[Pharmacokinetic monitoring of 5-fluorouracil may improve the clinical benefit with an individualized regimen-a case report].

Serum levels of 5-fluorouracil(5-FU)were measured in a patient receiving pharmacokinetic modulation chemotherapy( PMC), with 5-FU, as well as a combination of oxaliplatin and infusional 5-FU plus leucovorin(FOLFOX). A 77- year-old man presented with unresectable multiple hepatic metastases after abdominoperineal resection of rectal / carcinoma, and was successfully treated by PMC. The patient initially received infusional 5-FU at 750 mg/m(2) once a week, and showed a partial response. Serum 5-FU levels were higher at night, and the peak concentration of 5-FU was / 398 ng/mL. After 13 months of PMC, second-line chemotherapy with FOLFOX was initiated because new liver metastases had appeared. After 4 cycles of FOLFOX4, progression was observed, and the concentration profile of 5-FU / was measured. The area under the concentration vs. time curve(AUC ngxh/mL)was smaller with FOLFOX4 than with PMC, so the FOLFOX6 regimen was tried instead. The AUC increased and disease progression was suppressed. This case shows that individual adjustment of the dose and regimen based on pharmacokinetic monitoring can increase the clinical benefit of fluorouracil.