Nakata et al. Journal of Experimental & Clinical Cancer Research 2010, 29:15 http://www.jeccr.com/content/29/1/15 Page 4 of 7 Table 1 Comparison of pharmacokinetic parameters of gemcitabine (GEM) in plasma between administraion of GEM alone and GEM+S1 Day 1 (GEM alone) Day 15 (GEM+S-1) P-value Cmax (ng/ml) 15833 ± 2477 AUCinf (hXng/ml) 8467 ± 1092 T1/2 (h) 0.12 ± 0.033 14924 ± 5828 8384 ± 2915 0.153 ± 0.069 0.604 0.7406 0.1594 GEM was intravenously given at a dose of 800 mg/m2. S-1 was orally given at a dose of 30 mg/m2. Cmax, maximum plasma concentration; AUCinf, area under plasma concentration-time curve from time zero to infnite time; T1/2, elimination half-life. Titers are expressed as means ± SD (n = 6). P-values were examined by two- sided paired t-test after log-transformation. be better than GEM monotherapy, although a true eva- luation requires data from the ongoing phase III trial (GEST study). Our results demonstrated that pre-administration of S-1 did not increase Cmax, AUCinf or T1/2 of plasma GEM (Table 1, Figure 2). Nakamura et al. performed a PK study of GEM with S-1; S-1 was given orally at a dose of 30 mg/m2 twice daily for 14 consecutive days, followed by a 1-week rest. GEM 1000 mg/m2 was given in a 30-min i.v. on day 8 and day 15. In six patients with metastatic pancreatic cancer, the PK parameters of Cmax and AUCinf for GEM were examined on day 8. It was concluded that their data were similar to those of GEM single-administration, as determined in a phase I study [11] carried out by other investigators [12]. Figure 2 Plasma concentrations of gemcitabine (GEM) after administration of GEM 800 mg/m2 alone (open circles) and GEM 800 mg/ m2 + S-1 30 mg/m2 (closed circles).