Background: QUASAR is a large trial of adjuvant chemotherapy for colorectal cancer in which clinicians could choose to deliver a standard adjuvant cytotoxic chemotherapy regimen, 5-fluorouracil (5-FU) and L-folinic acid (L-FA), in either a once-weekly or a four-weekly schedule. We report results of a non-randomised comparison between these schedules with respect to survival, recurrence and differential toxicity.
Patients and methods: In a factorial (2 x 2) trial design, QUASAR compared high-dose (175 mg) versus low-dose (25 mg) L-FA and levamisole versus placebo. The dose of 5-FU was fixed at 370 mg/m2 and although the recommended schedule was i.v. bolus delivery, daily for 5 days repeated four-weekly for 6 months, a significant proportion of randomising clinicians were constrained to deliver once-weekly 5-FU-L-FA for 30 weeks.
Results: Four thousand nine hundred twenty-seven patients were entered into QUASAR between May 1994 and October 1997, eighteen hundred twenty-nine of whom have recurred and sixteen hundred eighty-nine died. Similar numbers 2370 vs. 2559 were treated with the once-weekly and four-weekly schedules and the demographic features of the 2 groups were well balanced: stage C, 73.3% once-weekly vs. 71.0% four-weekly; colon, 68.0% vs. 68.3%; high-dose FA, 50.1% vs. 49.9%; levamisole, 49.3% vs. 49.3%; females, 40.2% vs. 41.7%; median age (years) 62 vs. 61. The risk of recurrence and survival were similar regardless of schedule: three-year survival was 70.6% once-weekly vs. 71.0% four-weekly; three-year recurrence risk was 35.6% once-weekly vs. 35.5% four-weekly; But, the once-weekly regimen was much less toxic: number of patients for whom toxicity was reported (once-weekly: four-weekly), stomatitis, 37 vs. 337; diarrhoea, 260 vs. 440; neutropenia, 20 vs. 153.
Conclusions: The once-weekly regimen is much less toxic than and, apparently, about as effective as the four-weekly schedule. This suggests that the toxicity of 5-FU-L-FA adjuvant chemotherapy could be reduced substantially by weekly scheduling without compromising efficacy. Alternatively, efficacy might be enhanced with equal toxicity by more dose-intense weekly FU-L-FA regimens. However, this conclusion from a non-randomised comparison needs confirmation in prospective randomised studies.