Effects of plasma concentrations of 5-fluorouracil on long-term survival after treatment with a definitive 5-fluorouracil/cisplatin-based chemoradiotherapy in Japanese patients with esophageal squamous cell carcinoma

Background: A substantial body of literature has accumulated during the past 20 years showing the plasma concentrations of 5-fluorouracil (5-FU) to correlate with clinical response and/or toxicity in colorectal cancer, and head and neck cancer, but little information is available concerning effects on long-term survival. Here, Japanese patients with esophageal squamous cell carcinoma (ESCC) were followed up for 5 years after treatment with a definitive 5-FU/cisplatin (CDDP)-based chemoradiotherapy (CRT), and the association between prognosis and the plasma concentration of 5-FU was evaluated. Methods: Forty-nine patients with ESCC, who were treated with a definitive 5-FU/CDDP-based CRT, were enrolled. A course consisted of the continuous infusion of 5-FU at 400 mg/m(2)/day for days 1-5 and 8-12, the infusion of CDDP at 40 mg/m(2)/day on days 1 and 8, and the radiation at 2 Gy/day on days 1 to 5, 8 to 12, and 15 to 19, with a second course repeated after a 2-week interval. Plasma concentrations of 5-FU were determined by high performance liquid chromatography at 5: 00 PM on days 3, 10, 38 and 45, and at 5: 00 AM on days 4, 11, 39 and 46. Results: The overall 5-year survival rate was 42.9%. Age (P = 0.020), body weight (P = 0.019), and disease stage (P = 0.048) affected the survival, and the survival depended on the clinical response assessed at 1 month after the treatment (P = 0.001). Higher plasma concentrations of 5-FU resulted in a better clinical response (P = 0.043), and trended to prolong survival (P = 0.321). Conclusions: The long-term survival after treatment with a definitive 5-FU/CDDP-based CRT possibly depends on the plasma concentrations of 5-FU, and further clinical studies with a larger number of cases are needed to clarify the relationship between them.