Double alternate modulation of high-dose 5-Fluorouracil by interferon-alpha-2b and phosphonacetyl-L-aspartic Acid in patients with advanced colorectal-cancer.

We conducted a multicenter phase II trial in patients with advanced colorectal cancer to investigate the antitumor efficacy of double alternate modulation of high-dose infusional 5-fluorouracil (5FU) (60 mg/kg/48 h = 2400 mg/m(2)/48 h) by interferon alpha-2b (IFN alpha) (10 MU/dose s.c. prior to and halfway 5FU, uneven cycles) and phosphonacetyl-L-aspartic acid (PALA) (250 mg/m(2) i.v. 24 h before 5FU, even cycles). Cycles were given weekly for 4 weeks and once every 2 weeks thereafter. Twenty one patients with progressive or symptomatic disease were treated ambulatory. Two patients (10%, 95% confidence interval 1-30%) achieved a partial response. Therefore, this schedule of double alternate modulation of 5FU is unlikely to be superior to single modulation of 5FU in patients with advanced colorectal cancer. Since no grade III/IV toxicity (WHO) occurred during 251 cycles, which is in contrast to our previous studies using the same 5FU schedule, it might be possible that alternate modulation allows more intense 5FU schedules compared to single or double modulation schedules.