The combination of HCPT and 5-FU synergistically inhibits tumor growth in vivo . SW1116 cells were subcutaneously injected into the flank of athymic nude mice. The tumor at 50 mm3 to 60 mm3 volume was treated with 10-hydroxycamptothecin (HPCT) by intraperitoneal injection (5 mg/kg), or 5-FU (10 mg/kg) or a combination of both for 5 days. Tumor growth was measured every week after the treatment for a duration of 6 weeks. Data are the means ± SD of tumor size per mouse (n = 6). *P <0.01, compared to the 5-FU or HCPT treatment alone; #P <0.05, compared to PBS treatment.