Background & objective: Toxicities and response are different when patients with advanced colorectal cancer were treated with standard FOLFOX6 regimen. Serum level of dihydropyrimidine dehydrogenase (DPD) relates to efficacy and toxicities of chemotherapy containing 5-fluorouracil (5-FU). This study was to explore relationship of DPD to serum concentration of 5-FU in colorectal cancer patients treated with FOLFOX6 regimen, and their correlation to treatment response and adverse events.
Methods: Serum level of DPD in 72 patients with colorectal cancer was detected by high-performance liquid chromatography (HPLC) before chemotherapy. Serum concentration of 5-FU at steady state was detected by HPLC after patients received FOLFOX6 regimen. Treatment response and adverse events in the patients were assessed.
Results: Serum levels of DPD were normally distributed in 72 patients (ranged 1.55-5.94), while serum concentrations of 5-FU at steady state were not (ranged 141.1-1 741.9 microg/L). Serum level of DPD was negatively correlated with serum concentration of 5-FU (r=-0.460, P < 0.01). Occurrence of adverse events was lower when 5-FU concentration was less than 600 microg/L than when 5-FU concentration was more than 600 microg/L (P < 0.05). The mean serum concentration of 5-FU was significantly higher in patients with complete response and partial response than in patients with steady disease, and progressive disease (513.9 microg/L vs. 409.8 microg/L, and 259.3 microg/L, P < 0.05). Serum level of DPD was lower in patients suffered oral mucositis and diarrhea of grade II-IV than in patients suffered oral mucositis and diarrhea of grade 0-I (P=0.016, P=0.047). Serum level of DPD had no relation with treatment response of the patients (r=0.312, P=0.078).
Conclusions: DPD level and serum 5-FU concentration vary a lot among patients with colorectal cancer. DPD level negatively correlates with serum 5-FU concentration. Serum concentration of 5-FU correlates with treatment effect and toxicities.