DOXIFLURIDINE IN COLORECTAL-CANCER PATIENTS RESISTANT TO 5-FLUOROURACIL (5-FU) CONTAINING REGIMENS

Doxifluridine(5-dFUR) is a fluoropyrimidine derivative, which is prefe rentially converted to 5-fluorouracil (5-FU) within tumour tissues. Al though the activity of 5-FU in metastatic colorectal cancer is well re cognised, resistance to this agent is frequently observed and remains its major limitation. The aim of this phase II study was to evaluate t he activity of oral and i.v. 5-dFUR in metastatic or locally advanced colorectal cancer patients, who had been previously treated with a 5-F U containing regimen in either an adjuvant or metastatic setting. We t reated 48 patients who, on the basis of tumour progression during, or within 8 weeks of the discontinuation of 5-FU therapy, were considered 5-FU resistant, 14 of the patients received 5-dFUR 3000 mg/m(2) as a 1-h i.v. infusion, combined with L-leucovorin 25 mg/dose on days 1-5, every 3 weeks; the remaining 34 received oral 5-dFUR 1200 mg/m(2) for 5 days followed by 5 days off. Oral L-leucovorin 25 mg/dose was admini stered 2 h before 5-dFUR. On the basis of WHO criteria, 4/14 (29%, 95% CI 4-51) partial responses were noted in the i.v. treated patients, a nd 4/34 (12%, 95% CI 1-23) in those treated orally. The radiological e xaminations documenting the response were a CT scan in 4 cases, ultras ound in 2 and NMR in 2. The median response duration was 6 months (ran ge 3-11+), whereas the median time to treatment failure was 4 months ( range 2-17). The responses were achieved in cases previously treated w ith a median of 9250 mg/m(2) (range 5500-18650) of 5-FU. No CTC-NCl gr ade 4 toxicity was observed, although grade 3 diarrhoea occurred in 5 of the orally treated and in 3 of the intravenously treated patients. This is the first report documenting the efficacy of 5-dFUR in patient s resistant to 5-FU therapy, and suggests that there is an absence of complete cross-resistance between these two fluoropyrimidines. (C) 199 7 Elsevier Science Ltd.