Weekly high-dose infusional 5-fluorouracil (HD-5-FU) combinations in the treatment of advanced breast cancer: results of phase I/II studies with weekly 24-hour infusion of HD-5-FU plus high-dose folinic acid (FA) alone and in combination with paclitaxel and cisplatin.

Unlabelled: Our Phase II study results demonstrating high efficacy and low toxicity for a weekly schedule of high-dose 5-fluorouracil/folinic acid (HD5-FU/FA) in intensively pretreated metastatic breast cancer prompted addition of paclitaxel to this regimen in a phase I/II study in outpatients.

Treatment: Patients were treated with HD5-FU (24-hour infusion)/FA (2h infusion prior to FU) weekly for 6 weeks (d1, 8, 15, 22, 29, 36) and Paclitaxel (3-hour infusion) was administered additionally on day 1 and day 22, q day 50. During Phase I we chose the following dose levels (dl): Fixed doses of FA d11-4 500 mg/m2 followed by HDFU, 24-hour infusion d11: 1.5, d12: 1.8, d13 and d14: 2.0 g/m2. .3-hour infusion of Paclitaxel on day 1 and day 22 d11 to d13: 135. d14: 175 mg/m2. D14 was chosen to be further evaluated during phase II. Results of an interim analysis were presented.

Patient characteristics: 46 patients entered this trial during phase II and had the following characteristics: age 46 years (26 to 70) WHO performance status 0/1, metastatic disease sites 2.5(1 to 4). All patients had bidimensionally measurable disease. PRETREATMENT: 9 patients had received adjuvant chemotherapy, 16 patients prior chemotherapy for metastasis, and 21 both adjuvantly and for metastasis. Of 29 anthracycline-pretreated patients, 25 had anthracycline-resistant disease.

Results: We observed the following results in 35 evaluable patients: CR 3% (1/35), PR 51% (18/35), SD 40% (14/35). PD 6% (2/35). RR (Response rate) was 54%, 95% confidence interval 36 to 76%. The response concerning 20 patients with anthracycline resistant disease was: RR 55% (11/20). Median number of treatment cycles per patient was 3 (1 to 5), time to maximum response 2 months (1 to 5), remission duration 8+ months (2 to 17). Median survival time is not yet reached.

Conclusions: The combination of paclitaxel with weekly HDFU/FA is well tolerated in the second-line treatment of metastatic breast cancer and indicates high efficacy also in anthracycline-resistant disease. In an ongoing phase II study, we examine the addition of cisplatin to the regimen in the first-line treatment of metastatic breast cancer. Those trials confirm that infusional weekly HD-5-FU plus folinic acid is of considerable interest in the treatment of advanced breast cancer. Randomized studies are warranted.