Aim: We retrospectively investigated the relationship between IVS14+1 G > A genotype of the dihydropyrimidine dehydrogenase (DPD) gene with plasma concentration of 5-fluorouracil (5-FU) as well as adverse reactions in 80 patients with locally advanced or metastatic colorectal cancer.
Patients and methods: Eighty patients with un-resectable locally advanced or metastatic colorectal cancer were treated with Folfox-6 regimen, which repeated every two weeks for at least three cycles. Single nucleotide polymorphisms for DPD gene were analyzed before chemotherapy by high-resolution melting (HRM) analysis. The plasma concentration of fluorouracil was measured by high performance liquid chromatography (HPLC) after continuous infusion of fluorouracil over 12 h in each cycle. The average values of plasma concentrations in each cycle were calculated, and the factors related to plasma concentration of 5-FU were screened by stepwise regression.
Results: All patients were divided into three groups according to the predictive confidence interval of plasma concentration of 5-FU, and the average plasma concentrations of fluorouracil in each cycle of these three groups were less than or equal to 26.83 mg/L, 26.83-40.62 mg/L, and more than 40.62 mg/L, respectively. Stepwise regression analysis showed that the plasma concentration of fluorouracil was associated with myelosuppression, hand-foot syndrome, diarrhea, overall survival (OS) and DPD genotype. In efficacy, the median progression-free survival PFS (mPFS) and OS (mOS) of group 2 and group 3 were both significantly higher than those of group 1.
Conclusions: Among the advanced colorectal cancer patients receiving fluorouracil-based chemotherapy, those with plasma concentration of 5-FU above 26.83 mg/L can obtain better survival; for patients with heterozygous DPD IVS14+1 mutation, 5-FU dose should be appropriately reduced according to last plasma concentration to reduce adverse reactions, while the homozygous ones should avoid application of 5-FU and its derivatives.