetic alterations specifically due to previous treatment intolerances. Prevalence of the alterations along with demographic characteristics of patients are reported. Results: UGT1A1 genotyping was performed in 278 patients prior to initiating chemotherapy and 12 patients were excluded due to insufficient sample. A total of 266 patients met the inclusion criteria. The median age was 66 years (IQR: 26-92). Males constituted a higher proportion of the population compared to females (M: F = 147: 119). Colon (n-81; 30.5%) and pancreatic (n-80; 30%) cancers were the predominant GI malignancies. Fifty five percentage of patients (n-146) had metastatic disease. The distribution of the UGT1A1 variant genotype is showed in the table below. Conclusions: The prevalence of heterozygous and homozygous of UGT1A1*28 polymorphism in GI cancer patients in the Appalachian region is 51.5%, consistent with the reported literature. Homozygous and heterozygous UGT1A1 *28 alterations constituted 13.2 and 38.3% respectively. Data collection for pre-emptive chemotherapy dosage adjustments and adverse events is ongoing to integrate testing for UGT1A1 polymorphism routinely for all GI malignancies cancer patients starting irinotecan chemotherapy.[Table: see text]